Forest a/sez/ment

O.Hein/dijk

pudoc

Centre for agricultural oubli/hlng and documentation lUageningen 1975 Abstract

Heinsdijk, D.; 1975. Forest assessment. Pudoc, Wageningen, Netherlands. 359 pp.: 11 tables; 1800 ref.

Forest assessment is the evaluation of forest lands and stands, and their general management, taking into account all uses to which they are put. For such assessment, one must consider history, topography, climate, soil, produc­ tion, economics of timber, ecology and nature conserva­ tion, and social functions including recreation. The treat­ ment of these subjects mentions present trends, and de­ scribes temperate, subtropical and tropical circumstances.

UliiLIOTHEEX DEK LANDBOUWHOGESCHOOL WAGEN INGKN

ISBN 90 220 0550 X

© Centre for Agricultural Publishing and Documentation, Wageningen, 1975

No part of this book may be reproduced and/or published in any form, by print, photoprint, microfilm or any other means without written permission from the publishers.

Cover photograph: KLM Aerocarto

Printed in the Netherlands Centent/

PREFACE 1 1 INTRODUCTION 3 2 GENERAL OUTLINES OF FOREST ASSESSMENT 6 2.1 The public attitude and forest laws 6 2.2 Changes in land-use 8 2.3 Sustained yield 9 2.4 Forest reserves and security 11 2.5 The amenity of forests and trees 12 2.6 Damaged forests and wilderness 14 2.7 Adjusted management 16 2.8 The multiple base of forest assessment 18 2.8.1 Relations between man and forest 19 2.8.2 The use and abuse of fire 20 2.8.3 Burning and shifting cultivation 22 2.8.4 Afforestation 23 2.9 Ecological considerations 24 2.9.1 Climatic and atmospheric considerations 24 2.9.2 Edaphic circumstances 26 2.9.2.1 Chemical soil properties 26 2.9.2.2 Physical soil properties 26 2.10 Surveys and forest management 27 2.10.1 Maps 28 2.10.2 Site classification and its mapping 29 2.10.3 Forest inventory 30 2.10.4 Growth measurement and growth prediction 33 2.11 Forest assessment 34

3 HISTORICAL REVIEW 37 3.1 Trends in the development of forest utili­ zation 37 3.2 The collectors 38 3.3 Fire 40 3.4 The forest and primitive agriculture 41 3.4.1 Integration of forestry and agriculture 43 3.5 The forest and primitive animal husbandry 45 3.5.1 Apiculture 48 3.6 The forests and old civilisation 48 3.6.1 The forest in mythology 48 3.6.2 Prehistoric forest exploitation 50 3.6.3 Deforestation in the Mediterranean Area and the Near East 50 3.6.4 Deforestation in Western Asia and China 52 3.6.5 The past situation in the temperate regions of Europe 52 3.6.6 The situation in the Far East 56 3.6.7 Past and present situation in the Americas 59 3.6.8 Forestry in Africa 60 3.6.9 Forestry in New Zealand and Australia 61 3.7 Man-made forests and exotic tree species 61

4 MAPPING AND MAPS 63 4.1 Origin and development of mapping 63 4.2 Terrestrial mapping in forested regions 66 4.2.1 Mapping inside forest areas 67 4.2.2 Vegetation maps 69 4.3 General use of aerial photographs— 70 4.3.1 Development of aerial photography 70 4.3.2 Photogrammetry versus terrestrial survey 72 4.3.3 Demarcation of property borders 73 4.4 Aerial photography in forestry 74 4.4.1 Demarcation of borders inside forests 75 4.4.2 Forest type mapping 75 4.4.3 Area estimates 76 4.4.4 Contour mapping 77 4.4.5 Scale and type of photographs 78 4.6 Remote sensing 79 4.7 Colour and false colour photography 80 4.8 Radar pictures 80 4.9 Forestry maps 81 4.9.1 Types of maps 81 4.9.2 Photomaps 82 4.9.3 Costs of maps from aerial pictures 83

5 THE CLIMATE 84 5.1 Definitions 84 5.2 The climates of the past and recent changes in the atmosphere 85 5.3 The macroclimate 88 5.3.1 The main climate factors 88 5.3.2 Climate classifications 89 5.3.3 The influence of forests on precipitation 91 5.4 The microclimate 9 3 5.4.1 Microclimatic factors 93 5.4.2 Solar radiation 9 4 5.4.3 Light intensity and growth 96 5.4.4 The temperature inside and near the forest 9 8 5.4.5 Air movement 101 5.4.6 Air humidity 103 5.5 Shelterbelts 104 5.6 The introduction of exotic species 106

6 THE SOIL 107 6.1 Introduction 107 6.2 The role of water 109 6.3 The physical soil properties 110 6.4 Erosion 112 6.4.1 Erosion by water 113 6.4.2 Erosion by solid material 116 6.4.3 Erosion by wind 117 6.5 Chemical soil properties 120 6.5.1 Nitrogen 120 6.5.2 Phosphates 124 6.5.3 Potassium 126 6.5.4 Calcium 128 6.5.5 Magnesium 130 6.5.6 Sulphur 131 6.5.7 Other elements 132 6.5.8 Organic matter 133 6.6 Classification of soils and soil mapping 136 6.7 Manipulating the forest soil 137 6.7.1 Removal of litter 138 6.7.2 Burning 138 6.8 Forest soils and water 141 6.8.1 The supply of water 141 6.8.2 Land-use and water supply 142 6.8.3 Irrigation in forestry 143 6.8.4 Drainage in forestry 144 6.8.5 The influence of forests on total stream- flow and silting 144 6.9 Tillage and fertilization of forest soils 145

7 FOREST SITE CLASSIFICATION 149 7.1 Early site classification 150 7.2 Site classification and undergrowth 150 7.3 The productivity of natural forests 155 7.4 Site assessment 157 7.5 Forest site mapping 159 7.5.1 Topographic maps 160 7.5.2 Climatic considerations and seed provenance 160 7.5.3 Soil maps and other environmental factors 162 7.6 Site and management 163 7.6.1 General considerations 163 7.6.2 Site and fertilization 166 7.6.3 Site and tillage 166 7.6.4 Site and irrigation or drainage 167 7.6.5 Site and man-made ground 168 7.7 Conclusions,site,management,and environment 168 FOREST INVENTORY 173 8.1. Introduction 17 3 8.2 Identification of tree species 173 8.3 Tree assessment techniques 176 8.3.1 Weight assessment of wood 176 8.3.2 Measurement of wood volume 183 8.3.3 Tree volume and tree volume tables 186 8.3.4 Changes in wood utilization 190 8.4 Stand assessment techniques 19 3 8.4.1 Tree counting 193 8.4.2 Stand volume assessment 19 5 8.4.3 Sampling 200 8.4.4 Repetitions of inventories 206 8.5 Growth assessment techniques 208 8.5.1 Growth of trees 208 8.5.2 Growth of stands 209 8.6 Trends towards complete tree utilization 213 8.7 Assessment of minor forest products 215

THE ECONOMIC ASPECTS OF FORESTRY 218 9.1 General considerations 218 9.1.1 The international aspects of wood production 220 9.1.2 Managed wood production 221 9.2 Flexibility in wood production 222 9.3 The economic base of forestry 225 9.3.1 Poplar: an example demonstrating some financial aspects of wood-growing 226 9.3.2 The value of forest land 229 9.3.2.1 Returns from timber lands 230 9.3.2.2 Regional rentability in wood growing 231 9.3.3 Yields and costs 233 9.3.3.1 End harvest and thinnings 233 9.3.3.2 Cultivation costs 235 9.3.3.3 Annual costs 237 9.4 Wood growing and its possible integration 240 9.4.1 Co-operation in wood production 240 9.4.2 Stimulation of wood growing and special forms of co-operation 242 9.4.3 The aspects of integrated tree growing 246 9.5 Wood production outside the forest 249

10 DECISION MAKING IN FORESTRY 251 10.1 The future of wood utilization 251 10.2 Future land-use 255 10.3 The rotation 256 10.4 Other aspects of decision making 257 10.5 The social function of forests 259 10.5.1 The forms of forest recreation 259 10.5.2 Costs of forest recreation 261 10.5.3 The outlook for forest recreation 262 10.6 Conclusions 2Ç3 LITERATURE 269 INDEX 346 Preface

Some years ago, Mr. J.F. Wolterson, then director of the Forest Research Station in the Netherlands, pointed to the lack of a general book on the aims of forestry and its role in the management of natural resources and human society. The need was not for a book written for specialists, but for workers in other disciplines who needed some general information on the aims and methods of forest management and its economic and social background, in the past, pre­ sent, and future. Or in short: forest assessment. At first, the intention was to restrict the subject to tropical and subtropical regions, where the need was grea­ test. It soon became apparent that a description of events in other areas was indispensable. The scope of the work was therefore broadened considerably. Because of the immensity of the material, collected from literature and other sources, Chapter 2 was written as a survey for the general reader. This chapter also includes odd facts that do not fit in the subsequent chapters 3-9 in which the main topics are treated in detail. Many details from literature and minor remarks have been printed in small-point letter, so as not to disturb too much the general course of the text. I am greatly indepted to the Central Organization for Applied Scientific Research (TNO) for its financial support and the Forest Research Station mentioned above for techni­ cal assistance. Many people helped to collect the necessary details. Suffice it to name Miss G.H. Jansen of the Library of the Forest Research Station, Mr. C.P. van Goor (its sil- viculturist) and Mr. Wolterson for carefully reading the manuscript in its various stages. The manuscript was edited and revised by the Centre for Agricultural Publishing and 2

Documentation (PUDOC), largely by Dr. E. Meijer Drees whose outstanding help in reducing the originally much bulkier manuscript to a handier size cannot go unmentioned. To them and all the unnamed workers who assisted in crea­ ting this book I offer my thanks.

Goes, August 19 74. I Introduction

Already in ancient times people around the Mediterranean and in China recognized the large-scale reduction in the earth's forest cover to be anthropogenic. Nevertheless only in relatively recent times has man seriously tried to stop further deforestation, to maintain the wood productive ca­ pacity of the forest, and to combat erosion and to secure water supply for domestic, agricultural and industrial pur­ poses.In the last decennia, man has realised that forests also play an important role in recreation, an essential condition for the mental welfare of mankind whose numbers are increasing so rapidly. Forestry has to keep in mind all these aspects; management has to adapt its policy to the multiple purpose of the forest. In the beginning, the forest was a source of food, both from plants and animals, and it supplied fuel and some wood for simple housebuilding and comparable purposes. When agri­ culture appeared on the scene, forest patches had to be cleared. As a rule their soil productivity soon decreased so much, that new clearings had to be regularly made, giving rise to what is now called shifting cultivation. The aban­ doned patches, when regularly burnt, were often very suit­ able for grazing and were maintained for that purpose. It is only much later in the history of mankind that trees were felled for their saleable wood and real forest exploitation started. At present both burning and cutting have assumed such large proportions that the earth's forest cover is seriously endangered. There is great concern about global environmental pro­ blems caused by 'man's impact on the climate1. Attention is focused on the "buildup of carbon dioxide from fossil com­ bustion' (1039) in the atmosphere, which can be counterba­ lanced by tree growth, because carbon is locked up in the wood. Forest growth can offset increases in carbon dioxide 4 in the air; forest clearing ^especially in the tropics) can accelerate such increases (1302). The best measure to counter this danger is the planta­ tion of new stands. This 'plantation forestry' guarantees a regular wood supply so that the forest becomes an inexhaust- able source of raw material. Great amounts of carbon dioxide are stored in the standing wood of the trees, and in the timber for future use by man (the storage time for the wooden parts of houses averages 20 - 30 years)(444). In raising tree crops, there is a change at present to quick-growing, high-yielding species to produce large quan­ tities of fibre. This involves not only techniques resem­ bling those applied in agriculture (fertilization, drainage or irrigation, selection, etc.), but also an increase of labour. As, especially in more advanced regions, labour is expensive, mechanization is necessary. Consequently, management traditions of 'classical fores­ try' (that still predominate in Europe) with long rota­ tions, burdened with high labour and management costs, have to be replaced by modern economic principles. To be effec­ tive, management areas have to be expanded; small forest owners have to co-operate to establish them. Such a concen­ tration must include the wood-working industry, and it is even imaginable that production and industrial wood process­ ing have to be included in an 'integrated wood industry' as known from the USA. - Forestry needs land. So does agriculture. And as food pro­ duction is more important than wood production, in more ad­ vanced countries only submarginal agricultural land will be available for forestry in the future. In sparsely populated areas where shifting cultivation or large-scale cattle bree­ ding are still common practice, this stage has not yet been reached and large quantities of valuable timber are burnt, even in 'legal' forest reserves, much to the annoyance of foresters. Repeated burning, combined with raising domestic animals in a semi-wild state, may in the long run reduce 5 soil quality to such a low level that reasonable agricul­ ture becomes for ever impossible; in dry regions it may even result in entirely unproductive land. 'Reasonable' means here: concentrated on the better soils where high production together with mechanization, fertilization, etc., can counteract the steadily rising labour wages needed to attain an acceptable living standard for the population. On the other hand, with the demand for better agricultural soils forestry may regain some of its territory, as happens now in western Europe. The situations and tendencies mentioned above do not ap­ ply to forests that have to be maintained (or re-establish­ ed) for protection purposes, including the combat of damage inflicted by (chemical) mechanized agriculture and the emis­ sion of poisonous gases by industries upon the regional ecology. The goal must be a stable situation in which agriculture and forestry, together with recreational and industrial requirements, each play such a role that a lasting equili­ brium is reached on a sufficiently high level to satisfy the reasonable demands of everybody, even naturalists and scientists. In this versatile complex of problems, forestry must first assess all factors directly or indirectly pertaining to its field of activities before it can initiate management di­ rected towards future integration of production, recrea­ tion, the physical and spiritual welfare of the people, and to be understood and supported by everyone. 2 Generell outline/ of fore/t o//e//ment

To assess means to carry out a valuation, to make an esti mation of a certain situation, to review and judge it. In a given forest area assessment involves, in the first place, an overall classification and appraisal of the land and its relation with natural and man-made surroundings. It has to be based on the best uses of the stands, on the highest possible financial profits and the services the forest renders to soil protection and allied subjects, to recreation, and to science. These are all internal manage­ ment problems; they have to be solved realistically so that traditions and sentiment do not influence decisions. Were bare lands are involved that might be suited both fo: afforestation and other purposes, such prejudices are ab­ sent and forestry has to compete in a normal way with other possible land uses. Only where the forest has to provide for soil protection and the regulation of water, has assessment to start from 'a priori' considerations.

2.1 The public attitude and forest laws

In most parts of the world, forestry "Has lost the battle for land: agriculture, animal husbandry, house-building, etc. have won. In many areas this battle still continues and recently a new competitor has entered the picture: recrea­ tion. It is unavoidable that forest stands have to be sacri­ ficed for recreation; however recreation and forestry can often be complementary, although at the expense of wood production. In many parts of western Europe hardly any fores is left for true unrestricted production. 7

The public often shows little respect for the trees in the recreation forests: they consider them more or less as their own property, areas where they may 'mess around' as much as they like. Nevertheless they definitely remain in favour of the forest, which is apparent from protests that arise when 'beautiful' old stands have to be cut. In Germany, where the public is very 'forest minded", inquiries in the south have revealed that 80 % of the visitors were aware that the stands were managed, only 2 - 11 % considered this management distur­ bing, and only 1 % criticized clear-felling and the resulting heavy transport along the roads (1798). In the USA, since 1905, the forest service has obliged all managers of national forests to make annual cutting plans (1447). In 1970 it became evident that these forests were not utilized to their full ca­ pacity and that the harvest could be increased by 66 % if there were enough funds made available for road-building and intensified manage­ ment (1137) . During an US Senate hearing in 1971, this suggestion was met with cries such as 'rape of the national forests',most probably due to the temporary ugly outlook of mechanized clear cutting (207). In 1970 and 1971, the USA Forest Service could not even 'put up for sale its allowable annual cut of commercial timber' because 'court actions by preservationists and others caused delays and can­ cellations (896)with the result that lumber prices were pushed up­ wards (1569). Such an interference by outsiders, declaring forests more or less 'untouchable', does not encourage private landowners and investors to spend money on improving their property. But it is also doubtful whether the proposal to ban from the forest all such entertainments as children's playgrounds and campings and so provide tranquility and se­ clusion, as has been proposed in Switzerland (467), will be­ come acceptable. The public attitude, including that of agriculturists and industry, towards the forest has to be regulated in some way to prevent undesirable deforestation or damage, and to control or assist private forest owners in their management, either by technical or financial aid. The resulting forest laws have to be taken into account in the evaluation of the forest and in its assessment. 8

2.2 Changes in land-use

The 1 hands-off' attitude of the government towards soil occupation is, for most regions, a thing of the past. The losses this attitude has caused are enormous and to repair them is possible only on a small scale. Nevertheless at­ tempts to reforest are regularly made in many countries, and at present in some of them even agricultural lands are withdrawn from the production of first crops because far­ ming has become unremunerative.In some cases it is even possible that agriculture and forestry regularly alternate on the same area. In the USA the process of change is already well under way: up to 1963 13.2 million hectares had been withdrawn from agriculture; an increase to 20 million is expected by 1980. For Europe, 10 million hectares are planned for 1975 (440). Between 1958 and 1968, in South Carolina 27 % of the farm forests (720 000 ha)shifted from farmers to non-farmers, including all kinds of people 'showing from none to the most intense interest in timber growing' (827). During the same period, in north-west Florida 128 000 ha agricultural land was converted to forest, offsetting the loss in forest area to other types of land-use (826). In north-east Flori­ da, 204 000 ha commercial forest was converted into pasture, urban developments and arable fields, but 128 000 ha became commercial forest again (998). From 1938 to 1966 the forest area of North Carolina increased by 760 000 ha to a total of 8 million (824). During 25 years, up to 1969, the change for Georgia was an increase of 1.8 million hectares forest or a gain of 21 % (909). But between 1957 and 1967, the gain for Virginia was only 2 %, hardly replacing the 200 000 ha of commercial forest lost to other land-uses, while at the same time 1.2 million hectares of these forests shifted fron farmers to non-industrial private ownership (825). In the Netherlands, soils too poor for agriculture have 9 long been considered good enough for forest. Therefore the average annual wood production has always been low, a mere 2.8 m3 (214). Recreation forests were established on better soils near large cities already many decennia ago (681), but it is only recently that such soils have been planted with production forest, mainly poplars. The forest law of 1961 (15) prohibits decreases in national forest cover and the clearance of forests without replacement on soils of at least equal quality. If this law could be made more flexible, a redistribution of forests would ensue. However, the stands that are urgently needed for wood pro­ duction would have to be safeguarded.

2.3 Sustained yield

The idea that old stands have to be cut, and should be replaced by forests with much shorter rotations, fills many foresters with horror. Perhaps they have a bad consience, about insufficient care of the stands in the past, or na­ ture in general, that now leads them to conservation at any price. Or the long rotations may be a relic from the times that forests played an important role in hunting (631). How­ ever people often do not realize that dense stands are not very suitable for maintaining many herds of game, so that it is a misconception to suppose that the old forest con­ sisted solely of dense stands: most forest lands were 'woody grounds and fruitful pastures privileged for wild beasts and fowls of forest, chase and warren to rest and abide in the safe protection of the king, for his high de­ light and pleasure', as described for England (597), kept 'safely and stringently for sport1 (596). Whatever the reasons for protection were, no thought was given to caring for the forests until they became scarce and property boundaries had to be established (1185). Be­ fore that, management could hardly begin. 10

In Europe, forest economy started its development some 500 years ago. 'The unlimited quantities of charcoal needed by the rapidly growing metal industries for their blast furnaces, melting houses and foundries, the wood ash, needed for the glass industry, the fuel- wood needed for the pans of the salt works and finally the enormous requirements of construction and firewood in cities and industrial centers, soon brought about difficulties and bottlenecks in wood supplies....Wood became important and precious and there developed an interest in the necessity to protect forests against further clea-, ring, to maintain them, manage them, increase their yields and to en­ sure their value in the future 1 (403). It was soon recognized that annually no more wood than the stands were able to grow should be harvested. The pure exploitation stage, whereby forests were manipulated as 'in- exhaustable1, changed (though in most regions far too late) to planned managed harvesting, with the stands treated as a 'renewable' natural resource (1799) to avoid future wood scarcity. As the elementary principle, that of 'sustained yield' has generally been accepted: 'the scientific mana­ gement of forests for the continuous production of goods and services' (1762). In Western and Central Europe this principle has been ge­ nerally accepted. In other regions development is still un­ der way and it seems worthwhile to illustrate this with a few examples. After some local preliminaries (e.g. in the Great Lake Region, where at the end of the 19th Century most of the forest had disappeared (1788) before a first step to sound management was taken (1605)), the USA Sustained Yield Forest Management Act of 1944 introduced the prin­ ciple of stability in community forests, though it implied an 'orderly change rather than a fixed condition' (389). "The act also authorized federal foresters 'to make co-operative agreements with other willing landowners '(845). In 1960, the Multiple Use-Sustained Yield Act adapted the principle of sustained yield defined as the 'continuous' achieve­ ment and maintenance of the high-level output of forest resources with­ out impairing the productivity of the lands (1605). In Canada, with its 443 million ha forest lands (440), Ontario was the first to start regeneration of cut-over and unproductive burned areas (for its 'crownlands') (385). In 1945, British Columbia intro­ duced a policy of annual cuts based on a sustained yield. Though lack of inventory data hampered its application (1506), in 1971 35 Tree Farm Licences were granted for about 4 million ha, to be managed on a sustained yield base according to previously drawn-up management plans (605). For the 24 million ha of unsatisfactorily stocked but 'potential" ly productive forest lands', it was suggested to give 'priority ratings' in planting to guarantee the perpetuation of wood production (296). 11

Ideas about the forests of Northern Canada differ. Some people prefer a kind of sustained yield to avoid 'the abuses of forest li­ quidation' (1121), others consider it more important to spend avail­ able money on opening-up and regeneration of good forests in easily accessible areas and to fix 'the rate of cutting more according to market demands than to silvicultural restraint' (1137). Or to put it bluntly: ' not to miss excellent opportunities for today in the enthu­ siasm for saving for the future'(1431). In the Siberian taiga, wood cutting is regulated 'in accordance with technological calculations' (1611) (whatever that means). In general, it will cause a decrease in forest area. In European Russia, between 1940 and 1965, approximately 50 million ha over-mature forests were cut over, which were regenerated or replanted (1612) according to the principles of sustained yield. In Malaya, the annual cut of the rain forests was fixed on a sus­ tained yield basis with a rotation of 70 years. This simple arrange­ ment did not work, because after 15 years only an area of about two annual cuts was covered with regeneration (1420). Sustained yield has always implied the re-establishment of forest in the same place. Recently this has become ques­ tionable, however, because moving forestry from one piece of land to another need not endanger production nor does it necessarily harm the soil. In such cases 'static fores­ try' based on strict local sustained yield principles has to be adapted to 'dynamic conditions' (1788). Even transfer to another country may be justified if conditions there are more favourable for production or for the wood-working in­ dustry. Except, of course, when the forest has to fulfill other tasks instead of or besides its production function.

2.4 Forest reserves and security

Next to forest areas set aside for recreation and compar­ able purposes, and for the future ('production reserves'), reserved forest areas may be needed for emergencies such as wars (759), to protect watersheds against erosion, to gua­ rantee water supply, and to prevent avalanches. Such forests have a static 'area' function (358). This does not mean that all exploitation has to be prohibited, but it has to be a- dapted to the given circumstances (878).

Switzerland supplies excellent examples. In most of its forests wood is harvested (1581), though as a rule not by large clear-fellings (1016). 12

Only poplar and willow plantations on agricultural soils are excluded from close supervision by the community (394). The importance of such forest reserves for wood production has also been stressed in Austra­ lia: they should contribute as much as possible to the national wood industries (992). The idea of reserving forest areas for strategic purposes and emergencies is already old. In the Roman empire, old forests were regarded as savings and, according to Pliny, only coppice of sweet chestnut (Castanea sativa) was regu­ larly used (1185). A similar idea is the French principle (in the Code Civil) that only the wood increase (the inte­ rest of the savings) of a forest may be harvested (1353). A French forest economist remarked that the 'imperishable' forest owners, such as the state and the church, have always to regard tree stands as a 'heritage' from which cutting haS to be rigorously regulated so that they are continuously maintained for the benefit of future generations (398). Con" sequently it is hardly surprising that the French forests, having been treated a long time in this way, have grown too old and at present produce so little (752) that reassessment of their management is considered urgent (248).

2.5 The amenity of forests and trees

In sparsely forested regions, public opinion has always strongly opposed cutting beautiful trees or stands because they are 'untouchable eternal natural-.values1 which have to be preserved (1011). Forest services often show the same ' tendency, though they are more selective in deciding which stands have to be saved.

How far the interest of the public may go is apparent from a 60 ha big beautiful stand in Japan that receives annually some four million ; visitors, spending 1.3 to 2.1 million dollars in the neighbourhood (call culated on commercial wood this stand would have yielded $ 6000 a year)j (1177). The French forest service maintains some magnificient oak standsj ('séries artistiques') where the trees remain until they perish, unlessj they become dangerous (1547). Recently in the New Forest, in England, considered a national heritage, conversion into conifer stands was stopl ped and hardwoods were given a rotation of at least 200 years with fel"j ling restricted to single trees or small groups to maintain the forest'^ beauty (1756). 13

In the Netherlands, for a similar area, it was proposed to main­ tain the original forest structure along the roads (where the public can see it) and to change the rest into production forest "before the trees come crashing down' (1478). Exaggerated tree and forest saving will ultimately lead to non-management, creating wilderness. Such areas, extreme­ ly rare in developed countries (536), may have a scientific value, but they are of little importance for general recrea­ tion. Instead of creating wildernesses it is more sensible to turn extensive areas into one big 'Garden of Eden', to be enjoyed by millions as proposed in the Netherlands (156). Most private forest owners try to preserve the amenity of their stands and to manage them at the same time. In the eastern part of the Netherlands, scattered forest patches have been planted for this purpose between arable land (194), as has also been done in England (1156) and in the southern part of the USA (1267). Such stands have also a healing ef­ fect on the ecology of agricultural regions (1627) and still serve wood production without impairing sport or amenity functions. The urban regions of the USA, occupied by almost 100 million people, have many neglected wood lots kept for pleasure. For these it was re­ garded 'imprudent, at least, if not downright extravagant1 to write them off completely for wood production (490) Australian farmers were advised not to plant solely for wood production but also 'as part of the overall conception of beautification and amelioration of the home­ stead surrounds' (209). The care for hedges, roadside and park trees, closely con­ nected with forestry, is a very old problem. The earliest known roadside tree plantings, in China during the Chou dynasty (1122 - 206 B.C.) (1307), became part of the land­ scape, adding to its beauty. The people sought them and loved to repose in their shade. Trevelyan wrote about the trees in England: 'The trees were hedgerow timber scattered over the countryside, or park trees preserved for their beauty, or covers planted for game', and in 1880 England 'could boast of finer trees than any other country, if judges by aesthetic, not by com­ mercial standards' (1558). 14

Inventory data show that the standing timber in such plantations can become substantial. In 1965 - 1967 it was estimated for England at 34.1 million (953), in 1968 in the Netherlands (oak, poplar and willow) along roads at 2 million m3 (267). If famous trees or avenues are involved, cutting for the safety of traffic can cause serious trouble (1730). These trees should be replaced as soon as possible by older sap­ lings (354). Sometimes it is possible to call in the assis­ tance of tree surgeons or 'arborists' who turn old trees into living monuments (120). The most difficult point is how to maintain the amenity of selected stands,tree strips, groups, etc., as sooner or later they will all die of old age. At a congress of the International Federation of Park and Recreation Administra­ tion it was remarked that such trees also have to be mana­ ged according to a certain rotation plan to guarantee an overall 'sustained presence', though not locally (which obviously is impossible) (728).

2.6 Damaged forests and wilderness

It is still unknown how to cope with damage due to neglect during 'traditional' management and due to air pollution. Damage not only reduces production but also has an unplea­ sant impact on the amenity of the foreätrlandscape. In the European mountain areas, the reforestation of abandoned crop- fields (13) is often hampered by lack of skilled labour (878): the farmers that carry out selective cutting in winter may have moved (466). Inhabitants from cities cannot take over this work. On the con­ trary, their arrival may cause much trouble: unorderly road and house building may further erosion, degrade the beauty of the landscape, and frustrate long-term reforestation plans (29, 551, 875, 876). In France, this 'social fallowing' (1364) has resulted in an increase of forest fires due to lack of sufficient prevention(64). For all this the social revolt among the housewives has to be blamed: they do not want to live in solitude on the land and prefer the snug company of others (74). 15

If left unmanaged, the forest cover turns into a kind of wilderness. The general public is not yet aware of this consequence. The 'wild' forest patches in Czechoslovakia, left alone since 1838, show a structure similar to that of a tropical rain forest: a confu­ sion of small and big trees with fallen or broken specimens, here and there some uniform forest growth or an open place (1737). The accumu­ lation of debris makes these forests susceptible to fire, especially where they consist of conifers. The wind can cause in most cases considerable damages, as proved during the heavy storms between 1966 and 1968 occuring in Switzerland, West Germany, Austria and France, and in 1972-1973 in Northwest Europe (1573, 498, 1622, 1145). Only good management can raise wind-proof stands, such as those of spruce and beech in Austria (1044), or protect them against the prevailing winds by properly directed exploitation. Even the stock of game has to be 'managed', a surplus causing too much damage to young and older trees (1239, 877, 432). Recently attention has been focussed on the damage done to trees by industrial emissions, either near densily po­ pulated areas or from factories established on isolated, cheap forest lands (1580, 484). Atmospheric sulphur dioxide can, already in low concentrations, considerably harm trees (915); already 0.5 mg per cubic metre air can be fatal, 0.03 mg during longer periods (1687). For spruce already a concentration of 0.01 mg/m3 air has shown to decrease height growth, though much depends on the nutritional levels of other alements (1037). Investigations with lucerne and gladiolus in the Netherlands have re­ vealed that these plants can serve as indicators for the amount of SO2 in the air (1270); in Sweden the same was found for tree leaves (935). Comparable data are known for fluorine, which at present causes by far the greatest damage (162) (up till 1968, in Europe on some 400 000ha (176)). Investigations in the USA and in Germany have shown that damage done by air pollution can be traced from aerial colour photographs (1691, 796). At present, the increasing amounts of hydrochloric acid set free by burning garbage containing chlorinated polymers (plastics) result in abnormally high quantities of chlorine in the leaves of nearby trees causing distinct injuries (790). Forestry is not allowed simply to abandon such endangered areas. It has to look for less susceptible species or treat­ ments reducing the effects of air pollution, either because alternatives for production are absent, or because the fo­ rest has to remain for protection or recreation purposes (98). Especially on rich soils (1037) the outcome may still be satisfactory as the injurious effect of air pollution 16 seems to be counteracted by other favourable circumstan­ ces (406).

2.7 Adjusted management

The preceding sections have shown that so many factors play a role in management that a purely economic-silvicul- tural approach to forest assessment is hardly possible. The necessity to establish paths for walking (1055), to call in the help of the public in establishing plantations (as in Iceland (864) and in China (346)),and so on requires highly flexible foresters. The image of the American forester, di­ viding his time between 'tree planting and the fire-tower1 (1427), and that of his European colleague with his authori­ tarian attitude as protector of nature and wildlife belongs to the past. Both have become managers, and as State fores­ ter mostly, or as a rule, of 'primarily non-production forests' (332), who, nevertheless, have 'to meet the ever increasing demand for wood, wood fibre, etc.' (780). This requires an integration of expensive amenity (1245) and pro­ fitable exploitation (989). Where the outcome is negative, forests are neglected or abandoned (595) , unless special aid comes in. Neither the public, nor the foresters object to sustained yield as a basic principle. But in applying it, opinions may clash:some foresters do not want to~sacrifice produc­ tion for uncertain long-term prospects (391), the public is inclined to prefer a change from 'sustained yield' to 'sustain without yield', which means not to consume the accu' mulated forest wealth. Even in inaccessible areas where, as yet, no public is present, the forester will have to decide if and when a change from pure exploitation towards sus­ tained yield management seeking to 'maximize long-run social and private welfare' (817) is feasible (1621). One of these areas has been the southern part of the USA where, around 19 30, cut-over forest land was cheap (one 17 dollar or less per acre (32)) and where before the year 2000 the Third Forest is expected to yield more than half of the USA's wood (the first forest was the virgin forest, the second the one planted thereafter, the third will con­ sist of selected high-yielding species) (1694). Another area is that of the tropics and subtropics, 'en­ dowed with highly favourable conditions for the establish­ ment of man-made forests capable of producing wood at de­ livered costs substantially lower than comparable invest­ ment efforts in the north temperate countries' (1137). Many tree species native to these regions, or exotics, show such an outburst of growth in their youth that with short rotations high annual yields may be expected (1521, 660). Here forest assessment has to assist in deciding on the feasibility of creating new forests and on their mana­ gement (383). Between 1925 and 1935, New Zealand experienced a 'planting boom' with radiata pine (Pinus radiata) resulting in large quantities of pine logs around 1967. Woodworking industries had to be extended, but this was not possible in view of the drop in pine planting after 1935 (1152) and because no wood 2te from other areas would become available . Another possibility is to adjust management by shifting from one piece of land to another in a given region. Atten­ tion to this point was paid in the discussion around the new French forest law of 1963 (916, 917). For Australia it was remarked that, in changing from agriculture to forest land, trees have to be selected that assure a good growth rate 'not committing the forester to maintain such a rate by ex­ pensive fertilizer and complicated treatment', and that it is essential that the whole region gains 1 from a pattern of agriculture and afforestation which is complementary rather than competitive (932). The Dutch, not being overtly forest- minded but progressive in the preservation of green land- £ Here adjustment was impossible due to lack of former long-range plan­ ning in planting. 18 scapes called 'nature' (104), will most probably not ob­ ject to the planting of tree stands in typical, wide open agricultural regions as long as the abandoned stands are not cleared. Internationally, the trend to widen the sustained yield principle so that the basic concept for the long-range provision of forest products includes the whole earth, has to result in growing wood in those places which give the highest return. This idea is already well understood by the internationally orientated wood-processing concerns. Deve­ loping countries with warm humid climates can then enter world wood markets and attract wood-working industries.

2.8 The multiple base of forest assessment

Today's forest assessment has to emerge from its old- fashioned European 'splendid' isolation which put the trusteeship for the forest and its 'game' population entire­ ly into the hands of foresters. At present, especially in more populated regions, foresters have to co-operate with the representatives of the general public, without which, it cannot function anymore. Consequently forest assessment will not only have to study, but also to explain the basic requirements needed for promoting healthy forest growth and its maintenance. Only then, can the valuation of the 'social and 'economic' aspects of forestry be clarified and, if sa­ crifices have to be made, they can be made acceptable to the taxpayer or forest owner. This does not mean that history and tradition, which always have been important in forestry, should be brushed aside. But, as expressed by a Dutch au­ thor on this subject: 1 contemplating about its historical aspects we will have to research the situation of today in order to formulate the management directives for tomorrow' (230). At first sight this attitude seems outmoded. Modern so­ cial and economic aspects of forestry, and the present ten­ 19 dency towards short rotations, seem to force the forester to drop the idea that a forest is a thing of eternal value of which he is the keeper. If, however, the short-rotation plantations are compared with coppice and the high forest with the natural forest reserves of the past, the objects to be managed have not essentially changed. The effects of past management can still be seen today; at present they may be troublsome, or can be enjoyed (1018). This heritage, especially in the latter case, make it worth­ while to study past forestry and even the customs of primi­ tive cultures with the emphasis on social aspects.

2.8.1 Relations between man and forest

Forests, like deep waters and the sea, are dark, opaque regions; they contain the mysterious unknown (775). Their trees are often outstanding in shape or size, and attract the attention of the forest dweller. These huge plants pos­ sess something special; they resemble personalities living in close contact with spirits and other superhuman beings. Damaged trees may bleed (1678), some are not cut because they are regarded as holy, as the banyan in India (the wa- ringin in Indonesia, a Ficus) , the 'kankan'tree (Ceiba pen- tandra) in Surinam. Primitive woodcutters may apologize to the big tree or, when they are Christians, say a prayer, be­ fore they begin their murderous task. In Europe, in olden times, the tree feller rapidly cut three crosses in the stump when the tree was toppling over to provide the tree spirit with a new sanctuary (1775). The fairy tales, myths and legends in Europe mention wild men living in the forest, personifications of the rough, un­ couth archetype of primitive man, whose vitality and in­ stinct were symbollically represented by the roots of Ygg­ drasil, the tree of life (1593). Forests and large trees were regarded as masculine. The female element, the friendly female spirits, were represented 20 by the smaller trees, the flowers and the fruits, so that women had to care for the gardens (1775) and to remain close to them so as to be protected and certain of securi­ ty and peace (1574). It is interesting for those who are accustomed to forest life to observe the behaviour of occasional visitors: they never feel very happy. Forests seem to have a depressing influence on them, they stop singing, talk softly, never shout. As soon as they reach the forest border and over­ look a broad river, the sea, or another large open space, they return to their original (often loud) mood. This also may explain why modern tourism prefers more the forest bor­ ders: the public not only wants some shade against the sun, but it feels safer when protected from the rear. It is curious that, nevertheless, so many people oppose the cutting of forests, despite their out-of-bounds effect. Human nature is more complex than reason expects.

2.8.2 The use and abuse of fire

Occasionally forest or grass fires are caused by light­ ning, but in most cases man is to blame. In the past he used fire to enlarge his hunting ground, to chase game in a certain direction, and for better visibility to protect himself against attacks from enemies. In still older times, his ancestors who dwelled in wooded regi"o"ns, had no reason for burning; on the contrary: they needed the forest as a cover. The northern Australian aborigines, prevented the cypress pine (Callitris glauca) from taking over, by burning the accumulations of woody debris in the eucalyptus forests to avoid crown-fires (at the same time destroying seedlings) (742). The early settlers in the south of the USA protected their pine stands by burning to pre­ vent the invasion of hardwoods (273). During the 19th Century, tra­ vellers in the Pondorosa pine (Pinus ponderosa) region of the Sierra Nevada, USA, observed that 'in spring the old squaws began looking for little dry spots of headlands or sunny valleys and as fast as dry spots appeared, they would be burned. In this way the fire was always the servant, never the master' (148) (preventing large fires). 21

Broadleaved forests in permanently wet areas hardly ever burn. In regions with short dry periods the danger of fo­ rest fires exists, though as a rule restricted to ground fires caused by man. Natural fires due to lightning, are rare here: the accompanying showers soon extinguish them (227). The longer the dry season, the greater the danger, especially when, as in the mountainous regions of Eastern Java, large quantities of dead twigs and leaves have accu­ mulated (226). Most endangered are conifer forests consisting of pine, spruce or fir; their needles and twigs contain highly in­ flammable resins. Even in normally wet regions a few rain­ less weeks can result in some losses due to burning: in the Netherlands 9 ha in 1961 to 89 5 ha in 1959, of a total forest area of 200 000 to 250 000 ha was burnt (971, 232, 231). in the much drier southern France the danger of forest fires is often so imminent that wood debris are sometimes removed and burned in containers to prevent fires (1772). This is a kind of controlled burning, also practised in the USA (223). Frequent fires may cause essential changes in the land­ scape: extensive grass plains (in the tropics especially with lalang, imperata cylindrical or moors (of heather, Call una vulgaris, in northeast Europe) replace the forest and regrowth with pioneer or secondary tree species has to wait until burning has stopped for several years (on heath in Europe: birches and Scots pine (229)). In many tropical regions repeated burning serves both to prevent the return of tree growth and to stimulate that of young grass sprouts, an excellent fodder. In Scotland fire was the object to encourage the early growth of fresh grass, so as to give the lifestock an 'early bite' when pasture was scarce (404). 22

2.8.3 Burning and shifting cultivation

In the past, with the exception of Australia, all abori­ ginal agriculture on a large scale in wooded regions has started with clearing forest growth and burning the debris (743), the ashes serving as a fertilizer. This method is still common in many tropical regions, and when (as is the rule) the fields are regularly changed from one place to another, this method is called shifting agriculture, or for short: shag. Shag is very suitable for thinly populated areas where the farmer still depends on manual labour (535) It becomes untenable with fast population growth, as it is unable to raise the per capita production (768) and merely provides subsistance for the farmer and his family. When shag, stimulated by population growth or other circumstance is thoughtlessly applied on a large scale, or leads to ex­ tensive grazing areas, soil degradation results. It is un­ suitable for raising staple food. The latter may be illustrated with an example from New Zealand. There the Maoris changed from crops grown in the forest to potato growing on a large scale (a crop intro­ duced between 1767 and 1775) , selling this produce to out­ going ships and settlers. This development caused large- scale forest destruction as too much land was burned in a short time (251). Ages ago, when permanent agriculture was still unknown, it would have been ridiculous to ask whether it was justi­ fied to burn huge amounts of wood for shag. Today, however, with virgin forest reserves dwindling, the reaction is: extravagant and wasteful. Such a reaction is really una­ voidable when one reads that for the Ivory Coast in the period 1956 - 1965 2 800 000 ha dense forest were cleared from a total (in 1956) of 9 800 000 ha (905). There is al­ so concern about the ecology of the world: the spectacular opening-up of the Amazon Region has aroused much comment (1566). 23

In tropical regions, shag has never been combined with wood exploitation, let alone with wood trade or wood in­ dustry. Where forest exploitation has started in these regions, the forest is never entirely cut but solely a few fancy tree species are selected and among those only the best specimen. Relatively favourable is the situation in Malaya and its surroundings, where the forests contain a high percentage of useful timber, so that this area pro­ duces 30 to 50 % of the tropical hardwood (523); in most other areas the situation is far worse. The progress in the direction of a more integrated complete exploitation is lamentably slow. The exceptions are few. In Malaya and Indonesia areas have been reserved for the production of firewood for the tin mines where all wood is cut. In Brazil complete exploi­ tation is needed for iron mines (828). Recently, in Uganda, future crop fields are cleared from wood debris to make charcoal also for melting ore (813). To stop shag, or to replace it by some form of permanent agriculture, is extremely difficult. It would be necessary to introduce some form of birth control (769), to open up the country and to intensify education. Insiders familiar with the situation in the involved mostly far away corners of the earth, see it as a practically unsolvable problem. Foresters and forest conservationalists merely hope that in the end some of the virgin forest will be saved for the study of their ecology, so notoriously neglected in the past.

2,8,4 Afforestation

Forestry has tried for soine 200 years to counterbalance forest destruction and overcutting by establishing artifi­ cial stands. These attempts have been successful in most of Europe, Japan, in North America, and here and there in 24 former colonial regions; elsewhere the production forests have been pushed towards mountainous and remote places where exploitation and management are, at least for the moment, less economic. To restore a reasonable situation, new forests have to be planted in accessible places, but not necessarily with native species or the traditional ones: new so-called exotics from other parts of the world may be suitable as well. A very good start has already been made with pines and eucalypts.

2.9 Ecological considerations

Once a certain area has been selected for more or less sustained wood growing, an assessment has to be made of its ecology, mainly with reference to the climate and the soils.

2.9.1 Climatic and atmospheric considerations

For tree growth, temperature and rainfall are the main climatic factors: their annual values, their fluctuations during the year, and their extremes. It is still uncertain whether forests influence the climate, either on a local scale (e.g. the rainfall (524)) or over the whole earth. However it is obvious that inside tree stands, and close to them, the climate differs from that in open places. Silviculture has to keep this fact in mind in establishing plantations. It is also unknown in how far forests (or their removal) change the composition of the air. Its oxygen content is surprisingly constant, though only one thousandth of the 21 % (994) is not produced by photosynthesis (1333). But the carbon dioxide content of the air has increased by 25 % during the last hundred years (1008), due to combus­ tion of fossil fuel and perhaps of wood. 25

As compared with other vegetation types, forests are the most efficient producers of organic matter (1669). They store it in their biomass and thus cause inactivation of carbon. During this process they emit oxygen, but in a quantity estimated only at some 1/22 000 th of that present in the atmosphere (216, 52, 478). On the 'carbon dioxide problem' and its possible impact on the 'life sustaining capacity1 of the environment more data are needed, especially on 'the capacity and locations of the various carbon dioxide sinks', the oceans, the bio­ sphere and organic materials keeping it out of circula­ tion (1469). Wood in the form of timber, board, or paper also locks up carbon. But as compared with that stored in forests, the quantities do not exceed a few percents (444). This percen­ tage tends to increase, for instance by accelerated buil­ ding activities and by recycling old paper, as happened in 1970 in the Netherlands when the latter increased to 36% of the annual consumption (expected in 1980: 42%) (712). In several areas, foresters have compared the climate (or better: the atmospheric circumstances) in and near tree stands. That such stands break the force of wind and rain is obvious; they also increase evaporation. More recently it was found that they may play an important role in puri­ fying the air by decreasing the harmful gaseous and solid emmissions from industries (138, 592, 1703). Much depends on the tree species. Climatic studies are highly important for planting exotic species. To avoid disappointments with such attempts, as far as possible, the climate in the areas of origin and that in the new fatherland have to be compared. This comparison can be based on the normal climatic data, but preferably water balances calculated from data on évapotranspira­ tion (and temperatures) should be compared. Even then the forester must be aware of the involved risks: tree growth depends on more external factors (54). In addition, as stressed for tropical America, in many regions meteorologie stations are still very scarce (222). 26

2.9.2 Edaphic circumstances

After a favourable assessment of the climate for forest growth of a certain species in a given location, soil assessment has to decide whether healthy growth is possible. For this purpose both the physical and the chemical proper­ ties of the soil have to be studied.

2.9.2.1 Chemical soil properties

Until the end of the last century, forestry followed na­ ture as closely as possible in refraining from adding nu­ trients to the soil, as only small quantities were removed (with the wood, the part of the tree containing the lowest amounts of inorganic matter), except where 'raw humus' was collected, a bad custom still continuing in some regions. Later on, fertilization could not be avoided in establish­ ing forests on poor and often almost sterile soils. At pre­ sent, in northern Europe, fertilization is considered im­ portant for all stands. Exotic species may make special demands on micro-elements/ which have to be supplied.

2.9.2.2 Physical soil properties

Unprotected soils are immediately exposed to erosion by wind and water*:vegetation creates a buffer between the soil's top layer and the atmosphere, preventing excessive dislocation of soil particles. Forests are most effective for this purpose. In agriculture terracing is often the best solution. Since far back in history this method has been applied on

* The dust storm of 11 May 1934, transporting 300 million tons of top- soil from the dust-bowl of the USA, dramatically emphasized the danger of wind-erosion (81). In France, as a heritage of past forest destruc­ tion, still 4.5 million hectares land are damaged by water-erosion (1640). 27 a large scale, especially in regions which, in the long run, would otherwise have produced practically nothing. Beautiful examples have been supplied by the Incas in South America (29 5) and are known from the Sahara where, a non- Arabic population, in speech and customs allied to the Berbers;grow cereals and trees, and raise flocks of cattle in the mountains (350). In Indonesia, where the forest service wanted to keep the slopes of volcanic mountains under forest, others ar­ gued that the same protection could be achieved by perenni­ al crops and terracing (1322). If no stones are available and contour ploughing is not feasible, this terracing in­ volves excessive amounts of labour to keep 'the earth in place', as has been shown in the loess regions of China. Then a forest cover will be the most effective. Most difficult is the afforestation of moving soils, such as sand dunes throughout the world, and clay dunes in very dry regions. These soils are often of very poor quali­ ty. Various kinds of artificial methods, even temporary or more permanent irrigation, have to be applied to establish tree stands; their maintenance will always remain trouble­ some.

2.10 Surveys and forest management

Because the areas connected with forestry are usually extensive, all kinds of maps are needed, of which only a few special ones are made by the forester. Maps of geogra­ phy, topography, planimetry (topographical map without

contour lines), and soil-classification are mostly obtained from National Services, except in some undeveloped regions. These maps are used as the foundation for the typical fo­ rest management maps, such as for site class, age class, forest roads, exploitation. The data for these maps are obtained during surveys. The maps and the inventory data are the foundations of sound management. 28

2.10.1 Maps

Perhaps only for small wood lots and their owners, maps may be dispensable; in other cases they never are. Their scale depends on the accuracy of the underlying data, the accuracy in reproducing these data, and on the purpose for which they have to be used. In the beginning, map making was entirely based on ground surveys. Between the two world wars aerial photographs were used incidentally. Since World War II, surveying with the help of such photographs has become common practice. Even today, general terrestrial reconnoitring can not be fully dropped, however. It remains necessary for the esta­ blishment of property borders invisible from the air, and dealing with very irregular border lines. Such details can only be supplied from terrestrial sketches. Inside the forest cover the mapping of such details is often difficult: lack of visibility, especially in more or less natural stands, may necessitate the cutting of under­ growth and small trees, a cumbersome, time-consuming and costly procedure. Therefore, management or property maps usually show, besides rivers, only forest perimeters and ar­ tificial features such as roads, open strips separating compartments, and settlements or agricultural enclaves. Con' tour lines, when needed, can be copied from existing topo­ graphic maps, if available. In mapping details in the forest, a surveyor who is not a forester may meet various difficulties: he has to decide whether, a small open place, for instance, is actually open or part of a normal tree stand, or where really significant changes in the forest occur. The best solution is co-opera­ tion between a surveyor and a forester, the first being re­ sponsible for the frame of the map, the other by applying simple techniques, filling in the forest details. The development of aerial photography and adapted mapping 29 techniques have been a powerful incentive for forest mana­ gement. Unknown forests in less accessible areas could be assessed. It is no longer necessary to spend days and days in walking along transects to learn about extension and composition of forests: the interesting parts of an area can easily be selected on the aerial picture, and it has become much easier to judge the possibilities for opening- up and exploitation. For some regions, also in the tropics, ground survey has become almost obsolete. Only one difficulty still remains: aerial photographs do not supply any direct information on the species composi­ tion of mixed forests. The pictures may suggest the pre­ sence of certain species in the forest types that can be distinguished from the air, but for a detailed assessment this is insufficient. Here sampling in the field remains indispensable to make a complete inventory. Already some foresters prefer aerial photographs to the common white and black or coloured line maps, even for their daily work. Recently ortho-photomaps have been de­ veloped of the same quality as line maps, preserving all details and adding some other features. As their prepara­ tion costs considerably less time than that for making com­ mon maps,a more extensive use may be expected in the future.

2.10.2 Site classification and its mapping

'Site', a term frequently used in forestry includes the geography and the topography, the local climate, and the soil, or in short: the habitat. Starting point of its study is the natural habitat, including its vegetation as undis­ turbed by man. Because in most countries not much is left of the original vegetation,it must be reconstructed, if pos­ sible. For instance, for the Netherlands it has been con­ cluded that the beech (Fagus silvatica) is part of the ma­ jority of the forest associations, except on poor sandy 30

and very low (wet) places, and that its present distribut­ ion is caused by human influences (1323). Such investiga­ tions of what happened in the past are very useful in site studies. Site qualification should lead, theoretically, to a clas­ sification of soils according to general fertility. Obvious­ ly this is impossible, as various tree species react quite differently to certain soil characteristics. So site quali­ fication always refers to a certain species, e.g. Site Class II for Species A may correspond with Site Class IV for Species B on a certain soil type. Another difficulty is that site classification does not directly refer to the stand, the only criterion is to measure it: a damaged stand may suggest low site quality. Consequently only 'normal' stands can indicate site quality, which is usually measured as the average height of all trees or the predominant ones at a certain age. Site classification of mixed stands, especially when they are not even-aged, is impossible in this way: here tree height also depends on the species. In the pienter forests in Switzerland cutting is prohibited as long as the average tree diameter distribution has not yet been restored; this requires regular re-assessment. For a local change from one tree species to another, and for afforestations, site maps are very useful, both for the state and for private land owners. Their legend should ex­ plain which soil types are considered suitable or unsuit­ able for certain species. Examples are known from the Ne­ therlands (564) and the state of Sao Paulo in Brazil (561).

2.10.3 Forest inventory

The value of a given forest area and its potentialities must be expressed numerically. This involves an inventory, a stock-taking of the situation. 31

Though forest inventory mainly deals with the methods to obtain information on volume and growth (1470), it al so can give an idea about the composition of still unex­ plored forests and its merchantable timber. More exact measurements may include the verification of site quality and growth, or the effect of time on management. Such an inventorization may even include game or cattle, where 'site' means carrying capacity. Sometimes the damage done by these animals is counterbalanced by the income from hunting licenses or the retribution per head of cattle, but mostly the reverse is true: in Czechoslovakia the costs of protecting the forest against damages caused by game where five times the income from hunting (432). At the other hand the income from hunting licences or the selling of game can be welcome when the income from wood is low; as was recorded for one of the states of Western Germany during 1961 (1723). The most modern type of 'carrying capacity' refers to recreation. 'Looking for a sustained production of the highest quality recreation that is possible at acceptable costs', in 1957 the USA Forest Service put the distance between family camps at 30 metres and since 1960 the US Park Service allowed 4 to 7 camps per acre (1652). An of­ ficial of the US Park Service recently stated: 'we know exactly how many elk a park can handle ecologically, but not how many people'. For an unspoiled balance between nature and man, an answer to this question is urgently needed (1568). As a rule, foresters 'are prone to ignore forest pro­ ducts other than wood', though minor forest products such as bark and resins can have considerable value (1193). Mostly forest inventory concerns only wood. Firewood is more or less on the borderline (especially when converted into charcoal). It can be sold as a bulk product by weight °r in bundles, or in stacked pieces of the same length, its shape being of minor importance. With the present trend in wood production towards complete utilization, the weight 32 of the wood plays an increasingly important role. Nevertheless it will remain necessary for most purposes to determine volumes based on one or a few measurements of cut trees, or parts of them. Volume tables are useful here; they supply either real volumes (with and without bark) , volumes of the square logs that can be cut from them, the numbers of board feet, etc. For standing timber volume tables are indispensable. They are usually based on the diameter of the tree at breast height and either total tree height or length of the branch­ less bole. They give average values; application to a single tree may result in considerable errors. Again the outcome may be expressed in real or net volumes, bole and branch volumes, etc. When it is difficult to measure tree heights in the forest, volume estimates for stands are sometimes just based on the 'basal area' (the sum of the surfaces of the transverse sections at breast height for all trees of the stand) and an estimated average tree height, average bole length, etc. Another method is to measure all diameters, to calculate the average, and to select a few trees with this average diameter to estimate heights or, by cutting them, to col­ lect more detailed data. Multiplication by the number of trees then gives approximate data for the whole stand. It is more accurate to distinguish a few diamater classes and to select for each class one or a few~fc*ees to be measured completely (or to take their volumes from a volume table). Basic data for inventory work in old stands can best be collected during exploitation. Where this is not possible, and in all younger stands, sampling methods have to be applied or it is necessary to rely on ocular taxations. The latter often give, rather surprisingly, excellent re­ sults if applied over large areas in simple forest types and carried out by experienced people. Systematic and random sampling are based on measuring 33 plots of a certain size. In systematic surveys, these plots are distributed according to a previously fixed net­ work based on a certain percentage of the total area, the latter depending on the desired accuracy, the forest type, and the variability of the vegetation. In random sampling the selection of the plots is just left to chance. Theore­ tically both are free from bias, but only the accuracy of results from random plots can be evaluated mathematically. Fortunately, experience has shown that with the same num­ ber and size of plots, systematic sampling is more accu­ rate. As its execution is considerably easier it is gene­ rally preferred. To measure changes, the inventory has to be repeated. Such changes may refer to growth, to the effect of cutting- out trees, to damages, etc. Apart from calamities, in na­ tural, undisturbed (virgin) forests, over large areas, changes are zero in the long run. Repeated surveys (once in 10 or 20 years) have been car­ ried out for a long time in managed forests in Europe and in some of its one-time colonies. They provide the data for management on a sustained yield base in which harvest equals the joint production of the tree stands. They are indispensable for wood industries as a base for long-range sustained or accelerated yield planning.

2.10.4 Growth measurement and growth prediction

The growth of a tree can be deduced from its annual growth rings (if present) or obtained by regularly measu­ ring it (height and diamater, other characteristics when needed). For stands only the latter is feasible as thin­ nings and other incidental changes distort the picture. Here for each species permanent measuring plots have to be established, at least a few for each site and each age class, representative for a large area. 34

As an alternative, temporary plots can be used: they are measured only once. From the collected data, stand tables are calculated. Within each site class they give the relation between age and wood volume, previous thinning yields and other data, and they indicate what may be expected for the future. The trouble with such stand tables is that they refer to 'normal' stands, normal at present and normal in the past. As the ideas on normality and normal treatment have con­ siderably changed in the course of the decennia, many ta­ bles have become obsolete and predictions based on them have become doubtful.

2.11 Forest assessment

In forestry the traditional trend is to follow nature in assessing the best use of the stands, nature not only being most effective but also 'pure' and 'clean'. In many cases 'nature' is no longer clean, even where man does his ut­ most to protect or reconstruct it. It is impossible to pre­ vent wind and rain from depositing artificially created gases or dust on trees and forest floors,damaging flora and fauna, and changing the natural ecosystem. For forestry the only possibility is for it, to adapt itself to these changed circumstances, to make the best of it in maintaining healthy tree growth-,—-to establish stands that can fulfil their functions as well as possible. This is, at present, the main purpose of forest assessment; it has to result in drawing up a 'list' of possibilities for a given area, alternatives from which others may make a choice. Industries or landowners may consult it, the help of a forest economist or other people may be called in to supply additional details. Experience has shown that, when much specialized work is involved, assessment is best left to survey companies: they have the necessary experience, 35 personnel and equipment, they can coordinate activities better than government services or national or internatio­ nal organizations. For existing production forests the inventory part of assessment is of prime importance because it decides on the rotation, which part of the standing timber is capital , which part is harvestable 'interest'. At present the most pressing question to be answered is: have the traditional, mostly long rotations to be maintained, or should they be shortened, especially in view of improved methods and mecha­ nization? Or is perhaps a change to other species necessary, species better adapted to mechanical treatment, or giving higher yields? It may be possible that forestry will have to subdivide its stands into : 'full-production' tree stands for which wood production can be made efficient and econo­ mical, 'occasional-production' tree stands from which only selected trees can be cut to obtain a profit, and non-pro­ duction' tree stands. The following examples may illustrate some features of forest assess­ ment: a- A natural protection forest in a region with a rapidly increasing population needing more arable land was endangered because the con­ viction prevailed that virgin forests are a gift from God and thus belong to everybody. Technical assessment revealed that a certain tree species could be planted on a broad strip along its borders and that its establishment could be paid for by the timber from the clearings. It effectively protected the virgin forest because marv-made stands are respected. In this case the assessment data served forest protection by partly changing the natural habitat, b. An area along a newly built highway near a densily populated in­ dustrial region was to be planted (technically speaking) either with one or two conifer species or a broadleaved species. The fo­ rest strips along the road were to become very attractive for re­ creation. So it was decided to plant one of the conifers because such species keep the soil clean. The one was selected with the nicest smell. Basically this was an economic choice, adjusted to future recreation demands. c* To harmonize forest planting with environmental requirements, many plans have been assessed in Europe on their technical possibilities. 36

It had to be taken into account that the european farmer is reluc­ tant to set arable land aside for tree stands, firstly because he does not like to reduce focd production, secondly because it takes 20 to 60 years to return to agriculture again without suffering con­ siderable financial losses. Some years ago (before the end of 1974) the idea in Europe was to shift from dairy farming to 'beef-raising' (1781). Locally such a rearrangement could open the possibility to reshape the landscape by introducing more trees in small lots or strips making it more park-like and to supply shelter and protection against the wind avoiding an abrupt change to wood-growing. An accurate assessment would serve here the integration of agri­ culture and forestry, and perhaps recreation, resulting in three complementary forms of soil occupation. 3 Hi/torical review

A complete historical review of forestry all over the world is not within the scope of this book. Only a few salient points can be treated here, and the subjects dealt with have been selected in relation to the contents of the other chapters.

3.1 Trends in the development of forest utilization

In the far distant past our ancestors used forest pro­ ducts; collecting them was an essential part of their sub­ sistence as still can be observed today among some primi­ tive tribes (964). Their way of living changed considerably as soon as they learned the art of fire-making, which did not only protect them against cold, but also gave them po­ wer over the vegetation and, indirectly, over the fauna (417). The development of primitive agriculture and cattle raising is unimaginable without the use of fire, but it is only recently that man has realized the danger of the uncon­ trolled and unrestricted use of it in agriculture, leading to exhaustion of the soil, to erosion, and perhaps even to changes in the climate. To safeguard food supplies, artifi­ cial measures have to be adapted, modern management must take over, and primitive agricultural practices have to be abandonned. However, especially in the tropics, the change­ over to permanent artificial pastures and arable land is still a very troublesome procedure. Forestry exhibits a comparable development, better tools, concentration of people, transport facilities, etc., allow intensified forest utilization, though exploitation by simple means (comparable with mining) still dominates forest activities in many countries. Where, following the conserva- 38

tion of production areas, real forestry has taken over, the exploitation is succeeded by some form of regeneration or replanting, securing a permanent forest cover and lasting supplies. In many regions, because of the large-scale development of agriculture and animal husbandry the natural forest cover has a rather awkward position. The need for food, especially staple food, has always dominated so that clearing the fo­ rests has gradually become an almost ineradicable process, even where it serves no real purpose at all. In addition people often have a kind of inborn aversion to large, dark, mysterious forests. That some primitive people hardly ever leave them does not contradict this: they may have been for' ced to this way of life by hostile tribes, as the invaders of the fertile plains did with the so-called hilltribes. The forests have long been considered an inexhaustable source of soil and timber, available to everybody, with hard ly any commitment from the side of the occupant or consumer- Only in recent times has mankind realized that these fo­ rests, besides producing wood and playing such an important role in soil protection and regulation of water supplies, may come to an end. In developed countries this insight has resulted in the establishment of forest reserves, set aside for clearly defined purposes. Jn several developing coun­ tries, however,forests are cut and burnt indiscriminately, endangering the future well-being of the" neighbouring inha­ bitants.

3.2 The collectors

Today there still are a few nomadic tribes fully dependent on the natural forest, living on wild plants, fruits, fish, eggs and small game including such animals as snakes and li­ zards. Some of them are the Kubus (primitive inhabitants of South Sumatra, pushed away by more advanced Malayans (1073)) the Bushman (1326) , the pygmean negroes in Africa, and some 39

Indians in the Amazon Region. They actually give the im pression of forlorn beggars and mostly they are referred to as pitiful creatures (1597). This is the reason that on- ly-1 a few writers ,have ^ûcnrîhpddescribed x.them as leading a carefree life (964) (1345). As a rule survival! -jm y. tnethP ru-Leau,forest, without some form of agriculture, is possible only for people living in small bands, who can easily move to be at the right place in the right season for collecting fruits, catching fish, etc. The area they need for survival, their 'hunting'grounds, depends on the richness of their surroundings which also greatly influences their cultural development. The Indians along the northwestern coast of North America needed only a comparable small area for their subsistence: the men hunted or fished and the women gathered herbs, fruits or fuel in the magnificient forests nearby. Places abundant in edible plants were fenced in and respected as the property of the caretaker (1613). Crustaceans were plen­ tiful on the rocky beaches and each year large schools of salmon, easy to catch, dry and store, moved up-river to spawn. The forests provided first-class material for boats and housebuilding (192). Using stone-age tools, especially the Nootka's from the Isle of Vancouver, were highly skilled in woodcraft. As to food, the situation in Eastern Siberia was similar but open sea and luxurious forests were absent, so that the collectors had to lead a much simplier way of life (629), devoid of more advanced techniques or art development. Because of the many different types of environment, it is impossible to give even an approximate average area of hun­ ting ground needed per head. For the Mbuti's in Central A- frica, practising some agriculture, it has been estimated at 300 ha (1610); for the Indians of North America, at the time the European settlers arrived, at 700 - 800 ha (1148). An attempt to do the same for the Amazon Region and the taiga of Siberia gave nearby 'zero' densities (655,1734,629). 40

Collectors live, or must have lived, with the seasons. In the Amazon Region they gathered turtle eggs in the dry season (648), in other months paranuts (Bertholletia excelsa; (649) or palmnuts, and this must have continued as long as man has existed there (1042). This periodicity in food sup­ ply forced them to stay for some time in one place. From prehistorical sources we know that some tribes lived in caves during such periods (964, 247). They left behind refuse hills (192) or, as in the Middle Amazon Region, their old dwelling places have resulted in 'terra preta', 'black earth1 (648), due to waste in the same way as in bird colo­ nies (1670) . There is no evidence that these people did any harm to the forest: their mode of living was such that they became part of their surroundings.They lived in harmony with vir­ gin nature. A good example is the Tasadays tribe discovered on the Isle of Mindanao (Philippines) in June 1971, happily living in caves, eating frogs, freshwater crabs, grubs, palm fruits, etc. (996).

3.3 Fire

The only way in which the collector-hunter, dwelling in the open areas bordering the forest, could change his natu­ ral environment to a greater extent was by burning. Though the oldest remains of man-made fire,-found in China, date back 750 000 years (1571), it is still under discussion in how far the large steppe and desert areas in the warmer parts of the world are anthropogenous. But it is beyond doubt that fire has greatly extended them. Nature itself probably taught man to use fire for clear­ ing forests. It is estimated that during the period 19 39- 1958 in the western part of the USA 132 000 lightning fires occured in the forests (91) and that in 19 25 60% of the forest fires were due to lightning (707). From pollen ana­ lyses in the northern parts of Finland, Sweden and Norway 41 it has been deduced that between 5000 B.C. and 1200 A.D. lightning fires were the major cause of forest destruction (1347,779,1590). Early reports on Indians in North America blame them for their carelessness with campfires and bur­ ning prairies or forests for hunting (976), though they must have been well aware of the dangers involved: around their dwellings they created fire-breaks (by burning!) (1148). The Australian arborigines seem te have a pro­ found fear for bush fires caused by lightning (1649). The examples given above deal mostly with the highly in­ flammable coniferous stands. Deciduous forests are less prone to damage by fire. In the Netherlands, in the period before the start of agriculture, no naturally grown pine forests or extensive heath areas existed as nowadays and only during extremely dry periods did forests burn (1187, 59 3). contrary to the general opinion, tropical rainforests are, under special circumstances, also apt to burn, as oc­ curred in Surinam during 1928 and 1964, when the completely dried-out litter in the swamps caught fire (1643).

3.4 The forest and primitive agriculture

For the collector-hunter it took a very long time to change to the sedentary life of the primitive farmer (1345). His agriculture, perhaps more a kind of horticulture on small patches in the forest, must have started around camps or meeting places where the soil was rich in organic refuse, as our gardens which contains on average five times as much organic matter as other crop fields (1591). Remains of this Primitive farming, recently found in Thailand and assumed to be the oldest, date back 9500 years (1565). The crop probably consisted of fruit trees and vegetables or edible roots. Such garden-type cropfields are known under the name 'paramba' on the West Coast of India and on Ceylon (750), also met in South Sumatra, Borneo, in Melanesia and Polynesia. In the last two regions the indigenous people 42 are often called 'the gardeners from the Pacific'. They also keep pigs and built fences around their gardens (311, 920, 838). The Carina Indians, living in cattle country in the savanna region of Venezuela, are another example of de­ dicated gardeners (417). Population growth and the corresponding demand for more food have increased the plantation-type of agriculture in which forests are cleared;the felled trees are cut up or at least stripped of their branches and the debris is burned. As long as the soil, enriched by the ashes of the burned forest, yield a reasonable crop, it is kept under cultiva­ tion. Without fertilization in some way the soil is usually exhausted after one or a few years, the field is abandoned until a spontaneous secondary forest growth has appeared ma­ king the soil suitable for a second agricultural period. This intermittent agriculture is today called 'shag' (379). It can also be practised on grasslands, where uprooted gras­ ses are burned to serve as a fertilizer, as for instance is still done by the Bataks in Sumatra (1792). In 1957 it was estimated that on 36 million square kilo­ meters, inhabited by 200 million people, shag was still ap­ plied (1404). It is based on very old traditional occupation rights and is usually simply a primitive method applied haphazardly. Most writers consider it out of date and want to replace it by permanent forms of agriculture. Some types of shag are excessive, especially where"~the burned over a- rea is out of all proportion compared with that of the crop' fields (1583, 269). But if shag is properly regulated by controlled burning, maintaining sufficiently long fallow pe­ riods not hampering the development of a secondary tree co­ ver, this practice should not be rejected as long as the population density allows its application (379). There are examples of people changing back from permanent cropfields to shag, because it is a less complicated and time consu­ ming type of agriculture (773, 599, 1583). In Deli (Sumatra) another typical form of shag is applied to the raising of 43

the cash-crop tobacco. It is produced in a rotation system °f 8 years, during which one crop of high quality tobacco is followed by one crop of rice and seven years of seconda­ ry forest. Thus the soil recuperates and gets rid of influ­ ences detrimental to tobacco growing. In the past forest services all over the world have strong­ ly opposed shag, because it destroys the virgin forests at an alarming rate. To control the situation, forest reserves have been established not only to protect the communities against timber and fuel shortages but also to regulate the Agricultural use of the soil (751, 1374, 839, 1583). To abo­ lish shag entirely is neither politically nor economically feasible: it is part of a historical developed way of life (1273). The outcome can be a joint forestry-agriculture undertaking.

3'4.1 Integration of forestry and agriculture

Tree-raising and agriculture can be combined either sole- lY during the first years by cultivating food crops between the young trees, or more permanently between widely spaces trees. in former times both were common practice in Europe, and shortly after the second world war, this 'Waldfeldbau1 Was still applied in Eastern Germany (804). In France this sartage' has long been abandoned, but in Switzerland it still seems to be practised occasionally in chestnut coppi­ ces (Castanea sativa) (875). In the Mediterrenean the lat­ ter is still common practise (314) and in raising poplar trees (80) and cork oaks (Quercus suber) (433). Occasion- ally oak forests are specially managed for the cultivation of truffles (Tuber spp.) (1012, 1013), which are very va­ luable. in the English speaking countries the terms 'clea- ring1 and 'deadening' are used which also indicate the com- m°n form of shag (353). In Russia this form of forest-agri­ culture has not been applied since the beginning of the 20th Century (948). In the temperate regions, forest ser- 44

vices discourage the raising of trees together with agri­ cultural crops because it is assumed that tree growth will suffer (1135, 1088). In the middle of the 19th Century this type of tree-rai­ sing was introduced with much success in Burma by the Ger­ man forester Brandis (669) where it was applied in young teak plantations (Tectona grandis) during the first few years (1273). From Burma, this 'taungya'-system (taung = hill, ya = field) was brought to India, the Malayan Penin­ sula, Indonesia and, by foresters trained in India, to Afri­ ca (1583). In the tropics it is considered one of the best and cheapest methods of tree cultivation because it greatly reduces planting costs and guarantees (if kept under regu­ lar supervision) a good weed control (899). Using a short rotation which for wattle (Accacia decurrens) is ten years (396) , the differences in time with the common shag-fallow period become minimal. It can be applied, however, only in areas with a shortage of land suitable for permanent agri­ culture or shag where industrious farmers have the opportu­ nity to sell their surplus in nearby towns (479). Though the taungya-system has been, and still is highly beneficial to forestry and the rural economy, the farmer remains chained to the 'planting-stick and hoe-stage' of agriculture from the past (1689), which, if real progress has to be achieved, will have to be abandoned as quickly as possible. Another, often forgotten aspect of primitive agriculture is that it discourages care for the land. During the fallov period it turns into no-man's land (565), or the former fields are burned for grazing often resulting in soil de­ pletion (250). A somewhat different, but most spectacular form of taung" ya is the planting of rubber (Hevea brasiliensis) on aban­ doned shag-fields. Rubber, in 1867 brought from Brazil to England and from there to Ceylon, the Malay Peninsula (9 80),and Indonesia is planted by the farmers in small plot 45

lr» 1936/1937, in Indonesia such rubber plantations covered *•3 million ha (912), contributing substantially to the sconomy of the country.

3-5 The forest and primitive animal husbandry

Probably all large mammals at present roaming the open grass plains and savannas of almost the entire earth, are by nature forest-dwellers, living in rather scattered small groups and doing relatively little harm to the vegetation (even the elephants in Asia). Hunting them was rather trou­ blesome for primitive man and burning the forest on a large scale forced the animals to come to the open where they could easily be killed. In addition, the open fields sup- Plied so much more food that, notwithstanding extensive hun­ ting, they greatly increased in number. That the natural habitat of these animals is the forest, though probably with some small grassy clearings, is appa- rent from their present way of living: all withdraw to the shade during the hottest part of the day. Elephants (in Asia), even those assisting in forest exploitation (259), wisents in Poland, bisons in North America, deer and wild boars (in large parts of the world) still mainly live in the forest. It is even improbable that pampas, prairies or savannas have to be considered natural vegetation types *l242, 1282). in Nigeria the elephants have done conside- rable damage to the trees, so that the forest is unable to regain its closed structure (766) , probably because of their abnormally large numbers. °n the other hand it is true, that even a few animals, such as buffaloes from the neighbouring villages on Java, Itlay be a nuisance in young plantations (teak, in this case), So that in the past the trees had to be fenced in (1411). The only solution in such cases is to buy off the grazing- ri9hts of the surrounding population. However the damage ^one by these animals is probably less than that caused by 46 fires starting on herdmen's camp sites (351). In the past, the European oak forests, and to some de­ gree the beech forests, have played an important role in supplying pigs with acorns and other fruits. In Denmark, near the end of the 17th Century, the income derived from these animals was probably the only base for forest assess­ ment (1335): wood was present in such quantities that no­ body worried about it. A law in 1805 abolished in Denmark all forest grazing rights,except those for pigs(1005).In southern Brazil pigs are still kept in the Parana pine stands, fee­ ding on nuts (653). It was recently reported for Extrama- dura (Spain) that pigs can produce 11.5 kg meat on 140 kg acorns (1325). In addition, the animals are considered very useful (except in young plantations) by grubbing the earth. People occupied with animal husbandry are often nomads (1234), as for instance the Laps in northern Finland and Sweden (1764), and the tribes dwelling near the Sahara (350)- In Africa, some practise a kind of 'shag', sowing their bar- * ley on the way to the grazing grounds and harvesting the crop on the way back to their bases (1698). Between 1750 and 1850 forest grazing came to an end in Europe (1346) and was replaced by mixed farming: crops and animals on the farm, the manure used for fertilization. Un­ fortunately, in the tropics and warmer subtropics animal manure burns up so quickly that, except for garden plots, the available quantities are always insufficient so that the incentive to change to a more efficient management is absent (238). So in many regions of the world, grazing on wooded lands and inside forest stands was, and still is a necessity. It became a deep rooted custom, a legal right, which for example round the Mediterranean, in large parts of North Africa, and in the Near East led to overgrazing and desertification (1024). The normal stocking on natural grazing lands, including forests, with a rest period of 4 to 7 months a year, is 3 to 4 ha per head of cattle or one goat or sheep per ha(435)* 47

The actual figures for goats and sheep are much higher: in Italy 2.7 animals per hectare, in Spain 4.0, Morocco 2.3, in Algeria 1.0, in Tunesia 1.7 and in Greece 3.3. In addi­ tion fodder is collected in the form of leafy branches. For Italy an annual removal from forests of 70 kg by gra2ing and 18 kg by fodder collecting per hectare have been calcu­ lated (38). In the USA forestry has included forest grazing in its Multiple purpose planning by estimating carrying capacities, Maintaining rest periods, prohibiting grazing by goats, in­ troducing and sowing better forage plants, and avoiding any form of overgrazing (1255, 486). Attempts to regulate forest grazing in the Mediterranean region came in conflict with village societies clinging to their ancient rights (1023). Investigations have revealed that damage by grazing in young tree-plantations need not be disastrous. For longleaf Pine (pinus palustris) it was found that 'once green her­ bage becomes plentiful, browsing virtually ceases' and that a stocking rate of one head of cattle on 8 to 10 ha did not affect the establishment of planted or seeded pine up to the age of five years (1215). In New Zealand, where thin- ning is costly, foresters even tend to return to forest gra­ zing because widely spaced Pinus radiata (375 trees per ha) Pruned every year develop well and provide good winter gra-

2ing-iand for one head of cattle per two ha (86). Modern management can greatly diminish wildlife, as appa­ rent from research in the south of the USA during the con- Version of pine-hardwood stands into pure pine stands. It drastically changed the food situation for the game by era­ dicating fruit-producing trees and shrubs, so that the ope- n ing-Up 0f special, regularly spaced patches of forest has been proposed to stimulate the growth of forage plants, as a substitute for forest meadows (155). 48

3.5.1 Apiculture

In the past gathering of honey ( a substitute for todays sugar) and beeswax in the forest has played an important role in rural economy. For the Slavs living near the forest, it was even one of the main means of livelihood (218, 219). It has been recorded for one year in the 12th Century, that in the castle of Putiwl more than 80 tons of honey was sto­ red, and that a good tree could produce 100 kg per annum. Beeswax, however, was the main trading product, going via Nowgorod to the West (1330). Germany had its famous 'Nürn­ berger Reichswald', the honey forest of the Holy Roman Em­ pire (1018). After the Reformation in Holland the produc­ tion of beeswax dropped because the demand for church can­ dles decreased (1468). In Brazil bees are kept on a large scale in eucalyptus stands not only for the production of honey (952), but also because they are needed for the pollination of the trees (588). In 1968, for Australia a honey production of 17 000 tons was recorded; 90% came from forests (1193). In 1964, in Tanzania, bee-keeping was considered sufficient to re­ tain the miombo woodland forest reserve, which had been used for this purpose (1551) for a long time.

3.6 The forests and old civilization

3.6.1 The forest in mythology

The ancient Chinese writings mention that, in the time of 'T'ang the great conqueror', forests were worshipped as holy places. Later on this cult gradually changed towards the single tree, to be ultimately substituted by 'nothing better than a signpost' (501). Then worshipping passes into ani­ mism if the tree or pole is supposed to be occupied by an indwelling spirit (318). Worshipping sacred groves is still practised in India and 49

on Bali; it was probably very common in Europe at the time of the Druid (1552). Sacrifice of animals in such woods or to a tree is still known from Africa and India (501) and can be read in the Vedic manual of domestic rites (384). The belief in such spirits was deep rooted and has often resulted in bloody struggles between the worshippers of a single omnipresent God and primitive man, wanting to plant groves and to set up altars under the green trees (1236). North Europe had its Yggdrasil, the world tree of life and light (1009). Paradise had its trees of knowledge and life, the Near East its tree of the East, the West and the Middle (1686) and the Netherlands the holy Donar oaks which were cut down by the early preachers of the Gospel (1594). In the present western society the live specimen has been replaced by the plastic Christmas tree. From the great religions, Buddhism has always been nea­ rest to animism. Buddhists attend to their temple forests, replanting them when necessary. In China, Japan, Thailand and Indonesia they often preserve relicts of the original forest coverage (1307, 1309, 1284, 1642, 27). Colliers, the great friend of the Indians, considers the Incas of South America as the world's best nature conservationists, having made 'maximum human use of the land and the water, with total conservation' (295). The Holy Script and the Koran proclaim that everything on earth is made for man's convenience. This idea has stimula­ ted the continuation of large-scale destruction of forests around the Mediterranean. In this context it is hardly sur­ prising that Lowdermilk wrote, in 1947, an eleventh command­ ant, ordering the conservation of natural resources, to be managed by man 'as faithful stewards' (967). In modern times, the involved countries make heavy sacrifices in amending the damage done by their ancestors (1343). !n his behaviour towards forests, modern man is apparent- still governed by an instinctive fear or aversion which, as noted before, exerts its influence on the value of forests 50 for recreation.

3.6.2 Prehistoric forest exploitation

Stoneage people were able to cut trees with their axes and adzes. With the aid of fire, canoes were made (707) , even those up to 20 m long used by the Maoris in New Zea­ land (448). Because they lacked large pieces of wood, the ancient Egyptians had to build their boats of short pieces hewn from Acacia nilotica trees, mounted on keels of impor­ ted Libanon cedar (160). The need for cedar wood was pro­ bably the first occasion when shipbuilding entered foreign politics. Selective cutting, in favour of fruit-producing trees, and lopping for animal fodder, gave the light-demanding species a chance to predominate in the forest in Europe (464). For other purposes primitive man hardly needed trees: he had no tools to saw planks for building houses (twigs, grass and mud were sufficient); the forest yielded enough dead wood for his fires, and food raising was restricted to small open places. So, as long as he did not start burning, his influence on the extension of the forest cannot have been significant. It was organized agriculture, cattle rai­ sing and the concentration of people in fertile valleys, to­ gether with advances in techniques that changed the picture.

3.6.3 Deforestation in the Mediterranean Area and the Near East

It can be taken for granted that the old civilizations of Sumeria and Egypt were founded in more or less wooded areas. Near the temple of Pharaoh Echnaton (1377 - 1358 B.C.) the remains of 76 tree and shrub species have been found (1170). In the Middle Ages, Egypt seems to have, temporarily, pro­ tected what still remained of its forests for shipbuilding 51

(1170). To blame a change in the climate for their disap­ pearance seems unacceptable (242). As to the area around the Mediterranean: in ancient times it must also have been covered by forests, or at least a woody vegetation. The best example is the Lebanon, once cap­ ped by half a million hectares of cedar (Cedrus libam), now almost void of it (1170). In Turkey deforestation lasted until 1839 before atten­ tion was paid to the forests of the Anatolian Plateau. Pre­ viously (and later also), the religious authorities had de­ fended the holy right that wood and water,commodities given by God to man, could be used without restriction (1072, 137). Plato (427 - 347 B.C.) mentioned that, in his time, Atti­ ca had only relicts of the old forests (1170), so that the Greeks had to buy their timber elsewhere (528). The goat was blamed for it (160) , though Albania, with a comparably rugged country and also many of these animals, is still to­ day for 47% covered by forest (437, 1025). Most forest-history reviews start with the Near East and Hellas (528, 160,1341,1048) because there for the first time incidental attention was paid to forestry problems. But m the countries mentioned above this did not result in forest Protection, despite the criticisms on state authorities of Aristotle and Cicero (1675). The Roman Empire mistreated its forest to such an extent that southern Italy and Sicily became almost treeless (1343). The country had to import wood from North Africa (350) , so that in Rome (and also in Jerusalem) firewood was sold in the markets by the pound (1341). Pliny (A.D. 23 - 79) re- Ported a scarcity of this commodity for large parts of Italy (1048). Spain and North Africa lost most of their forests due to mining and shipbuilding (97) followed by extensive grazing. Later on, Florence prohibited by law the cutting of fo­ ists one mile below the mountain summits of the Apennines, but it had to withdraw this decree and the glass industry 52 caused a large-scale depletion. This lasted until after tho end of World War II before the countries around the Mediterranean started large-scale reforestation (543).

3.6.4 Deforestation in Western Asia and China

Apparently the city civilization founded about 2300 B.C. in the Indus valley has always used baked bricks for its flat-roofed houses, though it must have consumed large quantities of wood for fuel from forests which have now to­ tally disappeared. Again the Islam with its sheep and goats is often considered to be the evil-doer (1552, 1098, 721). The densely populated parts of Middle and South China must have been covered by forests. Their clearing has cau­ sed widespread ruinous erosion over an area of 160 million hectares, especially within the huge loop of the Yellow Ri­ ver (1061, 1452). At the beginning of the Chinese empire (1500 B.C.) forests on the hills were incessantly cut down, often to get rid of wild animals, snakes and vermin (277); by some writers believed to have been mainly non-Chinese aboriginals of whom a few still survive in Tibet, Taiwan and Hainan (423).

3.6.5 The past situation in the temperate regions of Europe

After the conquest of France, the Romans divided the coun­ try into 'fundi' or 'villas' which included parts of the forests, intended either for the cutting of firewood or for timber exploitation. This is one of the oldest forms of fo­ rest management (718). Later on, France maintained its relatively advanced posi­ tion in preservation and management of the national forests by the law of 1376, setting apart the royal forests in the richly wooded belt around Paris and those of Normandy for the supply of shipbuilding timber. Exploitation had to be 53 carried out in parcels of 10 - 15 ha and 16 to 20 good seed trees had to remain (718, 73). In 1969, Colbert issued more detailed instructions (352): inventories had to be made and management of practically all French forests had to be strictly planned, again to guarantee an ample supply of shipbuilding timber. It was soon discovered, however, that administration and strict exploitation rules alone could not create forestry. Consequently Réaumour recommended in 1721, in addition, sowing and planting, and Buffon propaga­ ted in 1739 the reforestation of waste lands. The new fo­ rest law of 1963 was set up to guarantee the biological e- quilibrium of the country and the supply of forest products, whereby the management of private forests was also put under state supervision (916). North and east of the Rhine the Teutonic and German tribes established, already in early times, communities called 'Markgenossenschaften' (agricultural village communities), in which the forests, usually surrounding the agricultural fields, were common property. Later on, these forests were split up into private lots, but some parts remained under joint ownership till the 20th Century (1685, 1675, 1389). In Indonesia exist still such forms of tribal (Dajaks-Bor- neo) (1354) and communal forests. The very promising development of forestry in Central Europe was interrupted by the Thirty Years War (1618-1648). It revived towards the end of the 17th Century (1389). In *•713 von Carlowitz wrote his 1 silvicultura oeconomica in which he paid much attention to the sowing of Scots pine (Pinus sylvestris), already started in 1348 to Nürnberg by stromeir to provide the metallurgy industry with charcoal, followed in 1514 in what later was called the Mastbos in Dutch Brabant (1733) and practised in 1580 and 1595 in Schleswig-Holstein (Northwest Germany)(630). The planting and sowing of spruce (Picea abies) in the mountains of the **arz was well underway in 1719 (1330). Forest treatment Was refined, and forest assessment based on scientific prin­ 54 ciples became a necessity. According to Mantel, 1757 can be called the year in which German forestry reached maturity, especially after von Moser had published his book on forest economy introducing the 'Nachhaltighkeit1 or 'sustained yield1 which is today the cornerstone of forestey all over the world (1017). The Netherlands, like England without sufficient forests, had to import wood from the Baltic states and, in sometimes immense rafts, from Germany, Switzerland and Alsatia (73, 1412). In southern Germany, timbers exported for ship-buil­ ding purposes were known as 'Hollander' (1609). In the 18th Century, the Dutch forests were apart from those planted around some landowners' manors (1468), in a deplorable condition (1667). This situation lasted till the beginning of the 19th Century when, under French influence, attention was paid for the first time to reforestation. As in most other European countries, national forests were sold under the impact of Adam Smith's theories (1442). So it is not surprising that, up to 1864, Holland and especi­ ally its navy, showed a lively interest in tropical wood species for shipbuilding (1144). In 1899, after a period of reclamation of heath and moorland for afforestation, a National Forest Service was established. The first forest law, regulating forest management and protection was applied in 1922. In Middle Europe, where forestry has devèloped along the same lines as in Germany and France, Switzerland occupies a special position. Its forests mainly serve to protect moun­ tain slopes against erosion and avalanches. Reservation for this purpose started in 139 7 in Andermat, a village near the Gotthard Pass, where the forest protection alone, in the sense of not cutting trees, was obviously insufficient, so that special silvicultural methods had to be developed to maintain the forest coverage on a permanent base (466). In England, even at the time of the Norman conquest, fo­ rest destruction must have been wide-spread (256). In the 55

Middle Ages it was estimated that the country was only for 15 % covered by unmutulated forests and for another 15 % by heavily over cut stands (1329). In Ireland and Scotland some forests were even cleared for combatting banditry(1110). In 1542 England introduced a law to protect forests.lt pro­ vided rules to exclude grazing and to reserve and grow trees with heavy branches and curved stems suitable for shipbuil­ ding by wide spacing and heavy thinning(1558).But soon the depleted English forests could not meet the market demands and from the middle of the 16th Century the country had to import wood. The ensuing timber trade greatly influenced other European markets and those of the British colonies. Englands oldest wood supplier was Norway, followed by Ireland. Yew wood (from Taxus baccata) for bows was fur­ nished in such large quantities by other West European countries that it almost became extinct there. Oak (Quereus robur and Q. petraea), pine (Pinus sylvestris), spruce (Picea abies) , pitch, tar, potash, honey and beeswax were obtained from the Baltic area, first in competition with the Hanseatic League, later on with Holland (840). Oak, extensi­ vely used in shipbuilding, had to be of first-rate quality (73). Its exploitation soon removed the best trees from the forests of Eastern Europe and even the famous Polish-Russian forest of Bialowieza did not entirely escape (1700, 203). During the World War I England became aware of its vulne­ rable position and, after it, started a large-scale refores­ tation programme under the administration of its Forestry Commission. The Russians were pushed into their forests by the Mongo­ lians (849), where they protected themselves by building a forest-wall called 'bolschaja sassetschnaja tscherta'. It Was completed in 1566, long 1100 kilometers and in 1638 guarded by 40 000 soldiers (218, 219) • obliged the far­ mers to raise food on forest soils applying long fallow- Periods. When in the southern part of the Baltic region high-quali­ 56 ty timber became scarce, wood trade shifted to Riga. To reach this harbour, rafts moved along the navigable Russian rivers and timber was pushed over low watersheds along slip- roads (the so-called woloki) from regions as far away as the Ukraine. To preserve the Russian forests for the benefit of ship­ building, Czar Peter I (about 1700) ordered strict protec­ tion. Later, in 1782, it was abolished and up to 1888, the moment the first forest law was enacted, every owner could do with his forests as he wished (217). The real forest countries from northern Europe lost fo­ rests to mining and moderate agricultural intrusions; as a rule not followed by grazing. In Sweden, however, already 300 years ago excessive cutting of forests was prevented in an indirect way by restricting steel production, making less demands on the tree stands (646, 1787, 1519).

3.6.6 The situation in the Far East

Already during the Chow dynasty (1122 - 255 B.C.) China could boast of a Forest Service for the preservation of vir­ gin forests, for reforestation of denuded lands, and for planting trees along newly built highways. Later on, more attention was paid to the raising of fruit-trees such as the walnut (Juglans) and the tung-oil tree (Aleurites). The Chinese love trees, as apparent from" "their traditional arboriculture which developed into a fine art, and the an­ cient practice of P'an-tsai, the creation of miniature landscapes dominated by dwarf trees (1307). Today these in­ born qualities provide a sound base for the large-scale re­ forestation activities in progress (1407). In Japan, during the Tokugawa period (1603-1868), the feu­ dal lords carefully preserved their valuable forests. After 1868 they were converted into national, communal and for a small part into private properties. In 1879, the Forestry Bureau of Japan was established and management and protec­ 57

tion of all forests started. Today these forests play an important role in the economy of the country (1086). During the colonization by the Spaniards, the Philippine forest was mainly used for timber for shipbuilding (550, 1620). In 1863 good forest legislation was introduced, but it remained a paper law (1526). The Americans, taking over in 1900, did not change much; the excellent forest laws were never rigidly enforced. The result was that in 1966 the rate of forest destruction was considered alarming (437, 139 8). As in Taiwan, intrusions in the national forest were justified by the cry 'land for the landless' and left un­ punished (1564). Only education and a feeling of responsi­ bility for its own environment will be able to change the attitude of the rural population (1433). The forests in the wet areas of Indonesia have much in common with those of the Philippines. In both countries the Dipterocarpaceae predominate and such well-known species as Pinus merkusii and Eucalyptus deglupta occur (1089, 1221, 434, 455, 608). When, in the 16th Century, the Dutch arrived in Indonesia, they found extensive forests of teak (Tectona grandis) be­ longing to kings or nobility. Their rights were taken over by the colonial authorities (1173). The 'father of fores- try', Dirk van Hoogendorp (1761 - 1822) propagated between 1784 and 1799 the conservation of these teak forests (1617). In 1808, management was started to safeguard timber supplies for shipbuilding (215); foreign foresters were engaged (1783) , and in 1897 a Forest Service was created (380). In 1941, on Java 800 000 ha teak and 839 000 ha other forests Were managed on a sustained yield basis regulated by detail— ed management plans(110).On Sumatra with a much wetter climate, the pinus merkusii forests were brought under regulated management for the production of turpentine (1214) and the swamp forests near Singapore followed for the production °f timber and charcoal (755). In addition, throughout the archipelago forest reserves were established to safeguard 58 future production, to preserve nature and wildlife, or as a protection against erosion. The Dutch liked mahogany (swietenia spp.) and cedar from the Caribbean so much that in 179 8 they started raising these species as exotics; cedar without success, but maho­ gany from 1879 onwards successfully (191, 1441). The export of teakwood from Burma can be traced back to Nebuchadnezzar in the 6th Century B.C. From 1752 onwards, teak was declared a 'royal' tree, only to be disposed of by the king. During the occupation of the country, starting between 1852 and 1855, these rights were taken by the Bri­ tish. In 1856 the teak forests were put under management, minimum cutting sizes were prescribed, yields were calcu­ lated and working plans projected which functioned up to World War II (1115, 480). Initially the teak stands were rigidly protected against burning; later around 1908 pro­ tection was limited because worthless tree species that were also protected impeded the regeneration of teak (1115, 225). This shows that protection against fire is not bene­ ficial under all circumstances, as has been affirmed later by the controlled burning today practised in the USA and Australia (1656, 1673, 687, 950, 982). Thailand, bordering Burma, established in 1896 a Royal Forest Department, regulating and controlling forest ex­ ploitation on a technical basis, following the rules ap­ plied in Burma. For teak, yang ( Dipterocar~püs élata) and other species a rotation of 150 years was chosen, or selec­ tive cutting based on a cycle of 30 years(1003,330,19,1339). In Indochina, the French colonial administration esta­ blished forest reserves and took care of their regeneration (1327). Among them were the natural teak forests in Laos & bordering those of Burma and Thailand (133). The country never had an important wood export; apart from some timber sent to China, the production served local consumption.

£ very probably having extended into Southern China (1160). 59

3.6.7 Past and present situation in the Americas

When in 149 2 Columbus discovered America, its shoreline was densely wooded (343). However, in the interior were plenty of non-forested areas and secondary forests created by man. Especially Central-America must have been populated heavily during certain periods; for instance by the Mayas living in Guatamala and Southern Mexico (1795). In 1522, the Aztecs were already city-dwellers, with wood markets and probably sacred groves too (534). From the composition of the forests, here and there, it can be deduced that once, long ago, they must have been cut-down (221). Later, for North America, it was said that 'archeology should be made part of the ecological equipment' to make correct conclu­ sions about their original virgin composition and struc­ ture (339). The constant wars and the timber scarcity in Europe main­ ly during the 17th and 18th Century forced France and Eng­ land to import ship-masts from North America, so that Ame­ rican lumber became an important element in international trade and colonial politics (343, 840). Besides timber, naval stores from Virginia and North Carolina were shipped to Europe (1203). In the colonial days, American forest le­ gislation mainly served to protect the forests for the sup- Ply of timber for shipbuilding. After the USA became independent, large-scale uncontrolled clearing of forests caused so much erosion and soil destruc­ tion, that for the first time in history, a spontaneous fo­ rest conservation movement was born. In modern times, it re­ ceived a solid basis in the Multiple Use-Sustained Yield Act °f 1960, regulating the use of the American forests in the best and most modern way (1605). Central and South America were occupied mainly by Portu­ guese and Spaniards; their military posts developed into c°lonies and ultimately into independant countries (343). 60

Their first forest laws were copies of those in their home countries, unrealistic and unrelated to the totally diffe­ rent circumstances (829). The Caribbean Area and Central America became wood sup­ pliers for European navies. The Amazon Region became famous for its rubber trees (Hevea) (980), Southern Brazil for its Parana pine (Arau­ caria angustifolia) (367), and Argentina for its quebracho (Schinopsis spp.) used for tanning, competing with oak-cop­ pice in Europe (502, 1187). Mexico was one of the first countries to initiate an ef­ fective conservation of 'forest and water1, based on its 1917-constitution (1063, 534). Cuba started reforestation in 1905 (549), while Southern Brazil and Chile created ex­ tensive man-made forests. Since 1910, in Brazil, eucalyptus has been raised in plantations (1136); in Chile Pinus radia- ta is supposed to cover 97 % of the national wood consump­ tion around 20 25 (461). Remarkably in Argentina, Chile and Brazil exotic tree species play a dominating role in af­ forestations.

3.6.8 Forestry in Africa

On their arrival in South Africa, in 1652, the Dutch star­ ted to cut trees for shipbuilding and burned the nearby fo­ rests to establish agricultural settlement to such an ex­ tent that they practically disappeared (105, 1233). Very soon it was necessary to import tree species for planting, with the result that in 1958 approximately 1000 different species and varieties were under trial or in arboreta (461)i to gain data on production and wood quality. Organized forestry started in 1880. Between 1886 and 1965/ 304 000 ha plantations of Acacia decurrens were established for the production of tannin (370). In 1966 389 000 ha pine and eucalyptus plantations were available for the timber, pulp and paper industry (349). 61

Colonial Africa is a late-comer in forestry. Except for teak, in 1904 introduced in Togo by the Germans, its more creative activities do not date back much further than 1930- 1940 (1254).

3.6.9 Forestry in New Zealand and Australia

The North Island of New Zealand, originally completely covered by forests, has been fully denuded for agricultural purposes, resulting in severe wind-erosion. The situation could be saved by the introduction of exotic tree species, in 1962 covering an area of 350 000 ha (1154). The export of eucalyptus seeds from Australia, the world over, has given a powerful impulse to the creation of man- made forests. In turn the country was assisted by the in­ troduction of exotic pine species, providing easily workable highly estimated industrial wood (485).

3.7 Man-made forests and exotic tree species

In retrospect we should be very grateful to all emperors, kings, noblemen, church leaders and politicians who, in the Past, for whatever reason, have contributed to the preser­ vation of natural stands or who have re-established the fo­ rest. Nevertheless their activities have been entirely in­ sufficient and the fact remains that the forest cover of the world has to be extended to meet the growing demand for forest products, for better soil protection, and for recreational purposes in densily populated regions. For ex­ tension purposes forests have to be established on places where they formerly occurred and also there were, as far as man can remember, they have never been (439). To answer the question, which trees have to be planted, the forester can choose from a large number of indigeneous and exotic species. The latter make it possible to create valuable 62 stands where the indigeneous timber has little or no value, and where natural tree growth is scanty. Species planted by tree-lovers in their gardens or in small plots, from far away or nearby, can supply valuable information. People do not realize that even most so-called native species are imported: in the Netherlands the seeds for the Scots pine stands came from Germany and Eastern Europe (1330, 1323, 1468) and some writers assume that, during historical times, it was no longer indigenous. In Europe spruce (Picea abies) was brought from the mountains to the plains; in 1648 the European larch (Larix decidua) was moved from Austria to Bamberg (in Germany), in 1861 followed by the Japanese larch (Larix leptolepis) from Ja­ pan; in 1827 the Douglas fir (Pseudotsuga menziessii) was imported in Europe from northwestern America, etc. (416, 1285, 1636, 564, 1047). All these species, and many more, have become part of the European forest, in the same way as in many regions the eucalyptus from Australia has become an essential element in the country landscape. 4 mopping and mop/

4.1 Origin and development of mapping

The oldest maps were based on memory or notes and resul­ ted in crude sketches like those we draw on the backs of envelopes. Their scale was arbitrary and changed from one part to another. A well-known example is the map of northern Canada drawn by an illiterate Eskimo shown in Raisz1 book 'General Geography'. Very probably this Eskimo, and other primitive people, have an inborn feeling for direction and distance; many ancient maps are due to this amazing pheno­ menon (641). Some collectors and hunters still depend on such an instinct. Modern man surveys the country from the air, obtains a bird's-eye view of the area he is interested in, and then draws a rough sketch. Obviously the next step in this proce­ dure is to call in the help of aerial pictures. The first real maps were made 13 Centuries before Christ by the Egyptians. They served cadastral purpose and were drawn by clever surveyors to facilitate imposing taxes. Primitive maps, assumed to be even older than the art of writing, were made (up to the middle of the 19th Century) by the inhabitants of the Marshall Islands. They consisted of connected nerves of palm leaves, indicating directions by which the islands, represented by small shells, could be reached (198). Eratosthenes, from 275 to 195 B.C., living in Alexandria, started scientific geography by making a map of the then known world (already considered spherical) including the British Isles, parts of Siberia, India and Ceylon, and the Mediterranean. He substituted the orientation lines by la­ titude parallels and longitude circles, forming rectangles 64 on his projection (841). He even estimated the world's cir­ cumference at 40 000 km. Three centuries later, Ptolomy (641) made the world one sixth smaller by overestimating the surface of the inhabited world, a notion persisting till the 17th Century when Mercator (1541 A.D.) and Hondius (1610 A.D.)made their globes(83).The inaccuracies in sizes and distances, causing a shrinkage of the unknown world, were among the reasons why Columbus, at the time of the dis­ covery of America, thought he had landed in Asia. The maps made by the Romans served military purposes: to indicate the roads along which their soldiers had to march from one settlement to another, from 'villa' to 'villa'. These maps are called 'Peutinger maps' after a German map collector in the 16th Century (198). On one of them, cover­ ing the northern half of Helvetia (Switzerland) are shown, very probably for the first time, forest borders, i.e. those of the Black Forest (634). The early Europeans were interested in real mapping sole­ ly for navigation purposes. Their sea-charts originate from the 'periplos', a kind of report about voyages in the Medi­ terranean. In their more advanced form they contain all in­ formation needed for good and safe navigation, occasionally including important harbours, and they show solely the con­ figuration of the coasts. The oldest periplos is from 330 B.C. Much later the Portuguese included the coasts outside the Mediterranean area, for Africa even up—to the Cape of Good Hope (83). During the 'age of discovery', starting at the end of the 15th Century, Portuguese and Spanish sailors, with their crude compasses (a piece of magnetite with a straw floating in a bowl of water) mapped great parts of previously un­ known shores. In 1494, as suggested by the Pope, they drew a line at 45° longitude, 270 leagues or 1500 km west of the Cape Verde Islands, that served as a division between East and West: all discoveries to be made west of this line were for the Spaniards, all those east of it for the Portu­ 65

guese (83). On his supposed way to India, in 1500, Pedro Alvares Cabrai landed in Brazil near the place Cabralia, south of Salvador. The shore-map, made by Cantino, shows dense fo­ rests (great parts still present today) inhabited by colour­ ful parrots, which must have made a vivid impression on the seamen (198). Another map made by Cantino, labelling 1 the land West of Greenland' was also inside the Spanish part of the New World. Nevertheless he included it in the 'Terra del Rey de Portugall'. The accompanying description shows a country covered with forests containing trees excellently suited for ship-masts (914). In 1602 - 1603, the famous red­ woods of North America, overlooked by Sebastian Vizcaino, were in 1769 discovered by a party of explorers travelling over land (211). In mapping the European countries, the 16th Century's Dutch geographers were the most prominent: in 1570 Ortelius made his first map-book, later on translated into other lan­ guages; in 159 5 Mercator corrected his maps in accordance with information received from various sources. The Mercator projection which is still used today was applied for the first time. From the title of one of Mercator's books the name 'atlas' was introduced (420) and became common usage. Already in 1586, the 'Low Lands' or the 'Seven Provinces' of the Netherlands had their own atlas, compiled by Orte­ lius (347). Another well-known specimen is the 'Atlas Appen­ dix' of 1630 made by Blaeu, containing maps of Europe. On the Polish part it shows several densily wooded areas, among them the famous Bialowieza forest along the border with Rus­ sia (832). The difficulty in indicating forests is obvious from the maps made by Tibanius for the Black Forest in South Germany (17th Century): all features are in relief, so the trees, mostly restricted to mountain tops or watersheds obscure much of the background (1172). Commonly forests were indi­ cated by scattered trees, or the areas were left blank. 66

This procedure, a kind of negative mapping, is still fre­ quently met with on newly made topographical sheets. More detailed land-mapping improved considerably when (in 1670) the English surveyor John Ogilby started using a wheel to measure distances along roads and trigionometric methods (known in the 16th Century). In 1669 , Abbé Jean Picard started land triangulation based on the zero meridian of Paris. It also served to determine the circumference of the earth. A more exact location of the continents overseas became possible after the invention of the chronometer by John Harrison in England, where it was officially accepted in 1772. It enabled the determination of longitude, not only important at sea to measure distances, but also on land for the location of astronomical stations used as tie-in points in surveying (19 8).

4.2 Terrestrial mapping in forested regions

As a rule a forester uses topographic maps and adds de­ tails for specific purpose. The difficulty is that, except for artificial stands with distinct plant rows or natural stands with cutting fronts, forest areas show no clear bor­ derlines. In one place they gradually become scattered groups or single trees, in other places the border is ob­ scured by shrubs forming transition zones b-&tween forest and tree, scrub or grass savannas. Under the heading 'Mapping of woodlands' the instructions of the US Geological Survey state: 'The accuracy in the location of woodland-outlines for maps to be published on a scale 1 : 62 500 will be based upon the location of the principal salient features only, the intermediate details between located points being sketched. In general, the location of the corners of a small quadri­ lateral tract and additional locations of the principal bends in the outline of a larger tract will be sufficient'. 67

Under woodlands are classified: 'all timber, woods or brush, whether alone or mixed, of suf­ ficient stand and height to impede ordinary travel or af­ ford cover for small detachments of troops' (146). Perhaps the oldest forest demarcation was that carried out in the Lebanon during the reign (A.D. 117 - 138) of the Ro­ man Emperor Hadrian, when an attempt was made to delimit the remains of the cedar forests (Cedrus libani) marked as an imperial domain. This is evident from almost a hundred inscriptions carved on rocks in the northern half of the Le­ banon Range. Many of them appear on sites now void of fo­ rest or even scrub (1074). Where man has changed forest borders, either by cutting or by burning, orientation may become very difficult even with the aid of a good map. Though already in 1692, the Dutch East Indian Company possessed maps of the teak forests on Java, the more accurate survey around 1800 soon revealed that without marking the borders in the field, the value of the surveys was doubtful. Because marking is costly, it was not until 1888 that a start could be made with surveys based on fixed and numbered corner stones (694). To establish reserves in forest areas with a population heavily pressing for more crop fields, the borders must be kept open and regularly guarded. For this purpose in Europe and America many forests are even fenced in (1267).

4.2.1 Mapping inside forest areas

Lack of visibility greatly hinders surveys inside forests, especially on flat country. In the dense tropical rain fo­ rests one can hardly see anything beyond the next tree. So in the beginning of forest exploration all knowledge on what was present inside large forest tracts, or in what direction the rivers were flowing, had to be based on information from local hunters or expedition reports. For instance, in 1857, the British Government commissioned Captain John Palliser, 68 geographer and big game hunter, to explore large parts of Canada and to pay attention to 'the nature of the soil, its capacity for agriculture, the quantity and quality of its timber, etc.' (1465). The data collected up to 1891 by the US Geological Survey were insufficient as a base for delimi­ ting forest reserves; special surveys had to be made (1271). In many regions of the world forest mapping is inadequate. Mostly forestry starts where civilisation (agriculture, in­ dustries) stops. In such areas even the most elementary data on the configuration of the land may be missing, so that the Forest Services have to employ their own surveyors or to es­ tablish Survey Departments to fill in the gaps. This is the reason why surveying is still taught to forestry students. A terrestrial forest survey may start with dividing the stands into compartments guided by topographic data or maps. Timber surveys can start after division lines have been cleaned so that the surveyor does not meet with difficulties in measuring distances and directions by simple means, such as a plane table or a theodolite. For large tracts, in unknown territory, this is not the usual procedure. In most instances, terrestrial surveys are done there along evenly spaced parallel lines(transects cut out in the forest) , as carried out during the national sur­ veys of 1921 - 1924, 1936 - 1938 and 1951 - 1953 covering all Finland (733). Along these transects, the topographic details are located and later on assembled-in an overall map. Obviously the accuracy of this map depends on the spa­ cing of the transects and the length of the measured sec­ tions on each transect. For restricted areas a modified and more exact way of this type of survey is to divide the forest into squares, e.g. one by one kilometer, which of­ fers a better opportunity to control distances and direc­ tions. Later the transects can be used in establishing com­ partments or exploitation sections. The resulting maps are very suitable for hardly explored forest regions, they are useful as an expedient in develop- 69

ment activities. In 1947, it was estimated that a quarter of the USA was still covered solely by such so-called 'sub­ standard reconnaissance type maps' (511).

4.2.2 Vegetation maps

Small-scale reconnaissance type maps or overall maps are in common use in plant geography. They are of much interest to forestry if actual or primeval forests are indicated (908). One of the oldest for less known regions drawn by scientific expeditions is that for the Amazon 'hylaea' by von Humboldt (1306). During World War II many expeditions needed this type of map during searches for wild rubber (Hevea brasi1iensis) and chickle (Achras sapota) in South American forests the latter for the chewing gum industry (673). Vegetation maps can be based on the structure of plant communities, their general appearance as observed in va­ rious parts of the world (forests, savannas, grasslands, etc.), or they can start from plant associations characte­ rized by their composition (1069). In the latter Europe is far advanced, mainly in the school of Braun-Blanquet (867). Vegetation and landscape maps, such as made for Bavaria in Germany (1 : 500 000) give the natural vegetation types within climatically homogeneous areas as influenced by soil conditions (1394). Such maps are very useful to establish correlations between natural vegetation and soil (868). Traditionally forestry pays more attention to nature than agriculture and will profit more from such maps (1117). A most remarkable use of vegetation maps has been in tra­ cing the influence of grazing by goats in Turkey: the animal was less destructive to the forest than man (836). 70

4.3 General use of aerial photographs

4.3.1 Development of aerial photography

In 1858, soon after the invention of photography, the Frenchman Gaspard Felix Tournachon made aerial pictures from a balloon. In 1887, a German forester tried to assemble aerial forest pictures into a map (1471). During World War I this technique gradually improved, but is was not before the period between World War I and II that the technical and economical possibilities were more thoroughly explored. At a later stage they were extended by the discovery of very sensitive films and the design of equipment for making se­ ries of pictures from fast-moving aeroplanes and even space­ crafts( 400). Canada was first in regularly using aircraft to make sketches from the air. This work started in 1919; between 1921 and 1924 8.8 million hectares forest was surveyed (1471). Though the details were inaccurate , results were adequate in view of the low value of the land (1099). For a general application this method has become obsolete, but it is still used for filling-in details or to correct exis­ ting maps. Afterwards it was again Canada that started using pictures taken overboard called obliques (high-obliques when the ho­ rizon is included, low-obliques when the""horizon does not appear on the photographs). During World War II the US Air Force applied the so-called trimetrogon system for the construction of World Aeronauti­ cal Charts. For this method the plane carries three cameras s one in the middle for vertical pictures, and two at the si­ des for high-obliques. These three pictures, taken simulta- nuously, cover a stretch of the earth's surface from horizon to horizon perpendicular to the flight direction. As a rule they are not used for more detailed mapping (above 1 : 40 000), but in the Amazon Region they have proved to be 71

suitable for drawing reasonably accurate and detailed maps 1 : 200 000 (651). At present vertical photographs are pre­ ferred, as applied since 1929 for forestry purposes in Ca­ nada. The importance of aerial photography is apparent from the following examples. In 19 24, the Irrawaddy Delta in Burma had to be remapped (old scale 1:250 000), either by terrestrial or by aerial sur­ vey. The costs of the latter were about half that of the ground survey. Later it was shown that especially for the densily forested parts, the terrestrial survey never could have produced the same details (793). The second example refers to the Philippines , where land registration started in 1909 and covered in 1964 about one third of the country. Application of the oldfashioned ter­ restrial survey would have taken at least 100 years. The ca­ dastral survey based on aerial photographs, started in 1958, produced excellent results, with regard to accuracy, speed and expense (1030). During the period 1920 - 1930 activities in aerial photo- work for forestry purposes in Germany were based at the Forest Research Institute in Tharandt, near Dresden. Because good topographic maps were available, photogrammetry (as it is called nowadays) could not be considered a great improve­ ment, and the shortcomings of aerial pictures for exact con­ tour mapping under forest were still obvious at that time (1683). The USA had a slow start. In 1926 photographic mapping was carried out by the Forest Services in Montana and Idaho (757), in 1934 aerial pictures were used in timber cruising in the Mississippi bottomlands; in the late thirties the forests of the well-known Tennessee Valley were mapped from the air (1471). In the Netherlands experiments with aerial photographs started in 1928 for the more wooded, southern parts of the country. The outcome was rather disappointing: trees and 72 shrubs obscured details. Later, in mapping the big rivers traversing the open parts of Holland, the results were ex­ cellent. In 1932 it was decided to use aerial photographs in replacing the outdated topographic maps 1 : 25 000 (1355). Such photographs proved to be indispensable for the survey of forests,wastelands and trees growing along roads, as car­ ried out in 1937 by the Forest Service (266). Between 19 29 and 19 32 the mangrove forests on the isle of Banka (Indonesia) were mapped from aerial pictures. The maps were considered excellently suitable for management purposes (810). In 19 35 a start was made with the aero-triangulation of parts of New Guinea (now called Irian). This Dutch attempt attracted world-wide attention. After the work was inter­ rupted by World War II, the Netherlands again occupied a prominent place in aerial phototechniques, mainly through the International Training Centre for Aerial Survey, founded by one of the pioneers in photogrammetry, Professor Willem Schermerhorn (1358).

4.3.2 Photogrammetry versus terrestrial survey

Photogrammetry involves the numerical and graphical re­ presentation of form and dimensions of objects whose images are measured. It usually refers to the earth's surface (488). Now that it is so widely applied, one may--marvel at the huge amount of hard work (and money) done by those plodding through the fields and the forests carrying out their tire­ some job in remote areas, often under adverse conditions (1363). All concerned will be grateful that most of this fieldwork has been abandoned; for forestry purpose this is for an important part due to the stimulating influence of Spurr's writings (1472). 73

4.3.3 Demarcation of property borders

On aerial pictures forests often hide topographic fea­ tures. This causes two kinds of errors: the planimetrie and the altimetric. Both have to remain within certain li­ mits, depending on the survey and the object. For the cen­ ters of big cities in the Netherlands this limit is 3.5 cm, for agricultural and forest lands 14 cm (1356). In the USA the accuracy has to be such that 90% of the errors in ele­ vation has to be smaller than half the contour line inter­ val (1488). In fixing property boundaries and forest bor­ ders it is mainly the planimetrie accuracy which counts. High precision terrestrial mapping in intensively culti­ vated regions is expensive and time-consuming.With aerial photographs the boundaries of each property or parcel of cultivated land can be presented in such a way that they can be reconstructed at any time in the field. Even changes in the course of rivers, the establishment of new roads, etc. should not upset the value of the map. Details invisi­ ble on pictures, have to be added by terrestrial surveys (1360). The whole procedure is rather simple, but an Ame­ rican writer complains that from the legal point of view this type of mapping is not always regarded as reliable (law-wise). Unnecessary trouble can be caused culminating in high additional terrestrial survey expenses (414). In 1955, the Cadastral Service in the Netherlands esta­ blished a special photogrammetric branch which started pro­ duction in 1957 (1361). The land registration adapted an 'incomplete negative' system: without registration of the deed no transfer of property is possible, but registration does not guarantee the deed to be legally valid and only if the owner agrees that the property as identified from or on an aerial picture is correctly defined, is the picture (or the resulting map) accepted as its description (1159). Mostly the survey of forest property borders and their cadastral registration is of no concern to forest services. 74

In the USA, however, the cadastral survey of the 72 mil­ lion hectares of National Forests with their 250 thousand miles of boundaries and covering 10% of the lands and wa­ ters is in the hands of the Forest Service ( 806). The sur­ vey is based on the country's 6 mile square townships with their division into quarter sections, etc. Properties are not based on exactly located points but on the position of a salient point whose coordinates are connected with cor­ ners of a (sub)section (1159). These corners are fixed with the aid of aerial photographs, replacing those pre­ viously indicated on (often lost) trees or fenceposts (806, 1773, 1000). As a rule three reference points in the field are needed for identification; a special technique has been developed for areas covered by trees and scrub (637). In all questionable cases the relocation of corners involves consultation with the local people (1664) or acting in ac­ cordance with the law. In Germany a comparison between forest areas measured from aerial pictures and those from good cadastral maps re­ sulted in one case in a difference below 1% (889) and for another smaller area in about 3%. Such results have to be considered excellent and acceptable (1294).

4.4 Aerial photography in forestry

After World War II the situation in Norteh America re­ quired a quick re-assessment of previously considered uneco­ nomic forest stands (1735). This led to a rapid development in the use of aerial photographs and the application of con­ siderably more refined techniques in their preparation and interpretation. Many attempts have been made to apply the outcome in other countries, especially those of the less explored subtropical and tropical regions. The results whether positive or nega­ tive, or successful only to a certain degree or under special circumstances, will be discussed below. 75

4.4.1 Demarcation of borders inside forests

Forests under regular management are, in flat country, as a rule divided into rectangular compartments. In the hills and mountains the form of these compartments is usually ir­ regular, depending on the topography. As a rule they are se­ parated by treeless strips often used as roads or as a pro­ tection against fire. Their mapping from aerial pictures is easy, especially when they are straight (266). As a rule each compartment contains several stands, dif­ fering in age or composition. To trace their borders, the study of the threedimensional view (stereoscopial) of the pictures is necessary. The resulting demarcation lines, es­ pecially if they are not straight, are more accurate than those obtained by terrestrial surveying, where only a few border points are measured (1294). In Europe, the use of photo-interpretation for forestry purpose is only slowly growing because most forests have been mapped already by classical methods and there is no economic need for revision (1677). Here the photographs are more used for general purposes, such as the projection of reforestation plans on existing topographical maps (874), for national forest and timber surveys (1167, 1186), or to ntake an inventory of widely scattered small parcels (955). Por the last purpose the Netherlands supplies a good exam- Pie: the limit for stands was 0.5 ha (267), while a sample from the eastern part of the country revealed that 41% of the parcels was between 0.1 and 1.0 ha (194). This also may indicate that hardly any mapping of stands inside compart­ ments had been included.

4.4.2 Forest type mapping

Mapping forest types is based on natural forests, inclu­ ding second-growth stands, classified according to their general appearance (their physiognomy) and independent of 76 their floristic composition. Sometimes such types are easily separable on aerial pho­ tographs, e.g. where a conifer forest borders a broadleaved forest, or where a dryland forest borders swamp or marsh forest. But as a rule the photo-interpreter is faced with transition zones. The forester who knows the situation in the field can identify the forest types and is thus better qualified to interprète the picture than the photogramme- trist (647). The resulting forest type maps resemble vegetation maps more than stand or management maps (1793, 1626, 1421, 1166). Where no specialized teams or survey companies are avail­ able to take over the photogrammetric part of type mapping, foresters have to do this work. This is regrettable because they have to pay too much attention to the geodetic part of the survey work, for which they are, as a rule, not suffi­ ciently qualified.

4.4.3 Area estimates

After the forests have been classified according to stand or type,the usually very irregular areas they occupy have to be measured,either from the photographs or from the maps deri' ved from them. A polar planimeter is considered best for this purpose,but as its use is rather time-consuming,a line grid may replace it.Such a grid is a transparancy with equidistant lines;it is put on the map or photograph and the total length of the lines inside one forest type represents the surface o£ this type.Of course before(or afterwards)it has to be estimât' ed which surface one length-unit represents on the map;this depends on the mutual distance of the grid lines and the scale of the map (1151,1167). An even more practical method is that of the dot-grid with points printed(on a transparant paper oi other material)at regular distances representing squares of 3 certain extension (1472). For mountain areas the calculation has to be corrected because a square on a mountain,being clo" 77

ser to the camera,will have another scale than one in a val­ ley (20). Under special circumstances measuring a few samples may give sufficiently reliable results, which is important when the area is large and covered by scattered parcels. This method is often used for national or reconnaissance surveys (107, 995). Dot grids give results as accurate as planimeters (devia­ tion rarely over 2%) (1470), so that, except for small sur­ faces, they are preferable in forestry (1488). In inaccessible regions, emphasis is less on area esti­ mates than on rapidly obtainable preliminary information at low cost. Therefore foresters, especially in the tropics, are often more interested in vegetation maps than in highly accurated and expensive maps (1362, 1359, 1324, 135, 1557).

4.4.4 Contour mapping

To open up a forest area and to start management topogra­ phic maps with contour lines are needed. Such lines can be obtained from the stereoscopic view of pairs of aerial pho­ tographs, but this is only possible where sufficient open places are present or when the forest periodically sheds its leaves (broadleaved forests in temperate regions and some subtropical regions in winter, in the tropics in areas with a long dry season). In all other cases the contour lines have to be traced over the tops of the trees. Without correction for tree height it is considered impossible to draw contourlines with intervals below 20 m and to obtain an accuracy as prescribed for America (see under Section 4.3.3.). In Irian (Indonesia) and Surinam this 20 m was shown to be justified after a terrestrial check in dense tropical forest (1358). For topographic-cadastral maps 1 : 10 000 in Switzerland the accuracy in height has to be + 1.5 m, for the national maps 1 : 50 000 + 2 m (1303). A recent development is the use of radar in mapping the earth's surface. In Surinam the resulting profiles gave an 78 acceptable approximation (1359)of the country's configuration. The conclusion is that, though photogrammetry has for most purposes outmoded classical terrestrial survey methods (1357) , its value in constructing contour line maps for a- reas under dense forest is restricted and ground survey will have to take over again. But for tropical forest lands this kind of detailed surveying is so costly and time-consu­ ming that probably nobody is willing to pay the price (1359).

4.4.5 Scale and type of photographs

Forest owners often can not afford to carry out their own aerial surveys; mostly they have to depend on pictures made for non-forestry purposes by governments, oil companies or other agencies. From the standpoint of the foresters, these pictures have certain déficiences so that it has been sugges­ ted to supplement them with large-scale photographs of selec­ ted areas (1248, 1348). This solution is quite suitable for less accessible regions, but in Europe it has little sense as most trees can be reached by car. The usual photographs are black-and-white. For detailed work the scale is mostly 1 : 10 000, allowing the identifi­ cation of single coniferous trees. For overall mapping, e.g. in tropical forests, 1 : 40 000 is suitable (1488, 1231). Larger-scale stereoscopic pictures are less suitable for the study of regional landscape because tlxey cover smaller areas per photograph (1082). In addition they increase the number of pictures, making mapping more expensive and sto­ rage more difficult, and, especially for tropical forest canopies with large crowns, the contours of the crowns are often blurred and heavy branches may resemble single crowns. Because of the construction of super-wide-angle cameras mounted in high-flying jet airplanes, it has recently be­ come possible to make good aerial pictures 1 : 70 000 and even 1 : 120 000 from which excellent planimetrie maps (maps without contour lines) 1 : 50 000 or even larger can be drawn (659). The advantage is, particularly in tropical 79

regions with their often clouded afternoons, that a much greater area can be covered in one flight. Whether space photography may assist in mapping inaccessible forests is doubtful, as, e.g.,'its three-dimensional resolution' is in­ ferior to that of ordinary photographs because only minimal parallaxes are recorded (1714, 1713, 298). On the other hand they cover such large areas of the earth's surface that they may be useful to indicate non-forest and forest areas (297). To identify single trees species or to separate conifers from broadleaved trees, foresters have looked for other types of photographs than the panchromatic ones. Well-known are the infrared pictures taken with films less sensitive to the green part of the spectrum but whose sensitivity ex­ tends into the infrared. Indeed on the infrared prints the constrasts, especially between coniferous and broadleaved tree stands, are often more apparent, simplifying interpre­ tation and demarcation (1019). But the borders are less clear, resulting in a slightly blotted appearance which makes the pictures less suitable for photogrammetic work (1298).

4.6 Remote sensing

The infrared part of the spectrum is also used in remote sensing by applying scanners. In forestry this method has proven highly successful in spotting open or smouldering fires because infrared rays are also emitted at night and penetrate smoke clouds (1116). Their most spectacular use, however, is in spotting (and mapping) sick trees. Such trees are assumed to have a higher temperature than healthy ones because their decaying roots have a reduced capacity for absorbing moisture and distri­ buting it, resulting in a decreased transpiration (1149). In the Netherlands this phenomenon has recently been used for mapping the vitality of less healthy spruce plantations 80

(1490) and, in Amsterdam, for spotting sick roadside and park trees damaged by gas leakage, bitumen or other causes (689). Most writers are convinced that in the future remote sen­ sing will play an important role in forestry, though much research will still be needed (522, 300, 258, 21, 663, 683).

4.7 Colour and false colour photography

Forestry can greatly benefit from large-scale colour pic­ tures. In the USA they have been used with success in tra­ cing Douglas firs (Pseudotsuga menziesii) damaged by insects (1690). As the costs involved are still high, general appli­ cation seems not yet justified (1726, 1248). Nevertheless in East Germany their application (with Russian material) is considered promising, notwith-standing the cost which is five to six times higher than panchromatic pictures (1726). This type of film, called spectrazonal, is fully accepted by Russian photo-interpreters in the search for natural re­ sources, because the colours, differing from natural plant colours, greatly facilitate identification of details (1298, 438).

4.8 Radar pictures

Since World War II, the use of radar has^ecome wide­ spread. At present it can make pictures of the earth's sur­ face resembling black-and-white photographs. Radar is unique among the more commonly used sensors in providing its own illumination: radio waves. These waves re­ turn to the receiver-recorder in a modified form depending on the properties of the object's surface (1298). Recent studies have revealed that the reflexion of open woodlands differs from that of compact crown canopies, that pine or fir react differently from broadleaved trees, etc. (1113). 81

Thus it is expected that radar will become an additional tool in the interpretation of vegetation images. This may be especially useful for less accessible regions (1112). In addition it penetrates clouds, which often greatly ham­ per normal aerial photography, especially in wet tropical regions. These photographs and also those taken by spacecrafts, produced in large numbers, will most probably make it ne­ cessary to apply some kind of automation in mapping and interpretation according to prescribed grey-scale densi­ ties (902).

4.9 Forestry maps

4.9.1 Types of maps

Mapping always starts with a map on a relatively large scale with geographic and topographic details and border lines. It serves as a base, if necessary after adequate reduction (1312) for a soil map, for a road or railway map, for a forest stand map, etc. For management purposes the scale may be between 1 : 5 000 and 1 : 20 000, depending on the intensity of the operations to be carried out. For more extensive forests with large ma­ nagement units, for maps indicating protection forest to be treated only superficially, or for maps mainly used for over­ all purposes 1 : 50 000 or even 1 : 100 000 or 1 : 200 000; may be suitable. When broad overall forest coverage maps have to be pre­ pared from aerial photographs, uniform interpretation is necessary first, especially when the work has to be carried out by more than one photo-interpreter (9 86). In such cases an interpretation key is useful (62). In the past maps were always drawn. With the increasing use of aerial pictures, these conventional maps are gradu­ ally being replaced by the photographs themselves. After 82 the user has become accustomed to read them, they often supply details which cannot be transferred to drawn maps (1096).

4.9.2 Photomaps

The first photomaps were mosaic-maps prepared by joining, as well as possible, parts of pictures not rectified on tilt or scale. They can be used for overall views and may be rea­ sonable accurate for flat country. Controlled mosaics, com­ piled from rectified photographs based on triangulation come much nearer to being correct. They have been extensively used for drawing planimetrie maps, for vegetation maps such as those of the northern part of Surinam (1793), and for the economic maps such as that in Sweden (761). The trouble with this kind of photomap is that in hilly and mountainous regions its distances and areas are not accurate because within a single photograph differences in scale occur (see 4.4.3). The introduction of the orthoscope has eliminated the in­ accuracies inherent to controlled mosaics. This instrument transforms all images to one scale by scanning simultane­ ously the pairs of stereoscopic pictures and it corrects errors due to the configuration of the terrain (1634). It is also able to add contour lines at selected intervals. On the resulting polyester base sheets, pr-operty boundaries and other details not visible on the photographs can be added by scratching, as has been done in the Netherlands in preparing maps for development projects in South Korea, Saudi Arabia and Mauritius (1800). Technicians expect the orthophotomaps to be an important step forward in automation of map production (43). Sweden uses it already for its economic maps as they are less ex­ pensive than the controlled mosaics used previously (761). Cartographers in the USA and France are very satisfied with the results: the automation and the short time needed be­ 83

tween taking the pictures and finishing the orthophotomaps are considered very favourable (1272, 1161, 386). In forest management such maps may become very useful, for instance for wood industries extracting their raw mate­ rial from a certain area around their factory, for the mani­ pulation of their wood supplies, and as a guide in establi­ shing tree plantations. In addition they can become avail­ able for the mapping of scattered tree stands (eucalypts in Brazil) (1454), for land-use planning, for the study of private woodlots (1156), or to adapt forest policies to landscaping. Furthermore they may serve management control when compared with newly taken aerial photographs as done in East Germany in counts of fall-out trees (1382).

4.9.3 Costs of maps from aerial pictures

As a rule the aerial photographs are supplied by the go­ vernment, which strictly controls their use.In 1962, in the USA 89 out of 199 forest industries used federal prints, 58 a combination of federal and private ones, and 33 had ob­ tained them by special contract from survey companies (60). When survey and subsequent mapping are carried out by a private company, contracting has to be done very carefully according to the advice of specialists (61). The costs per hectare mainly depend on the area to be flown: the larger it is, the lower they are per hectare. Furthermore, the scale of the photographs plays an impor­ tant role; data from 1967 (170) mention per 100 km2: photos 1: 70 000 , maps 1 : 100 000, with contour lines $ 230, without contour lines $ 100; photos 1 : 40 000 , maps 1 : 100 000, $ 380 and $ 210, respectively; photos 1 : 20 000, maps 1 : 50 000, $ 1240 and $ 590, respectively. Of course the present costs will be higher, but their ratios may have remained the same. 5 The climate

The study of the climate has become an intergrated part of silviculture in the introduction and evaluation of exo­ tic species and their varieties to guarantee a healthy tree-growth (1111). Seed directories give the place where the seeds were collected so that climates can be compared (436). Publications on the so extensively cultivated pines and eucalypts (1089, 434) stress the importance of climatic considerations, so that a rather comprehensive treatment of this subject is necessary. Also in general silvicultural handbooks, climatic data receive ample attention (1603).

5.1 Definitions

The climate of a given place or area is a summary of the physical characteristics of the corresponding atmosphere; it covers a certain (often long) period. The general trends (1530) are studied in climatology. The study of the aggre­ gate of weather conditions (833), in short the daily weather (and its forecast) belongs to the field of meteorology. Both, as a rule, start from observations collected in the open under standardized conditions, with the aid of a pluvio­ meter for the precipitation, in a so-called meteorologie cage for the temperature, etc., installed at places repre- sentive for larger areas. The results, characterizing the macroclimate, do not present the ecoclimate, the atmosphe­ ric conditions under which plants and animals live, which may be quite different (e.g. inside a forest, on steep slopes, in deep valleys, on mountain tops). But the correla­ tion between both climates is sufficiently high to permit the ecologist to use the macroclimate as a basis for climate classifications and the study of their geographic distri­ bution. 85

Still more deviation occurs between the atmospheric cir­ cumstances inside the vegetation, near the soil, etc., or even inside the bole of a tree. Here the term microclimate is adequate, and in the upper soil layers it is even possi­ ble to speak of the soil climate.

5.2 The climates of the past and recent changes in the atmosphere

As well-known, during the past Ice Ages, glaciers covered much larger areas than they do at present. The underlying long-term (secular) changes in climate still continue, as proved by the retreat of the glaciers in the Rocky Moun­ tains and the European Alps (rather curiously not in the southern hemisphere) (1616). They should be kept apart from annual fluctuations, which are quite 'normal'. Already a small change in the climate may have consider­ able consequences. An average temperature increase of 1° C over a longer period results in a gradual move of the fo­ rest border over 200 m upwards. Such an increase has actual­ ly been observed on the northern hemisphere, but since 1945 the temperature seems to have remained at the same level or has had the tendency to decrease (469). Along the northern border of the Eurasian taiga an increase in temperature(and rainfall)has been blamed for an expansion of bogs and peat- land,causing the death of trees(1796).Or has this expansion been caused by a lowering of the temperature leading to less evaporation? During the last fifty years this process seems to have reversed(1289),but much caution should be taken with such conclusions: the northern forests regenerate after the undergrowth with its humus-layer has been burned,so that de­ creased burning may well be the cause(632).Obviously it is difficult to separate climatic and anthropomorphic border lines (1418). Learned men in ancient Greece and Rome already knew that the alteration of periods favourable and unfavourable to tree growth result in growth rings indicating the age of 86

the tree. This applies as well to regions with a distinct summer and winter as to those with an outspoken dry and wet season. When the climate is more or less the same throughout the year, such rings are absent, except when wood growth stops due to profuse flowering and fruiting (which may even happen twice a year). In general, the width of a growth ring indicates the over­ all character of the weather during the year of formation: a moist year gives a wide ring, a dry year a narrow one. To get an idea about such widths: southern pine (Pinus Elliot- tii), the most important softwood in the USA, normally forms (at breast height) rings of 4 mm (830). Differences in width of successive growth rings, measured in stands of old trees on distant places, may be correlated and allow conclusions on dry and wet periods. This backdating procedure (991, 653), known as dendrochronology, is not infallible, however; espe­ cially when very long periods are involved, for which no me­ teorologie data are available, it has to be supplemented by other data (242), e.g. from geology. One remark has to be added to this method. The width of a growth ring does not solely depend on the weather but al­ so on the place of the tree in the forest or savanna: sup­ pressed trees grow slower than dominant trees. In back-tra­ cing climatic events those specimens have to be selected for which light, competition, exposure and soil have re­ mained essentially the same for long periods (508). Elliot was the first to apply this method in tracing long- term climatic changes. He and his followers have included sequoia (Sequoiadendron giganteum) up to 3200 years old, Douglas fir (Pseudotsuga menziesii) up to 500 years old, dwarfed limber pine (Pinus flexilis) up to 1600 years, and brittle pine (Pinus aristata) up to 4500 years. From the last, with the help of its living and dead wood, it was possible to count back to 5150 B.C. (1664). These countings were used to control carbon dating, the 'essential basis for pre-historical chronology' (1299). 87

At present modern equipment measures 1200 to 200 rings per hour (1628) and dendroautographs (508, 1251) can auto­ matically register the sometimes very narrow growth rings on living trees. Of late much attention has been paid to possible changes in air temperatures due to changes in the composition of the atmosphere. It has been speculated that an increase of carbon dioxide due to large-scale burning of fossil fuel might, besides stimulating assimilation (a kind of green­ house effect), increase the temperature. Data from the Netherlands, collected since 1940, have shown that winter temperatures tend to decrease, however. Certainly this does not prove that the carbon dioxide has no influence: the ef­ fect of carbon dioxide may be masked, by that of dust par­ ticles lowering the heating by the sun (1370). Equally uncertain is the influence of the large-scale cut­ ting and burning of tropical forests in Brazil (Amazon area), Asia (Borneo) or central Africa on 'the large-scale atmos­ pheric general circulation'. Our knowledge on the air move­ ment over tropical regions is still too scanty to allow conclusions on water vapour and heat transports (1150).How­ ever man-made effects on the latent heat balance of water va­ pour (1697), especially in tropical regions,cannot be ex­ cluded 'a priori1 (470). The Sahara is often cited as an example of climate changes due to human influences. Some 5000 years ago a savanna-like vegetation was present there where now almost nothing grows ; in historical times its southern border has moved some 200 km to the south (242). The latter is certainly due to man (1106), and 'the nomad is not so much the son of the desert, as its father'. This also applies to the arid zone of In­ dia and Pakistan, where during the reign of Alexander the Great the climate was more or less the same as today (140). Neither climate changes are responsible for the dryness of the Russian Plain, the Caucasus and Central Asia, nor for that of the Colorado Plateau in North America, the Pacific 88

Coast of South America and the arid parts of South Africa, where plentiful evidence points to the absence of changes in aridity in historical arid even in not too old prehisto- rical times (849 , 44, 1537).

5.3 The macroclimate

5.3.1 The main climate factors

The main climate factors influencing forest growth are light, temperature and rainfall. Snow falls only in winter when tree life almost stagnates, and though its damaging influence (breaking branches, causing avalanches) may be important, it will not be considered here. Water occurs in the atmosphere and on and below the sur­ face of the earth as a liquid, a solid and a gas (1662). As a gas it influences the transpiration of the plants. In its liquid form it causes rainfall, normally only indirectly influencing tree growth by supplying the soil with water from where it is taken up (together with solved nutrients) by the vegetation. Light is needed as the source of energy in the assimila­ tion process during which the plants build up a stock of starch. This process needs water, and its speed depends on temperature. Hence these three processes must cooperate. Of course other factors also play a role :the plant has to qet rid of the surplus water, the transpiration process again de­ pending on temperature and, in addition on relative air humidity and wind. Light, temperature and rainfall vary from moment to mo­ ment, from day to day, and from season to season. For fores­ try, to make long-term decisions, it would be very conve­ nient if such changes could be predicted. But at present scientifically justified predictions are still impossible: in the past they only have 'been identified by the time they ended '(1530). 89

5.3.2 Climate classifications

For the vegetation as a whole, among the factors light, temperature and rainfall the first plays a less important role as it is strongly correlated with temperature. Thus all older climate classifications, among which that of Koppen is best known, are based solely on temperatures and precipitation, both their annual averages and their fluc­ tuations during the year. Soil, fauna and vegetation have adapted themselves to the various ensuing climate types and thus are factors of a more secondary nature (1225). Arctic and antarctic regions, and very high mountain a- reas are devoid of vegetation due to the low temperatures. Near the North Pole the forest limit coincides approxiama- tely with the isotherm of 10° C for the warmest month (1212). Near the equator an average annual temperature below 0° C causes eternal snow and the natural forest border practical­ ly coincides with the limit of this snow when no other fac­ tors such as strong winds prevent tree growth. Another borderline is found where evaporation starts to exceed the supply of water by rain, either during a prolon­ ged dry season or throughout the year (833): below this li­ mit evergreen forest is found only on places with a more or less permanent high groundwater level (e.g. the gallery forests along rivers). Ultimately there is a forest limit where the rainfall be­ comes insufficient for trees to survive, such as around and in deserts. Where forests occur (or occured in the past), the basic factor is not rainfall itself but the relation between rain­ fall and évapotranspiration (evaporation from the soil and the plant surface plus transpiration by the plants). This was first worked out by Möhr for Java (Indonesia), later on in a more exact way by Thornthwaite and others. The central place in this type of classifications is occupied by the potential évapotranspiration (PE): the évapotranspiration 90 of a vegetation-covered surface under conditions allowing unrestricted transpiration. In general, PE increases with temperature, sunshine and wind speed, it decreases with rising relative air humidity (1560). Theoretically differences in vegetation should not af­ fect PE if a completely uniform vegetation cover is present The high values for forests have to be explained by the ve­ ry uneven surface of their canopies causing a higher absorb tion of radiant energy than a simple plane and other vege­ tation types. Furthermore, especially for coniferous stands the albedo (being 15% as compared with 25% for agricultural crops) must have some influence. So do deep root-systems. To calculate the PE for various climatological circumstan ces the world over, rather complicated formulae are applied One of them, also used by Thornthwaite and more or less ge­ nerally adopted in forestry, uses mean monthly temperatures an annual heat index deducted from these temperatures, and a factor to correct the unequal monthly daylength (1560, 1561). As to the 'water balance' (the relation between rainfall and PE), the potential, optimum or unrestricted évapotrans­ piration is considered very significant. By plotting, per month, the average rainfall against PE, it can easily be de tected whether, and during which months, less rain is fal­ ling than necessary to counterbalance PE. Shortages can be supplied by the soil as long as it has an easily attainable reserve. As soon as this stock becomes considerably smaller the soil will not be able anymore to eliminate the diffe­ rences between PE and precipitation, so that already long before it is completely dried out, a deficiency can become apparent. Recent investigations suggest that, in most nor­ mal soils,at least the equivalent of a 30-cm deep water layer must be available for the root area of plants before a deficiency becomes abvious (1561). Seasonal climatic variations can be mapped. Such maps may serve to define 'site'; to indicate the circumstances un- 91

der which certain forest types or tree species can grow, and where the growing conditions are optimum.

5.3.3 The influence of forests on precipitation

The influence of forests on precipitation measured out­ side the stands is restricted to promoting the condensa­ tion of water vapour in the air above and alongside the forest, whereas that inside the stands also depends on the interception by the tree canopy, which may have a positive or a negative effect. As, in general, the condensation of water vapour resul­ ting in precipitation takes place at great heights above the earth's surface, a forest cover can hardly have more influence on the rainfall than other forms of vegetation. Only when the condensation takes place near the ground, forests with their cooling effect can increase precipita­ tion. Such condensation occurs more often in mountain a- reas than in flat lowland regions and only here do forests influence the distribution of precipitation (1675). Never­ theless some authors accept an increase in rainfall due to orographic circumstances, in amounts up to 3% in temperate climates (1473, 1079). Probably the conclusion must be that 'at the present time it is certain that any increase in precipitation due to the presence of a forest is bound to be very small' (524). That forests influence the quantities of water reaching the soil surface by intercepting rain, and due to their évapotranspiration return more to the atmosphere than an open field, is quite another point. Not all rain coming down on the forest reaches the soil. For small showers interrupted by sunny periods up to 90% remains in the crowns and evaporates there (1662). To mea­ sure the quantities of water reaching the forest floor it is necessary to include the water dripping from the leaves and the twigs and that flowing down along the trunks. Older 92

German data indicate that for coniferous stands one fifth to one third, and for broadleaved stands one seventh to one fifth of the rain is lost in the crown canopy. Newer German data are for spruce (Picea abies) 32.4% in summer and 26.0% in winter, and for beech stands (Fagus sylvatica) 16.4% and 10.4%, respectively (524, 409). For Russia are given: deciduous stands 6 to 9%, for pine (Pinus sylvestris) 15%, and fir (Abies alba) 20 - 30% (157). Investigations in the Eiffel (Germany) have revealed that beech forest regions annually discharge 200 mm more water than spruce regions, which has a significant effect on the value of catchment areas (344). This was confirmed in the Netherlands, where the drainage from lysimeters as compared with that in open sandy country was for H-vear^old broadleaved trees 57%, for pine of the same age 27% (1705). The same trend was found in the USA (1786). For completeness' sake it has to be mentioned that from the rain reaching the forest floor under fir 0.37%, under oak 5.7%,under maple 5.9% and under beech 12.9% to a maximum of 22.3% had run along the stems. Newer data from Europe are: spruce 0.7%, beech 11.6% (524 , 409); for America: short- leaf pine (Pinus echinata) 1 - 5%, lodgepole pine (P.contor- ta) 0.1% (815). On the other hand, fog and low-hanging clouds increase the quantities of water reaching the soil (1662, 799). On the Tafelberg (South Africa), on Mount Wellington (Tasmania)/ and at the Pacific Coast of the USA this kind of precipita­ tion has a distinctly favourable effect on the vegetation, especially on the survival of seedlings (1473). Though it was difficult to measure the quantities for a catchment area in Australia the resulting additional dis­ charge was estimated at 2 - 5 inches annually (306). 93

5.4 The microclimate

5.4.1 Microclimatic factors

The microclimatic factors refer to the atmospheric circum­ stances in the immediate surroundings of the plant or, some­ what more widely, to the atmosphere inside the vegetation cover. For a tree, these circumstances do not remain the same during its life. Its seeds land on a more or less moist soil and germinate there. As a young plant it needs light (though often low quantities are sufficient) and it has to be protected against drought. Later on, the result of its struggle for survival will depend more on macroclimatic conditions. These changes in ecological requirements indi­ cate that, for a good understanding of forest tree develop­ ment, various factors have to be studied, both separately and interdependently, before conclusions can be drawn on the influence of the macroclimate on the vegetation as a biological unit. As the precipitation has already been treated under Sec­ tion 5.3.3, the factors needing further discussion here are: solar radiation, light intensity, temperature, air movement and air humidity.

Table 1 Light intensities inside the forest as compared with those outside, (in %) for Europe (524)

Beech Oak Ash Birch Fir Spruce Scots pine Fagus Quercus Fraxinus Betula Abies Picea Pinus sylvatica robur excelsior alba abies sylvestris leaves leaves leaves with with without with without with without leaves

2-40 26-66 3-35 43-69 8-60 39-80 20-30 2-20 4-40 22-40

Similar data are known for America (1473) 94

5.4.2 Solar radiation

Part of the solar radiation is reflected or absorbed by the atmosphere. From the remainder often important quanti­ ties are reflected by the earth's surface and lost again: for water this amounts to 3 - 10% (so that it appears dark on aerial pictures), a forest reflects less than bare soil (only 5 - 10%), grass and crop fields 13 - 30%, snow fields 75 - 95%, and closed cloud canopies 60 - 90% (524). The radiation intercepted by a tree layer varies with its composition and with the season. Only part of the light reaching the upper layer of a forest penetrates to the soil, but not all forests behave in the same way in this respect, as apparent from Table 1. Solar radiation reaches its maximum when the sun is in its zenith. So on the equator the average annual temperatu­ res are highest, although in the subtropics and temperate regions the longer days sometimes result in almost as high temperatures in summer (1666). This radiation is necessary for photosynthesis, by which (with the help of chlorophyll) carbon dioxide and water are synthesized to carbohydrates. During this process oxygen is liberated. The higher the temperature (up to a certain limit), the faster this process. For a spruce plantation (Picea abies) in Germany it was estimated that from the radiation energy 3% was used to heat the—sjpil, 2% to heat the biomass (the organic matter of the plants) above the soil, 0.5% to heat the air between the trees, 63% for eva­ poration, and 31% was returned to the air above the stand (101). Data from East Germany on mixed stands of Scots pines (Pinus sylvestris) and beech (Fagus silvatica)indi­ cate that during a sunny day in autumn the forest returned one third less heat to the atmosphere than grassland, so that one third more is available for evaporation (977). Field crops use rarely more than 2% of the incoming light energy for their physiological processes. As deduced 95 from wood production, for forests this percentage is some­ what higher (1669, 666). Measured by the biomass, a forest is the most effective storer of radiant energy as it accu­ mulates 70 - 77% of it in its perennial parts (1321). Though a forest absorbs more energy than other vegetation types,its internal daytime temperature remains lower than that of the air outside the forest because, one could say, the amount of heat is distributed over a much thicker layer. At night the situation is the reverse: the air between the crowns cools, moves downwards, and is replaced by the rela­ tively warm air from the lower layers. The higher the trees, the slower the drop in temperature. This is one of the rea­ sons why coffee in the high mountain areas of Java (Indone­ sia) is planted under a tree canopy: it prevents night frosts (187, 1481). To study light intensities in the forest, photometers have to be placed at different heights above the soil, and above the crown canopy up to at least twice the height of the trees (524, 102, 402, 399). The resulting measurements shows a sharp decrease from the top of the crown canopy towards the forest floor, being more pronounced on a sunny day than on a cloudy day because in the latter case diffuse light has a bigger share in the total quantity. With regard to radiation, the tropical rain forest with its gloomy interior and the dazzling brightness in the tree tops and clearings, occupies a special place. Older light measurements, away from sunfleeks, have revealed that 0.5 to 1.0% of the daylight reaches the herb layer (1308), whereas in the Okumu Forest Reserve in Nigeria at noon, when 20 - 25% of the forest floor was covered by such flecks, the total quantity of light reaching the floor still was on­ ly 3% of that outside the forest (428). Light intensity, and thus energy uptake, inside forests is inversely proportional to their density, both in natu­ ral and regularly thinned stands. Measurement of light in­ tensities inside stands gave the following percentages com- 96 pared with those outside the forest (Table 2). Table 2 Percentages of sunlight penetrating the tree canopy

Pinns Picea abies Abies balsamea resinos a

not -to heavi­ not lightly heavily moderately ly- thinned thinned thinned thinned thinned Bowmont Forest, England (451) 0.81/1.85/ 4.92/8.12

Switzerland(1618)2.4/2.6/7.3

Quebec, Canada (1619) 5.9/7.6 8.0/10.3 8.7/10.7 6.6/10.2 In mountain areas the so-called topographic shading may cause substantial losses in insolation, in narrow valleys sometimes exceeding 30% of the annual total. The degree of shading can be mapped (919), which may be very important in planning afforestation (1588). In general, settlers pre­ fer the sunny side of the mountains and leave the others to the forest, as has been demonstrated for the valleys of the Alps, where 85% of the inhabitants live on the sunny southern slopes (161). For other phenomena connected with this subject see Sec­ tion 5.4.4.

5.4.3 Light intensity and growth

As mentioned already, the energy supplied by sunlight is needed to form starch from carbon dioxide taken up from the air (assimilation). In the reverse process, predomi­ nant during the night, this starch is broken down again and the ensuing energy (together with the material derived from the starch and small quantities of salts from the soil) is used to build up new cells and tissues. In borderline cases, just sufficient new matter is sup­ plied to keep the plant alive. The corresponding quantity of light, assuming that no other factor is limiting, is the 'compensation point'. It is at roughly 1 - 2% of the full sunglight (1473). For young, isolated growing Pinus cembra 97

in the subalpine region of Austria it has proved to be somewhat lower, between 0.4 and 2% (1587). As soon as the quantity of light exceeds 2%, a young tree may start growing, and the more light is available, the faster its growth will be. For some species there is a maxi­ mum however, that should not be exceeded lest damage be done to the plant (the so-called tolerant or shade-bearing species), whereas others do not develop well under cover (the so-called light-demanding species). The borderline is not always clear: some species are intermediate, others demand shade in their youth and like their crowns in full daylight when grown-up. A thumb rule is that trees which give much shade when old need shade in their youth. The following data may serve as an illustration. Fir (Abies alba) and beech (Fagus sylvatica) seedlings grow better at low light intensities than in the open, oak (Quercus), Scots pine (Pinus sylvestris), larch (Larix) and birch (Betula) show contrary trends (1225). In Canada, black spruce (Picea mariana), white spruce (Picea glauca), balsam fir (Abies balsamea) and white cedar (Thuja occiden- talis) were raised at 13, 25, 45 and 100% daylight: white cedar was tallest at 45% and heaviest at 100%, black spruce, white spruce and balsam fir grown at 13% and in full light produced the same twig weight(without leaves)per qram of fo­ liage, suggesting that they utilized the incoming light more efficiently when grown in the shade. The registered faster growth of black spruce was the result of more foliage (962). For the germination of southern white cedar(Chamaecyparis thyoides), considered a shade-bearing tree, a light intensi­ ty of 16% greatly reduced germination, though some seeds still germinated at 1% light intensity (949). Seedlings of loblolly pine (Pinus taeda) can survive under conditions in which they hardly increase in weight; as seedlings they tolerate much more shade than as saplings or larger trees (1657). 98

5.4.4 The temperature inside and near the forest

The chemical processes inside the plant are influenced by the internal temperature which can be measured by stick­ ing a thermometer into the shaded side of the bole. It was found to be some 0.5° C below that of the surrounding air, and that the heat penetrates the wood at a speed of 2 cm per hour (101). For the sunny sides of the bole the diffe­ rences are much greater, which should be kept in mind when raising trees with thin bark in full light (1080). By establishing twin stations, the temperature inside and outside the forest can be compared. This started in 1862 in Tharandt (Eastern Germany), and comparable investigations were done later (524). The early data showed that the mean annual air temperature at 1.50 m in the forest was 0.58° C lower than that in the open field (1675). According to nume­ rous other European observations, the average annual tempe­ ratures around the boles are some 1.0° C below that in the open ( in summer 1.1°, in autumn 0.7°, in winter o.l° and in spring 0.8°). Similar values have been found in the crowns (101). Data from North America indicate larger reductions for the maximum temperatures, in July up to 4.4° C, in January up to 2.0°, and increases in the minima by 3.3° in January and 3.7° in July. The highest values have been found at high elevations where radiation is strongest. Exceptions occur, however: the maxima at 1800 m in pine forest in the San Bernadine Mountains were only 0.4° C higher in January and 2.8° in July than in the open (815). Camparable data for deciduous forests in the Copper Basin (Tennessee) are: in winter 0.3° - 1.1° C higher (1473). In the Sierra Nevada (USA)it was observed that during windless weather in spring, lodgepole pine trees (Pinus contorta) can have a warming effect, making the weather more agreeable to skiers (1079). The explanation is that the dark needles absorb quite some radiation and thus, as 99 their temperature increases,the trees warm up the sur­ roundings (1344). For tropical regions general data are available from Gabon (Africa), with mean monthly maximum temperatures outside the forest of 31.3 and 27.7° and mean minima of 23.9 and 21.7° C, respectively (264). In the tropical rain forests the mean maxima and minima in the upper part of the crown and near the ground appeared to vary much more than in the temperate regions, where the temperature in the upper crown parts are assumed to be comparable with those in the open field (see Table 3).

Table 3 Temperatures (in °C) at different levels in tropical rain forest (1305)

Place in height Temperature vegetation above dry season wet season ground (m) mean mean mean mean maximum minimum maximum minimum

Panama crown top 26 35.7 27.1 second storey 17 30.8 24.0 undergrowth 0.2 27.1 26.0 South Nigeria B storey 24 33.9 24.0 30.9 21.8 undergrowth 0.7 29.7 23.9 26.8 23.3 Philippines top of tall trees trees 35-40 32.5 19.6 31.3 20.6 second storey 18 27.5 20.8 27.3 21.4 under storey 27.5 19.9 26.9 21.0

x Upper storey minus emergents

Topography and exposure can have great influence on tem­ perature. Near the bottom of a forested valley in Bavaria (Germany) the variation in daily temperature in October was 9.0° C, in May 11.7°, while at the highest parts of the slopes it was lower: 3.4° in May and 4.9° C in July (100). In Indiana, a wind-protected wooded gorge showed lower maxima and higher minima at its bottom than on its slopes (741). In the Netherlands, diurnal variations at the top of a low hill were smaller than those on the ad­ jacent plain, which was ascribed to a descent of cold air (941). 100

In Norway, between 1861 and I9 60, the length of the vege­ tation period of the trees was shown to be closely corre­ lated with the fluctuations in summer temperature (1508), which must have greatly influenced assimilation, especially near the timberline where a slight decrease in temperature can completely stop water intake (100, 56). Recently it has been proposed to study such topics (and other complicated relations between climate and vegetation) in simulation models (1655). The climate in clearings depends for an important part on that of the nearby forest. To characterize such open places, a size-index has been used: their diameter divided by the average height of the surrounding trees. Measure­ ments in the Brandenburger Forest (Western Germany) have shown that open places with an index 1.25 are fully protec­ ted against night frost, that this protection is only mode­ rate at 1.50, and that above 2 the damage can be consider­ able. Later data have indicated that during cold nights in spring and summer, the minimum temperatures decrease al­ most proportionally to the diameter of the open place be­ tween 12 and 47 m (size indexes 0.46 - 1.82) (524). Inves­ tigations in Czechoslovakia have shown that an index of 0.7 results in a microclimate practically identical with that inside the surrounding tree stands. Elliptic clearings with the long axes running WNW.-ESE. had a microclimate favour­ able for the light-demanding Scots pine ..(Pinus sylvestris) on sandy soils (857). All low temperatures, either permanent, periodical or in­ cidental, are harmful to trees, especially during their youth. When they occur regularly and are, so to say, part of the local climate, the plants become adapted to them, but when they are exceptional (abnormally late night frosts)/ as often occur in Belgium and the Netherlands, it has been advised to clean the young plantations of grasses and weeds to further air movements, whereas for nurseries the use of blowers has been recommended (1373, 517,34). 101

When the temperature falls below -10 to -20° C, man and machines can hardly work anymore, which is especially im­ portant in northern countries (14). Cities have a higher temperature than their surroundings: Berlin was 1.5° C warmer than areas 15 - 18 km away. Most remarkable was, however, that for a wooded region only 3 km from Berlin no difference was found (1365). The explanation could be that because forests absorb more heat radiation they return twice the quantity to the air than bare country and one third more than other vegetation types (1589). As already indicated in Section 5.4.2, in temperate re­ gions radiation, and thus temperatures, are strongly influ­ enced by topography: northern or southern slopes differ considerably. Near the equator the situation is different: the sun rises so high that valleys, also those running north- south, receive full light for the whole day.

5.4.5 Air movement

The heat taken up by objects on or near the earth's sur­ face is returned to the air in their immediate surroundings. This air moves upwards, or is transported horizontally. The wind velocity, the strength of the wind (524), or still more accurately the quantities of air moving horizontally from one place to another,is determined by the air pressure gradient between the two places (1665).The surface of the earth, bare or with vegetation cover, acts here as a brake. The friction layer is between 1000 and 1500 m thick (524), and a freely blowing wind at sea level moves at a speed of about two thirds of that at 600 m (244). Wind strongly promotes évapotranspiration (1473), resul­ ting in a decrease in temperature of the leaves. Especially when the wind is cold, this cooling may be dangerous, where­ as warm winds may be as harmful in speeding-up the evapora­ tion too much, in particular when the soil is frozen and the plant cannot compensate losses (243). On the other hand wind 102 increases the circulation of carbon dioxide. Strong winds more or less constantly blowing from one di­ rection may result in asymmetrical or even one-sided crowns. If such winds, near the sea, carry salts, the outcome may be disastrous. Vegetation, and especially forests, not only deflect the wind near the earth's surface but also slow it down: in the Wagon Wheel Project (USA), where before deforestation the wind velocity averaged 1.8 km/h, it rose afterwards to 5.7 km (95, 815). Wind profiles, giving the wind velocities along an ima­ ginary transect, supply useful information. In Switzerland they showed that 546 m from a forest border the forest had reduced the velocity to 11% (1126), and that scattered trees on meadows resulted in a reduction of 25.5% (1129). In Canberra (Australia), after forty years of ornamental tree planting, a remarkable decrease in wind velocity was observed (607). Trees and shrubs are often planted to serve as windbreaks (1543, 1544), also along sea coasts (96), to protect agri­ culture and other land. They are even considered to make the climate more pleasant (678, 858). Damage by mechanical wind action, occurs more frequently, causing windfall or windthrow. The danger is greatest when the trees are in full leaf, wet, or loaded with snow (541). Species with a shallow root system, such...as spruce (Picea abies) are more susceptible to windthrow than deep-rooted ones (726). Tree height is important here: in England stands have been classified in those expected to be blown down when they are 35 - 50 feet high, those between 45 and 60 feet, and those which can be expected to reach the full rotation age (515). For New England (USA) it was remarked that hurricanes and many storms have dominated the life span of most of the forests (1473). The heavy storm of 13 November 19 72 has reminded the Dutch that saving tall old trees can have its natural limits (672). 103

5.4.6 Air humidity

Apart from the small quantities taken up directly from the surface of the leaves, higher plants receive their wa­ ter via the roots from the soil. Superfluous water can be disposed of by guttation (formation of droplets on leaves), but the normal process is by transpirations via the stomata. These stomata are closed when the loss of water threatens to become too high; they open when the plant wants to get rid of water. Transpiration thus depends on the internal situation of the plant and on the humidity of the air layer in its immediate vicinity. Atmospheric circulation removes this layer,or diffusion can spread the water vapour(815).Both increase transpiration,if the air humidity is not too hiqh. This humidity can be expressed in two ways: the weight of water per volume air (the absolute humidity), or the quantity of water vapour as a percentage of that in water- saturated air (the relative humidity). The absolute humidi­ ty has proved to be practically the same in the tree crowns and near the ground, as well as in the nearby open. The water vapour easily mixes with the air masses and rapidly enters the general atmospheric circulation (815). The in­ crease in water vapour pressure inside the forest, also where it could be measured (1675, 524, 939, 978), is so small that it has practically no influence on bioclimatic circumstances (1367). The relative air humidity behaves in quite another way. If the absolute humidity remains the same, it strongly decreases with a rise in temperature, so that inside the forest the lines of equal relative humidity and those of equal temperature are isomorphic (524). Conse­ quently the slightly higher relative humidity inside forests is due to the lower temperature, when compared with the open (815). As an average these differences amount to 4 - 5%, while on open places inside the forest such differen­ ces hardly can be registered (1367). 104

5.5 Shelterbelts

Many methods have been devised to protect young forest plantations and other crops against permanent sunshine and strong winds. They range from stone walls to mats (96,1127, 1130), from hedges or coppice strips (245, 939) to the planting of napier grass (elephant graas, Pennisetum pur­ pureum) in tree nurseries (271)to real forest belts. Al­ though forest belts may cause eddies at their lee-side (243), their efficiency stands beyond doubt. They may exer­ cise their influence over a distance several times their height and may also affect the microclimate in other ways (72). Shelterbelts of trees were established many centuries ago in several European countries. They may consist of oak coppice {Quereus robur; in Holland), of alder coppice or trees (Alnus glutinosa; lower parts of the Netherlands also to protect fruit trees (940)), of elm (uimus; soils with high groundwater in Denmark), of poplars (the Nether­ lands; much Populus nigra var. italica), or of various more shrubby plants. In Denmark, between 1938 and 1946, 15 000 km of such strips have been planted.Shelterbelts with 48% open areas in their profiles, extend their favourable influence over more than fifty times their height (1449). In Versailles (France) it was found that sheltering may decrease évapotranspiration by 22% (183, 184), but in cen­ tral Russia an increase may result where snow settles in the shelterbelts, which otherwise would have accumulated in low places only (410). Ten-row shelterbelts in Nebraska demonstrated that accu­ mulated snow is a very valuable source of water in wind­ breaks: the snow trapped in the 'north five rows' provided them with two additional inches of water (1340). Since the 19th Century, shelterbelt planting has received increasing attention in Russia, culminating in the Plan for the Transformation of Nature in 1948. The idea was to ere- 105

ate an interstate belt of forests, 5300 km long, protec­ ting 5.7 million hectares of farmland against dry winds from Central Asia (217). In 1959 it extended over 2800 km (1584). Normally this belt consists of three strips each 60 - 100 m broad, 100 - 200 m apart (219). In general, rus- sian shelterbelts cover 2 - 4 % of the farmlands (963). Be­ sides improving agricultural production, they annually pro­ vide 2 to 3 m3 timber and 2 to 3 steres firewood per hectare. The Russian example stimulated other countries to follow. Between 1952 and 1956 795 km were planted in Bulgaria, serving 8057 ha farmland. China has planned shelterbelts for the so-called'dry sea'(11 million hectares) covering 6 to 10% of it (1061). The strips enclose diamond-shaped fields of 24, 48 or 96 ha (1308). Some years ago 2.5 mil­ lion hectares of cropfields and 2 million hectares of pas­ ture were ready (1343, 1684). The Prairie State Forestry Project of the US Forest Ser­ vice launched a campaign to protect the crops on the drought- stricken Great Plains. Between 1935 and 1942 some 217 mil­ lion trees and shrubs in 24 000 km shelterbelt were planted, spread over 30 000 farms ( 1447), originally covering an area of 90 000 - 100 000 ha from the Canadian border to the Texan Panhandle. Already in 1938 it was stressed that such belts have to be managed well; now that the plantings are 30 to 50 years old, this problem becomes pressing (1422, 615). In Australia cattle does much harm to such belts, hampe­ ring their regeneration and making fencing-in desirable (209). In New Zealand the Forest Service warned against mutilating the trees by cutting their tops to stimulate branching (a commonly practice in the Netherlands for pop­ lar hedges) which makes them worthless for timber produc­ tion (739); proper underplanting was recommended. In addition to the countries mentioned above, shelterbelt Planning is being investigated or carried out in Canada (252), Japan, Israel and Italy (527). 106

5.6 The introduction of exotic species

The great differences in climate and atmospheric condi­ tions, even within relatively small areas (as obvious from the proceding sections), raises the question in how far sil­ viculture has to take them into account in establishing plantations, especially of exotic tree species. Many of them adapted well to their new surroundings, both in rela­ tion to temperature and rainfall (humidity) (270). For in­ stance Pinus radiata(from California) grows in New Zealand at an average annual temperature of 7° C whereas this is 10° C in its home country. The same applies to pinus hondarensis and p.caribea in Argentina, where they can stand tempera­ tures as low as - 4° C, much lower than in their country of origin (545). 6 The /oil

The soil is that part of the earth's crust in which plants root; it includes the deeper layers that influence the pro­ perties of the rooted area above it. Soils reflect the com­ bined effects of the parent material and the influences un­ der which they have developed. Next to the climate, among these influences the vegetation (the forest) plays an important part. But the relation be­ tween forest-soil and forest is two-sided: the vegetation depends for an important part on the soil, but it also acts upon the soil via the organic debris it produces and the organisms it allows to live under its canopy, particularly micro-organisms. The latter determine for an important part the physical soil properties of the upper layers, which play the main role in the forest (1706, 1297).

6.1 Introduction

The direct influence of the soil on the vegetation is re­ stricted to the rooted layer. For short-living agricultural crops this layer may be only a few decimeters deep, but tree roots often penetrate several meters. How deep not only de­ pends on the species, but also on the watertable. Mango trees (Mangifera indica) in North Bihar (India) are known to form sinker roots up to depths of 4.70 m to continue growth during the dry season (1531); grasses on the Great Plains of the USA reach depths of 1.50 m (374); in Eastern Nebraska (USA) alfalfa (Medicago sativa) draws upon subsoil water down to depths of 30 feet (1340). Since the beginning of the 19th Century, soil chemistry has been restricted to the study of the rooted layer for agricultural crops. Von Liebig (1803 - 1873) framed the 'law of the minimum' which states that plant growth is li­ 108 mited by the element (or simple chemical compound) that occurs in a quantity just sufficient to sustain growth. An­ other approach was made about 1870 in Russia by Dokuchaev, who did not consider the single chemical properties but who studied profiles, basically down to the unweathered rock, in relation to climate, physiography and biotic en­ vironment. This branch of soil science is now called pedo­ logy. More recently pedology has resulted in soil classi­ fications entirely different from those arising from pure­ ly chemical considerations (374). In forestry, the study of both soil chemistry and pedo­ logy is necessary; together they are called 'forest soil science'. This term might suggest that forest soils basic­ ally differ from, e.g., agricultural soils or savanna soils; but this division has become outmoded and it is advisable to consider the study of forest soils a part of general soil science to enable a better integration of forest mana­ gement and general soil assessement. Basically a soil is the product of the substratum and its relief, the climate, the biosphere, and time. On the other hand, the biosphere influences substratum, relief and eco- climate, so that the result is an intricate network of mu­ tually dependent properties. In this network precipitation and temperature play the leading role. The weathering of rocks induces a succession in the vege­ tation, beginning with algae and lichensA in not too dry or too cold regions leading to forest. Mainly through the organic matter (decomposing plant material and animals) the biosphere starts and continues to act on soil formation. The ultimate outcome is a more or less ripe profile with various horizontal layers (called horizons), mainly resul­ ting from the interactions between climate and biosphere. The time required to reach such a stage depends, next to the properties of the bedrock or sediments, on the inten­ sity of these interactions. 109

Relief and topography have an additional influence on this process. On a steep slope erosion may interfere by removing the upper soil layers. A high watertable may pre­ vent the elusion of components normally disappearing to greater depths, or even supply new ones. Catastrophes such as volcanic eruptions and heavy flooding may add new lay­ ers or upset normal soil development by erosion.

6.2 The role of water

Water plays a dual role in the physiology of the plant: it is necessary to maintain the internal chemical processes and it serves as a solvent to transport the plant nutrients. In addition it is the medium through which the substances derived from dead organisms are returned to the soil (1473). And, ultimately, water plays an important part in soil for­ mation, with or without the aid of organic breakdown pro­ ducts. In a natural vegetation this recycling process is more or less closed; in agriculture the crop harvest inter­ rupts it. Where the rainfall is more than sufficient for the growth processes, the surplus evaporates from the soil, forms a high groundwater level, disappears into deeper soil layers, or it runs off superficially. Short dry periods are easily overcome by the water reserve kept in the soil, longer dry periods may be counterbalanced by a high groundwater table, but in other cases the plant has to adapt its physiology to alternate dry and wet periods. With the water, many nutrients disappear to regions out of reach for the plant roots (they may enter other ecosys­ tems, however (173)). Often they accumulate at a certain depth forming enriched horizons which may be brought to the surface by deep ploughing, as has been done on a large scale in the Netherlands (1143, 1542, 688, 1717). The medium water enables agriculture and forestry to raise crops and 'play a primary role in man's dealing with the 110 soil' (1596). However, recently, especially in highly in­ dustrialized countries much attention has been paid to drinking water coming from underground resources. It has been suggested that the relation between forest soil and water supply should be studied, that tree species that use much water, grow quickly and have high yields should not be planted and that preference should be given to open tree stands with less water evaporation (144).

6.3. The physical soil properties

To be suitable for plant growth, a soil must contain air, water and solid particles of various sizes in the right proportions at all times. It must be sufficient open (po­ rous) to permit the right amount of rain or irrigation wa­ ter to enter, but not to such an extent that percolating causes an excessive loss of water and plant nutrients. It must retain moisture to a degree sufficient to supply the plant roots with all the water needed, but not so reten­ tive that undesirable watertables are maintained. It must be reasonable aerated so that all root cells can obtain oxygen at all times, but not to the point that contact be­ tween roots and moist soil particles is practically im­ possible (374). It must be sufficient substantial to pre­ vent trees from toppling over. Soils consist of mineral particles of various size and organic matter derived from plants and animals. The mine­ ral particles larger than 2 mm, such as pieces of rocks and pebbles, are usually excluded from the detailed ana­ lysis, but in soil descriptions they have to be mentioned under the indications 'stoniness1 or 'rockiness'. In the mechanical analysis of the smaller mineral particles as a rule four size classes are distinguished: I = 2.0 - 0.2 mm, II = 0.2 - 0.02 mm, III =0.02 - 0.002 mm, IV = :0.002 mm, called sand, loam, silt and clay, respectively. Their quantities are expressed in percentages. In the Nether­ Ill

lands the fraction 12 mm is called gravel, 2.0 - 0.05 mm is sand, C 0.05 mm is loam, 0.05 - 0.002 is silt, C 0.002 ( = 2 ^um) is lutum (1600 , 70). For plant growth the most important particles are those between 0.5 ^um and 1.0 ^um because there are ions on their surface forming the 'adsorptive complex'. This complex, which includes the finer organic material, is in equilibri­ um with the ions in the soil solution from which the plants take up their nutrients ( 374). The soil particles usually occur as aggregates and, to­ gether with the pores between them, they determine the structure of the soil (1028). Under normal conditions, the pores are partly filles with water, partly with air. Lack of air means lack of oxygen and causes abnormal root deve­ lopment (1706), as apparent from the total root length. Even periodical water-logging can cause severe root morta­ lity, making the tree susceptible to infections (45). Such decreases should not be confused with those due to old age, as has been demonstrated in Finland for 110-year-old spruce (Picea abies) and Scots pine (Pinus sylvestris) (45). The percentage of solid particles is seldom below 26 or over 60, but in exceptionally dry soils the air volume may be over 75% of the total volume and in dry peat it can even reach 84% (1097). Older data from Germany give for beech forest soils a porosity of 57 - 59% ; for Switzer­ land porosities of 65,4% at a depth of 0 to 10 cm to 42.6% at 1 m have been observed (262). Compact, so-called hardpan-layers can impede root pene­ tration (1531); in Main (USA), under spruce-fir stands (Picea and Abies spp.), bulk densities between 1.50 and 1.80, and even up to 2.00 (corresponding with porosities of 44, 32 and 24%, respectively) have shown to be impene­ trable to tree roots (997). In agriculture adequate liming and fertilization improve soil structure by increasing infiltration capacity and the efficient use of water. In forestry, where such measures 112 are as a rule impracticable, natural soil improvement caused by roots, animals, etc., predominates. Already in 1789, long before Darwin's famous publication on this sub­ ject, White remarked that earthworms could greatly promote vegetation growth by loosening the soil (975). More recent research in Germany has shown that these worms can prevent, or at least considerably lessen, the formation of raw humus by loosening the upper soil layers, thus stimulating aera­ tion and root penetration, and by bringing organic matter and organisms to deeper layers, thus promoting mixing of mineral and organic soil material. Both activities increase that of the adsorptive soil complex and decrease leaching (1720). Unfortunately, the study of the subterranean root functions is notoriously difficult and laborious (308). Wood transport, cattle and an excess of visitors can greatly harm the structure of the forest soil, as may be noted during and after rainy periods for highly plastic soils where impressions made by footsteps remain visible after the cause has been removed (1028). Only with cattle are such disturbances important, however. In loamy soils, fire makes the upper layers more compact, in extreme cases even as hard as bricks, thus decreasing porosity. In more sandy soils no substantial changes occur (1297). Where burning is an essential part of agriculture (sometimes also of silviculture), it has been found that when superficial organic horizons are not completely con­ sumed by fire, changes in pore space and infiltration may be too small to be detected (1280) (for further comments see Section 6.7.2).

6.4 Erosion

Erosion is the transport by water, snow, ice or wind of soil particles from their original site to another place. Its intensity depends on the properties of the soil, the climate (mainly the rainfall), the configuration 113

of the land, and the density of the vegetation. It may be due to anthropogenic as well as to natural causes. Erosion is a continual process of surface planation, a normal geological phenomenon which, through the ages, has played a predominant role in the creation of natural land­ scapes (127). Before man 'started tampering with the land­ scape on a large scale' the USA eroded at a rate of 3 cm per 1000 years; from solid and dissolved loads discharged by rivers, the present quantity has been calculated to be twice as much (1280).

6.4.1 Eros ion by water

As long as, during rainfall, the water reaching the soil is absorbed, there is no erosion. But as soon as the drops hitting the soil dislocate soil particles, splash erosion starts and muddy water flowing down through natural ope­ nings (pores) plugs these channels, or, when the topsoil is saturated with water, the water streams over the sur­ face, accumulates in shallow depressions, or moves on,ac­ celerating in speed, carrying with it increasing quanti­ ties of surface soil and thus causing sheet erosion, ulti­ mately the quantity of water, and its speed, may increase to such an extent that deeper soil layers are also attacked: this results in gullies carrying water only during and shortly after heavy rainfall (gully erosion) (374). The run-off water ultimately collects in more or less permanent streamlets, most common in regions with high rain­ fall and on lands with low absorbtion capacity (127). With an increase in volume and velocity, this water may cause rill-erosion in making deep, backward moving incisions in­ to the soil surface, or it may collect in creeks and rivers, often partly filled with water supplied by the subsoil (groundwater from springs). The idea that forests can prevent erosion has to be re­ jected. Even a dense stand on a reasonable pervious soil 114 often cannot prevent sheet erosion. Rivers, especially when streaming fast, can attack their banks and swallow large quantities of soil, even when co­ vered with dense forest. Although the Amazon River streams through untouched forest land, it discharges every second 220 000 m"^ of muddy water into the Atlantic (1417) and the silt has built up a huge delta in the sea. The quantities of soil displaced within its basin (eroded and sedimented again) is enormous. The water-erodibility of a soil depends on the amount of fine and organic material (cementing agents forming large, water-stable aggregates), on its chemical proper­ ties (Ca and Mg cations seem to diminish erodibility), and on the altitude, for example in California it was found that the same type of soil eroded 2.5 times as fast at an altitude of 2200 m than at 600 m (366). That bare soils erode much more than those covered by vegetation is well-known. During strip-mining in the USA, from 1 275 120 ha exploited land, 816 240 needed special treatment in 1965 against further deterioration (1601). From a watershed strip-mined for 6.4% of its surface du­ ring 1957 - 1959, 15.65 tons material eroded per year per hectare, as against only 2.88 tons under comparable un­ disturbed circumstances (1523). In the Wagon Wheel Gap area in Colorado, studied between 1919 and 1926,the watershed area with a compact clayey loa­ my soil discharged only 2.15 kg solid matter per ha per year before clear-cutting;afterwards it increased to 18.8 kg (95). In the erosion-control area in Kisnana(Hungary) the run-off water from loam soils covered by forest contained on avera­ ge 4% silt(with a maximum of 20%),after deforestation rea­ ching 70%(75).In Emmental(Switzerland)two areas were compa­ red,the first for 97% covered with forest,the other for 35%; between 19 42 and 19 52 the washed-down solid material amoun­ ted to 50 and 160 m^ per km^, respectively (233, 237). More recent studies of Swiss areas gave for 1952 conside­ 115 rably higher figures in areas covered for 14% and 29% with forest; building activities were partly blamed for this increase (1128). The character of the vegetation and the litter (the or­ ganic matter on the soil) also play an important role. In New England the moisture retention capacity of a humous layer 1-2" thick showed a water retention capacity of 0.5 to 2.0" in coniferous stands, whereas for layers 3 to 6" thick, it was 1.0 to 2.5" (1576). For a chaparral -covered region in California burning the undergrowth increased erosion almost 30-fold (705). In Australia the coniferous tree plantations, by their dense coverage, gave a much better protection against soil erosion than the native open eucalyptus stands (983). In the Harz mountains (Germany), forest soil covered by litter showed an annual erosion of 4.18 g per m^, whereas the bare forest soil lost 1798.7 g (1653). In addition it was obser­ ved that broadleaved stands forming mull (which strongly glues the soil particles together) eroded considerably less than soils covered with raw humus (667). Road-building may cause heavy erosion in hilly and moun­ tainous areas. The critical angles for banks are between 5 and 10°, when covered with forest between 20 and 30° (for cropfields 1 to 7° I) (822). Thus roads through fo­ rests have to be carefully planned to avoid excessive ero­ sion (1293), especially where wood is extracted (878).Along highways passing through protection forests strips have to be added to the road profiles to catch the soil carried away by rain from the banks (1198). A further control is possible by putting obstacles in the run-off channel, e.g. by covering them with some kind of vegetations as done in Canada by planting Russian thistle (Salsola pestifer) and dense mats of brown grass (Brösum inermus) (172) in gullies and roadside ditches (253). On fine sands in Texas and Oklahama grasses have proved to be better protection a- gainst erosion than trees, while on more compact soils the 116 differences were small or negligible (127). A vegetation cover does not only decrease erosion, it also acts as a silt-catcher. For the taiga in Siberia it was noted that bogs, in which the run-off water settles down, can be very helpful (1101). The preceding examples show the important role of forests in combatting erosion caused by water. It is based on a combination of properties. Firstly, the forest breaks the force of the rain, thus reducing splash erosion and, assis­ ted by the litter, greatly diminishes the danger of silting- up of the upper soil layer and thus maintains the premeabi- lity of the soil and decreases or prevents sheet erosion, gully erosion, and so on (1640). Secondly, less water rea­ ches the forest floor, and it takes much more time to ar­ rive there than is does in the open. Thirdly it diminishes the intensity of rain showers hitting the soil. The total effect is that, as a rule, forests substantial­ ly decrease or even prevent erosion, thus protecting the lower lands against mudstreams and the silting of water basins, whereas water supplies become more regular.

6.4.2 Erosion by solid material

To cause erosion, the acting agent has to move, as does water (see 6.4.1) and wind (see 6.4.3), and also ice, snow and even sometimes the soil. The eroding capacity of glaciers is enormous, but not directly important for forestry. Moving snow, forming avalanches, may be very harmful to the forest and various methods have been devised to combat them, unfortunately not always with success. From the standpoint of the forester they are not very important. The same applies to landslides, but it seems worth while mentioning that they may be caused by the forest itself: when trees become so heavy that the steep soil cannot carry their weight anymore. This also applies to very loose soils, 117

or soils that are able to take up so much water that trees have hardly any grip on them, as is the case with some marls even on almost flat places (53, 1513). Overpopulation of game can accelerate erosion by tramp­ ling and overgrazing (1153).

6.4.3 Erosion by wind

Wind erosion, the displacement of soil particles by air, is limited to locations where the soil surface is exposed. It is a selective process, involving only the loose par­ ticles. These can be moved by suspension in the air, or they are dragged and rolled, or jump along the soil sur­ face (surface creep or drifting). Suspension is, as a rule, possible only for particles below 0.1 mm. A mechanical analysis of dust blown from Texas and Oklahama to Clarinda (Iowa) over a distance of 500 miles contained 97% silt plus clay. Deposited 300 miles away it contained 4% sand or particles over 0.05 mm (374). As a rule wind erosion is a serious problem only in arid and semi-arid regions. Under special circumstances it may also occur in wet areas, if the soil is very loose, or winds are exceptionally strong (e.g. along seacoasts). The condition is always that the original vegetation has been removed in some way, or that the soil is bare by nature. The appearance of vegetation, either by natural processes or by planting, interrupts this process (815).The establish­ ment of shelterbelts can be sufficient if their mutual dis­ tance is less than about ten times their height to prevent the wind reaching the soil at full speed. Trees and forests are good dust-catchers. Investigations in industrial areas in Europe have revealed a reduction of originally 9000 dust particles per litre air to 4000 in open field, to 2000 in the nearby forest. Spruce stands (Picea abies) can catch 30 tons per ha, fir stands (Abies alba) 35 tons and beech (Fagus sylvatica) 68 tons before 118

being 'saturated' (397, 592). Large-scale wind erosion was first studies in the USA; later on it appeared that comparable phenomena are wide­ spread in other regions (388). The role of forestry in combatting this type of soil ero­ sion has always been troublesome because trees have to be planted on places where it is difficult to raise them. To fulfil their protective function, they must branch to the ground, have large crowns, be resistant to wind and drought, deep-rooted and (if possible) provide fuel and timber (554). To illustrate the importance of this type of shelter- belt, some data from various regions are presented below. In North America the early European settlers paid much attention to wind protection, but after the introduction of mechanization the picture changed (81). During the 1930s, when in many areas the topsoil of the cropfields was blown away, wind protection was started again (1288), but at present the area subject to damage by wind is still esti­ mated at 80 million ha (127). In China aeolian sand deserts cover about 97 million ha. Here economically useful trees are planted (1308), notwith­ standing the difficulties in raising and maintaining them, as all work (planting, watering, manuring) has to be done manually. At present, however, it is considered as 'one of the major accomplishments of our time' .(.1343) • In Europe one of the tasks of forestry has always been to assist in protecting arable land against drifting sand. In 1788, France started with the establishment of the well- known Pinus pinaster stands on the dunes of Gascogne (1226). Today they cover some million hectares (more than all other French coniferous plantation together), of which 100 000 ha belong to the state (1040). In Denmark, already in 1780, the farmers were invited to plant trees to prevent sand drifts (1449, 1497). In 1791, Portugal started reforesta­ tion of dunes south of Vieira (261). As far back as 1440, 119

in Holland drifting sands were secured by grasses, mainly Ammophila arenaria, which still today is used for this pur­ pose. Much later (from 1805 on) trees were tried out, but recent research has revealed that success is only possible if the plantations up to 2 km from the sea are started in valleys and are protected by shrubs (756, 589). In the cen­ ter of the Netherlands plantations have been established on drifting sand first secured by other means (134). They have grown satisfactorily, their quality depending on the thickness of the driftsand layer (1651). India has 20.7 million ha deserts and 8.4 million ha alluvial plains to be secured against wind erosion and drif­ ting sands (1474). In establishing plantations one of the most serious problems is how to protect them against goats, as grazing areas for these animals are very scarce (142). Along the Indian coasts Casuarina plantations are created, also serving recreational purposes (1283). This tree, ori­ ginating from Indonesia, now grows practically everywhere near the sea, both in subtropical and tropical regions. In Senegal, where it is called 'le filao', it is also sucess- fully used for securing drifting sand dunes (492). In Israel the tree species known to combat wind erosion are Eucalyptus camaldulensis , poplars (along irrigation canals), Pinus insignis and P. maritima, and Acacia cyano- phyila (as large seedlings) for dune fixation (553). In northern Nigeria, in the Sudan and Sahel regions (bordering the Sahara), the establishment of shelterbelts covering about 10% of the arable land costs some $ 300 per acre, of which 90% has to be spent on fences against goats (1104). In the European part of Russia forest belts have for a long time been created as a protection against wind ero­ sion. Today palissades of grasses are used to shelter sap­ lings and seedlings (1297, 219). In the arid region of Cen­ tral Siberia, extensive protection strips are planted, e.g. the 110 km long and 2 km wide 'Burcharsky sasIon' strip to 120 protect the Buchara oasis against sand blown in from the Kysyl-Kum desert. In 1961 222 000 ha was secured in this way (219).

6.5 Chemical soil properties

Normally plants take up their nutrients (except carbon dioxide, oxygen and some of its nitrogen) in the form of ions from the water around their root tips. The involved processes are very complicated so that even a superficial treatment is impossible within the scope of this book. Only the most important points will be discussed here. One general remark has to be added. Under undisturbed (natural) conditions, the vegetation (the primary forest) has adapted its floristic composition to the given chemi­ cal properties of the soil (1512). Species requiring higher amounts of certain inorganic chemicals will not be able to maintain themselves. Consequently, clear deficiency symp­ toms can be expected solely under more or less 'abnormal' circumstances, such as in plantations. Of course the same applies to physical soil conditions, but there the phenome­ non is less obvious.

6.5.1 Ni trogen

Nitrogen is a constituent of all living cells, where it occurs both in the cytoplasm and the nucleus. Table 4 shows that the amounts vary considerably with the age of the trees, the involved tissues, and the month. In the soil, the quantity of nitrogen of the upper layers indicates, generally speaking, its fertility. Under natu­ ral forests it varies between 0.1 and 0.3% in the upper 15 cm (1706) and it decreases to 0.05 - 0.12% at 100 cm (975). A total amount of 0.2% in the upper layers seems sufficient for the healthy growth of most trees. The annual consumption of a forest is rarely over 40 kg per ha (1706). 121

Table 4 Nitrogen contents of tree leaves and wood, in percentages of dry weight

Origin Species Age in years, Leaves Wood or month

Russia Tilia spp. 2.81 (1297) spruce (Picea spp.) 1. 12 0.07 Populus spp. 0.21

USA Loblolly pine 8 0.95 (1536) (Pinus taeda) 30 1.22 4 0.16 56 0.03

Tropics common range 0.57-0.71 (103) teak (Tectona grandis) 0.92 Liriodendron tuli- pifera 3.01 Murea crassifolia 1.78

Brazil Pinus elliottii 1.06-1.79 (560,93) Araucaria angusti- folia 1.46-1.60 Europe oak (Quereus robur) May 3.7 (1,815) September 2.4 maple (Acer) May 2.3 September 1.8 spruce (Picea abies) May 2.8 September 1.6 dead leaves 1.0

For the podzols in the Netherlands, with 5% organic mat­ ter in the upper 25 cm, a nitrogen content of this matter between 1.6 and 2.0% is considered sufficient for a healthy forest cover. This corresponds with 0.08-0.10% for the en­ tire soil (557). For South Africa a case has been mentioned of a soil un­ der Pinus patula with 27 000 kg decomposing organic matter per ha in which the nitrogen content was 0.98%, in its A horizon 0.20%; whereas another soil belonging to another type contained 103 000 kg with 1.21%, and 0.28% nitrogen in its A horizon (282). But these are exceptions. Tropical soils normally contain little nitrogen, though rather high values may also occur (Ghana; see Table 5). 122

Table 5 Nitrogen contents of some tropical soils

Location Soil type, hoiizon Altitude Nitrogen % or vegetation

El Salvador (818) 2200 m 0.03 1500-1800 m 0.05 pine forest 800-1700 m 0.04 5- 500 m 0.08 Amazon region A horizon 0.04-0.23 (819) B horizon traces-0.07

Ghana (16) ochrosol 5 cm 0.454 160 cm 0.057 oxysol 7,5 cm 0. 189 165 cm 0.032

The Amazon data were confirmed during a UN-FAO soil survey which also gave only traces and very low percentages (1453).

In the tropics and subtropics the nitrogen amounts are often higher during the dry season, probably due to the eva­ poration of ascending capillary water (463,1693). A similar phenomenon was observed in the Netherlands and Germany, where after dry winter periods the nitrogen quantities per ha were up to 90 kg higher than after wet winters (1197, 497). Nitrogen cannot be taken up directly from the air but so­ lely (in the form of nitrates, or better NO^) from the soil (in rare cases as NHj[ ) . The nitrogen compounds are provi­ ded by several sources. Small quantities are formed by lightning. Burning of organic matter during forest fires may be important in some places: the same applies to com­ bustion of fuel, so that the concentration of NC>2 and other nitrate compounds above the ocean is lower than above land (28). High amounts cause air pollution: among 214 million tons of foreign matter recorded during an inventory in the USA in 1968, 1.2 million consisted of nitrogen oxides (less than 1%) (356). From the pollution quantities measured du­ ring 1966/1967 it was calculated that the amounts of ammo­ nia and nitrate ions ran parallel with those of the solid particles, amounting to 102 ^ug/m3 air, 45 ^ug, 40 ^ug and 123

21 ^ugr above urban, suburban, agricultural, and more re­ mote areas, respectively. These percentages decreased where industry was absent (970). The annual quantities of nitrogen in the soil supplied by the atmosphere were esti­ mated for Central Europe at 7 - 14 kg per hectare (1081), for France at 11 - 14 kg (1225), for North America at 6 - 8 kg (975), for the Netherlands at 6 kg (717) and for Eng­ land at 6.65 - 8.80 kg (257). Much larger are the quantities of nitrogen supplied by the action of soil bacteria, root bacteria and mycorrhiza. Among the bacteria, Azotobacter is able to fix nitrogen from the air in an aerobic environment, Clostridium in anae­ robic surroundings. The first needs a slightly alkaline soil with a minimum pH of 6. Its optimum activity is at 20° c (149 6). Under favourable circumstances it produces 28 - 57 kg nitrogen per year per ha (374) which, after the death of the organisms, becomes available to the plants. The root bacteria (Rhizobia spp.) live in nodules in or on the roots of many plants, especially of Leguminosae. The importance of this plant group is apparent from the fact that sometimes 30-40% of trees in tropical forests (Amazon Region) belong to this family (652). They produce much more nitrate than they need themselves so that, after the death of the roots, they can also supply other plant species. The production by Leguminosae may be considerable: herbaceous species such as clover and lucerne give 110-220 kg per year per ha (1496). Plants from other families are known to produce comparable quantities: Alnus spp. 62 - 220 kg, Casuarina equisetifolia 60 kg, Podocarpus (no quantitative data) (1496). Alnus has a wide range because under favourable conditions no bacterial root nodules are formed (696). Mycorrhiza are fungi living in symbiosis with trees and other plants. They form a mycellium cover around and partly in the rootlets and are very useful to the host, not only providing it, after dying with nitrogen (perhaps taken up 124 from the air) and other nutrients (1062, 152), but probab­ ly also in stimulating the activity of nitrogen-fixing bacteria as was found for pinus radiata (1281). The success of pine species and other pioneer conifers used in affores­ tations is due, besides their modest water and nutrient re­ quirements (1123), to these fungal activities (613). On good soils, with better decomposition of organic matter, the influence of mycorrhiza tends to disappear.

6.5.2 Phosphates

Plants take up phosphorus (usually expressed in quanti­ ties P2O5) from the soil. It originates from weathering mineral particles (mainly apatite), from decomposing orga­ nic matter, and in practically negligible quantities from the air (for Berlin-Dahlem estimated at 0.30 kg per ha an­ nually (866), for England at 0.35 kg (257)).It has been, and still is, a point of discussion among soil scientists, in how far the phosphate in the mineral particles is avail­ able, or can be made available for plant growth. At present the tendency is not to look for P2O5 solely among the ions adsorbed to the small soil particles (mainly from decompo­ sing organic matter and fertilizers) (1710, 931). Fungal mycelium exuding acids may contribute in opening up the mineral reserve (837). The amount of P2O5 in forest soils varies considerably.Re­ gistered amounts per hectare in the 0-30 cm top layer are in pine forest (Pinus sylvestris) 16.5 kg (Germany) to 164 kg (Poland), in spruce forest (Picea abies) 18.9 kg (Sweden) to 92 kg (Germany) (1630). Recent American inves­ tigations on Pinus contorta mention limits of 2.2 and 5.0 g per m^ for the A horizon and 3.8 g for the litter which is quite low (1100). In Australia, the lowest levels in the plants to avoid deficiencies were found to be 24, 29 and 66 ppm for Pinus elliottii , P. taeda and P. radiata, respectively (738). 125

For seedlings ground rock phosphate proved to be less ef­ fective than soluble phosphates, unless thoroughly mixed with the topsoil near the roots (123). Loss of P2°5 in the forest by leaching is small, not so much because under natural vegetation it is gradually re­ turned from the subsurface layer to the surface layer (196), but mainly because most of it is locked-up in the flora and fauna, as has been demonstrated for the thin layer of organic matter (125) in tropical South America. In keeping it there as a reserve, the pH seems to play an important role (124). The complexity of the situation is accentuated by the necessity of minute quantities of phosphates, besides mo­ lybdenum and vanadium, for microbiological nitrogen fixa­ tion (1228). So, in the tropics, nitrogen deficiency can sometimes be prevented by phosphate fertilization (463), for which diammonium phosphate serves best (633). This is quite in line with the observation that in Central Europe low phosphate and low nitrogen concentrations go together (887). Plants need phosphate for cell division so that it is concentrated near the most actively growing parts such as root tips and shoots (374). Thus deficiency results in de­ generation of buds, causing abnormal growth. In addition, a bluish red, purplish red or violet colour develops in the leaves. Elimination of the deficiency leads to an increase in carbon dioxide assimilation, in better uptake of other nutrients (especially nitrogen), and in better growth of root hairs (1531). A level below 0.10 % P in the leaves cau­ ses deficiency symptoms, 0.14 - 0.16 is sufficient (493). In the tropics, 0.09 - 0.29 % is common, but teak (Tectona grandis) may contain over 0.5 % in its leaves (103). As with nitrogen, at the end of the growing season foliar phosphate decreases due to migration to stem and branches (975). 126

6.5.3 Potassium

The main mineral sources of potassium in soils are ortho- clase, microcline, muscovite, biotite and secondary alumi­ nium silicates. As a rule the element is plentiful in the upper soil layers (0.15 to 4.0 %); quantities usually in­ crease with depth (975). In addition, considerable quantities may be supplied by rainwater: in Ghana, during 1959, it was estimated that for some stands 17.5 kg was added per ha directly to the soil by rain, and 221 kg with water dripping from the crowns and running down along tree boles, all supplied by dust storms during the dry months coming from the Sahara (1162). For Europe these quantities have been estimated at 2.05 - 11.6 kg per year for Germany, at 3 kg for Sweden, and for England at 2.84 - 5.78 kg (together with the rain and drip­ pings from the crowns and the tree boles this amount be­ comes 52.0 kg) (866, 257). As plants are able to absorb mi­ neral nutrients with their leaves (865) ( in Germany spray­ ing spruce nurseries showed good results (1036)), it can be assumed that during rainy periods part of the dust is taken up immediately. This phenomenon could have its prac­ tical consequences: in Finland every year 100 000 ha is fer­ tilized from aeroplanes, in Sweden up till recently 300 000 ha, and this method has been applied for 70% of all ferti­ lized forests in Norway (1338, 598, 7601^ As with phosphates, potassium occurs in the soil in three forms: solved, adsorbed on clay minerals and humus particles» and in the minerals from which it is released by weathering (the main reserve). An adequate characterization requires an evaluation of all these forms (1710), as done for five- month-old Pinus radiata in America. Here the conclusion was that solution or adsorbtion 'was generally a function of K added', while for the mineral particles the uptake is 'un- doubtly related to differences in lattice structure' of the minerals (1639). In general, from the more or less normal 127 quantity of 2 % potassium, one fifth is readily avail­ able (374). In natural forest soils, the exchangeable potassium (K2O) ranges from 50 to 200 ppm (1706). More detailed data are known from Finland (top layer 59 - 94 ppm in the dry soil) (l),from the USA under red pine (Pinus resionosa) 78 kg per ha (1707), from Germany (poor soils less than 40 ppm, medium soils 40 - 100 ppm, good soils 100 - 200 ppm) (1555). For tropical soils the data range from 20 to 200 ppm (463). In the long run, probably silting, especially on sandy soils, will contribute to K nutrition (1511). Scots pine needles collected in Russia on sandy desert soil con­ tained 0.02 % potassium, on better soils 0.53 - 0.60 % (1297). In Ghana, litter from 40-year-old secondary forest showed in the wood 0.05 % potassium, in the roots 0.35 % and in the trash 0.76 %; from coastal thickets the potassium contents were for wood 0.39 % and for leave litter 1.41 %. In the former Belgian Congo an 18-year-old secon­ dary forest produced litter with in the woody parts 0.64 % and in the leaves 1.24 % (1163). Potassium occurs in all living plant cells, in quantities up to 25 % of the ash. The highest amounts are found in the growing parts, such as buds, yound leaves and new roots, where the element plays a regulating or catalytic role in growth. Deficiencies cause a decrease in carbohydrate for­ mation. In association with phosphorus, potassium influen­ ces nitrogen utilization in the build-up of amino acides and amides, hence shortage results in a decrease of protein production (915). When present in excess in the soil, pot­ assium may accumulate in the plant, though never to a dama­ ging level in trees (24). Shortage symptoms have been observed on Dutch and German soils in Scots pine stands (Pinus sylvestris) where needle tips turned yellow at concentrations below 0.30 to 0.35 % (1777, 556), or even below 0.55 % (855). In Northern Ame­ rica, soils classified as being subject to potassium defi­ ciency had always been disturbed by man (excessive use of marginal forest soils or burning); when dry, their ex­ changeable potassium content ranged from 20 to 60 ppm for the top 18 cm, and from 10 to 20 ppm for the next 10 to 30 cm (1511). In Europe, tree stands on eluted sandy soils and on drained peatland seem to be especially vulnerable (1541). 128

6.5.4 Ca Ici um

In the soil, calcium occurs in many minerals, among which calcium carbonates (CaCOß or CafHCO-j^) are the most fre­ quent and also the most important because they are relative­ ly well soluble and readily put Ca cations at the disposal of plants. A drawback of this solubility is, however, that these carbonates are easily transported downwards, so that deeper soil layers may contain more of them than the sur­ face layers, as demonstrated by the calcium percentages in the horizons of three podzol profiles with 1.7 - 0.17 - 0.07 % in the A2, 2.2 - 0.78 - -0.19 in the B, and 5.9 - 0.97 - 0.25 in the C horizon (1383) Accumulation of organic debris can reverse this phenome­ non: in such cases the A horizon shows more calcium than the B horizon (758). True calcium accumulations are not rare, but they occur solely in dry regions and are the re­ sult of periodically ascending groundwater: red desert soils in South America have a high calcium content only in the upper 25 cm; under grassland high concentrations may occur as deep as 100 cm or more (1204). Calcium accumulates in the leaves during the growing season, (contrary to ni­ trates, phosphates and potassium), and its rate of disappea­ rance during decomposition of the litter is lower than that of phosphates and potassium, and practically equals that of nitrogen (320). . Most of the calcium disappearing from the upper soil layers reaches the groundwater and ultimately the rivers. So the calcium contents of the rivers give a rough estimate of the quantities involved in the soils: the Blue Nile con­ tains 6 mg per liter, the White Nile 5 mg (463). Direct measurements in soils gave for New Zealand annual losses of 15 kg Ca per ha (1194); for a highly permeable podzol soil in New Hampshire (USA) the inflow amounted to 1.5 kg per ha per year and the outflow by seepage to 6.1 kg (173); for forest soils in Austria lysimeter measurements indicated 129

annual losses of 33.3 kg (1366). Among the cations Ca++, 4- Mg , K and Na , measured in the outflow of watersheds in the Frazer Experimental Forest (Rocky Mountains,USA) Ca++ contents showed the highest amounts. How much this is may be judged from the remark that 'if net annual losses of ma­ terial in drainage water are calculated as weathering rate of CaCC>3, geological erosion would remove a foot of mate­ rial in 78 000 to 195 000 years' (1477). A high calcium carbonate percentage of the soil furthers decomposition of organic matter and thus speeds up the rate of turn-over of all inorganic components. The quantities of calcium in the nutrient cycle can be estimated from litter analyses. For deciduous Terminalia-Shorea plantations near Varnasi (India) it has been calculated that the annual calcium turn-over is 184 kg per ha, for teak plantations near Dehra Dun 131 kg. Comparable data from New Zealand are 46 - 86 kg, from England (for Quercus petraea) 14 - 15 kg, which is exceptionally low (1416). Other European data indicate re­ turns of 34 to 67 kg by falling leaves (975). Healthy Scots pine needles in Finland contain 0.15 to 0.18 % calcium, birch leaves 0.63 to 0.91 % (1295). Pinus elliottii needles in Florida contain about 0.42 % calcium (195), those in Brazil between 0.13 and 0.50 % (average 0.25 %) ( 560). Relatively high percentages are known from the tropics: teak leaves 0.81 % (103). The highest occur in arid areas: Salvadora persica up to 7.05 % (1401). Calcium is a constituent of the middle lamella and assists in making the cells more selective in their uptake and re­ lease of chemicals. As, in general, rapidly growing root tips show high calcium contents, the element must play an important role in cell division (374). Furthermore it is used to remove superfluous organic matter by storing it as calcium oxalate in special cells. Under natural circumstances calcium deficiency symptoms in plants are rare. A shortage may cause chlorosis and sub­ sequent dropping of leaves (279), but data from the USA in­ dicate that this happens, in general, only on soils with less than 25 mg Ca per kg dry soil (49 4). Matters are not so simple, however, as appears at first sight, as demonstrated by a form of chlorosis observed in 130

Germany (1777, 1776) and Turkey (887). There a surplus of calcium in the soil causes the so-called induced chloro­ sis. It is, most probably, due to inactivation of iron, or iron and magnesium, in an environment rich in calcium. As not all tree species react in the same way, it is possible to speak of a certain degree of calcium tolerance. In Ame­ rica pinus ponderosa and Scots pine have been found to be highly tolerant (1502). Calcium deficiency levels of the soil can be indicated by the calcium contents of the leaves. For Germany a limit has been estimated at 0.15 to 0.20 % of the dry weight (854), or somewhat higher at 0.24 % (1555); for eucalypts in Brazil levels at 0.16 and 0.32 % have been observed (591).

6.5.5 Magnesium

Magnesium occurs in many minerals, such as the slowly weathering serpentine, hornblende, augite and hyperstene, and the more quickly decomposing olivine and biotite (1097). The highest quantities are in dolomite, a sedimentary rock chiefly consisting of calcium and magnesium carbonate. As this dolomite weathers more slowly than limestone, the a- mount of magnesium available for plants is usually consider­ ably lower than that of calcium (374): sometimes soils for­ med on a substrate consisting for one thi-rd of magnesium minerals contain only traces of it (1002). It has often been alleged that the Ca++: Mg++ ratio in the soil is more important than the actual magnesium con­ tent. In forests soils it commonly ranges between 3 : 1 and 5:1, but deficiencies seem to be independent of this ratio: in pot trials plants grew well on a ratio 30 : 1 (1706, 915). It seems that in coarse soils the amount of easily so­ luble magnesium has to be higher than in other soils for plant growth: less than 112.5 kg per ha made suppletion 131

necessary (24). In nurseries, Pinus banksiana needed for a healthy growth 63 kg, P. resinosa 79 kg, and P. glauca 93 kg (1637) per ha. For 47-year-old plantations of Picea abies, Scots pine, oak and Castanea sativa in England, magnesium percentages in dry material a- mounted to 0.06 - 0.02 - 0.08 - 0.09 % in leaves and branches, to 0.019 - 0.020 - 0.022 - 0.020 % in the boles, and to 0.07 - 0.07 - 0.04 - 0.17 % in the litter (1192). These data corroborate the general trend that stems con­ tain less inorganic matter than other plant parts. The chlorophyll molecule contains one magnesium atom, so that green plants cannot exist without this element. In ad­ dition it plays a role in the uptake of phosphorus. The highest concentrations are in growing tissues. Deficiencies result in yellow or other brilliant colours in the foliage. The minimum percentages vary. For Picea abies 0.07 to 0.16 % of the dry weight seems to be normal, for Pinus radiata 0.08 %, for Scots pine 0.115 to 0.176 %, and for Eucalyptus alba 0.27 to 0.52 %. Deficiency appears between 0.02 and 0.11 % (915). German data tend to be lower: Scots pine 0.02 to 0.038 %, Picea abies 0.02 to 0.03 %, Pinus strobus 0.03 %, larch 0.02 to 0.06 % (1777). Growth factors may be coupled: in Austria trees on dolo­ mite soils have been found to suffer from potassium defi­ ciency caused by high magnesium contents in the soil, as proved by fertilization stimulating nitrogen and potassium intake (852).

6.5.6 Sulphur

Though sulphur normally occurs only in small quantities in the soil (average perhaps 0.15 %, mainly as sulphates (374)) and is rarely included in soil analyses, a separate treatment seems justified in connection with the role it Plays in air and soil pollution. Under normal circumstances the sulphur in the soil originates from the minerals pyrite and gypsum. A limestone soil in the Netherlands contained 0.05 % SO3, a podzol 0.36 % in the upper layer, and 0.06 and 0.13 % in the leached parts of the A horizon (758). Dried-out red and yellow podzolic soils in 132

Australia contained 125 mg S per kg, krasnozem soils 1100 mg (1712). The saline swamp soils under mangrove forest (mainly consisting of Rhizophora and Avicennia spp.) contain abnormally high quantities

of SO^; in west Africa values for sulphur in dried samples amounted to 1667 and 1760 mg per kg (670).

In the plant, sulphur is a constituent of proteins. With dead leaves it returns to the soil where it is easily leach­ ed. For the Amazon Region it has been estimated that per ha in this way annually 5.5 kg SO2^ is carried away, assumed- ly totally replaced by the atmosphere. In Sweden an annual input of 5.6 kg S per ha is considered normal (1163).

S02 and H2S, occuring in the atmosphere, may especially in highly industrialized regions add considerable amounts of sulphur to the soil. Such quantities can be as high as 6 to 30 kg per year per ha, with maxima exceeding 180 kg (975). For less industrialized regions as for example Ire­ land these amounts are much lower; in Pinus contorta stands 3.5 kg per ha (1175). Deficiencies of sulphur in trees are unknown, but lower limits have been established for the leaves: picea abies 0.13 %, Scots pine 0.15 %, Betula verrucosa 0.21 % and Eucalyptus alba 0.21 % (915).

6.5.7 Other elements

All other elements present in the soil are taken up in only very small quantities, even those -us-ually present in abundance (such as iron). This group contains iron, manga­ nese, zinc, copper, boron, molybdenum and chlorine. Their physiologic functions are only partly known. Deficiencies can often be cured by fertilizing, either in the normal way or by spraying, or sometimes even by in­ jections or nails driven into the stem as done for orchard trees suffering from zinc or iron shortage (1383). Iron, though no constituent of chlorophyll, is essential for its formation. 133

Manganese plays a role in the oxidation-reduction balan­ ce of the plant, especially in connection with iron and nitrogen metabolism. Jack pine (Pinus banksiana)seems to be highly sensitive to the ratio between manganese and iron in the soil: the seedlings show chlorosis when Fe/Mn is be­ low 2 (890). zinc is needed in some enzyme systems of plants. Copper activates a group of oxidizing enzymes and is a constituent of certain proteins. Boron has a still obscure function, but lack of its tends to increase the loss of phosphorus from plant roots. Defi­ ciency has been shown for beet plants causing heartrot (921). Molybdenum seems to take part in the nitrogen metabolism and in nitrogen fixing by bacteria. chlorine has some function, but it is not exactly known which (374). In Australia deficiency has been observed on sandy soils far from the sea (1196), but for most plants sodium chloride is highly poisonous in quantities over 0.2 % in the soil. An exception are the salt-tolerant trees of the mangrove forests, with 2.91 - 5.11 % NaCl in the soil (1306). Soil analyses in the USA have shown that the minimum quantities for Pinns resinosa plantations are 6.1 kg per ha for Mn, 1.6 kg for Zn, 0.8 kg for Cu, 1.3 kg for Bo and 0.4 kg for Mo (1707). It has been denied that, under natural conditions, défi­ ciences in these elements can occur because natural plant communities must consist of species and genotypes adapted to the soil (1512). Whether this is true may be doubted, but certainly deficiencies become more apparent in plan­ tations »especially those of exotics.

6.5.S Organic matter

When the aerial parts of a plant have fulfilled their task they drop to the soil surface where they form, together 134 with the refuse of other organisms, a layer of litter. Under the influence of water, air, bacteria and fungi this litter gradually decays and the resulting products collect in the upper mineral soil to form humus. When this process proceeds rapidly, the result is a mild humus or mull; if it goes slowly, large quantities of organic matter become involved, many plant parts remain easily recognizable, and acid humus or mor results. Mull and mor differ in various respects. In mull the li­ beration of ammonia proceeds more rapidly than in mor, in mull bacteria and Actinomycetes are consistently more nume­ rous, and fungi predominate in mor (1532, 1455). Calcium carbonate in the A-^ horizon gives rise to mull (1085). Sam­ ples from 40 locations in the Cascade Mountains, USA, showed that neither the thickness, nor the weight of litter accu­ mulations on the forest floor are significantly associated with elevation, aspect, slope or topographic position (1736). But for the Harz Mountains, Germany, under 120-year-old beech forest a northern slope had 4 cm of litter and a 20 cm thick top layer infiltrated with humus whereas on the southern slope they were only 1 and 2 cm, respectively (1731). In all cases the forest type plays an important role, and as this type greatly depends on elevation, this factor indirectly has a great influence. Ultimately the organic matter is broken down into soluble inorganic compounds so that it becomes -available again for the vegetation. In addition it plays an important part in the aeration and water retention of the soil and in the binding of ions (555, 1794). The degree of decomposition of the organic matter can be expressed as the ratio of carbon and nitrogen indicating that between carbohydrates and proteins (the C/N quotient): the lower it is, the more the decomposition process has ad­ vanced. A value between 15 and 20 indicates mineralization (202): for alfalfa it is 13, for sweet clover 16 (374), for fresh manure with straw 25. For agricultural purposes 15 135 has to be preferred (1346). For Dutch agricultural soils it is supposed that annually 1.5 to 2.0 % of the stored organic matter is mineralized (847). For freshly fallen forest litter C/N is very high: some data from the USA give 147 for loblolly pine(Pinus taeda) , 139 for red maple (Acer rubrum), relatively low are 65 for ash (Fraxinus) and 72 for sour wood (Oxydendrum arbore um) (293). In the Netherlands, fresh larch needles, which were very resistant and contained 0.75 - 1.30 % N, decomposed very slowly (747). The rate of mineralization is highest in the tropics. In forest soils in the Congo 51 % of the nitrogen in the fresh litter had mineralized after 10 weeks, 61 % of the phosphorus, 93 % of the potassium, 50 % of the calcium, and 82 % of the magnesium (1163). In Kade (Ghana) a 40- year-old secondary forest dropping its leaves throughout the year had a decomposition rate of 1.3 % per day (1162). A very particular case is the mangrove forest. Data from Africa indicate that for the mineralization of the sulphur in its litter more oxygen is needed than is normally pre­ sent (670), so that decaying wood may become impregnated with oxidizable sulphur (621). The amount of litter on the forest floor is often con­ siderable. Recent data give per hectare taiga forest 30 000 to 45 000 kg, for broadleaved temperate forest 15 000 kg, for subtropical forest 10 000 kg and for tropi­ cal forest 2 000 kg (1320). Special circumstances may cause large deviations from these averages (see also 6.5.1). For tropical regions ex­ cessive accumulations of organic matter can be caused by stagnant groundwater very close to the soil surface and very poor in oxygen. In the waterlogged swamps of Surinam these 'peat' layers may be 2.5 m thick, in the dakama sa­ vanna forest (Dimorphandra conjugata)o£ the same region, they usually range between 40 and 60 cm but also here cases with 2.5 m (mainly dead leaves) are known (430, 944). 136

Such peat formations also occur in other savanna forests (943). Less excessive, though still quite abnormal for tropical regions, are the 10-cm thick layers on white sand in the musununga forest ( a kind of savanna forest) along the Atlantic coast of Brazil (658). These layers are probably due to an extreme poorness of the sand inter­ fering with the microbiological activities in the soil (758). Comparable cases occur in the subtropical part of Brazil, where plantations of Pinus elliottii form litter layers, while the surrounding natural forest and eucalypt stands have an almost bare floor. Here the explanation will be that the pine needles are so resistant to decom­ position by micro-organisms that they accumulate and form mor (612, 1211).

6.6 Classification of soils and soil mapping

A soil survey is based on soil descriptions classified on their morphology and (when possible, which is not alway so (1600)) on their genesis. This can be done in a purely scientific way, or in combination with practical use for agricultural purposes (fertility, tillage possibilities, drainage, etc.) (791). Soil descriptions are, as a rule, made on soil profiles: vertical sections extending from the surface to the unal­ tered parent rock, or at least including-41xe deepest roots The soil profile is a two-dimensional vertical cut in the top layers of the soil, by which the changes in horizontal direction are only weakly recognized and consequently can be described. Recently the American Soil Conservation Ser vice has accepted the property 'pedon' (126) as the smal- lest-tri-dimensional-volume that can be called 'soil' and the concept of 'polypedon' as a group of contiguous pedons (762). From a number of such descriptions a soil classifica­ tion can be drawn up. Again it may be purely scientific, 137

or it may be focussed on pratical purpose, or a balance between both has to be found (791). So, during soil sur­ veys for forestry purposes, special attention can be paid to features of interest to tree growing: in Australia the results of P2O5 data had to be taken into account as they indicated the suitability of the soil for planting exotic pine species (154). On the other hand in Belgium, soil sur­ veys serving the establishment of orchards appeared to be also useful for forestry (1546), and in Germany it was re­ marked that soil survey organizations should provide a uni­ form classification (106) in co-operation with a forestry specialist (791). The ultimate result has to be a soil suitability map in­ dicating management possibilities (positive and negative, limitations in use e.g. in connection with erosion, etc.) and yield predications (site classes) (374). An example of a suitability classification is that prepared by the Insti­ tute for Soil Mapping in the Netherlands (1625). It also presents classes for broadleaved and conifer stands suiting the Dutch climate (938). The maps are indispensable for fo­ rest management, though their value depends on the 'calibre of the underlying knowledge gained from studies in soil - forest relationship'(1300). One special case should he men­ tioned here: a study on Dutch peat soils has indicated that on the better ones poplar, ash and willow can be rais­ ed successfully (936). So it is obvious that the Dutch do their best to further the use of soil maps (564, 1140, 937). In the next chapter the relation between soils and yield of forest produce will be considered in more detail.

6.7 Manipulating the forest soil

Since the middle of the last century, when the tree stands were gradually more intensively managed, it has been observ­ ed that, during their life cycle, forests can change their habitat, as a rule (though not always) to the detriment of 138 their production capacity. Even when calamities due to air pollution and neglect are not considered. This is main­ ly due to direct or indirect human activities. Such changes concern the organic substances in and on the forest floor, the physical properties of the soil (its water household and erosion), and its chemical properties determining the available quantities of nutrients and the possible improve­ ment by tillage or fertilization.

6.7.1 Removal of litter

For a long time (756)»forest litter has been used as a bedding for stall-fed cattle and horses, or as a fertilizer in agriculture and horticulture. Its removal from the fo­ rest always means an interruption of the nutrient cycle harmful to tree growth, especially on sandy soils (1541). In the Netherlands it has been observed that when the forest litter under Scots pine (Pinus sylvestris) was re­ moved, afforestations on podzols decreased annual wood growth by about 2 m3 per hectare (558). The ensuing growth disturbance can, in new plantations, often be cured by ni­ trate fertilization, or by using green fertilizers such as Sarothamnus, Lupinus or alder (Alnus), together with appro­ priate tillage (559), though in Germany it was found to be only a short-term solution (1719). A rather exceptional case has been not-ed. in New Zealand: it was caused by an overpopulation of imported game and characterized by 'a steady reduction in the depth of fo­ rest litter on all areas frequented by hoofed animals 1(610).

6.7.2 Burning

Burning transforms organic matter into ashes. During this process nitrogen volatilizes, the quantity of exchangeable cations shows a substantial increase, and the pH rises, which can be very beneficial, especially in very acid 139 soils (1163 , 1538). In the subtropics and tropics, manual or mechanical clearing, dragging, and piling of material to be burned, disturb or harden the topsoil in some places. These ef­ fects can be avoided by using crushers (1752) spreading the material to be burned over the whole area. Experiments on various soil types in Missouri (USA) have shown that annually repeated burning reduces the infiltra­ tion capacity by an average of 38 % after 5 to 6 years (975). In western Oregon (USA), on severely burned soil patches, the aggregation of the clay plus silt fractions in the 5 cm topsoil decreased by 20 % compared with unburn- ed soil (374). Nevertheless, an occasional wildfire can be useful: a biologist has found that, in some national parks in the USA, a fire every ten years restores the natural balance when disturbed by too many wood beetles (1567). Controlled forest fires are allowed only where their be­ neficial effects outweigh their detrimental effects or pos­ sible dangers (66). They may prevent natural reforestation of open places needed as feeding grounds for wild animals, preventing migration of game (1439). Already in 1890 it was suggested in the USA that control­ led fire fits in the silviculture of longleaf pine (Pi nus palustris) to combat brown spot needle disease and to re­ duce dangerous litter accumulations. It could not be prac­ tised on a large scale, however, until tractor ploughs be­ came available. Afterwards, during the decade 1950 - 1960, an average of 250 000 acres was ploughed annually in the national forests of the Coastal Plain, both along proper­ ty borders and on crosslines, to prevent backfires and to control break-overs. If weather conditions became unfavour­ able it was even possible to plough the whole endangered area (1331). To keep the fire under control, it should be applied du­ ring the cold season, when the upper litter layer is dry 140 but deeper litter layers are still moist, and when winds are steady. Backfires (forcing the fire to spread against the wind) is the most common technique; strip,spot or flank firing may also be appropriate (302). Investigations in northern California have shown that burning reduces the total nitrogen content of the soil, but not to a serious degree (from 451 to 139 kg per hec­ tare)(816). In northern Arizona the ratio bacteria/fungi was found to be higher in burned soils than in unburned soils (512), due to the increase in pH. From literature and a symposium in Charleston (South Carolina) it can be concluded that controlled burning hard­ ly influences the physical properties of the mineral soil (241) (see also 6.3), nor did it affect nitrogen minerali­ zation. A few indications pointed to an adverse effect on the qualitative and quantitative composition of the fungal and bacterial flora (770) but, on the other hand, under loblolly pine (Pinus taeda) increases in nitrogen fixation could be associated with annual burning (771). Other inves­ tigations have shown no significant changes in phosphate and potassium in the upper 10 cm soil layer, increases in calcium and magnesium in the upper 5 cm but not at depths of 5 to 10 cm (1682). From a review of the 19 40 - 1970 literature for the sou­ thern part of the USA on the effect of prescribed, usually biennial burning there was no indication—of a decrease in soil productivity (1508). Plantations of longleaf pine (Pinus palustris) in Alabama (USA) benefitted from burning during the first two years after their establishment (521). In Finland, burning has been recommended before planting Scots pine (Pinus sylves­ tris) (1633), while pine and spruce (picea abies) seedlings grew better on soil patches burned 3 to 5 years before ger­ mination (1608). 141

6.8 Forest soils and water

6.8.1 The supply of water

For a long time, in Europe, foresters have regarded water solely as a factor causing erosion, landslides and inunda­ tions. From this starting-point a begin was made in France, between 1825 and 1830, with the reforestation of denuded and eroded mountain slopes in the Alps (491). Mostly, tree planting has to be complemented by securing the soil, propping-up slopes, and breaking the force of running water (torrent control) (1246). This work has steadily been rationalized; at present prefabricated mate­ rials (synthetics, reinforced concrete, prestressed con­ crete, and steel) are used in the control of avalanches (863). In Lichtenstein (east of Switzerland) such measures have even been integrated in landscaping to safeguard both agricultural production and recreation (208). At present, emphasis has shifted to the need for more household and industrial water for a growing population, whereby a good management of watersheds has become most significant (981). This compels today's forestry to look for the most efficient belance between annual and seasonal water supply and forest, its composition, its density, its maintenance and the relation between évapotranspiration and erosion (753). As can be seen from the following data no general rules can be given. In a semi-arid region in Colorado (USA), with an average annual rainfall of 61.2 cm, the virgin forest cover permit­ ted a run-off of 25.7 cm per year. After selective cutting it increased to 33.7 cm, a rise of 8 cm, sufficient to add one hectare to every four hectares irrigated land (127). In humid regions, increases in streamflow mostly do not occur before 20 % of the forest basal area in the stands has been cut; up to that point a faster growth compensates the ensuing surplus of water (381). 142

In Denmark and Finland, trees distinctly influence the groundwater table (depending on their root system; flat or deep reaching) which may cause drainage problems for peatland that is forced to store more water (699, 644). If water supplies have to be increased, a change to species with a longer dormant period (lower transpiration) may be appropriate (552).

6.8.2 Landuse and water supply

In watershed and catchment areas it is often difficult to decide on the treatment of slopes: leave them to nature, or use them for production? The result are often unpredict­ able. In Davis County (USA) the years 1923 to 1930 were characterized by destructive floods caused by overgrazing. The establishment of contour trenches and the prohibition of grazing caused the natural vegetation to reappear and floods stopped, though no changes in the annual water yields could be recorded (309). In the Abdolfskloof catchment area in South Africa, high floods increased during winters following 'veld' burning, but had already returned to nor­ mal one year afterwards (77). In an overgrazed area in East Africa, trampling caused the appearance of a xeromor- phic vegetation, notwithstanding a reasonably distributed annual rainfall of 75 cm (1222). On the other hand, a forest cover maintained to stabilize the soil may levy a heavy toll on water supplies (1049). In East Afrika,a change from a bambu cover to a pine plantation first showed an increase in streamflow of 13 %, but it di­ minished with 7% when the trees were 7 years old(1223). In South Africa, pinus radiata plantations, on catchment a- reas previously covered by scrub, caused losses in stream- flow of 26 to 35 % (78). A comparable phenomenon is known from South Africa (76) and Utah (1513) , where the establish­ ment of a riparian vegetation along creeks and irrigation channels caused considerable losses in water by evapotrans- 143

piration. In the South African Republic, the catchment areas to be conserved cover about 4 % of the national territory. They yield 85 % of the water discharged from the mountains so that careful management is highly important (1699). In one of these areas a removal of 33 % of the trees from a 16- year-old Pinus radiata stand by thinning increased the out­ flow by 50 % (1780). The conclusion is that as a rule a forest cover is fa­ vourable, but that each case has to be judged on its own merits.

6.8.3 Irrigation in forestry

Where trees have to be planted in arid and semi-arid re­ gions as a protection against wind erosion, to provide shade, or for wood production, it may be necessary to im­ plicate temporary or permanent irrigation. In Pakistan, 47 000 ha shisham forest (Dalbergia sissoo) was planted on land irrigated by canals, while the more recently introduced eucalypts show promising results (802). In Cochabamba, Bolivia, Eucalyptus globulus is grown in valleys on irrigated land where it shows an average annual height increment of 3 m (the initial irrigation cost« ac­ counting to only 10 % of the total planting costs) (1022, 1021). In Israel, irrigation is applied to trees to secure initial growth (835). Throughout the not too dry areas a- round the Mediterranean region the tree seedlings are plan­ ted on ridges to catch the scarce rainfall and preventing erosion (1105, 147). In Tunesia water is supplied from little basins built around the seedlings (1782). A quite modern aspect of 'irrigation' is that applied for the purification of drinking water in Frankfurt (West Germany) where chemically processed water from the Main River is pumped in the town forests where it is left to seep through the soil before being used (397). 144

6.8.4 Drainage in forestry

Drainage of forests or areas to be afforested has always been a matter of great concern in the lowlands of north­ eastern Europe. It involves ploughing furrows or making ditches (1059) to increase the thickness of the well-aera­ ted soil-layer, especially in the spring and summer, to further tree growth (698). It can also accelerate run-off (894). Depth and spacing of the ditches or furrows depends on soil type, groundwater level and other circumstances (720). From the total forest-swamp area of 6 600 000 ha in Fin land, in 1958 1 205 000 ha was drained and it is expected that within 30 to 50 years all swamps will have been treat ed, resulting in a 20 % increase of their wood production capacity (642). Something analogous is expected for the 6 400 000 ha swamp forest along the Atlantic coast and the Mexican Gulf in the USA, of which in 1960 about 400 000 ha had already been drained (1638) and where already in 1955 all know-how and equipment was available to proceed (304). A too heavy drainage, lowering the watertable to a level where the tree roots cannot reach it anymore, can be detri mental , however, mainly for species needing much water (such as Alnus glutinosa and various Populus and Salix species in Europe). It may cause drought damage, especially in older trees, and a considerable increment reduction. Most remarkably, the symptoms closely resemble those caus­ ed by chemical air pollution (590).

6.8.5 The influence of forests on total streamflow and silting

The old controversy about forests being benificial or not to the quantity of water they put at the disposal of the surrounding country, the total streamflow, is still going on. The point is, that it is difficult to estimate 145 the total streamflow: water can disappear through porous strata to great depths and supply wells (or rivers) many kilometres away without reaching the main drainage system of a watershed (704). Such sub-surface streams can often be observed in holes dug in river bottoms during a dry sea­ son, where they excape measurement. Russian writers, though admitting that forests on small watersheds decrease the quantities of run-off water, are convinced that annual run-off from larger forested catch­ ment areas are generally greater than those from less fo­ rested open watersheds (158). Probably the most important effect of forests is that they decrease the quantity of silt carried downwards, so that heavy damage to expensive waterworks and diminishing water-storage capacity of reservoirs are avoided (127). The reservoir above the Çubuk Dam in Turkey lost a third of its capacity between 1936 and 1960, that in the Gêtre de Gave River in France 85 %, and the Algerian waterworks were put out of service in less than 40 years (543). A ready-made solution is impossible. Afforestation of the catchment area may decrease the silt content of the water, thus avoiding silting-up, but it may diminish the streamflow by causing a too high transpiration of the ve­ getation. An excessive purification of the water can make it unsuitable for irrigation purposes, as apparent from the abrupt changes caused by the Aswan Dam in Egypt (1491).

6.9 Tillage and fertilization of forest soils

In Europe, and especially in the Netherlands, insuffi­ cient timber production has always been a stimulus to im­ prove the productivity of forest soils by applying fertili­ zers or manure. One of the oldest treatments is adding lime to speed up the mineralization of mor litter (1541) during afforestation of heath lands (911). In the past, the soil of poorly developing spruce (Picea spp.) plantations in the 146

Netherlands was worked over, their mor layer was cut up and the land received 20 to 40 ton manure per hectare. The results were unsatisfactory (557). Another old Dutch method,dating from 1892, was to sow green manure crops before planting, or to add basic slag (15 - 17 % P2O5), crushed bones (another phosphate ferti­ lizer since the early 19th Century) (421), lime, kainite, etc. Since 1902 experiments with fertilizers in this field have been carried out more systematically (1466). In 1914 a committee was set up to publish the results, and in 1935 it was decided to give the fertilization experiments a fir­ mer scientific base (1286). Later the research was put in the hands of the Forest Research Station. It will be obvious that such shifting,often encountered in forest research work, cannot have favoured an early solution of the pro­ blem. Forest stands are sensitive to loss of organic matter in the soil (1722). Tillage accelerate its mineralization, leading to a reduction of soil fertility, especially on sandy podzols where the nutrients easily disappear (555). The decision to be made on tillage or fertilization of forest soils, either before planting or later on, and the interpretation of its effects, can be based on soil or on leaf analyses, or an a combination of both. Foliar analy­ sis, to which much attention has been paid, may be useful to trace deficiencies such as those caustng chlorosis or die-back (1554), and, where no deficiencies are found (1555), to obtain an impression of nutrient relationship. However they are unsatisfactory for decision making (563) or to predict a response (1702). To illustrate the complexity of the involved problems some examples may be cited. In a number of stands of red pine (Pinus resinosa) in the USA the amount of nutrients per branch, or the needle weight per branch, accounted for 60 to 65 % of the varia­ tion in growth (1001). A study of the variation in nutrient 147

content of black spruce needles (picea mariana) indicated that it was related to age, to crown class (dominant, co- dominant, suppressed), and to season, whereby growth and yield showed the highest correlations with the nitrogen contents (968). For natural stands of cottonwood (Populus deltoides) it was found that the variation in height in­ crement of six-year-old trees was related to the calcium, potassium and phosphate contents of the upper foliage and to the potassium content of the lower foliage (1696). From investigations carried out in the Netherlands and in Canada it can be concluded that, to explain such pheno­ mena, data from experiments performed under very strict circumstances are needed (562, 620). In Europe, tillage and fertilization of forest soils on­ ly enter the picture when it is necessary to restore damage caused by the removal or organic matter, or to counteract a rise in soil acidity due to planting conifers not native to the location (or due to sulphur dioxide reaching the soil from polluted air as mentioned by a German writer recently). The proposal to add calcium to the soil to keep the sub­ soil water pure, concerns the welfare of the community and not that of the forest, so that it should be paid for by the community (1595). Fertilization is a production tool. If applied to stands near the end of their rotation, investment time Is short and the effect can easily be evaluated. In young plantations the wait for returns is so long, and the improvements are usually so small,that fertilization probably will never be­ come efficient (1632, 1334). The same conclusion was reached in Finland and Norway from fertilization experiments with Scots pine (190) and spruce stands. For the latter only ni­ trogen had a temporary effect, improving wood production for a five-year period (789). Fertilization efforts carried out in Saxony, Germany, da­ ting back to 1903 - 1906 for beech and Scots pine, to 1930 for Scots pine and spruce, and to 1948 - 1952 for more coni- 148 fers, alder and poplar on very poor sandy soils (774) in­ cluded both new plantations and stands of 51 - 61 years old. The results were compared with those obtained in Au­ stria with spruce and Scots pine 34 - 68 years old (99). The results were such, that economically they had to be considered doubtful. In subtropical and tropical regions, where rotations are often short, it will be much easier to draw conclusions on the efficiency of tillage and fertilization. Though hardly any data are available on this subject, it may be predicted that the outcome will show large variations due to diffe­ rences between soils and species. Recently, several new fertilization methods have been in­ troduced, which have become important in forestry. Fertili­ zers packed in tubes are applied in nurseries around the seedlings (1136, 1077), or put into plant holes (376, 342). The latter may contain animal manure, powdered mineral fer­ tilizer or crushed stones (785,377,1058). Application after planting has to be done carefully so that no roots or ten­ der stems are scorched (377). There have been continuing advances in the production, the quality, and the applica­ tion of fertilizers, reducing costs and simplifying me­ thods by avoiding hand labour, e.g. by calling in the help of aeroplanes (1507). As a rule, fertilization does not only influence tree growth but also the development of scrubland grass. This may be favourable when it results in a litter, that decom­ poses more easily or unfavourable where it causes heavy root competition. In grazable woodlands it may considerably in­ crease the forage resources (923), also for game (749). Luckily, there is no evidence that in catchment areas fertilization pollutes the groundwater (682). 7 Forest zite cla//ification

At the time foresters started managing natural tree stands, the production capacity of forests was considered to remain constant, 'a fixed and immutable feature of the locality' (1538) or 'site'. This site can be qualified, either in harvestable quantities of wood or minor products per area, by extrapolation from what is present, or with the aid of tables, growth curves or other means. For tree species to be grown outside their natural dis­ tribution area (either geographically or ecologically),the productivity of the site cannot be estimated in advance and generalized: here it has to be established per species, so that one plot is qualified differently for, e.g., oak, beech, pine or spruce. The improvement of forest management soon needed a more precise classification. The choise fell on the average wood volume produced per year up to the moment the stand is con­ sidered 'ripe' to be cut, the so-called rotation period (or for short: the rotation), as a rule valid only for nor­ mally closed stands under normal management. The latter criterion is far from exact. With time, the idea of 'normal management' may considerably change. Neder- theless a forester is often obliged to evaluate or assess the economical suitability of his measures, taking into ac­ count the growing capacity and health of his 'sites' as well. So, assessement, as a rule, involves prediction. In forested areas nature can assist in this procedure, and long experience can prevent great errors. To check this knowledge, and for all occasions where no previous experien­ ce is available, data on topography, climate, soil and bio­ logical site factors will have to be integrated to reach a reasonably reliable estimate of site quality (1473). 150

7.1 Early site classification

Probably Cato (234 - 149 B.C.) was the first to write on site or fertility classification. He described nine classes of soil according to the vegetations, beginning with vine­ yard land and ending with vineyard forest land (a mixture of vineyard and forest serving both wine and timber produc­ tion) and pasture-forest land. Theophrastus (372 - 287 B.C.) discussed the influence of habitat on tree growth, for in­ stance by remarking that on northern slopes the forest grows better than on southern slopes (1048). During the opening-up of the Russian forest area for agri­ culture, the habitat was indicated by simple old Slavonic terms, that in the beginning of the 20th Century were in­ cluded in the forest.type classification of Morozov, Krye- dener, and others (219). Examples are 'bor' for pine wood­ land on sandy soils, and 1raman' for densely growing stands (usually spruce, Picea spp.) on fertile loamy soils (1297). Finnish foresters first followed the Russians in distin­ guishing dry forest land covered with mor litter, moist forest land covered with mor litter, low forest lands, swamp forest land, land characterized by mixtures of spruce (picea abies) and broadleaved tree species, forming peat or moors, and swamp forest with pine (Pinus sylvestris)on peat or in moors. According to Cajander, this was a useful classification for southern Finland, bcrt- it could not be applied in other parts of the country or to European fo­ rests in general.

7.2 Site classification and undergrowth

The integration mentioned at the end of the introduc­ tion to this chapter can best start from the natural vege­ tation cover, from forests (almost) undisturbed by man. *• Here three ways are possible: (a) to consider the forest as a whole, including both tree species and undergrowth, 151

(b) to consider solely the undergrowth of small plants, and (c) to consider solely the tree species (possible on­ ly in highly mixed stands). To classify soil fertility on the virgin undergrowth (case b), it must be assumed that a high degree of equili­ brium has been reached between plant community and soil (often indicated by the term climax vegetation) (809). In areas where, for ages, man has manipulated the soil and the vegetation, or where trees have been raised outside their natural environment, the reconstruction of the vir­ gin plant cover may become very difficult. Species such as Alnus incana used for underplanting Scots pine stands in Western Europe can now be found in places where they would never have occured if left alone; in the Netherlands Quer- cus rubra and Prunus serotina,both imported from North Ame­ rica, do very well (1006, 746), but they hamper the semi- natural plant cover to such a degree that at present their import is greatly regretted. An extreme case is Iceland, where, after the last Ice-Age the flora was not enriched by migration from other regions. Since 189 9 trees have been planted there with success, and especially Larix sibirica is doing fairly well (151). Here, the unfortunate geogra­ phic situation has hampered the development of a virgin forest vegetation. Cajander's classification of the Finnish forests, drawn up in 1909, was so successful, mainly because there were no disturbing factors as mentioned above. His classifica­ tion refers to natural tree stands of normal density and is independent of the composition of the tree canopy. Ba­ sically he followed the Russian main division, and he sub­ divided the classes according to the undergrowth in distin­ guishing a lichen type, a Calluna type, a Vaccinium type, etc. (246). Later on, for each type growth curves (and growth tables) could be drawn up for the various tree spe­ cies and they were used for a forest inventory of the whole country. They could even be applied to burned stands and 152 for forest patches previously used for agriculture. How­ ever in the latter case the undergrowth had become much richer than normal because the decomposing litter during its agricultural occupation had enriched the soil (espe­ cially in nitrogen and phosphates) (871). Later (in the older stands, to which the types apply) the soil returns again to its original state (748, 1630). Research carried out in Finland, checking Cajander's classification, showed that foliar analyses cannot replace this system, but soil analysis were more reliable(2, 1629); litter analyses from moors and bogs for the 10 to 20 cm thick top-layers showed a satisfactory correlation (1607). For northern Finland (Lapland), the undergrowth indicates fairly accurately the site fertility, but the correlation between site and its water-holding capacity was considered more significant (1631). Also in northern Sweden, Cajander's method had success (1538). A study on afforested peat land north of Stockholm revealed that 'the best relationship between forest growth and environment appears to be that between growth and plant community' (695).This applies to other regions also poor in plant species: in the Austrian Alps, under conditions free from disturbing human influences, the productivity of larch (I.arix decidua) , spruce (Picea abies) and Pinus cembra was closely related to the composition of the undergrowth of small plants (325). ~ - In the USA, attempts have been made not to consider the undergrowth as a whole (the combination of all species) but to select a few'indicator species' in estimating site productivity in stands of longleaf pine (Pinus palustris). In one case the correlation was as high as 0.913, in an­ other only 0.556. The conclusion was that for 'deep soils with droughty surfaces it was necessary to select more deeperly rooted indicator species that better reflect the deep soil environment' (685). Basically this method does not differ from that of Cajander's forest types (871): 153

solely the 'indifferent' species are left out of conside­ ration. Nevertheless it can not be denied that the less numerous the number of species necessary for an identifi­ cation, the more practicable the method of soil fertility determination is. In Europe, with the aid of sample plots, many floristic forest types based mainly on the undergrowth of small spe­ cies plants and shrubs have been described or reconstruc­ ted (so-called forest 'associations', not to be confused with the American associations mainly based on combinations of tree species). Recently, such descriptions have been based more on the vitality of the plants and their struc­ tural function in the vegetation layers (691). Such associations may serve various purposes: the study of the behaviour of a tree species in its natural surroun­ dings (as for example, for the European larch, Larix deci- dua) (1043); the search for the circumstances under which a tree species yields most (shows the highest wood growth rate) (1641) or performs best in competition with herbace­ ous plants and shrubs (986); the appreciation of their ef­ ficiency as site indicators (1146) (Terminalia in the Sudan before planting teak) (449). Some authors suggest that only natural forest associa­ tions can be maintained on a sustained yield basis, which means without disturbing the nutrient equilibrium, and that any other vegetation cover is detrimental to the natural environment (625). Admitting that the 'biological metabo­ lism passing through the vegetation is of dicisive signi­ ficance for the formation and the development of soils' (1296) , the restriction has to be made that 'sustained Yield' need not involve a closed nutrient cycle. Even under a natural vegetation cover, all soils constantly lose small amounts of nutrients to the underground, especially in humid regions. They reappear in spring water: near Münden (Hanno­ ver , Germany) under sandstone soils, such water contained a quantity of CaO equivalent to an annual loss of 25 - 75 154 kg per hectare (1525). Furthermore it has been alleged that only natural (stable) forest communities, or their artificial reconstructions, are able to fully protect the environment (144). Opponents insist that well-tended artificial tree stands for wood production protect the environment much better as they are better taken care of, because of their high value (452). Whatever the truth may be, it cannot be denied that in Europe many conifer plantations (especially of Pinns syl­ vestris and Picea abies)have greatly decreased soil ferti­ lity, mainly due to accelerated leaching caused by the for­ mation of highly acid 'mor'. There are, however exceptions (spruce and pine stands grown for two or more generations showing no production decrease) (626, 697), and in some English investigations no clear differences between the modifying influence on the soil of various exotic and na­ tive tree species were found (1191). In Brazil, the common belief is that eucalypts wear out the soil, but coffee planted on a soil that had been under eucalypts for the previous 37 years, showed that it was still in excellent condition (702). Research in Italy, Morocco and Spain have revealed that, instead of reducing the fertility of the top soil (inclu­ ding relatively poor soils), the planting of eucalypts even enriched it with nutrients from the subsoil (736). Com­ parable results are known from the northern part of Hessen (Germany). There, in areas covered with mutilated natural forest (mostly beech, Fagus sylvatica), conifers such as Scots pine (Pinus sylvestris), spruce (Picea abies) and later larch (Larix decidua) were planted. They considerably improved soil productivity and the softwood stands became fully integrated in the landscape, serving both economy and recreation (784). The conclusion must be that in production forestry defi­ ning the site by natural forest associations (if they can be identified!) is less important than in protection fo­ 155 restry where the maintenance of such associations is, most probably, easier than that of stands of foreign species. Nevertheless, the description and evaluation of such natu­ ral associations as ecological indicators has become, and will remain an integrated part of site assessment.

7.3 The productivity of natural forests

The natural forest represents an equilibrium between wood production and losses due to the natural death of trees (37). Consequently in the definition of productivity only the trees that stay alive during a certain period, say between two measurements, can be included. For the tropical rainfo­ rest the meaning of such data is rather doubtful,but an annu­ al production of 5 tons dry above-ground wood per hectare (337) seems a reasonable estimate. In the Amazon region, for trees over 25 cm diameter at breast height an annual Production of 4 m3 bolewood has been calculated (656)*. These quantities cannot be harvested without disturbing the equilibrium: it is disturbed as soon as the first tree is cut (337). When cutting is continued on a somewhat lar­ ger scale, the wood volume is not suitable anymore as a measure for the natural habitat, which usually means the soil quality. Thus stand height and density are better in­ dicators to estimate the productivity when cutting has to start or has already started. When a site has to be evalu­ ated for afforestation purpose after clear-felling, as a rule only a comparison with experimental plantings can pro­ duce reasonable data on production capacity. That cutting in the natural forest always distorts the Picture has been shown for mixed forests in East Germany, where in the past in a natural forest containing much beech

* Data from Thailand for total material production, also for the tropical rain forest, amount to 337 kg per day per hectare, from Cambodia to 323 kg (812). 156

(Fagus sylvatica) all other (undesirable) species had been cut (1200). The reverse often happens in tropical forests when only a few highly estimated species are harvested. Natural growing conditions to be maintained for the pre­ servation of nature, its flora and its fauna, can be at­ tained only by protection, by setting aside all productive and commercial considerations. Research in this field is urgent (355). Foresters, especially in Europe, are inclined to believe that their stands should be cared for in such a way that deviations from the natural situation must be 'healed' as far as possible. To restore the disturbed ecosystems, also after clear-cutting, the natural succession of plant commu­ nities should be considered. In such a way forest produc­ tivity should become dependent on the integrated results of all factors influencing the forest ecosystem (533). This standpoint can not really be maintained: reforesta­ tion of the natural ecosystem is nearly impossible. Even the forests of Angkor Vat, in Cambodia, cut down four to six centuries ago, still differ from the nearby primary stands (1306). Comparable examples are known from Central America (221) and Surinam in places used for agriculture hundred of years ago. In Europe, 'maintaining' natural forest associations has mainly implied cut-over or cut-out stands, which were then left alone for spontaneous regeneration or replanted with the same species. The latter may have improved pro­ ductivity, but the original structure of the forest has changed. The results have been, at best, 'more or less na­ tural forests', in certain respects resembling the 'virgin' associations, as obtained from purely artificial conifer stands replaced by mixed broadleaved forests (1349). The motivation behind such measures has never been quite clear, except for the establishment of stands solely for soil conservation purposes. The possibilities to amelio­ rate the site and to increase the productivity of purely 157

artificial forests have in general been ignored.

7.4 Site assessment

The correlation between site and forest cover can best be studied during soil mapping (362, 220, 518). It supplies the best information to the forest manager (1785). Where the natural vegetation is strongly damaged, or ab­ sent, site classifications depend more, or entirely, on soil studies (1553). Selected edaphic characteristics then serve to indicate site quality, such as depth of ground­ water (in the Netherlands (938)), soil porosity (poplar in Switzerland (1304)), soil depth (in Norway (892, 893), Sweden (1540) , and England in combination with undergrowth (338) or soil depth and soil colour (in Zambia (1342)). For the karst regions of North Dalmatia (Yugoslavia) soil depth is considered the most significant feature for refo­ restation (873), in the Rocky Mountains (USA) the water- holding capacity of the three feet topsoil layer has shown to be the most important factor for tree growth (303). The natural vegetation, either as a whole or through in­ dicator plants, can supply important information on soil fertility (1721). In East Germany, where application of fertilizers is based on the study of such relations, for Scots pine (Pinus sylvestris) the undergrowth on dry sites better characterized the water and nitrogen content than on moist soils (1575). If only data on the soil are available for a reforesta­ tion programme, it is advised to start, in the same region, with a study on the relationship between tree growth and soil characteristics under equilibrium conditions (373). Such equilibria, in undisturbed natural forest areas, still exist here and there in less developed regions, some parts of North America and northern Europe, and in some of the southeastern European countries. In other regions such stu­ dies can start f?rom re-established or approximately natural 158 tree stands (625)• Where even these are not available, nutrient research will have to substitute (or complement) such studies (888, 776, 563). For a simple site description the Russian method can be followed (see 7.1). In the Riding Mountain National Park (Manitoba, Canada) indications such as 'aspen site' and 'white spruce site' have been accompanied by soil descrip­ tions (1328). For regions where still some virgin plant cover is present, this method is probably the best. After sufficient experience, the results may be extrapolated to experimental plantations and even to secondary ecosystems such as crop fields and meadows, if they are surrounded by virgin forest, 1 through their common ties to certain physio­ graphic positions'(925). Site assessement indicates where forests can grow, what species are natural to the given site, and which trees (either indigenous or exotic) can be raised. Such assesse- ments may be accompanied by production estimates, especial­ ly where comparable stands are still present,or with the aid of site-class tables, if available. From such data, apply­ ing normal rotation productions can be estimated, as for instance done in the Netherlands by establishing two produc­ tion classes: »6.6 - 10 and -10 annually per hectare (564). More precise data can be misleading. « In some parts of Europe very precise site assessements have been carried out. The Institute för-Forest Science in Eberswalde (East Germany) started such work in 1926 (744). In western Thuringia (East Germany), forest assesse­ ment was accompanied by landscape descriptions and data on climate, geology, soils and past human influences, with detailed analyses of plant associations, all culminating in advice on the choice of tree species and their silvicul- tural treatment (745). Site assessement not only serves wood production but also «• indicates the value of a forest area as a watershed cover and for the supply of drinking-water. In the White Mountains 159

(USA) the differences in forest cover could be correlated with differences in water regime and in potential contri­ bution to streamflow (301).

7.5 Forest site mapping

After the assessement of a certain area for growing fo­ rest, the ensuing soil or habitat classification has to be mapped. Especially for less explored regions, this type of mapping may become a complicated operation: topographic, climate, soil and (if available) geological and vegetation maps have to be superimposed to integrate all site factors. Data from measurement plots in tree stands, or from similar situations nearby, have to show the correlation between site factors and production. The area for which a conclusion is possible on the most suitable tree species (including exo­ tics) can be marked, sometimes accompanied by data on growth (excellent - good - medium, and expected annual production per hectare). Site mapping is possible everywhere and is not restricted to forest areas: it may cover agricultural lands belonging to various landowners, and other non-forest lands. In Austria, the construction of comprehensive regional forest site maps, including non-managed forests and non- forested areas was considered part of the general forest policy (754), in Australia as a tool in land-use planning (473), in the Netherlands and in Brazil as a basis for plan­ ning new forests(561,564).In Canada it served the rehabili­ tation of agricultural lands and the development of rural areas,and it was included in land-inventory work;it also gave wood production estimates(988). Theoretically it is possible to devise from such maps the ecologically and eco- mically most desirable forest cover (516) , but for practi­ cal reasons it is better to take the actual landuse pat­ tern into account as well (1706, 127). 160

7.5.1 Topographie maps

Foresters seldom prepare topographic maps, so that they have to use existing ones as a base for their work. In Sao Paulo (Brazil) such maps (1 : 1 000 000) were Used as a base for site mapping in planting slash pine (Pinus elliottii) and Parana pine (Araucaria angustifolia) (561). The relation between site factors and topography is often close. It can be identified by correlating gradient classes in soil moisture content, porosity, temperature, etc. mea­ sured from the top of a hill or mountain downwards. The re­ sults can assist in site mapping of large forest areas, such as in Canada (450). In southern Jersey (USA) regres­ sion equations including slope and distance to deep valleys (determining drainage) were used to predict the growth of yellow poplar (Liriodendron tulipifera). In the Allegheny Mountains of West Virginia (USA) slope expressed as a per­ centage of the distance between ridge and bottom, and steep­ ness was used for the same purpose in oak forest (Quercus spp.) (1235, 1767).

7.5.2 Climatic considerations and seed provenance

In Finland, measurements of temperature and tree growth on 396 sample plots have shown that the difference in yield capacity between good and poor sites ia-distinctly smaller under unfavourable than under favourable climate conditions (643), making the value of fertilization in cold regions questionable. This also applies to Sweden, where it was concluded that under such conditions the expenses for site mapping are not justified and that it would be better to substitute plant sociological mapping (1539). In New Zealand , the study of the site quality for Douglas fir (Pseudotsuga menziesii), loblolly pine (Pinus taeda), slash pine (Pinus *elliottii), longleaf pine (Pinus palustris) and radiata pine (Pinus radiata) was significantly correla­ 161

ted with the mean diurnal temperature range during the gro­ wing season and the mean temperature of the coldest month (740). In Turkey, site typified by rainfall (humidity) depends on its distance from the sea (1778). How important even small differences in the climate are may be demonstrated for such a small, country as the Nether­ lands, where in the south the growing conditions for Corsica pine (Pinus nigra spp. laricio) are considerably better than in the north, due to the thermic and hydric regime which in the south somewhat more resembles that of Corsica (1111). In northern Norway, the study of the microclimate and its mapping for management purposes has revealed that severe night frosts during the growing season at the bottom of sheltered valleys may turn areas well below the timberline into non-forest lands (1118). For its wood production, Argentina heavily depends on exotic tree species (1075). Besides Salix, Populus and Eucalyptus species, many pines have been tried out. After 21 years of experiments, among 17 pine species only Pinus eliiottii, P. tadea and P. patula showed promising results (546). From 1962 on, the experiments were continued with 21 additional species. The plots were located on maps with the aid of lines of equal average annual rainfall and tem­ perature; for the experimental stations water balances were calculated (89). Such balances were also drawn up for the State of Sao Paulo (Brazil) (548) and, as a check, for 16 places throughout the world where radiata pine had been im­ ported with success. The outcome was that only where the climatic pattern was similar to that of the natural habitat did introduction prove to be successful (547). For tree species with a wide distribution, often showing various ecological types, the provenance of the seeds is very important (1623). In Europe, this was realized in the first half of the 19th Century for Scots pine (Pinus syl­ vestris). Trees from Riga seeds showed a much better growth than those gathered in Germany, France or Scotland. 162

All these examples show the importance of climatic consi­ derations in selecting species for large-scale plantations, both in their native country and elsewhere. Because of the many factors involved, only carefully planned experiments may lead to practical results.

7.5.3 Soil maps and other environmental factors

Experience has taught that, in classifying forest sites for exotic species, the importance of the climate should not be over-emphasized: trees can often adapt themselves quite well. An outstanding example is the picturesque mon- terey pine (Pinus radiata) from California (USA) which de­ velops into a forest giant in Australia and New Zealand (1279). In other cases an import may be tended so well that it grows much better than in its home country (1268), or because damaging insects or fungi are absent. The common belief is that eucalypts, in a proper climate, have a very high yield (both of wood and of essential oil (895))and become fully adapted to new circumstances (e.g. in Brazil). It should be kept in mind, however, that to de­ velop their potential productivity they need a reasonably fertile soil (such as that of abandoned loamy crop fields (657)), and that, where this condition is not fulfilled (as on sandy soils), their growth will be as poor as in many regions of their country of origin;-— When a tree species is considered to be fully adapted to the local climate, the soil determines its productivity. To assess it, soil maps are indispensable. They should be of a general nature so that their use is not limited to forestry purpose, and link up with national or (preferably) world-wide soil classifications so that they can serve as a base for the import of species from elsewhere. The first condition is fulfilled in the Netherlands where the maps of the Soil Survey Agency Institute (564) supply profile descriptions, stand data, the results of chemical soil ana­ 163 lyses, etc., which also facilitate the explanation of aber­ rations (937). One drawback of such general maps is that they cannot show every detail so that they usually give soil groups or soil series (1718). If more information is needed for spe­ cial purposes, additional data have to be collected, as with sitka spruce (Picea sitchensis) in England, where the moisture content of the B horizon was needed for site asses- sement (808). For trees it is not always easy to detect such site factors: the death of radiata pine (Pinus radiata) in Argentina due to clay pans (88) could hardly have been foreseen.

7.6 Site and management

7.6.1 General considerations

Production forests have to be managed on a sustained yield basis, which means that the financial profits must be as high as possible and remain so in future generations, even under unnatural circumstances (496). For instance, (in the USA) mixed stands of loblolly pine (Pinus tadea) and hardwoods have to be manipulated in such a way that the growth of the valuable pine is favoured (846), and (in wes­ tern Europe) the forester has to protect Picea abies against competition from Fagus sylvatica (1139). To serve this purpose, trees can be taken outside their natural range. For the northern hemisphere such a displace­ ment can be 150 - 250 km northwards or southwards, or up to 200 m in altitude (1701). Planting trees on sites or in areas unsuitable for their healthy development can lead to excessive landuse and de­ cline of soil fertility (627). Hence, the forester must have the opportunity to compare the circumstances on his bare land with those on still forested areas by studying the vi­ tality and structure of the natural forest vegetation, even 164 if this is already badly damaged (17, 1213, 690). For exo­ tic species he has to wait until older stands are available, which may take a long time (851) and can considerably post­ pone large-scale extension of afforestations. To assess large areas, aerial photographs can be used to trace differences in height or density of the forest vegeta­ tion. In the tropics such studies are preferable to those on botanical composition because of the complexity of the latter. Even such an apparently simple vegetation such as the 'cerrado' in central Brazil still has 20 - 30 different dwarf tree species per hectare and, all together, contains 657 different woody plants (1318). Height and density of the vegetation vary with the growing conditions, in particular with the water holding capacity and the available nutrients. A study of the litter will com­ plete the data for site classification and its mapping; it should include the decomposition time to evaluate the nutri­ ent system, often indicated with such terms as oligotrophic (poor, acid),mesotrophic (medium) and eutrophic (rich, more or less basic) (1660), excessive formation of debris and its influence on soil and growth (387), and the possibili­ ties of amelioration by artificial means ( 1384). Also the effect of burning (and prolonged fire-protection) on the composition of the forest must be taken into account (1598). The duty of the forester is to treat the forests and the other lands under his care 'in the most appropriate way in accordance with the objective of management'(1426) . Hence, site classification and site mapping will be of little va­ lue if the aspects of their application remain obscure (1328). Therefore, during site assessement, full attention has to be paid to the possible means by which wood produc­ tion, or the sustained presence of forest growth, can be maintained or improved. Site mapping has to prove its value in management. In Hessen (West Germany) such mapping involving that of cli­ mate zones, natural plant associations, soil profile de- 165

scriptions, and data on water holding capacity and the nu­ trient system (51), has already been carried out for 70 % of the state forests. It has substantially changed long- term planning, especially in the choice of the tree spe­ cies (1784): tree stands on too dry places were excluded from wood production to maintain their protection func­ tion, and from the maps it was possible to spot stands sus­ ceptible to windthrow, especially spruce (Picea ahies) on wet places (684). If a soil is supposed to be capable of producing a cer­ tain quantity of wheat, it is just assumed that the farmer applies the most suitable techniques (1495). This also ap­ plies to forestry: if on a certain site, poplars with a rotation of 25 years are stated to have an annual produc­ tion capacity of 10 - 15 m3 per hectare, it is assumed that selected seedlings or saplings were planted, that during the initial years the plantation was cleaned, and that care of the individual trees has been taken e.g. by pruning (564). Mostly the forester, in assessing site quality, will take it for granted that management follows such generally accepted rules and he will (tacitly) integrate them in his site mapping. In many cases, however, he will be obliged to indicate how the existing situation can be improved, either by better soil treatment applying 'agricultural' techniques, or by planting tree species which will be more profitable. That this is no mere theory can be demonstrated with an example from northern Mississippi. There, pines, especially loblolly pine (Pinus tadea) performed much bet­ ter than red cedar (Juniperus virginiana) (290). They Proved to be excellently suitable for improving the produc­ tion capacity of eroded old cropfields; the thin loess top- soil was rehabilitated and protected against further erosion. 166

7.6.2 Site and fertilization

Fertilization of nurseries, the application of fertili­ zers (or manure) to plant hole, or planting seedlings with fertilized soil attached to their roots, has become common practice in many regions. Site evaluation has to take this into account. On fertilizing older stands, opinions are still controver­ sial. It has often been suggested to speed up litter decom­ position (526), to make the trees more resistant to sick­ ness, to damage by game (378) and to industrial emissions (153). Whether it is useful to increase yields is doubtful (1334); here much research is still necessary in experimental stands (1138). Only in northern Europe does the fertiliza­ tion of almost mature stands (some five years before harves­ ting) seem promising with a good chance of becoming inte­ grated in site qualification (636).

7.6.3 Site and tillage

Although in the past tillage of heathland was applied on a large scale, it has had no lasting favourable effect in Denmark, or in the Netherlands except where compost was ad­ ded to the deeply ploughed soil (933, 1779, 960). The same negative outcome has been observed in Italy during refores­ tations in the Alps (254). It seems, ïföwever, that in the southern part of the Netherlands oak (Quercus spp.) cannot be planted without working the soil, so that this measure is an integral part of site qualification and management. For species with short rotations, such as the exotics in Australia, soil preparation could have a lasting effect, but even this is still doubtful (1305). The same applies to the eucalypt plantations in Brazil with rotations of about 7 years. For Zambia, where fully mechanized soil pre- paration is applied in afforestations, the time is stil1 too short to draw a conclusion (23). 167

For those parts of the tropics and subtropics where 'taungya' is practised (see 3.4.1) , the situation is dif­ ferent. Here a superficial tillage with a hoe is indispens­ able for the agricultural crop and thus has to be fully in­ tegrated in site assessement and its mapping.

7.6.4 Site and irrigation or drainage

Contrary to fertilization and tillage, the lasting favour­ able effect of irrigation or drainage on tree growth is in­ disputable. The best example is Pakistan where, since 1866, forests have been planted on irrigated lands. The local po­ pulation benefits in various ways from these stands (fuel, recreation) but demands for more crop fields with emphasis on efficient agricultural methods makes the survival of the stands doubtful (1408). The techniques involved in afforestation in semi-arid regions, where the supply of additional water is crucial for tree growth, are not yet clearly understood. Perhaps high costs have to be accepted because of the indirect be­ nefits to erosion control, shelter against wind, etc. (1510). Here site valuation depends on the solution of technical problems and the involved financial consequences have to be adjusted to future productivity. In Finland, originally poor forests showed such an in­ crease after drainage that their production capacity became equal to that of the neighbouring dry stands (1301, 1292). In Lapland drainage increased the annual wood production with 4 m3 (to a total of 8 m3) per hectare, which was quite considerable for that region (719). Drained forest areas in Finland showed considerable growth increases during 5-20 years for Scots pine (Pinus sylves­ tris) and during 10 - 30 years for spruce (Picea abies), while no evidence was found of the set-backs that are often observed after tillage or fertilization (1397). In Russia, 3 annual improvements of 2 - 3 m per hectare were measured; 168 they began 2 to 4 years after the initiation of drainage (219). As a rule drainage has to be included in site evaluation, or at least its possibility has to be mentioned and mapped.

7.6.5 Site and man-made ground

Man-made soils are found in polders, on stone heaps of coal mines, in rubbish dumps, and on comparable sites. In the last two cases, afforestation will probably never be mo­ tivated by economical considerations (823). However, the successful planting of poplar and other tree species on lands recently reclaimed from the Zuiderzee (Holland), is an example of what can be achieved (664). In the USA, strip-mined lands in the anthracite region of Pennsylvania were afforested to protect the loose earth or debris against erosion. The choice of tree species was based on experimental plantings (324, 622). In Denmark at­ tempts have been made to plant areas were lignite strip- mining has been practised (1229). In such cases the growing of trees, also serves to beau­ tify the landscape. Here site valuation becomes complica­ ted: the best solution seems to base the assessement on small experimental plots with hardy pioneer tree species of proven value (823).

7.7 Conclusions, site, management, and environment

Site-assessment has normally to be carried out per region. It is best suited to evaluate forest landuse as part of a (regional) environment, and to give guidance to forest mana­ gement so that the forest functions in the general interest. Site evaluation directives for production purposes and protection are well documented, while resulting forest ma- nagement is evident in the field. Unfortunately, however, 'in environment issues, the data base for decision making 169 remains weak' (1438). For instance, in the USA, in res­ ponse to a questionnaire, on 'timber cutting policy , fo­ resters and the wood industry supported an 'efficient re­ source utilization and a desire to avoid physical waste of forests, while conservation groups defended, in the pu­ blic interest, the preservation of mature timber stands 'for aesthetic values or other intangible qualities' (567). In the eyes of the general public, care of the forest means: preventing clearcutting, protection against fire, wild-life protection, and maintainance of the last rests of 'nature' for recreation, both in rural and urban sur­ roundings. Indeed clear cutting commonly looks ugly, especially in the tropics where for shifting cultivation the remains of the forest are even burned, or where only the heavy logs are taken out leaving behind an often utterly destroyed forest. Where lovers of outdoor-life come in close contact with such a case, it ' provokes intens reactions against foresters' (567). On the other hand, selective cutting without harming the general structure of the tree stand, often escapes the pas­ ser-by. The drawback is, however, that such exploitations are often uneconomic. In highly mixed forests, especially in the tropics, this selective cutting is normal. Here usu­ ally only one or a few species are involved, and if they occur in small numbers the harm to the forest is limited. Where many trees are harvested, the result may even be worse to look at than when trees are cut down and burnt for shifting cultivation. It is possible that the trend towards complete tree utilization will change this. In Michigan (USA), an experimental, completely mechanized harvesting Method, applied to aspen stands, whereby 'whole trees - bark, limbs and leaves intact - were chipped' on the exploi­ tation site, leaving a clean area behind, it has been re­ marked that 'the lack of slash may make the clearcut more acceptable to the public'. An additional advantage was, 170 that wood production per hectare increased from 102 500 to 209 750 kg chips (1133*. If in this method timber and chips could be separated, and become economically feasible, site assessment would change and forest management could more intensively be directed towards recreational demands, cutting smaller areas with equal wood production. Fire and its effects on forest growth is considered,ei­ ther as the greatest destroyer of forests or as a tool in forest management. Fire cleans the soil and keeps invading saplings and scrubs out. No fire (in combination with strin­ gent protection against fires due to other causes) could have a far from beneficial effect on the landscape and the scenic quality of forest areas: extensive conifer forests (especially when young) are dull, uninteresting, sterile monocultures without game and flowers, devoid of clean open places sought after for camping and other forms of outdoor recreation. So, under certain circumstances, burning may be an effective 'landscaping tool1, and not at all essentially bad and destructive, and should be included in site assess­ ment, provided it can be kept under control (1060, 1224, 1206). An alternative is to cut parts of the forest, as done in Western Europe to maintain heath areas. The task of the foresters has always included the preser­ vation of wild-life, often in spite of the complaints of the neighbouring farmers (see also 3.5). Here the problem is how to regulate the stream of visitor's in such a way that the animals are not disturbed too much, to keep the number of animals within certain limits and to protect rare species (or even to reintroduce them) (777). Hunting can serve those purposes. A few examples may illustrate this. Game counts in the Engadin National Park (Switzerland) (224) revealed that during the period 1918 - 1971 the num­ ber of chamois (Rupicapra rupicapra) stayed at the same level near its maximum carrying capacity, but that deer % (Cerus elaphus) increased to 130 %, thus hampering the in­ crease of roes (Capreolus capreolus) and perhaps that of 171 the rare ibex (Caprea ibex) which decreased from 285 in 1962 to 148 in 1971 (it was zero in 1918) (1368). In the Bavarian Alps (West Germany) the period 1858 1962 showed an increase in the number of deer to 400 %, for chamois, deer and roe together to 240 %. This consider­ ably influenced the composition of the forest, decreasing the proportion of mixed stands (spruce, fir, beech, and others) in favour of pure spruce stands. The impoverish­ ment of spontaneous regeneration distinctly reduced the protective function of the forest against erosion and ava­ lanches (1241) . These examples more or less reflect the situation every­ where in Europe, where forest assessment and management are inclined to over-estimate the importance of the large fauna at the expense of productivity and protection, also by preserving open places and parts of valleys for mea­ dows to feed the game. Forestry, the protector of nature, should avoid accusa­ tions that it is destroying the remnants of natural land­ scapes to raise forests. Recently there was a most interes­ ting case about peatlands in Finland, where the public pro­ tested against their drainage for forest production purpo­ ses. The motivations were: 'the economic aspects of berry- Picking1, the recreational aspects (ignoring the fact that 'urbanned man do not yet seek health and recreation on Peatlands), the preservation of nature in general (for which purpose already several areas had been set aside), the detrimental effects of drainage on human environment, the lowering of groundwater tables, the increased flooding, the increasing humus contents of lake and river water, the increase of forest fire danger, etc. These arguments are father weak, and in view of the need for more wood, drai- nage has become a necessity. These ideas may be scarcely motivated, or vague. Nevertheless they have resulted in a Wore careful consideration of site assessment; recommen- 172 dations for drainage of poorly producing sites have been dropped, and increased attention has been paid to impro­ vement of already existing drainage (645). 8 Fore/t inventory

8.1 Introduction

Stock-taking in a given forest area not only involves measuring or estimating what is present at a certain mo­ ment, but it has to include the determination of future production possibilities (the productive potential). This kind of inventory has to start with the naming of the tree species, which may be quite troublesome in tropi­ cal regions (see 8.2) and perhaps the establishment of forest types, if less detailed, reconnaissance surveys are needed. Trees have to be measured by volume or some other method (see 8.3) to obtain a base for yield measure­ ments in stands (see 8.4), and ultimately assessments of future yield are needed to run the forest as an enterprise on a sustained base (see 8.5). Especially in densily populated areas, the forest often not only serves wood production but has to fulfill a num­ ber of additional purposes (such as soil protection and recreation) which stock-taking assessment has to take into account. For example sometimes less attention will have to be paid to timber-value and more to coverage or aesthe­ tic appearance. Ultimately, some attention has to be paid to the so-cal­ led minor forest products, such as resins and bark, which may be quite important in some regions ( see 8.7).

8*2 Identification of tree species

In temperate and cold regions the number of local tree species is usually restricted and, as a rule, there are sufficient botanists to solve any riddles in naming them (which means: to provide them with a Latin name). Excep­ tions occur among the over 500 Eucalyptus (1221) species 174 and varieties (of which 134 are commercially important (608)) where identification needs a specialist. The same applies to poplar clones (205). In the tropics the difficulties are much greater, be­ cause firstly there are many more tree species present, both regionally and locally. For Indonesia this number has been estimated at some 30 000 to 40 000 (369); in such a relatively small area as Puerto Rico and the Virgin Is­ lands some 500 tree species occur (951). A partical solu­ tion of this problem is to restrict forest inventory work to trees of large dimensions, thus only including all saw- timber species. In Nigeria this method reduced the number of species by about a half (60 species per hectare of 10 cm diameter or more, 32 of 30 cm or more) (1306). In the Amazon Region a limit of 25 cm resulted in 40 to 60 species per hectare, including those grouped per genus or family (655). How heavily mixed tropical forests may be is shown by an inventory of an estuary forest in the same region with 516 trees of at least 10 cm per ha belonging to 157 species from 36 families (1124). The second difficulty is the naming of the species. Local . names are often not sufficient. In 19 24, a Canadian author wrote: 'It's a wise tree that knows its own name'. He based this assertion on the ten vernacular names for Douglas fir (Pseudotsuga menziessii) and the eleven for yellow poplar (Liriodendron tulipifera) in British Columbia (929). To disentangle such confusing situations, handbooks (84, 49) or lists of vernacular names are needed. The greatest difficulties arise in tropical regions where many species still have no scientific name. Notori­ ous in this respect are the Lauraceae (655) (which also oc­ cur in the subtropics (848, 661)),,where often even a genus name cannot be given on complete herbarium material. The forest explorer need not be aware of this: he relies (at least in the beginning) on vernacular names supplied by some local man. It is only later that such names are check­ 175

ed in the laboratory with the aid of herbarium material. To collect this material, selected trees have to be fel­ led (climbing is sometimes possible, even monkeys can be trained to gather shoots, and in Australia eucalypt fruits are collected by shooting (1760)). This selection has to be carried out with great care to avoid unnecessary work: the 'tree namers1 have to be controlled, a study has to be made of stem forms and bark characteristics, etc. During the 1940 survey in southern Sumatra (Indonesia) over 200 km line-strips were sampled in this way, over 400 trees were cut (143), and the botanical material was iden­ tified at Bogor (1562). Unfortunately, fixed vernacular names for all tree spe­ cies in a certain tropical forest area are rare (368); their absence greatly hampers the study of composition and ecology (1766), except on a very local level in extreme habitats (489), such as in the practically pure stands of Agathis bomeensis (69) or the fire-resistant Melaleuca leucadendron forests in Borneo (1704). Most of the collected herbarium material will have no flowers or fruits. A specialized botanist must be avail­ able for an identification based on leaf and twig characte­ ristics. Though taxonomists were sceptical about the out­ come, a very useful key of this kind was designed in 1928 for Indonesian genera (418) , preceded by a description of bark characteristics of sixty tree species (1559). Recently a more complete table has been prepared for Surinam, inclu­ ding wood characteristics observable with a handlens (945). It is even possible to establish the relation vernacular name to scientific name by only studying wood anatomy, as has been proved in Sao Paulo (Brazil) and for Australian New Guinea and Papua, up to the genus and sometimes up to the species (661, 1319). Where a complete identification is impossible, botanical forest inventory work can be restricted to well-known com­ mercial tree species. However, such a temporary basis, es- 176

pecially in modern times, can become quickly outmoded or unrealistic, because as wood becomes scarce more and more species become marketable.For example in the 1964 survey along the Atlantic coast of Brazil, 41 % of the timber belonged to such species (662). In 1969 this per­ centage had increased to 67.4, due to the advances in wood research (1444). During such (and more complete) surveys it is often possible to combine various species under one quality class or price class (419), such as the various groups of meranti timbers (Dipterocarpaceae) in Indonesia, now exported on a large scale to Japan (1751, 568). Forest surveys solely based on uncontrolled names, or without tree names, however accurately executed, are worth­ less.

8.3 Tree assessment techniques

8.3.1 Weight assessment of wood

Weight and density Due to its irregular form, firewood was the last to be sold by weight and not by volume: per head load, shoulder load or car load (456). This still applies to charcoal, most minor products (resins, bark, latex, fruits, etc.; see 8.7) and to a few very valuable species among which the following are worth mentioning. Chips of rosewood (Aniba roseodora), also made from roots and branches, from the Amazon area are used in the perfume industry. Wood from stems, branches and roots of sandal­ wood ( Santalum album) (1716) are exported from India and Indonesia (1068) to China and used as an incense (mainly) (1276). Indonesia produces the black ebony wood (Diospyros spp.) which is mainly exported«• to Japan (1493, 1494, 159). Bra- zil has its jacaranda or palissander wood (Dalbergia nigra); recently a start has been made to harvest even the 177

old stumps. All the harvested wood of these species is sold per weight due to their value and irregular form. In the USA there are considerable amounts of pitch-soaked pine stumps, in 1962 estimated at 48 million tons, which, if exploited, will have to be sold per ton (807, 913). These examples show that volume measurements are not feasible (724) under all circumstances. It may be expected that with a more complete tree utilization in the future, selling by weight will be applied on a larger scale (1768). Then it has to be based on the density of dry wood (the weight of a volume dried at 105° C divided by that of the same volume water), though as a rule the air-dry weight is considered. Density varies considerably within one species; it de­ pends on genetic factors, the place of the wood in the tree, the stand (location, density, age), the climate, etc.(1680). A difference of only 0.02, amounting to approximately 12.5kg per cubic meter of stacked wood (1092), is certainly impor­ tant to pulp manufacturers( 1648);also because of the quanti­ ties of chemicals necessary during processing (92). The influence of geography on density is unimportant in Europe: for spruce (Picea abies) russian data mention 0.447, Finland and Sweden 0.453, southern Germany 0.459 and 0.452(359). In Canada, normal variations in weight are for Douglas fir (Pseudotsuga menziessii) 43 - 47 pounds per cubic foot, for western hemlock (Tsuga heterophylla)47-52, for western red ceder (Thuja plicata)31-35 (1434). Greater differences in density have been noted: 0.31-0.38 for white spruce (Picea glauca),0.28-0.36 for balsem fir (Abies bal- Samea)(92). In Mississippi(USA) the values for loblolly Pine (pinus taeda) and shortleaf pine (Pinus echinata) in­ creased from the northeast to the southeast (1092), for sitka spruce (Picea sitchensis), in England it decreased 0.011 per degree increase in latitude (415). For small Pieces or single logs the limits can be considerably wider. Poplars are remarkably uniform in this respect, though 178 the specific weights vary with the species from 0.37 - 0.47 (1046, 1269, 869, 576). The same applies to willows (Salix spp.) which are so important to the Argentina and Rumania: 0.39 - 0.46 (395, 869, 1275, 1274). For teak (Tectona grandis) in Burma, India, Thailand, Trinidad and Indonesia, values range from 0.526 to 0.661, and naturally grown and cultivated trees clearly differ in the specific weight of their wood (1396), though without showing any distinct local trends. Eucalypts strongly vary (from 0.36 to 1.00) , mainly de­ pending on the species. Intraspecific data are rather con­ fusing, so that proper selection for pulp production has to be emphasized (1314, 729, 1402, 1586, 434): for example for kraft paper, species should be grown with a low density because they show thé best 'burst' factors (related to the ratio between lumen diameter and fibre diameter of the cells, depending on growth and age) (1550). In the USA, a forest survey covering twelve states be­ tween the Great Plain and the Pacific Coast included maps indicating specific wood density per species (1763). The importance of such data has been demonstrated by weight checks carried out by a paper mill in Main, which showed significant differences between geographic origin,both for conifers and broadleaved species (616, 1680). As will be explained in Section 8.6 , it is often neces­ sary to convert timber weights into volumes, either metric or board feet (the volume of a piece of sawn wood 1' x 1' x 1'') . This conversion can be done with a high degree of accuracy if large quantities are involved (correlations up to 0.99 have been calculated for shortleaf and loblolly pine, Pinus echinata and P.taeda) (724). A paper company in Florida (USA) equals 6.6 tons to 1000 board feet tree-length logs (1378), but as a rule the mul­ tiplication factoj varies with the species and even old and second growth forests may need different values (901). In Canada, a comparison of weight-scaling and counting 179 with measured volumes showed that weight-scale methods and load counts to determinate the volume of mixed log loads result in errors up to + 2 % if at least hundred loads are involved (1120). In Norway, truckloads with fresh wood vary less in weight than in volume (1131). The same was observed in the USA for poplar (Populus) and fir bolts (Picea) (407). In northern Europe, weight-scaling followed by dry weight sampling is considered essential for such comparisons (1585) and it gave better results than determining volumes (1164) (except for bolts of pine, pinus sylvestris). Tree diameter growth is irregular, both during the year and the life of the tree. Within one species (or variety) it depends on site, stand density and age, and the more springwood is formed, the lower its wood density will be (1091, 675). Table 6 shows some of these variations.

Table 6 variations in density of wood black spruce (Picea mariana), USA (92) 0.22-(0.41)-0.80 balsam fir (Abies balsamea), USA (92) 0.20-(0.32)-0.57 loblolly pine (Pinus taeda), 15% summerwood -5 0.35, USA (1657) 65% summerwood -5 0.65 ditto, USA (1092) 10-50 years -5 0.43-0.55 Pinus pinaster, Portugal (1157) for 15 oldest rings-.0.420 from the ol­ der to 0.525 for the younger rings slash pine (Pinus elliottii), USA (1092) 10-50 years -5 0.50-0.59 Eucalyptus globulus, Italy (1350, 1351) 1 y. old 0.541, 26 y. old 0.773 Eucalyptus camaldulensis, 4 y. old 0.541 and 0.507, Italy (1350, 1351) 5 y. old 0.538, 26 y. old 0.765 Eucalyptus verminalis, Italy (1350, 1351) 5 y. old 0.613, 15 y. old 0.659 spruce (Picea abies), Germany (675) medium to good soils, heavily thinned 0.351 moderately thinned 0.396 lightly thinned 0.404 poor soils, heavily thinned 0.403 moderately thinned 0.425 lightly thinned 0.424 180

For sitka spruce (Picea sitchensis) it was possible to relate specific weight to a series of soils (suggesting edaphic influences (415)). Butt logs mav be heavier than other logs (1199). Sugi (Cryptomeria japonica) in Japan shows higher densities near the center than in the outer layers of the stem (781). In pine (Pinus sylvestris) and spruce (Picea abies) in Finland, the branches are heavier (oven-dry) (602), which also applies to some wood species in British Columbia (Canada) as shown by Table 7.

Table 7 Percentages of bole and branch wood, and corresponding density for some British Columbian tree species (1437)

% bole wood % branch wood density bole wood branch wood

douglas fir (Pseudo­ tsuga menziesii) 70.6 10.4 av. 0.45 0.50-0.55 western hemlock (Tsuga heterophylla) 77.3 7.7 av. 0.41 0.59-0.62 western red cedar (Thuja occidentalis) 73.2 9.2 av. 0.31 0.43-0.58

Growth not only influences dry matter production but al­ so wood strength. For instance (too) quickly growing culti­ vated ponderosa pine (Pinus ponderosa) resulted in timber clearly inferior to that of naturally grown trees (1091). Among different tree species this rule does not apply, however (186): fast growth is not always accompanied by low specific weight, the correlation is almost negligible (1791). Because the quality of wood for pulp production depends for an important part on its density (except of course for very heavy and very hard woods from the tropics),yields (and site assessments) should also be expressed here in (oven-dry) weights, and selection has to aim at trees with outstanding densities (686, 1789, 1790). In the southern part of the USA, in 1970 already 35 million of such 'super trees' were planted (570). Spotting them (preferably in 181

combination with outstanding growth) is possible during forest inventory work by taking increment cores from the trees (1545, 1090). This spotting can also be important to forest management improving its seed selection and so preserving superior trees (265).

Water content and density In the living tree the moisture content of the sapwood is always higher than that of the older wood (9 2). In ad­ dition, it often increases from the base to the top of the tree, or the reverse; branches, as a rule contain less water than boles (1190). Moisture content also changes with the season, a phenomenon to be kept in mind in draw­ ing up dry-matter weight scales (407, 1164, 359, 1132). Such scales can only apply to freshly cut wood because storage always causes loss of water (276) (except, of course when kept submerged). Consequently, the best measure for production is the quantity of oven-dry wood. For standing trees it can be measured by collecting cores with an increment borer, which gives reliable results (1352). From logs to be sold by weight, larger samples can be taken; they have shown to result in maximum errors for spruce (Picea excelsa) of 4.7 % and for beech (Fagus sylvatica) of 3.4 % (361). For some parts of the USA there are tables which give average green weights for numbers of logs per truck, from which dry weights can be estimated. A comparison with load weights showed errors up to 10 % with a mean of 0.4 % (503). In western Europe, where smaller quantities of wood are in­ volved, the most accurate data are obtained by collec­ ting from each load, at random, saw-dust samples with a small chain-saw. Because sampling and weighing during un­ loading is time-consuming, estimating the water content of such a sample by electric measuring seems preferable (360). 182

The influence of bark, cull and ice on weight Literature does not mention difficulties with bark during weighing unpeeled logs, though it may make up 8 - 20 % of their weight (1680, 1164, 1585, 322, 1199). The bark weight varies not only with age and habitat, but also with the season (407). The estimation of culled wood is difficult because it of­ ten cannot be seen from the outside. For its assessment, special 'cull surveys' could serve, before or after scaling, or ocular taxations are possible on externally visible de­ fects (1114). Scalers have quite some experience in estimating the quantities of mud and ice attached to logs (1164).

Weight tables for trees Tables to estimate the dry weight of standing trees are still very scarce. Some relate this weight to the diameter at breast height (DBH) and total tree height (H) (1263), some to D2H (as for slash pine, (Pinus elliottii)),others to H and the density obtained from increment cores (322 ). For loblolly pine (Pinus taeda) trees, the weight of 5 feet of paper wood bolts with a minimum top-diameter of 3 inch has been calculated based on D2 (1645). In Australia, for radiata pine (Pinus radiata) , provisi­ onal tree-weight tables have been prepared for the whole tree (including stump and roots), for the whole tree above the stump, and for the merchantable bole with bark. From them has been deduced that the total tree weight, including roots and needles, consists for 76.1 % of wood, for 54 % of merchantable wood, for 13.8 % of bark, and for 10.1 % of needles and cones (331). 183

8.3.2 Measurement of wood vol time

The most exact method to determine the volume of a piece of wood is to immerse it in water and to measure the quan­ tity of water it displaces. It is still applied in research and in some places in Norway (1165). In all other cases log or bole volumes are measured (or estimated) directly, either by comparing them with cylin­ ders, cones, or comparable mathemetical bodies, or by ex­ pressing their volumes in a number of sawn pieces (board feet, as a rule, one b.f. being the content of a piece of wood 1' x 1' x 1'') • The result is always an approximation, but may be quite useful if large quantities are involved. The idea of expressing volumes, even stand volumes, in quantities of crude product is already very old. In France, and probably also in other European countries, oak wood production was calculated on the squared logs a stand could produce (1208). After cutting, the net volume was calcula­ ted by measuring the girth (g) of the round logs (in the middle) and by applying one of the formulae

x L, (f)2* length (Li 'o,

giving a reduction of gross volume of 0.785, 0.545, and 0.503 respectively (1208, 1263). All these formulae are based on the same principle as the 'Hoppus quarter girth' method, extensively applied in Great Britain and its one-time colonies. The Chinese traders in Singapore reduced it to (0.7d)2 x L (d=diameter in the mid­ dle) , in addition timber imported from Indonesia had first to be recalculated from cubic meters to weight (for trans­ port) and lateron to volume according to 'Hoppus' rule (474) for the customs. In the USA the situation is perhaps even more complica­ ted, each region having its own rules. At present, all log rules authorized in the Forestry Handbook (486) and in other regulations start from top diameter under bark and 184

calculate volumes for 16-feet logs. In Canada the same procedure is followed, but a comparison with actual volumes has shown great differences (798). In New Zealand, the num­ ber of board feet per cubic foot true volume of round logs was shown to vary from 4.3 to 9.6 (510), so that 'board- foot measure (is) a particularly artificial concept, when,_ as becoming increasingly the case, products other than the one inch square edged boards are being'produced' (1470). Gross or true volumes are the best criterion for the as­ sessment of wood production capacity. For logs they can be measured to any desired degree of accuracy, but as a rule it is sufficient to use formulae containing diameter, and sometimes girth reduced to diameter (usually in the mid­ dle) and length, and a form factor (f) depending on the tree species and other factors: volume = f 71 diameter^ x length 4 Such values have been tabulated starting from diameter and length. Many variations are possible on this theme. In Huber's formula, used in the Netherlands (177) and Germany (1263), indeed the middle diameter is used: ? volume = 71 middle-diameter' x length 4 and is considered sufficiently accurate in all cases where normally formed logs are involved (126.3,). In the USA and Canada most tables start from top-diameters to calculate the volumed 16' logs, applying a certain tapering-off from the butt to the top (in reality a kind of form factor)(486) In South Africa, either Huber's formula or the Smalian for­ mula is applied for volume (348):

4 (cross-sectional area at top + cross-sectional area at butt)x length In the Scandinavian countries and Russia top-diameter is used, and sometimes also the butt-diameter or diameter near the butt-end of"the log (1165, 39). The biggest saw-mill in southern Sweden even uses a photo-electric installation to measure the incoming logs, a computer providing the volumes 185

(260). For Canada it was proposed to let the harvester- limber do this job for the tree-length logs; installing a measuring device in its collar-like top-unit moving from the base to the top of the log to be cut (1278). Serious difficulties can arise with deeply fluted logs (1306). For teak (Tectona grandis) in Indonesia special correction tables had to be drawn up (1727, 1728). With complete (integrated) tree utilization, most pro­ bably to be combined with weight scaling, these formulae could become obsolete (1769, 1770). For stacked wood, mainly firewood and pulpwood, the stems (and branches) are usually cut to equal lengths and piled in 'cords' (corde: French for rope), originally combined into bundles of approximately three cubic meters (1208). In Europe, the base of a stacked cubic meter measures 1 by 1 m, its height is 105 cm to account for the irregular top. in Canada and the USA a cord means 4x8x4 feet, equalling 3.62 m^. Reduction factors are needed to exclude the open spaces between the wood pieces. They range from 0.80 (for peeled paperwood (1263)) down to 0.68 - 0.79 (for unpeeled paper- wood (486, 39)) and can be as low as 0.47 for strongly Snarled firewood (39). The errors made in applying such percentages may be con­ siderable: for beechwood (Fagus sylvatica) in Germany de­ viations ranging from - 12 % to + 7 % have been observed. Comparable errors are made when the wood is directly loaded into trucks: again in Germany errors of + 5.6 % (for spruce, Picea abies) and + 5.4 % (for beech) are mentioned (361). The main cause is that stacking cannot be standardized: some people make compact stacks, others loose ones, and during transport the pieces tend to get stacked more densi­ ty. A solution is to measure surfaces on photographs of the ends of the stacked pieces? though this seems rather im­ practicable, in Canada this is sometimes done with truck- loads, resulting in an accuracy of + 2.4 % (520). 186

Cutting and stacking pieces (or bundling them) means hea­ vy labour (1527) and has in many cases been mechanized. For pulpwood and with tree-length harvesting, this work can be carried out in the factory (165), or in a semipermanent or movable 'slasher' (1648, 327), or by machines depositing the bolts along the forest roads (1740, 1741) followed by mechanical loading into containers picked up by self-loa­ ding trucks (164, 1577). It is even possible, already in the forest, to cut the wood into chips which are loaded or blown into carriers (1749). Then stacking and measuring volumes becomes superfluous.

8.3.3 Tree volume and tree volume tables

Except for some very experienced surveyors, everybody who wishes to assess the wood volume of a tree needs a table based on some measurable characteristics. Such tables can be calculated from exact measurements on bole sections of felled trees with the Huber's or Smalian formula, whereas the top section can be considered to be a cone. Branchwood is stacked. No table can be constructed for products such as walnut stumps (1203) (for veneer) and roots for fuel (China) (1452, 423). Where the trees cannot be cut, other methods are needed to determine volumes which have to serve as a base for tables: trees can be climbed (658, 94) (as done in telegraph-poles and for seed collection). With the declining interest in firewood, the importance of measuring branchwood decreased, until recently when deve­ lopments towards complete wood utilization increased it a- gain.A problem here is,how to get rid of the bark,as here the use of debarkers, especially the ring debarker, is still un­ economical »(1337). As a rule, trees are not cut immediately above the soil; nevertheless in«Austria the volume tables include the whole stem (57). In the USA one foot is excluded (1470); the well- known Grundner-Schwappach tables start above the root swel­ 187

ling (1375); in 1961 the International Union of Forest Re­ search Organizations recommended to include the whole bole and to discount for the stump with reduction factors (41). For the easily, directly measurable characteristics men­ tioned above, generally the stem diameter or circumference at breast height (DBH and CBH) and the total tree height (H) are used. In continental Western Europe and England DBH and CBH are taken at 1.30 m (51") above the soil (1470), in Russia 1•30 m above the root swelling(39),in the USA and Canada at 4' 6" (1.37 m); trees with high stilt roots or buttresses should be measured just above them. Forks may be considered separately (723) if their common basal part is short (1119), °therwise forks can be ignored. For diameters, the average between the largest and the one perpendicular to it, is the most accurate (the axes of an ellipse) , measured with a tree caliper. Determining the circumference, and later deducing DBH, is much easier and Sives practically the same results; differences between the two are up to 0.5 % (795). Recently, instruments for indirect measurement of DBH (no_t CBH!!) have been recommended (579). Their forerunner is the Biltmore stick (425), a ruler to be held horizontal- 1y at arms length against the bole and provided with a scale adapted to the length of the surveyor's arm. It gives reasonably accurate results (1470, 1263). More refined are the optical instruments, optical wedges or thin prisms (*21) , such as the German Bitterlich Relaskop, the Zeiss Teletop, and the Barr & Stroud dendrometer (1263). These Can also be used to measure diameters higher-up in the ti 'eesf but for practical purposes this is hardly feasible. Nevertheless such measurements are sometimes carried out the USA to determine the volume of trees (3-P sampling) selected either as representatives of a stand, or for very valuable trees; they may result in an accurate drawing of stem form from which its volume can be calculated 188

(580, 582, 624, 1057). Direct measurement of the height of a standing tree is possible only for a small specimen, if necessary with the aid of a telescoping rod(323).For higher trees a hypsometer is needed based on trigonometric principles. A well-known simple instrument is the Christen hypsometer which compares the height of the tree with a stick of given length placed at the foot of the tree. Other instruments measure the ang­ le between a horizontal line and that through the top and the base of the tree, from a certain distance. Tree heights can also, with a reasonable accuracy, be es­ timated from aerial photographs if both tree top and foot are clearly visible (730). To derive the wood volume of a tree from diameter and height, the formulae of 8.3.2 for logs can be applied, with the 'form factor1 now referring to the whole tree (1064). Practically any diameter of the lower stem is suitable, but obviously that on breast-height is preferable. It results in breast-height form factors, sometimes combined into form classes (458) (tried out in Europe but not sufficiently exact (722, 111)). After World War II, their use decreased, but recent investigations have again shown them to be quite suitable (429), especially when applied to the value (DBH)2 x H (345). Written in the form volume V = Kj . D2 . H (345) it is now considered very useful in British Columbia (Cana­ da) (429, 1429, 1430). Tree taper studies, based on thousands of measurements, have shown that DBH is representative for the lower part of the bole (1375, 635, 924), though sometimes the root swellings have to be left out of consideration (in British Columbia this is achieved by excluding the basal 4 % of the tree height (505), in Surinam, for Pinus caribea, 5 % (1646)). This has the drawback that instead of DBH, dia­ meters higher on the stem have to be measured, which for large trees may be difficult 189

In the USA, some volume tables are based on two dia­ meters: DBH including bark and diameter at 16 (4.80 m) higher under the bark, at the end of the first or butt log, being the most valuable one. For the second diameter only an ocular estimate is practicable. For the determina­ tion of volume a certain ratio (between diameters) or ta­ per is applied (486, 1470). For Finland similar tables were constructed by using a diameter 6 m above the soil (731). Of course all such tables give averages so that for a single tree the outcome may be quite different. This is in­ herent to all tables, and suggests that they should not be applied under circumstances for which they were not devised. So it is not surprising that different tree volume tables are used (650), for natural stands and plantations of Para­

na pine .Mr.Bc.ri. angustifalia) in Brazil (654), and that in Europe sometimes age classes are kept apart (1375). Special tables are available to estimate merchantable log volumes, often for groups of species such as broadleaved trees in the tropics (655, 658) or for cord volumes for Pines and hardwoods in the USA (486), or for pulpwood. Such tables have to be revised with every change m the exploi­ tation technique (538, 1071). The trees on which a stand volume table is to be based have to be selected very carefully; they have to be 'normal', representative for the whole stand, or better still for the species as a whole. They may be selected du- ring logging, as in Russia (39), and for the Parana pine in Brazil (650). Where no 'mature' trees are available, as for example in the Netherlands with Douglas fir (Pseu­ dotsuga menziessii) , 'normally formed trees' are taken (111),and in Germany trees felled during thinnings (635). For radiata pine (Pinus radiata) in Australia, 'subjec­ tively selected sample trees from permanent sample plots' serve as a base (315); in Indonesia sample trees of (Aga- this borneensis) with broken tops were reconstructed (457). 190

For Pinus pinaster planted in South Africa the trees with poor shape are rejected, clearly a selective choice (884). Obviously, the conventional tree volume tables are rarely based on ' a valid sample of the tree population to which they are applied1 (583). With a more complete tree utilization, such errors have to be avoided and: in addition, volumes have to be accom­ panied by quality appraisals derived from actual fellings (82). Hence (as remarked for pinus caribea in Cuba)'volume tables are not static and should be periodically tested against measured trees' (240). For the construction of volume tables a wide variety of methods is used whereby several types of correlations are applied next to using DBH and H: between the diameters at 0.3 and 0.7 of the tree height in Finland (880), taper fac­ tors for diameters with and without bark at various heights along the tree bole in Australia and New Zealand (315, 930)» the diameter at one third of tree height in Austria (1243, 19 3), or the ratio merchantable tree-volume to total tree- volume in Canada (703). For the transformation of sample tree data into volume tabulations, at present, mathematical methods are general­ ly applied; the curves drawn by hand have become obsolete (513). On the international level, often,difficulties occur in converting foot-inch measure into meters. In 1960 the Fo­ rest Service of India introduced volume tables in both sets of units. However this is unfortunately still an ex­ ception (326).

8.3.4 Changes in wood utilization m

Several times the preceding sections have pointed out that changes in the use of wood influence the way it has to be measured, and that for more complete wood utilization the (oven-dry) weight will become increasingly important 191

(in 19 30, in the USA, 7% of the harvested wood was used for fibre production, in 1966 it was 25% (468); in Finland it recently amounted already to 38% (727)). For the tropics, opinions differ. Some people believe that mixtures of tropical hardwoods can be pulped economi­ cally, as indicated for Papua (Australia) and Surinam (281, 710). Many species have been investigated separately with positive results (though crystallized mineral contents may cause difficulties)(1316). Near Libreville (Africa), even a high-capacity factory has been established for mix­ tures (1230) and the pulping of okoumé-wood (Aucoumea klai- neana) has been tried out (372). If this possibility proves to be realizable, it opens wide perspectives and might lead to a complete wood exploitation in tropical areas, e- ven more so than that in Sabah (Borneo) where all trees are cut that produce a reasonable sound log (mostly Diptero- carps) (495). Another step towards integrated utilization is the in­ creased use of waste ('slash', in the past left in the forest) and of refuse from sawmills and other woodworking industries (468, 260), because (as the 7th World Forestry Congress in 1972 formulated it) 'new techniques enable the use of planer shavings, sawdust, and even sander dust. The processes in turn result in the increasing availabili­ ty of chips and fiber for pulping and for widening the ran­ ge of panel products' the outlets for residues being cru­ cial for the survival of many saw-mills and plywood fac­ tories (445). The quantities of waste left in the forest are indeed considerable. After the tree tops had been cut off at 10 cm diameter, they amounted for white spruce wood (Picea glauca) in Canada for trees with a DBH of 15 cm to around 400 kg, for trees with a DBH of 50 cm 100 kg per log (805). In Finland for pine (Pinus sylvestris) and spruce (Picea abies)', the loss was found to decrease for stump sizes of 5 to 35 cm from 50.6 to 2.2 % (1076). In a saw mill the waste depends on the type of machine and the ul­ timate products. For Douglas fir (Pseudotsuga menziessii) in British Columbia a band saw gave 13.2 % slab wood and 14.3 % saw dust, a cir­ cular saw 13.8 and 19.9 %, a gang saw 18.7 and 16.6 %, respectively 192

(1434). Pulp manufacturers using sawdust seem to prefer that obtained with a 3/8" bite per tooth (1004). To avoid sawdust, in Czecho Slowakia spindels are used that produce 3.4 mm broad chips suitable for chip board (1753, 1390) (world produc­ tion in 1960: 1.86 million ton, 1970: 7 million (788)). Especially the harvest of pulpwood lends itself admirably to mechanization (1195). In Oregon (USA), a kind of shearer, 20" long, cuts 450 to 500 trees a day, and a 'logger-utili­ zer' separates the logs, deposits the bark in holes in the soil, and blows the chips into trailers, so that no human hand touches the wood (334). In Europe, mechanization usually stops with the chainsaw, though in Hessen (Germany) further mechanization was consi­ dered to save 30 - 50 % on labour costs (531) and mechanized thinning to reduce expenses by O.M. 100 - 200 per hectare (594) if restricted to cutting out rows of trees (for more refined thinning methods other equipment will be needed (1492)) .obstacles to further mechanization are in Europe the topography of the forest land, the mixture of species growing together, and the scattered stands belonging to ma­ ny owners (693). To produce chips and sawdust to be sold to pulp and paper factories,the trees have to be peeled at the mill. As ful­ ly automatic debarkers are too expensive for small bush­ mills, in the south of the USA special firms collect slabs (especially from the mills working smaller logs with rela­ tively high residues (1203)) and remove the bark (Vac-Sink ... system) (601, 614). -�--- Many variations on this theme are possible. Full-length trees can be brought to the mill, topped and treated there (1746, 1738), or all working-up in boards and chips can be done in one uninterrupted procedure (1739, 1742) as in 'Chip-N-Saw' units (201) where the chipped-up slabs are blown into lorries and sold by weight after being automa­ tically sampled (1745). In Sweden, such a unit is operated by one man, overlooking all operations with the aid of three television cameras (1399). Especially small logs lend 193 themselves to such automation(1032)considerably saving on labour:a mill in Georgia(USA),sawing some 2000 small logs per day,is said to need only five operators (1739), a mill in Ger­ many uses the same number to produce 100-200 m3 sawn timber per working shift (1750). All these changes make volume mea­ surements; troublesome, expensive and out of date.

8.4. Stand assessment techniques

8.4.1 Tree counting

After the problem of tree naming has been solved, quan­ titative inventory work can start. The simplest way is to count the trees per species (or group of species) on a certain area. During the 18th and the beginning of the 19th Century, in Europe, the demand for fuel being far greater than for saw timber, the assessment of forests was concentrated on areas, whose yield in steres firewood was known from ex­ perience (957). Apparently valuable trees such as oak

(Quercus spp.) have always been excluded. in France, up to the beginning of the 18th Century, these oaks were counted separately and sold per standing tree (1208). After the World War II this method was still applied in selling Parana pines (Araucaria angustifolia) in the south of Brazil and in many tropical regions where forests are not scarce, land values are low, and most of the fo­ rests belongs to the government. To regulate inventory work, a French system was applied as in tropical Africa; the forest is divided into squares (mostly one by one kilometre) and on each square the market­ able trees per species are counted before the area is put at the disposal of the licence holder (906, 294). For the Amazon Region a comparable method has been recommended for the widely scattered fancy species (one or less trees per ten hectares) such as Cedrela odorata, Cordia goeldiana ar*d Aniba roseodora (655). 194

Counting was gradually supplemented by estimating quan­ tities of timber, either expressed in wood volume, or in boards of standarized dimensions, handmade shingles, slee­ pers, etc. (1648) for which conversions are needed (486, 1263). A typical form of such an old-fashioned survey is that carried out in 1910 in the Apache National Forest (USA). There, on circular plots considered representative for large stands, the number of merchantable 16-feet logs was counted and an ocular estimate was made of the expec­ ted quantity of board feet (1027). For more accurate wórk, counting remains possible in even- aged stands if sample areas are used as a base to correlate, per hectare, numbers and volumes (or even numbers and quan­ tities of dry product, e.g. in pulpwood plantations; see 8.3.2). Mechanical forest exploitation, cutting entire boles (even if they are badly formed) and the speeding-up of the harvest, have made it necessary to introduce new ways of tree assessment (321). The easiest solution is to count the felled trees and to estimate afterwards, by sampling their volume (1278). As an alternative, this work can be restricted to the logs ente­ ring the timber yard (165). Various modifications of such a method are possible: in Ontario (Canada) the stands were qualified on the number of trees needed, to produce a cer­ tain stacked timber volume (in cords) (1648). Comparable methods are possible to estimate the produc­ tion capacity of working shifts: in Oregon (USA), for lodgepole pine (Pinus contorta) the number of harvested trees served as a base (1743) , in Sweden this number was supplemented by the average volume per tree (327). Where, iif plantations, mechanization has advanced so far that stands of not too heavy trees can be 'mowed down' and bunched, counting is necessary, as measuring volumes is too time-consuming (weighing is not yet practised in fores­ try). Indeed machines exist that are able to handle diame­ 195

ters (near the soil surface) of up to 40 cm or even 65 cm, shearing-off 70 - 120 trees per hour (1217); in Florida (USA), trees with an average base diameter of 17.5 cm were cut at a rate of 200 per hour (1748); for Sweden it has been estimated that fully mechanized harvesting can handle 8-9 trees per minute (1528). In North California (USA) machines bundle the cut trees (handling 35 in one turn) and load them on trucks with a capacity of 80 - 100 full-length specimens (1754); in Au­ stralia, the recently constructed thinning machines can re­ move rows of trees at a rate of 90 per hour (801). The examples given illustrate clearly the growing impor­ tance of the numbers of trees per area, whereby the impres­ sion is sometimes given that volumes come second. Invento­ ries will in their representation of results have to take these trends in mechanization of harvests into account.

8.4.2 Stand volume assessment

To determine the wood or timber value of a stand it is, theoretically, possible to measure all trees and to sum the results. Instead of measuring them, the volumes can be taken from a tree volume table (based on DBH and height, as a rule).Though per tree the error can be up to + 10 15 % (for abnormal specimens much higher), investigations in Germany have shown that with averages for large numbers the error is considerably less: for 2616 oaks (Qvercus robur) 0.0 %, for 4230 beech trees (Fagus sglvatica)+ 1.5 %, for 250 Scots pine (Pinus sylvestris) + 3.3 %, for 236 other beech trees + 4.9 %, and for firs (Picea abies) - 4.2 % (1263). Por reasonably exact calculations, measuring plots have to be established. As a rule on such plots all diameters are recorded and for some selected specimens the exact height and other characteristics are measured. The results of a great number of such plots are combined 196 to calculate stand volume tables which give (usually for even-aged pure stands) wood or timber volumes at given a- verage tree height and age, provided tree spacing is nor­ mal. A correction factor has to be applied for abnormal tree spacing. For unthinned plantations of red pine (Pinus resinosa) and white spruce (Picea glauca) in Canada, the average height of the 10 % tallest trees and the average spacing serve this purpose (1498). It may be remarked that not only spacing and volume are closely correlated, but also spacing and oven-dry weight of foliage, as an ex­ pression for crown-volume or growing-space (1499). Tables can also start from the basal area of the stand multiplied by the average tree height, to which empirical reduction factors are applied which appear to be fairly constant and mostly range from 0.45 to 0.50 (1263). For oak (Quereus robur) aged 130 - 150 years they may be as high as 0.54, for beech (Fagus sylvatica) aged 150 years up to 0.52, for 60-year-old spruce (Picea abies) 0.5-2; Scots pine (Pinus sylvestris) aged 30 years was an excep­ tion: 0. 44 (1209). Because of recent development in wood volume assessment, these methods have been considerable modificated, especi­ ally for more extensive forest surveys. Aerial photography, together with statistics and computors, are incorporated in designing adequate sampling methods-^ Although foresters often give the impression that they pay more attention to the methods than to the accuracy of the outcome, and though experienced surveyors are able to make excellent ocular es­ timates of stand volumes and other characteristics, these mechanical methods nowadays play an important role in fo­ rest assessment. * In forest inventories, general, regional or local tree- volume tables are used based on DBH or CBH and H. Only if 3-P sampling is'applied (see 8.3.3), whereby selected trees are measured optically in sections over their whole length, are no volume tables necessary (623). 197

Next to the common volume table, the Tariff Volume Tables are the best known. Because the estimation of tree height or its measurement cannot be done directly, it is subject to errors. Tariff tables are only based on DBH, CBH or ba­ sal area, the regression of volume on basal area being con­ sidered linear for trees of a given height (722), which in general has shown a satisfactory fit (571). With tree height, tree volumes change so that for every tree height a diffe rent 'tariff' has to be calculated. To select such a table, randomly chosen trees may be felled (723, 462). From properly checked tariff tables, stand volumes can be more accurately assessed than from general volume tables, alignment charts, or nomographs (the last being simplified volume tables) (317, 284). In France, tariff tables with intervals in height of 2 meters were prepared for Pinus laricico and compared with exact measurements they gave errors of 6 % (42). Those conducted in Soutt Africa, also gave errors, but involved less work and fewer costs (1237). In Indonesia such tables were constructed for Pinus merkusn plantations (956), ter in two versions for thinned and unthinned stands (1450). Local volume tables based on DBH only, omitting the estimation o the length of the tree bole, were tabulated for the Amazon Valley, showing only small differences from the volumes obtained with 9e^al tables (542). Tariff tables used in surveys of African rain forests 9 increased the error incurred only < ^ in use> including

In Germany many types of volume ana wri ^ ^,^4^ „ifK a ^ general volume tables, were checked. 30 experimen a anolvina the tal of 3317 trees and a volume of 2029 m* „ere surveyed applying the

tables and afterwards all trees were measured in sections, rences found ranged from - 0.39 to + 2.23 % ( Hence most methods using volume tables, if intelligently chosen and applied, are accurate. Recently, Bitterlich introduced the 'point sampling me­ thod" which he and the forest mensuration text books have extensively discussed (149, 1208, 1263, 39, 1470). This me­ thod of determining the basal area of a stand (not differ­ ing significantly from that obtained with a common tally (90)), uses an instrument, placed on a stick, with a verti­ cal slit through which (by turning around) all trees are counted that (at breast height) have a diameter surpassing a Previous fixed value. A thumb on an outstreched arm could 198 serve the same purpose. The principle of this point sampling method is that each tree tallied in this way, regardless of its DBH with bark, is included in the basal area, either expressed in square feet or square meters. It is most convenient to make the slit and the distance between the slit and the eye such that the number of trees immediately supplies the basal area of the stand. The relationship between the basal area and the number of trees counted can be expressed by the formula: G = 2 5 0 0( ^7) 2 .N in which G is the basal area in m ,• a is the width of the slit (2 cm); b is the distance of the slit to the eye (one meter) and N is the number of trees counted.Thus the number of trees counted will give the basal area of the stand in square meters (1503). Instruments in the form of prisms, as they are cheap and do not strain the eyes too much, are the most convenient (886). Tests in the Netherlands and the USA indicate a suffi­ cient degree of accuracy (1647, 872), but difficulties arose in Texas (USA) with border trees and specimens over­ lapping in the field of view;to obtain a satisfactory accu­ racy more had to be sampled (578). In Australia, doubtful trees are counted as half (316). When the sample point is close to the border of the stand, the^danger exists that open spaces or other stands occupy part of the viewing field, so-called 'slop-over'. Here a reduction factor is needed (1647). In Norway, counting proceeds along a pre­ viously fixed line of given length (1515). In tropical forests the results were disappointing, as sight was usually obscured by the undergrowth so that big trees at s'orne distance were difficult to spot, buttresses and other irregularities obscured the picture (725). For identification *all trees have anyhow to be looked at (cut­ ting the bark) from nearby, so that measuring them direct­ ly hardly can cost more time. 199

In purely random surveys, the observation point may be too near a large tree, blocking the view, but in the lite­ rature this drawback is considered negligible (1176). In dense young stands it may be impossible to find a place where all surrounding trees are visible; here the conven­ tional marked plots are more suitable (1516). When the stand basal area has been obtained, stand vo­ lume can be determined from general volume tables, stand volume tables (based on total basal area and mean height), tariff tables, etc. For Norway it was noted that stand volume tables may result in a general bias (mean 5 %) (1517). Affiliated with Bitterlich's method is that in which, starting from a random point in the stand, the distances to the six nearest trees are measured. This means that a circular plot just including these trees contains six spe­ cimens. Its radius is a measure for the density of the stand. The diameters (and heights) of all six trees have to be determined, and a table supplies the volume per hec­ tare (or some other quantity). Such a method is suitable for stands less than 5 ha in area and has to be carried out by well-trained technicians (1265). Another variation of Bitterlich's method is first to measure stand density by starting from a random chosen tree. The distance to the nearest and the next nearest are measured. The circle through the latter thus contains 2.5 trees; a formula based on its radius gives an estimate of the number of trees per hectare. This procedure has to be repeated several times; combined with DBH or CBH measu­ rements and height determinations it provides stand volu­ mes (1504, 424). 200

8.4.3 Sampling

Inventorization of a forest area, for whatever purpose, can hardly ever cover all stands and trees. Thus certain stands, strips, or other parts have to be selected that are representative for the whole area. Or in other words (only) samples have to be investigated. This has two advan­ tages: at the same costs much larger areas can be covered, and for the selected parts more refined methods can be ap­ plied (1369). Then it is not necessary to rely on ocular estimates, though with experienced surveyors they may give quite reasonable results (errors rarely exceed 5 %, prac­ tically never 10 %). Samples may be selected at random or systematically. At random means that the result represents an unknown 'true' value (for the whole, comparable with an average of a very large number of measurements) and that it deviates from this value only due to accidental causes inherent to the restricted number of observations. Then a set of mathe­ matical tools is available to judge the accuracy of the out­ come. Systematic sampling involves a regular, artificial scheme or pattern for the distribution of the sample areas over the forest. In such cases the outcome is not only afflected by accidental errors (due to the necessarily restricted num­ ber of samples), but it is also influenced by the pattern of distribution. The latter may be negligible, or it may be an important source of error, for example when an inven­ tory is made along strips and one of these stips happens to follow a river valley with a deviating forest vegeta­ tion. Thus with systematic sampling no true statistical methods arê available to judge the accuracy of the result£ .

St For more details on this subject may be referred to hand­ books (724 , 1 263 , 1470, 957 , 1 262, 1 386 , 504 , 1440). 201

Random sampling The sample being that part of the forest stand to be measured is generally subdivided into units. The mental idea in simple (or unrestricted) random sampling is that, in choosing a sample of n units, every possible com­ bination of n units should have an equal chance of being selected' (504). Exact random sampling is possible only when good maps are available provided with co-ordinates identifiable in the field. The units or sample plots to be measured have to be selected with the aid of tables containing random numbers. Such numbers can be used to locate the corner Point of a square sample plot. An example may illustrate this.4-u . Suppose the, area •=is a squarecmiare WJ.with its sides divided into 1000 units subdividing the whole into 1 000 000 units or plots. Then a table of random numbers may give for one selection the numbers 251 and 874, meaning the unit, with its sides 250 - 251 units from the zero point (one of the corners of the large square) in one direction, 873 - 874 units perpendicular to that direction. This has to be re­ peated until the desired number of plots has been selected. The big square, mentioned here, can be a map-sheet showing the irregularly shaped forest-complex to be surveyed. In choosing the map-units, the selection has to be repeated un­ til the desired number of units are inside the forest stands. When no suitable map is available, a preliminary recon­ naissance can serve to select, haphazardly, the plots. They may give a good impression of the variability of the stands (in composition, and in timber volume (655, )), but they cannot supply reliable data for the whole area.

They are only informative; such a selection is never un­ biassed. From the literature one gets the impression that to find fche exact location of a sample plot is no problem. In rea­ lty it is: simple instruments (or even pacing) automatical­ ly leads to the wrong place. If the location is found and 202 it is unfortunately a big tree or a dense thicket most explorers step aside, especially if a circular plot or point-sampling is involved. In Finland it was found that explorers are inclined to keep clear of thickets and dense stands even when they use a compass, which results in too low volumes (5 to 7 %) (834). In Sweden it was observed that it was seldom possible to return to a plot that had to be re-enumerated, notwithstanding the use of a good map, measuring tape and compass (1035). In all such difficulties aerial photographs have proved very helpful (1489), as has been demonstrated in the Ne­ therlands, where plots were marked with pieces of white hardboard before the aerial pictures were made (1487). The biggest problems, however, are met under dense, completely closed, forest canopies where even aerial pictures are of little use.

Systematic sampling As indicated before, systematic sampling refers to cases where samples are measured (or investigated in some other way) on plots or along lines (transects) previously arrang­ ed in a certain pattern. Where this pattern more or less follows a morphological tendency in the field, i.e. is not projected perpendicular to the topography, and runs parallel-wàth contour-lines, or follows a river (1406), measurements may be highly bi- asses. To evaluate systematic sampling results, it is possible to compare them with those of randomly chosen plots for the same area, but this is impracticable. In Sweden and Aus­ tria, the evaluation of their accuracy has been improved by grouping the sample plots at the corners of the systemati­ cally laid out grids (1034, 193). In the USA, 12 forest tracts were simultaneously sampled 'at random' and 'systematically1' revealing that, with the same sampling density, systematic sampling may give better results (1056). Comparable conclu- 203

sions have been reached in Finland (1168). It was recom­ mended to give the size of the systematic sample the same Magnitude as would be given to a simple random sample for obtaining a defined accuracy to attain at least the same results (1056). In a systematic survey, plot size has, theoretically, no influence on the result with the same sample surface percen­ tage. For tropical rain forest sizes of 0.2, 5 or 10 ha have been recommended (169). The smaller ones have the advantage that the explorer has to penetrate deeper into the forest, making the result less subjective. In Sweden the dimensions are 1.2 x 1.8 km,in Finland 1.2 x 1.2 km or 1.4 x 1.4 km, in Norway 1,0 x 1.0 km, in Austria 0.2 x 0.2, 0.3 x 0.3 or 0.4 x 0.4 km.* With the coming of good aerial photographs and better maps, it is not necessary anymore to connect all plots and transects; they can be located beforehand in equilateral 9rids, either projected on aerial pictures or topographical maPS (586, 1035). For small areas or unmapped areas systematic surveys can be done with the aid of transects traversing the whole stand at given intervals; a 2% survey is obtained by spacing the PQrallels of 10 m wide (enumerated strip) 500 m apart.

^mplincj density The more uniform a forest, the smaller the number of random' and 'systematic1 sample plots (or the total sample area) necessary to obtain a given degree of accuracy in es­ timation. For plantation forest in France, one 0.05 ha plot f°r each surveyed hectare has been considered satisfactory; lfc gives in stands of 80 ha for volumes an error of esti­ mate of io %, for uniform stands of pole-sized trees 6 % (*207). if quality appraisals have to be added (for which trees have to cut or climbed), sampling density has to be ^°dified (18, 906).

T his applies to the so-called 'tracks' along which to the left and e t right over a certain distance all trees are enumerated, or at cer- in intervals plots surveyed. 204

For random surveys, the number of plots of a given size can be chosen and depends on the coefficient of variation, the ratio of standard deviation and population average. In East Germany, based on a very large set of data, the coeffi­ cients of variation found were for: uniform stands 30 to 50 %, mean 40 %: for more open stands 50 to 60 %, and for irregularly grown stands with broken crown canopies 100 to 150 % (584). Sometimes sequential sampling is applied so that, during the work, it can be judged whether a suffi­ cient number of plots has been included to obtain the desi­ red degree of accuracy (1432). This all seems rather complicated, but extensive research and experience have revealed a certain uniformity in vari­ ation greatly facilitating decisions on sample size and number of samples plots of a certain size.

Aerial photographs and sampling In Canada, parts of the USA, Russia, and other regions with large forest areas, field sampling is based on charac­ teristics obtained from aerial pictures (1391) (such as crown density and tree or stand height) later checked in the field (1249), leading to stratification of the popula­ tion and resulting in stand volume classes (167). Such es­ timates have to be carried out by different photo-interpre­ ters to avoid bias, and the results -have to be compared with those of field plots (1487). In Minnesota (USA), a minimum of 40 to 50 comparable field plots has been consi­ dered acceptable (59). It was also concluded that aerial volume tables applied to mixed stands of pines and hard­ woods yield volumes not deviating more than 10 % from those determined in the field (58). For some hardwoods fo- M rests in the USA, a table has been constructed giving ave­ rage values of DBH, based on crown density and average tree height measured from aerial pictures. These extremely indirect volume measurements serve to trace stands con­ taining sufficient merchantable pulp and paper wood (1066)- 205

Por tropical forests it is possible to attain a certain volume class stratification based on photo-interpretation and sample plot enumerations in the field. For the Amazon Region, limits between 100 - 150 m^, 150 - 200 m"^, etc. bole wood per hectare could be established. But here the Problem was that exploitation was not interested in total bole wood volumes but in selected species, which could not be indentified from the aerial pictures. Perhaps in the fu­ ture this attitude will change and the interest will be more directed to total volumes (see 8.3.4).

Foresters, not yet chained to an armchair, have mostly the ability to make ocular estimates of stand characteris­ tics including volumes, with a high degree of accuracy. Re­ cently, statistically sound methods have been developed to assess the real value of such subjective or biassed esti­ mates. For a good control, the roughly estimated volumes may not differ for more than 30 % from their true value, being for experienced technicians or forest-assessors an easily obtainable goal. If the stands or single trees, to be ocularly estimated on timber volume include very valu- able heavy forest parts or single trees, to be put up for sale, these stands or trees can be left out of the ocular estimate and measured exactly. The stands or trees that have been ocularly estimated ar® listed with their predicted volumes. The estimates or Predictions for stands can be obtained in the field or from Serial pictures. Trees are only estimated in the field. Afterwards a random sampling procedure can be followed as a control and the data can be adjusted according to the °utcome (959, 1380, 1403, 581, 958). For stand assessment in Europe, list sampling was intro­ duced by Loetsch. Man-made tree stands are in parts of Eu- toPe mostly of a moderate size, although an ocular estimate ma de in the field is not difficult. The use of orthophoto 206 maps provides area measures and good impressions of stand density, making ocular estimates with the help of aerial pictures still easier (1644). Because of the high costs of surveying, executed by spe­ cial groups or teams of foresters, list sampling to be per­ formed by local foresters and controlled by experts could " have a future as a basis for management plans of cultivated forest stands.

8.4.4 Repetitions of inventories

A forest inventory gives a snapshot. A repetition after a year or a management period records changes (except per­ haps in untouched natural forests) in which forest manage­ ment is highly interested because they are essential for its policy. Such forest inventories repeated usually after 10 or 20 years have been practised in Europe and elsewhere for a long time. In Northern America they are called 'continuous forest inventories'.They were initiated by private timber companies (1514) and are especially recommendable for quick growing tree species in subtropical and tropical regions (1765). Opinions strongly differ on their proper execu­ tion: should they be carried out with the help of perma­ nent measuring plots, with randomly "chosen temporary plots, or should they continuously change to improve their ef­ ficiency (319). If such inventories solely serve to follow tree growth, permanent plots seem to be the most appropri­ ate (145, 514). All such plots can be placed at random, or systematically* For permanent plots a systematic distribution seems prefer­ able as being more efficient (1663), especially when the inventory has to be frequently (annually) repeated (1514). This system has the disadvantage that the plots are, as a rule, more carefully treated than the other parts of the forest, which results in a distorted picture of the whole 207

This has been one of the reasons why, in Europe, during the successive national forest survey 'marking' is avoided as much as possible. In the USA, the timber companies pool the results of con­ tinuous forest inventories to obtain better management di­ rectives (5). Furthermore,they regularly improve their enumeration techniques. Recently they have also introduced the 3-P sampling techniques which has reduced costs to one third and more quickly supplies better information. In this technique, the trees to be measured are not those of an exactly delimited plot, but are selected on their apparant diameter with the aid of a prism stationed at a certain Point. The results are combined with estimated heights,and those obtained with an optical dendroneter for the larger trees (1479). Forest surveys for larger areas can be carried out only once ( as in the Netherlands (266), and for the pine forests in Honduras (441)), or they can be periodically repeated. In the latter case they supply information on potential ,,wood production,, . and,j as in1 vi nortnemnorthern Europer and Austria, on changes that have occured in the forest cover. All known European national surveys (that are continu­ ously performed) are still based on a uniform geometric distribution of samples over the country (1033). In Fin­ land, 15 years elapse between two revisions, so that each Year one fifteenth of the surface is re-enumerated(586,732). This period is considered too long (735); the 10 years in Austria gives reasonable growth estimates when compared with annual removals and natural losses (193). In the results of such repeated surveys, rotation plays an important role obscuring real wood production potentials. Where, as in the Netherlands with larch (Lari* leptolepis) with an optimum at 45 years (1451), many older stands are Present, growth potential will be estimated too low. The same applies to Sweden, where it was concluded that a re­ duction in the considerable area of over-mature stands could release a timber reserve of 100 million »3, shorte­ 208 ning the rotation by ten years; the same done by 20 years would double that amount (1535).

8.5 Growth assessment techniques

8.5.1 Growth of trees

Diameter growth of a tree can be measured from annual growth rings (if present), either by cutting the tree, or with the aid of an increment borer. I The latter never gives accurate results because diameter increase is asymmetrically distributed over the cross sec­ tion. In South Africa, the width of the rings was found to be considerably greater in the direction of the prevailing wind (881); an asymmetrical crown results in wider rings under its broader parts. In Greece, borings at five places around the bole for the last two years varied from 26 - 33 mm, 25 - 30 mm, and 7-9 mm (529). For accurate measurements daily changes due to differences in tempera­ ture have to be taken into account, and seasonal fluctua­ tions must be excluded (1250). Consequently only averages over a number of years give reliable data. In addition, se­ veral trees should be involved to exclude accidental diffe­ rences (676). Diameter growth strongly varies witb_ the species and the ecological circumstances. The slowest growth occur.s at the forest limit in the high north and at high altitudes: there it is approximately zero. Eucalypts and the balsa tree (Ochroma bicolor) may grow extremely fast. Commonly trees growing in the tropics do not show growth rings. For incre­ ment estimates annual or periodical DBH measurements will have to be'applied (459). Mangrove in Puerto Rico showed an increment of 0.25 to 0.475 cm per annum (1650), cultiva­ ted Pinus merkuêii in Indonesia grew a minimum of 2.1 cm and a maximum of 4.7 cm in 17 months (459); increments of 4 cm per annum for Eucalyptus are no exception. Since 1920, 209

in Canada permanent 'increment' plots have been established; tagged trees are measured on diameter growth (DBH) every 5 to 10 years (619). In East Germany, annual growth was found to vary for trees of diameter classes 7.5 to 62.5 cm from

30 % to less than 2 % per annum (585)» Investigations in Finland have shown that for stands dia­ meter increases at different heights of the stem are so

closely correlated that one determination (at 1.30 m) is

sufficient (734). This also applies to single trees (1261). Height increases can be determined directly by measuring the same tree with an interval of some years. For most coni­ fers the distance between two successive branch whorls, one is formed each year, can be used (57). For top parts, measu­ ring is difficult, but the involved error has less influ­ ence the higher the tree is (1563). Another way is to cut the tree and to saw it into logs of, say, one meter. From counting the number of annual growth rings on each surface, past height growth can be deduced.

When, e.g. at the stem base the number of rings is 30, at

5 m 24, the tree has grown about 5 m in 6 years. A graph for the whole tree will supply more precise data.

8.5.2 Growth of stands

A natural stand shows an equilibrium between wood volume increase, and decrease due to the death of trees from old age, heavy winds, etc., or in short: the mortality rate. In the so-called pienter forests, 'selective cutting' of singlec • 1 trees attempts to. maintain__ • airi a Dbalanced diameter dis- tribution resembling that in virgin forests. In America it has been shown that such stands produce less merchantable wood than artificial even-aged stands (1661), though German investigations proved that their total dry matter produc tions are practically equal (800). Growth or productivity of even-aged stands can be deter­ mined with the help of repeatedly measured permanent plots 210

(or a large number of once measured plots) covering vari­ ous sites. From the results, graphs or so-called yield or site-class tables are prepared. They give, per tree species of known age, for a given stand quality or site quality the wood volumes. As a rule they correlate average height and age. Recently complaints have been made that the contribution supplied by tree and stand growth studies to management is 'still lamentably poor' (572). In planning management chan­ ges, indeed growth data are often essential, and research is unable to provide them because of the relatively long time necessary to collect such data. The site-class or yield tables mentioned above supply a schematic history of stand growth. The oldest is probably that of Cotta (1821 A.D.)(506) .The newer ones also contain data on thinning yields, and on volume, height and diameter increment, etc. They all give averages for 'normal' stands. Single stands may considerbaly deviate from the table data: according to research in Germany the differences in growth can amount up to 21 % (48). To trace and to correct this type of shortcoming, it is possible to construct tables with three entries: average height, age, and density (num­ ber of trees per surface unit) (1470, 654, 657, 129) or basal area (130, 197); stand form factors may be applied later on (340). The combination with basal area is used in the southern part of the USA. There, measurements based on diameter dis­ tribution have revealed that 'for large samples, yields of planted stands can be reliably predicted' (239). Whether such complicated methods are often necessary is doubtful, however. From investigations on slash pine plan- tationsfPinus ei liottii),it was concluded that 'within the range of sample data common to all studies, the estimates of yield are generally compatible', and that only with ex­ trapolated values and high densities do significant devia­ tions occur (131). 211

As remarked, site-class tables refer to normally managed, well-stocked stands. This is not strictly necessary, how­ ever. In Sweden it was proposed to base them on the initial spacing and the planned thinning programmes, both manage­ ment characteristics defining the desired type of 'normalcy' (33). In British Columbia it was found that in well-stocked stands of Douglas fir (Pseudotsuga menziesii) site class classification could be carried out by measuring four ran­ domly chosen trees (797), the same done by volume estimates by point-sampling, had to be carried out in 'fully stocked stands of normal density' (1435) indicating as 'normal' a kind of ideal situation. Sometimes tables do not cover all the possibilities. In Europe it was noted that the number of trees per hectare may exceed those in the tables, but this is never due to nature but to treatment (1095). Furthermore, emphasis has to be put on the local value of such tables (79 7): a nor­ mal 20-m high spruce stand (Picea abies) produces m Eng­ land 700 m3 wood, one in northern Germany only 500 m em­ phasizing the regional character of the tables (341). In fact, 'normal' or 'fully stocked' stands are seldom encountered.As mentioned above,,la„q in deviatinga cases a densi- ty4-,, factore ^ can be applied as a correction.coix-couj. Where this is im- Possible, the table values have to be reduced (rarely in­ creased) in accordance with ocular estimates defining a degree of deviation from 'normalcy • Another, though le« serious objection to site-class ta­ bles is, that they are based on the assumption that growth curves have the same general shape for all quality classes. This cannot be expected beforehand, though it may be true. Nevertheless, site indices defined with the help of growth curves are very handy to estimate productivity, and as yet ho substitute has been found |4U|. To avoid great errors unrealistic predictions, periodically repeated qualifi- estions can adjust former data. 212

The main value of site-index tables expressing wood pro­ duction capacities is in their application as correlation with site quality assessment for afforestation, and to judge alternatives such as a change to another tree spe­ cies. As suggested for the Netherlands, average production per site class per tree species involved would be the best parameter (431). As mentioned under 8.3.1 , tree-weight tables are still rare. A recent publication remarks on this subject: although tree-length logging and chipping to some extent reduce the need for information about numbers of bolts per acre and per cord, they are still needed in management programmes (129). This expresses a certain doubt on the future use of pure volume-productivity classifications. Perhaps, with advancing mechanized clear felling and thinning, the time will soon come when weights of oven-dry matter are added to such ta­ bles. This would make the switch from volume measurement to weight-scaling much easier. Growth of trees and tree stands strongly depend on leaf surface and leaf weight, the form of the crowns, and their place in the forest structure. Therefore much attention has been paid to tree-crown dimensions and to a lesser extent to the weight of its leaves.

At the end of the last century, in Germany^-data were published on the total weight of spruce (Picea abies) needles and their production capacity expressed in wood volume per kg dry-weight (1103). In Switzer­ land it was found, that on average a stand of pine (Pinus sylvestris) trees needs 1200 kg needles to 'grow' one of bole wood per annum (236); for 63-year-old spruce stands it was 2700 kg fresh needles (235), and for Abies alba 3200 kg (234). The width of the crown is of interest for the interpreta­ tion of aerial photographs, site and growth studies, etc. * mostly in connection with DBH. Because of its irregular form 'it is usually difficult to obtain an accurate crown- diameter value free from a considerable element of subjecti­ vity'(1470). Usually its visible borders are projected with the help of mirrors or plumblines on to the ground. Such a 213

projection can also be done by using polygons, delineating the living space assigned to the individual tree in a stand (including per tree part of the open spaces where crowns do not touch each other). The data obtained expressed in area, can be used for management purposes (thinnings), site-quali­ fication, and studying optimum growth per tree in a stand or for the whole stand (1264, 1505, 737). Sometimes the ratio crown. widta +-h to DBH is used. For culti- vated tropical broadleaved species,„,•„0 fhp value of 20 seems to be common as it is for north-temperate hardwoods. Most coni­ fers and eucalyptus species show substantially lower values (336). In the Amazon Region upper storey trees and emergents have average ratios ranging from 20 to 26 (655); red pine (Pinus resenosa) in Canadaj 18.5c; 4-r, 15.0 (168), and Abies s pp.

in Greece 20.12 to 9.02 with. L,_ a mean of 16.68 (50). Based on statistical analyses carried^ out fortor wnwhite spruce* (Abies in Canada, it was concluded 'that crown Width and DBH correspond similarly to differences in stand density so

that their relative size remains» _ constant„n„e4-ant' (1094).i Hence if crowns increase or decrease in widwidth , DBH follows. In South Africa, for radiata pine (Pinus radia it was found that crown-depth respondsj more stronglyofrnnalv to stand density than to crown-width (882). pruning (shortening the crown ep o exotic species improved the density of juvenile wood (5301.

Trends towards complete tree utilizatio

on a dry-weight basis, about 65 % of the wood fibre of a tree is in the merchantable bole I from the stump to the '0 cm top diameter), 25 « in stump and roots, and 10 % in the other parts (1771). To harvest stumps and heavy roots it has been proposed to tear out the smaller trees (255), this is impossible for deep-rooting species •»•*>•« those+.v in arid regions where, yvtn-f-c;roots oi«ioften reach great depths / '« example slash pine.VM»" .lliottil/reache. in South A- l«o« depths of 4.50 m (600). It is even possible to devise 214 equipment for collecting twigs and woody undergrowth for pulping although debarking has hampered its economic appli­ cation up to now (365, 614, 537). Large amounts of bark will always remain, however. They cannot be burned as this causes air pollution, but they can be mixed with earth to make compost for gardens, nurseries (853,1744, 3), or even returned to the forest, as tried out in Germany (1674). In 1969, Denmark, Finland, Norway and Sweden jointly in­ vestigating the utilization of branches, stumps and roots? again the bark appeared to be the main obstacle (603). Chipping at the cutting place supplies only a partial solution, though it is imaginable that all remaining waste is pulverized, mixed with a nitrogen fertilizer, and then blown around to stimulate tree growth (139), important es­ pecially after the harvest of hardwoods which have 15 to 40 % of their organic matter in the crowns (961). It is, however, not necessary to proceed so far. Exploi­ tation can also aim at harvesting more wood from the bole. In Canada, the inclusion of tree tops has increased paper- wood production by 6 to 10 % (786); in Germany spruce tops (Picea abies) now constitute up to 5.3 % of the harvested wood (26); in the USA more complete tree harvesting is considered necessary to combat labour shortage as most of it can be carried out mechanically in the mill yard (1747)• It was calculated that, if from all slash now left behind in the forest 10 % could be recovered the expected annual shortage of 100 million m in wood production in the year 2000 could be overcome (787). In all cases indicated above, volume measurement is hard' ly feasible, except for logs. Nevertheless in many regions volume measurements are still legally obligatory, or play such an important role in trade that weights cannot be ap­ plied directly and have to be calculated from volumes. For' tunately some European countries have begun paying more attention to weight scaling (1165), and in the USA the Na­ tional Forest Log Scaling Handbook of 1969 (1606) , recog­ 215 nizes it as a sampling method.

8.7 Assessment of minor forest products

Minor forest products are all vegetable forest products exclusive of wood. Though this definition includes fruits, they will not be considered here in particular. How important the natural forest n^y be for their production is apparant from a few data for Indonesia and the Amazon Region. Apart from rubber (from Hevea brasiliensis, which since 1913 has been considered an agricultural product)(122), 28 % of the export value of forest products in Indonesia m 1929 was from wood and 72% from such minor forest products (843). „1-ino nalms; 90% of the world These included rattan from climbi g P production(over 90% m• 1938)1QTOW9Q? 844)) anand turpentinev from i-ivai pt nu ç merkusi i s t ands(1068) . The resins harvested in natural pmus • „ rrnms has much decreased: in importance of natural resins and g 1938 the export amountedj_ ^ to4-/-\ 33"5"^ OUUnnn tore»,tons, in 1967 to only 10 000 ton (443, 979)*. In both cases the decreases are caused by exhaustion of the available sources, the replacement of natural products by synthetics, and by changing sociological circumstances. The following details on cultivated species are worth mentioning. Tanning materials were in the past mainly ex­ tracted from bark and wood of various plants, among which

in Europe the oaks (Quercus sPP) were the most important. For their production coppice was used. In the Netherlands in 1833 it covered a surface of 137 000 ha (1468)andwas under regular management with five site qualities and a rotation of 10 years. It produced 10 to 90 sacks of 65 kg bark per hectare (1187). In 1963 the production had entirely stopped (266) because of the competition of other natural and syn­ thetic tanning materials (370). These other natural tanning materials are mainly from wattle? bark (Acacia decurtens), cultivated on a large scale in South Africa and elsewhere

_ .ncn an<3 1967.the export value from minor Por the Amazon ^on'b«f® en. 18 0,while the wood export in- Products decreased from 23/5 million $ t creased from 0.5 to 4,7 (35, 36). 216 in subtropical regions, also (since 1919 (850)) in moun­ tain areas of Indonesia where yield tables indicate pro­ duction capacities between 2380 and 4030 kg fresh bark per hectare (yielding 440 - 770 kg tannin) for five site classes with a rotation of 7 years (and an important addi­ tional charcoal production) (1729). Cork is the bark of the cork-oak (Quercus suber). Fo­ rests of this tree cover some 2 000 000 ha around the Me­ diterranean. Yield tables are based on a linear relation with circumference at breast height (1135). The average age of productive stands is about 100 years. A harvest is pos­ sible every 9 years, resulting in 18 to 90 kg cork per tree, though one tree may produce as much as 225 kg. The thickness of the removed cork ranges from 1.25 to 7.5 cm (1203); 100 kg fresh bark give 62 kg dried cork sheets which, piled in cubic metres, weighs about 97.5 kg. Portugal produces 500 000 tons per year, 50 % of the world production and in 1965 comprising 17 % of the country's export earnings(1480)• Bambu, though not originating from real trees but from va­ rious very large grasses, is generally considered a forest product. The better species all grow wild on the Eastern Asiatic continent, but many of them are planted on a large scale in other tropical countries. On Java (Indonesia), where species were already cultivated in 1858 for tobacco fermentation sheds, a forest law of -1-89 7 affirmed that these 'forests' have to come under the supervision of the Fores­ try Service (1291). Besides being an important building material and used for a great many purposes in the local household, bambu can be used for paper making because it has very long fibres (about 2.5 mm, conifers about 2.8 mm), in India it is exten­ sively planted for this purpose. With a rotation of 7 years it can annually produce 3750 to 10 000 kg per hectare (275)/ the highest yidlds are obtained on irrigated land. When stacked, the heavy species weigh some 200 kg per m^. the leighter one 100 kg (1572). 217

Naval stores include such products as turpentine and Pine oil, all prepared from resins harvested ('tapped') from holes in the stems of living pine species (1203). The 'wounds' have to be regularly 'faced' or blazed, and the bigger the tree, the more resin it will produce, with an optimum when crown depth equals half the tree's height (286). Slash pine (Pinus elliottii) stands, 16 years old, with 200 workable trees per hectare, can produce 2350 kg Per year; when 26 years old and with 350 trees per hectare the production may reach 4 000 kg (128) During the time the trees are 'bled', their wood produc­ tion slows down, but these losses are compensated by the resin, yielding 15 times higher prices per kilogram than the wood (807). in the southern part of the USA selection has considerably improved resin production (617, 618). Whereas world production and consumption of resins are increasing, those in the USA have remained stable between 1946 and 1962 (807). Other countries, such as Spain, Portu­ gal and Greece, are taking over. Spain and Portugal use «nu. pinas ter, in Spain annually yielding up to 140 kg Per hectare (1445, 40). Greece is trying to improve the Production capacity and the working methods for Pi,us bale-

Pensis (1205)• 9 The economie o/pect/ of fore/try

9.1 General considerations

Man has always considered the forest as a nuisance, or worshipped it for its 'eternal value'. The latter attitude is still prevalent, and foresters are often considered 'despoilers of the forest scene, concerned only with the generation of income through timber harvest1 (814). This disapproval puts a heavy burden on forestry, espe­ cially where the work has to be mechanized for economic reasons. Thus the simple forest worker, the poor charcoal burner of old stories who provided the iron foundries with fuel (350 kg charcoal per ton melted iron (1419)) is fast disappearing. However labour still accounts for 70 % of the production costs, as against 25 % in industry and 45 % in agriculture (9). Hand labour has to be substituted by mecha­ nical tools involving fewer, but better trained, people. Mechanization in planting, thinning and harvesting cannot be avoided, although it leads to clear felling of large areas. (In Georgia, USA, it was calculated that only on sur­ faces of at least 200 - 300 ha was completely mechanized tree cutting economically justified "(1-759) ). It is quite understandable, however, that the use of helicopters and balloons, seriously considered for less accessible areas (10, 1755, 1758) and the transport of wood chips through pipelines (1556, 519, 974) from concentrated cuttings over large areas strengthens the aversion among the general pu­ blic to modern forest exploitation and forestry in general. It will be necessary to convince this public that building up and guiding the forest can be accomplished only by inci- « dentally destroying parts of it (1428). But if we assume that society will continue to need wood for various pur­ poses, which the same public can hardly deny, the forester 219

may be obliged to avoid all waste of material, to utilize his stands as completely as possible so that a maximum can be preserved for recreation and comparable purposes. This will also involve reforestation, preferably with high-yiel­ ding species (1158), and well-balanced integrated manage- ment programmes focussed on accelerated production. To obtain high yields, attention has also to be paid to exotics and genetic selection, in which the provenance of the seed is most important, as with Scots pine in the Ne­ therlands (1732) and with Pinus caribea and p. oocarpa in Congo-Brazzaville (1029). Even fertilization should be con­ sidered, though this seems practicable only with a minimum return of 8 % (in some cases it has been as high as 13.6 %) (1244, 206). The demand for wood is still growing. Hence lost capacity Wust be replaced, either by increased yield per area, by new plantations, or by import. This requires a local, regi- °nal or world-wide prognosis. The wood importing countries WÜ1 have to take into account the trend in the traditional- 1y wood exporting countries to prohibit the export of raw Material (logs) to further their own industrial develop­ ment. a certain war psychosis has often induced the same, So that in Europe and America the trend is not only to a- v°id forest destruction but even to let the stands become 0ver-mature, and so build up a reserve for emergencies (1266), at the expense of the owner. This saving principle long been practised in France for the state and commu- nal forests, and recently for private forests over 25 ha, either by applying a longer rotation, or by setting apart special stands equivalent to a quarter of the periodical­ ly allowed cut (371, 916). That such measures are followed requests for tax relief or comparable aid is not surpri­ sing (999)_ The reluctance to restore or ihcrease national wood out- put> especially when this involves higher costs, could mean the end of local wood industries. Internationally orienta- 220 ted enterprises realize this and thus tend to start activi­ ties in subtropical and tropical regions(660).The government of wood importing countries should further this trend by adequate research and loans, where necessarv.

9.1.1 The international aspects of wood production

In Europe and America, the wood trade is not protected so that prices follow supply and demand on the internatio­ nal market. Formerly, especially in Europe, the social ser­ vices of the forest (hunting, soil protection) did not im­ pair its modest rentability (507). However, at present the competition of other materials has, especially in the more advanced areas, so much lowered the rentability that the maintenance of the forest services has to be paid for by the community. Consequently the 'centers of gravity for wood production' have to 'shift away from the rich, densi- ly populated countries to the poor, scarcely settled re­ gions of countries where high productivity in dry matter per unit area can be achieved'(136) . Hereby forestry can be 'a vehicle for development', whereby the government takes care that the planter of new stands, or the licensee, is given a 'reasonable assurance for the preservation of capi­ tal involved'(606) to be invested on a long-term base. The country owning the forests can iäo much to make such investments attractive, e.g. by carrying out inventories, guaranteeing tenure (47), supplying tax reductions, by trai' ning personnel, and by controlling the quality of the pro­ ducts as in Malaya (1592). On the other hand the involved government must have the right to restrict logging, especial' ly on 1ar^as where, for one reason or another, it does not appear to be practicable to control subsequent use of the land, once such areas have been opened up by logging roads' « (446) and hence are in danger of being spoiled by burning, shifting cultivation and grazing (446). These dangers are 221 only absent in mangrove swamp stands, growing on seashore mud, as apparent from the newly initiated exploitation on Bangka and Belitung, near Sumatra, where the stands were logged some forty years ago for fuel to melt tin ore (141 )

9.1.2 Managed wood production

w, r,r*rtically unlimited quantities, For goods available m prac , air utilization is purely a matter such as seawater and air, uti , 4- MAfinl Only for scarce goods are technique and transport (1460). un y mar,aap our , , ^ ™ a .gtudy of how we manage our regulations needed, based on . when .s**** » H90). especially wnen resources to help satisfy our these resources are still renewable. mana- -, 0.4-^v rai-eaorv so that their mana Forests beloncr to the latter y rests belong t a„_tained yield, so that they have gement has to be based on su , . aua- 4-v,at- their productivity is gua to be managed in such a way t vermisted Thus, in a well-regulated ranteed for many years to com . h the- . the standing timber has, tne large-scale forest enterprrs , ^ ^ ma_

oretically, to be production by cutting, the chine (390) or 'capital , and the p - . +-ViA total annual wood in 'interest1, the latter equal t

crease (1185). connections between quan- This is the theory. Actually -, „unr and timing are never tity, quality, and harvest location

tailor-made, for two important reasons. theo_ p ^ wood seldom equals the theo Firstly, the quantity of cut . a

retical production (the interest) world mar.

great influence and he, in turn, depends .,ated ! ^,,11 v the vield is reguiatea ket. So, no matter how carefully th y ^ ^ fluctua. irv the forest, a fluctuating demand . Anormal circumstances such as ting cut (764). In addition, abnorma nnhllc Dres- i-K 1 overcutting, and public pres threatening „ars, always caus ^ ,sustained non-yield'.

•«. may turn 'sustained yie ^ Mre£uUy built-up age Heavy storms may completely up Netherlands „here, ccure distribution of stands, as ° doun (normal in 1973, on 2500 ha 750 000 mJ wood „as bro*

*. initial estimation. 222

3 dutch annual cut (590 000 m )(1145). The damage mainly involved old even-aged stands which, as noted for the period 1947 - 1967 for Switzerland (Neuchatel), are more vulnerable than pienter forests (453). Secondly, wood can be used for many purposes: for fuel it may be 'mature' after 3 to 10 years, the same species may take 200 years to produce high-quality veneer logs. This means that for firewood the capital is located on ,66.7 to 90 % of the production area, for veneer on 99.5%, provided a normal age-class distribution is maintained.

9.2 Flexibility in wood production

The preceding section has shown that wood production must be flexible. The originally East Mediterranean sweet chest­ nut (Castanea sativa) may serve as an example. Long ago, it was introduced and cultivated on a large scale by the Romans (934); in 1956 it still covered some 733 000 ha in Italy or 13 % of the forest area, and 8 000 ha in southern Switzerland (117, 1232). Its bark was used for tanning, its leaves contain a honey-like substance applied in biscuit making, the foliage served as fodder (476), and its fruits are excellent pig food and were regularly eaten by man before World War I and are still consumed throughout western Europe. The tree can be rais~ed as coppice for fuel (rotation 3 to 4 years); a rotation up to 15 years provides fuel, poles for viniculture and wood for fusts; a rotation of 36 to 40 years produces telephone poles; 90 to 120 years -3 old stands produce fruits and 2 - 3 m timber per hectarè per year (1232). Thus a relatively small area can provide various products and it is not too difficult to switch from one product to another. A change to a product that takes more time to mature involves a temporary sacrifice of income « to build up a heavier growing machine; cutting earlier means decreasing the wood capital and collecting savings. This example illustrates the past situation in large parts 223

°f Europe. Oak coppice with short rotations has, via cop- Pice with standards, been transformed into high forest with long rotations. The reverse has happened in shortening the average rotation with poplar-growing and the conversion of broadleaved stands with long rotations into coniferous fo­ rests with shorter rotations. At present the demand for pulp dominates the wood market. For the stands this means that the age supplying the highest average annual quantity of fibre is the economically most adequate rotation. Cutting earlier means liquidation of ca­ pital, cutting later without improvement of fibre quality leads to a less efficient use of capital. Duerr (391) described the trend away from saw-log rotations as follows: 'The force of economic progress, most notably the rising value of labour, drives us downwards through the list of big round wood logs to wood molecules, away from the forms °f wood that require much hand-labour and towards the forms of wood that lend themselves to mechanized flow-type Production'. în this connection the FAO, discussing the need for higher Wood production in Europe, mentioned that in many forests in Prance, Western Germany an Austria, some of the capital stock could be cut by reducing rotations (442). Opponents have argued, however, that the multiple functions of the f°rest in these regions and the often impracticable mecha- ^zed planting, together with the high wood production from Winnings explain the customary long rotations. The data f°r spruce (picea abies) in Table 8 demonstrate that large, seemingly less efficient 'growing machines' may be preferred to smaller ones (1484, 422). This sounds reasonable, but it is doubtful whether it is right to put so much emphasis on environmental influences to reach the mentioned production levels. Indeed Swiss data have revealed that about half of the total wood comes from thinnings, but it should be kept ir> mind that, as a rule, the Middle European forests are badly thinned due to the high costs (879). 224

Table 8 Wood production for spruce (Picea abies) under various circumstances

Site class, Rotation, Average Average Mean .annual Thinning in m at in years stan­ annual wood production yields as age of ding growth total , from thin­ percentages 50 years timber % in nings, in of total in m3 m3/ha m3/ha production

26 100 419 3.62 15.1 7.8 51 26 50 193 6.79 13. 1 4.5 34

18 120 271 2.85 8.1 4.0 49 18 60 111 5.85 6.5 1.8 28

Table 8 shows that thinnings considerably contribute to total volume yield. If included, the difference in yield for one rotation of 100 years (100 x 15.1 = 1510 m3) is higher than that of two rotations of 50 years (2 x 50 x 13.1 = 1310 m3). This indicates that one rota­ tion of 100 years is more favourable. On the other hand, when thin­ nings are (for some reason) unsalable, a rotation of 100 years pro­ duces less than two rotations of 50 years: 100 (15.1 - 7.8) = 730 m3, two rotations of 50 years 2 x 50 (13.1 - 4.5) = 860 m . For the other example 120 x 8.1 = 972 m3 as against 2 x 60 x 6.5 = 780 m3, or (with­ out thinning yields) 120 (8.1 - 4.0) = 49 2 m3 as against 2 x 60 (6.5 - 1.8) = 564 m3. To emphasize this trend it cannot be denied that in some areas wood from thinnings indeed plays no or only a decrea­ sing role in the production. So in the Bavarian spruce fo­ rests (Germany), the sawmill industry entirely depends on the heavy timber resulting from rotations of about 130 years because all small pieces and thinnings have to be left be­ hind as they belong to 'deficit assortments' for which the costs of extraction exceed the market-value (821). The same tendency has been observed in Sweden where, du­ ring the 1950s, half of the extracted timber came from thin' nings, in the 1960s about 30 %, in 1970 - 1971 only 25 %, the expected normal level for the future (611). For Austria the thinnings from coniferous stands dropped from 2 000 000 m^ in 1955 to 900 000 m^ in 1969, parallel with the pulp- wood price minus production costs from 280 to 205 Austrian * shillings (544). To improve ttfe situation it has been recommended to make better use of specialists and scientific institutions (1654)' 225

ar>d to participate in efforts, as already initiated in Swe­ den, to develop harvesting and thinning machines adapted to middle and western European circumstances (1529).

The economic base of forestry

The aversion of the 'classical' forester to short rota­ tions must be seen against the background of his education which made him firmly believe in the necessity of following nature as far as possible (859). Consequently he still often aPplies a forest rent theory in which, next to the soil, the forest itself is producer. This forest fund theory, as it ls called, considers all stands, natural or planted, with their soils, as unseparatable parts of the ecosphere. Hence Planting costs should be included in calculating the soil Value, soil value and afforestation costs belong together as one unit of the eternal forest cover (1026, 1381). addition, these theories presume that a soil once oc- CuPied by trees should remain under forest for all the years to come, without involving 'opportunity' costs (which ^eans that the profit made by using the soil for another Purpose is not accounted for) (357), and even excluding changes to another tree species or rotation (1219). p°resters who oppose the application of more efficient Methods and mechanization will be supported by the present Public mood that considers normal management detrimental to their precious environment. This is no base for economic forestry: the forest owner who has invested his money in W°od growing has the right to expect that he, or his chil­ dren or his firm, profit from his investment and efforts; the buyer of forest products must be sure that by paying * suitable price he can count on a long-term continuous SuPPly (1579) on which he can base his plans for the future Without fear for unexpected changes (305). Especially in decent times with their increasing demand for wood, it be­ 226 comes gradually more apparent that only in this way is an economically justified forest exploitation possible. In the next sections this relation between forestry and wood­ working industry will be treated more extensively.

9.3.1 Poplar: an example demonstrating some financial aspects of wood growing

When a farmer wants to produce wood by planting trees and, after some time cutting them, he needs capital to buy land, and for costs such as pruning, thinning, and taxes. On the capital (loan) he has to pay interest. His revenues include the end-harvest and possibly thinning yields. An example may illustrate thus: poplar on pasture, planted & in 1950, sold by stumpage in 1969 at the age of 20 years . Suppose in 1950 the farmer paid ƒ 2500 for one hectare of land, that the costs of planting 200 trees (C^) amounted to ƒ 730, and that the additional planting costs were: up to the end of 1951, C2 = f 115 and during 1952, C3 = ƒ 40. During the years 1950 to 1969 the annual costs (main­ ly taxes) increased from ƒ 26 to ƒ 55; on average he had to pay annual costs, e (e = expenses) = ƒ 40. Due to general increases in prices, at the end of 19 69 the market value of the land (without trees) had risen from ƒ 2500 to ƒ 8700, and the stumpage value of tfte-stand was ƒ 10 000. The costs, including the accrued interest for the expen­ ses Cj^, C2 and C3, and the 20 annual cost-payments e have to be subtracted from this ƒ 10 000 to calculate the pro­ fit made at the end of 1969. Table 9 shows the outcome för interest rates from 3 to 8 %. As compared with the general situation in Europe the return was satisfactory.

Data received from the Group of Dutch Forest Owners, in Dutch guilders (ƒ). 227

Table 9 Financial outcome of a poplar plantation at various interest rates, in Dutch guilders (ƒ)

Interest rate

3% 4% 5% 6% 7% 8%

Accrued costs at end 1969 2677 3124 3646 4275 4796 5589 f 10 000 minus accrued costs at end of 1969 = accrued land rent 7323 6876 6354 5725 5204 4411 Annual land rent 272 231 192 156 127 96 Approximate land value 9000 5800 3800 2600 1800 1200

A few remarks have to be added. The land value of ƒ 9000, at an interest rate of 3 %, is n°t very high: in 19 69/19 70 the expropriation value was ' 25 000 or probably much more. Annual increases in land Value were for 1968 estimated at 4 ~ 5 % (1109), in 1969 it was recommended to fix them at 3.5 % for poplar land (116), between 1937 and 1967 they were 11.5 % for average (Dutch) forest lands (1108), between 1957 and 1967 for iand plus stand 7.2 % (1107). The cultivation costs for the first three years (C^ + C2 + C3) amounted to ƒ 885 (without interest); during 19 40 - 1959 they ranged, in the Netherlands between ƒ 400 and ƒ 700 (?16, 1189), in 1961 between f 1613 and ƒ 1743 (118) being ^airly high because the newest figures from 1971 amount to '890 (1524). The data show that the farmer spent the right SuiTl for this purpose. Pruning costs were not included: this treatment was assu- to have been carried out by the (small) farmer and his ai flilyt who cannot afford hired labour (55). However in 1960 they were estimated at f 60 (1050), or based on 10 hours w°rk a year (900). The newest data from 1971, give ƒ 75 in the 4th and 7th year, ƒ 150 in the 10th, and ƒ 225 in the x4th year, totalling ƒ 525 (1524). Including these costs ln °ur example at an interest rate of 3 % this would amount to f 702 at the end of 1969, reducing the farmers accrued iand rent from ƒ 7323 (see Table 9) to ƒ 6621 giving a land rent (on the 3 % level) of f 243 and a land value of approxi­ 228

mately ƒ 8000 or ƒ 700 below its market value in 1969. Putting the rate of return, disregarding pruning costs, at 6 % would have resulted in a land value practically equal to the sum the farmer actually paid (ƒ2500, see above)- For the Netherlands this percentage was, in general, esti­ mated at 5.6 % (1050), or with a land rent of ƒ 479 to ƒ 331 in 1968 (12) which (as compared with the example) is very high. In general it was concluded that poplars on suitable pastures gave higher returns than dairy farming (1070). Later on it was remarked that poplar rows around pastures had to yield 0.11 to 0.13 m3 more per tree (age 25 years) to compensate the higher costs (119). In the example the rotation was 20 years. In general it is somewhat longer in the Netherlands (20 to 30 years) as then the wood is more suitable for making wooden shoes or veneer; for fibre wood it is shorter (1053). In Germany a rotation of 50 to 70 years has been proposed (1372) , for farm wood-lots in Australia it has been fixed at 15 years (1174) , in South Africa 20 years is customary (financially most profitable 13 to 15 years) (885). In Italy the rota­ tion ranges from 12 to 20 years, but the farmers are incli" ned to cut the trees already after 8 to 10 years (539). The conclusion is that in 1950 the farmer took the right decision. If he had invested the same sum in state loans his profit would have been only one ""third (though during the involved period the rent of such loans was low, ranging between 3.25 % in 1950 and 7 % in 1969 (525)). Past experience is often a guide for what to do next. In this case the farmer replanted (as requested by law (ll4l, 179)),and he had no reason to regret it as in 1972 the Eu­ ropean private forest owners considered poplar growing in rows o* on small lots one of the few types of wood raising still giving reasonably attractive returns (1188). « 229

9-3,2 The value of forest land

To judge the financial results of wood growing, Faust­ ina's formula from 1848 is still commonly used. It calcu­ lates all (expected) yields and costs (in money) to the year zero, the start of cultivation, and it results in what

is called the soil expectation value (Se):

r_a r b r q r Vr + Ta x 1.0p + Tfc X 1.0p " + ••• Tq x 1.0p - C x 1.0p Ä — , .,i » • 11 - - - E r i.op - 1 in which = net harvest value at end of rotation ( r years) T a ... Tq = thinning in years a ... q (some of which may be negative) c = planting costs ® = capitalized annual running expenses e P = interest rate, to be fixed later

addition, land may have a high speculation value, especially near expanding cities (1155), as for example in Switzerland where a piece forest land suddenly increased several times in price (870)• People anticipating such rises can push prices upwards (1409), even when a short-term change in occupation is not expected.Part of the profits are ^ue to devaluation of money,which finds expression in the purchasing value:industrial shares grown to a value of 356 in 1970 decreased in reality compared with 1950 to 159, forest values from 800 to 360 (405). Basically the formula represents the capitalization (present worth) a permanent periodic net income received at the end of the forest r°tation and at the intervals indefinitely thereafter (333). apparent from the example in 9.3.1, the level of p has dominating influence on the value of the forest land, chan­ ging there from ƒ 1200 per ha at 8 % to ƒ 9000 at 3 %. This level has been much discussed starting from the assumption that only special considerations permit it to be fixed lo- We* than that for other capital goods limited in supply,

^eed the capital good -land' has a certain fancy value and it withstands money depreciation much better than most 01"her investments. traditionally 3 % has been accepted, but it is doubt- whether the rate can be left as low in view of the Passent very high general level, even if it is expected the rate will settle somewhere between 5.5 and 7 % in the future (1715, 1287). 230

Where land is limited in supply but sufficient capital is available, forestry may continue as long as management does not (68) get into the red, under the motto: better a large but safe investment at a low profit percentage than a smaller riskful one (1676). The same argument can be used in preferring long rotations for very valuable wood, such as that of European oaks (382) , though this involves the danger of neglecting the stands (as on the Cumberland Pla­ teau in the Appalachian Region, USA, where management is restricted to the bare minimum of fire protection(67)). If capital is limited, it must be intensively used, give a high rate of return. In forestry this means planting quick growing trees, shortening rotations, in fact: raising 'tree crops', applying agricultural techniques. In West and Middle European government forestry, still burdened with tradition and the ensuing raising of heavy timber (842), will have to adapt itself and to rationalize its forestry to improve its low rentability and to stay out of the red. It must become better informed about modern ef­ ficiency in management and quickly apply new methods (1463,8, 677) assess alternative silvicultural practices and make decisions in timber sale problems (1377, 499).

9.3.2.1 Returns from timber lands

As apparent from the following data^ returns (especially when expressed as percentages of the forest capital) great­ ly vary, from incidentally negative to over 5 %.

Douglas fir (Pseudotsuga menziesii) in the Netherlands gives a return of 2.0 to 5.0 %, depending on site (1614). Larch (Larix leptolepis), in the same country, yields 3.4 % with a ro­ tation of 40 years (109). For oak (Quercus) (in Hessen Germany), based on fixed land values 0.2 * was calculated (1458). For beech (Fagus sylvatica), Scots pine (Pinus sylvestris) and spruce (Picea abies) the data for the same area were 0.25 %, 1.31 % and 2.00 %, respectively (1458). For state forests in Germany 1970 and 1971 net returns were of DM 14 and DM 9 per hectare, for private forests DM 7 and DM 4, respec­ tively, with land values of several thousand marks(l DM=$ 0.34)(1459)' 231

In Austria orivate forests over 1200 ha yielded 2.00 % in 1966, -TS" S IS, % in 1968, 4..0 ,1» »69 Cv«»,.

1.59 %). I»prove..„t =..« 5h« '«•»> «W M'*" For England returns are said to De genexax y 1725) cultural rates, up to almost 4 % < - (with 53 % of the

In the USA, where 75 % of the Q4 and where ^ owners standing timber) is privately owned r d * i =; an ave- h.ve be« - rage return (472)(notwithstanding the managed for non-profitable purposes (604 „ = due to the interest forest These variations are partly aue owners have in the other aspects of the forest besides eco­ nomic wood production, such as recreation and special in­ dustrial wood demands (1414, 1671), so that no tail made1models can be provided (987). Nevertheless it may be worthwhile to compare return and costs of the various forest management types with alterna­ tive investments (471). Hereby periodical yield surveys (1311) and up-to-date financial records (68), preferably for each forest compartment (1184), are indispensable. Normally such data serve to determine soil expectation va- 1, fhp ensuing most suitable lues from Faustmann s formula and , . x. rat-p) though it is practically rotation (at fixed interest rate;, 1 fnrpsts and only seldom for pri— never applied in communal forests vate forests. • ui« -ho asqess the value of forest As long as it is impossible to assess 1 1 ,^

-•3.2.2 Regional rentabilité in wood growing

Regionally, the financial position of private, communal and state forests strongly varies. In the Netherlands the state forests reported losses in­ creasing from ƒ 11 per hectare in 1961/1962 to ƒ 1970/1971 (1475). As to the private forests, the govern *ent was forced to supply, in addition to the already exis­ ting tax relief, direct financial aid to those who opened 232

their forests to the public (114, 113), an aid in 1972 considered too low in view of the damages caused by the visitors (182). Though lack of records greatly hampered judgement, it was estimated in 1969 that the Dutch owner lost ƒ 100 per hectare on management and ƒ 360 on landrent (115). Perhaps these figures are too high, but they were serious enough to propagate a separation between productive and improductive stands (665). In Germany the situation was hardly better: when in 1960 O the state had to sell wood at less than DM 50 per m , los­ ses were involved. Private owners were often in a more fa­ vourable position because they had to pay less overhead charges (679, 401). With a deficit of DM 24 on beechwood, DM 12 on oakwood, and profits of only DM 1 and DM 11 on pine and spruce wood, respectively (1210), the outlook was not too bright either. The same held for Austria, where all foresters cried out for application of more efficient methods and better planning (499, 188). Though in Denmark, during the period 1945 - 1956, the gross revenues for private forestry increased threefold, afterwards (up till 1966) even more efficient methods caus­ ed only a slight improvement (668). Between 1952 and 1961 in most places in England decreasing overhead costs, a change to piece-work, and savings on transport, kept costs more or less at the same level (922) Because there is a growing demand for wood and Europe has a wood-growing potential above the world's average, there is hope for future improvement in Europe (1476). For some other parts of the world, reports on return rates are more optimistic. In South African plantations returns exceed the general interest rate and may be as high as 15.1 % (883). For pines (at fixed lan$ prices) planting may result in 5.1 %, sowing in 10.2 % (375). A favourable circumstance is here that the land price seems to rise more slowly than its production value, at least for good sites, so that a rate of return 233

1 » — a ri hardlv be regarded as of 10 % (disregarding taxes) exorbitant' for some exotic species (5 •4.V, promising rentabilises for wooa gro ia other regions with ? Neu îealand and Japan.

Wing are South Amerrca, A dc»and for wood for They all show a large and ^^ ^ prl.

1 own use or export, their ^ an attempt to develop

ority is given to wood pr ^ ^ the overall economy the rural economy at the s °f the country (481)•

9-3.3 Yields and costs

I_ formula also need a The other factors in Faustmann's formula closer discussion.

9-3.3.1 End harvest and thinnings

* ^ arowing mainly depends on The earning capacity of woo g^

rod Ct »eight or volume P ° "" expected quantities can

The production can be prescribed 'table'-

be assessed from yield ta ^ glvlng ,normalcy' thinnings are increasingly 9 the appearance of '»nma"a^ ^"lltions in market pri-

Stumpage values apart o£ the stand, the

«s, mainly depend on the acce effectlVeness of sales

lnauS S «stance to wood "" '.° „e exploitation type and

ddl •wnagement (1692). In » " varloüs £orm8 are in-

the quantities of wood aval a ^ ^ gu&n_ v°lved (the more uniform the pr

titles, and the higher the o£ ^ exploitation

Where the owner himself ^^ ^ ^ many state

(cutting and transport to a ne and may cause se- for ests, the factor labour is i ^ labour

"ous trouble. In Germany, from ^ fourCola, „hereas

c °sts including social care ±ent working methods wood prices decreased and even 234 could not remove the difficulties (1457). An exception was the Forest District Tattin, where the buyer was allowed to take out his own wood and thinning was done mechanically. In 1965 this district made a net income of DM 31 per hectare while the state average showed a deficit of DM 28.5 (1067). On the other hand, leaving exploitation to the buyer may result in lower production per hectare because he will be inclined to harvest only what he can sell at a good profit. An extreme case often occurs in tropical forests where only heavy specimens of fancy species are cut and where many pieces of the felled trees are not hauled out because of defects (the rejected bole timber may amount to 50 %).. The result is mostly a wide discrepancy between survey and exploitation (1078). A check carried out on the Ivory Coast has revealed that from 24 species only 61 - 68 % of the bole-timber was harvested, from 8 species only 40 - 49 %, and from 3 species only 29 - 37 %, giving an overall average of 52 % (906). A study based on 320 farm forest properties in Sweden, together covering 21 000 ha, has shown a distinct negative correlation between forest size and annual yield per hec­ tare: on the smaller farms the owner supervises the work or even cuts the trees (-carefully-) himself (1520). Selling 'by stumpage' and mechanization increase harvest and prices. Combined with centralized sawing (pre-sawing for distribution to various mills) and chipping (of waste or wood residues), this results in a higher net output. Un­ fortunately this cannot be done in selection or so-called 'pienter' forest because of its composition and lack of machinery adapted to selective cuttirrg. Also it cannot be done where tree-cutting could attract too much public at­ tention; for reasonable large areas it is possible only in plantations and in remote regions where clear-cutting is still tolerated. This may seem an exaggeration, but in many parts of the world it is a reality. To please the public, selective cutting has replaced clear cutting along some scenic roads in the USA, although it"doubles the costs; stumps are cut extra low, loading facilities are far from the road­ sides, and slash is piled in clearings (990). Most important for the stumpage price are the transport costs per unit weight to the consumer. Thus, in 1826, von Thünen in his book 'The Isolated State' placed the forest 235

closer to the town than agricultural land. Today, distan­ ces are less important for the farmer, but in forestry the transport costs are often decisive in the selection of ex­ ploitation, afforestation and mill sites (285, 1015). For tropical regions these costs may be so high that exploita­ tion cannot be complete (1761). Gabon, the logs have to be transported 175 km by road and 250 km by water, on the Ivory Coast 400 - 500 km by road and 1000 km by water, ln East Cameroons 40 km by road and 500 km by rail (163) whereas for the annual exploitation of 7500 ha 10 km roads and 6-8 km trails had to be constructed per 1000 ha (426). Such road densities can be estimated at 10 - 13 m per ha; in Switzerland it is 82 m per ha inclu­ ding unpaved roads along compartment borders not more than 130 - 140 m aPart (1483). ïn developed densily populated countries, forest roads are increasingly frequented by tourists. Thus the owner has to pay more attention to their layout in connection with the scenery and their maintenance. The question arises who has to pay the additional costs (11). p°r Brazil it has been suggested that industries receiv­ ing wood from their own plantations can best be placed far

away from population centers so that they may substantially contribute to the opening-up of remote areas (1461). Wood exPort may be furthered because transport over long distan­ ts» in a large country as Brazil is practically identical Wlth export abroad (9 27). ^or assessment, 'the detailed nature of the existing (Potential) mapped transportation network is obviously of great importance in delineating market areas for supplies' (575).

9. 3 3 • J •> 2 Cultivation costs

In the Faustmann formula, after r years the cultivation c°sts c are appreciated as C x 1.0pr> C is mostly a lump Sum considered to have been spent at the beginning of the first year. With delayed planting, cleaning and natural re­ generation (see example in 9.3.1), and short rotations 236

(7 - 10 years) this can cause significant errors in cost estimates (333). Because, as a rule, these costs put a heavy burden on wood growing and thus make it less attractive, the govern­ ment often has to assist. In England, the costs to establish a Douglas fir planta­ tion was put at £ 53.5 per acre towards which the Forestry Commission paid £ 14.0. Then it was calculated that, with a rotation of 50 years, the anticipated value became posi­ tive at an interest rate of 4 to 6,5 (680), whereas at real costs it would have resulted in 4 to 5, correspon­ ding with a decrease in land value from £ 85.5 to £ 70.0 and from £ 34.8 to £ 20.0, respectively. A change in cultivation costs calculated for one rotation does not influence the culmination of the land expectation value, they only change its level (132). How much financial aid should be given for forest rege­ neration and afforestation? A general rule could be: in­ crease it up to where the less promising plantations pro­ vide net benefits equalling those obtained by discounting a future return (Faustmann's formula) equal to the initial investment or to the land value plus cultivation costs (1549). Sound technical assessment, not only for the smal­ ler landowner but also for the state or the industry may also be of assistance. Where industry pays part of the cultivation costs on land owned by others, it has to accept the risk of inadequate forest management. An alternative then is to buy land, though this will be a heavy burden (1393). Another solu­ tion may be to lease land, e.g. for a period of 25 years, against a fixed rent, as is done in the southern part of the USA (1695). 237

**•3.3.3 Annual costs Annual expenses include taxes, overhead costs, mainte­ nance of roads, etc. To get an idea of their magnitude Table 10 may be consulted.

Table 10 Approximate annual expenses, in Swedish crowns*, per hectare (taxes, overhead costs, maintenance of roads and buildings, amortiza­ tion, etc.) for different European countries over the period 1958 - l962 (1522)

Sweden Finland Norway Denmark Germany Austria Switzerland England

® ( far n°rth)-48 3-33 3 - 12 33 - 82 82-llS+ 39 - 45 10 - 103 about 35

+ ++ 1 Sw.Cr. = 0.24 $ (in 1974) Approaching Dutch data

Mostly private forest owners spend less than governments, which have certain obligations to the public (189). For c°mmunal forests, the annual costs are closely connected with local politics and depend on the amount of local taxes. It is also possible that these taxes be lowered by Cutting larger quantities of wood (1501). Annual costs exceed 'normality1 when more general consi­ gnations enter the picture, for example for making the f°rests under management, from the outside, accessible; involving the opening-up of adjacent undeveloped regions improving their infrastructure. For Indonesia it has been Pointed out that for the forest, with its maintained road Astern and housing facilities, this should result in a spe- ci*l 'management-value' for the land in which the extra c°sts spend have to be capitalized (329). Taxes on forest property and income from growing wood much discussed in private forestry. Taxes can be based °n the market value of the forest (as e.g. in England, Prance, Belgium and the Netherlands), or it can be assumed th*t the land has to remain under forest, and then tax it °n yield as in Germany, Austria, Luxemburg, Sweden, Norway, Switzerland and Finland (862)• 111 the USA, property taxes (essentially a taxation of 238 wealth) are considered unsuitable for the forest because the value of the standing timber dominates and owners are at the disadvantage of not being able to realize it before the end of the rotation (1711). In Connecticut, in 1950, the average land value assessments varied between $ 5 and $ 830 per acre, the corresponding annual taxes be­ tween $ 0.08 and $ 22.62. The conclusion was that in 85 % of the townships the accumulated taxes made wood growing with rotation of 80 years impossible (1797). Because property taxes should refer to the most profit­ able use of the soil, the forest with high recreation va­ lues near cities may suffer so much under the ensuing high taxation that they soon come into the hands of speculators (1010). To avoid this, the Society of American Foresters has formulated the desirable policy as follows: 'equitable taxation procedures include those based upon the use and productivity of the land. These procedures should recognize the values of recreation, wildlife, and water yield which accrue to the public from good forest land management' (1448). Opinions differ about whether income from wood growing should be taxed as capital gain or as income. Periodical cuts at long intervals, inherent to small properties, might be considered to occupy a position different from that of regularly producing enterprises (1695). The Society of American Foresters-comments that 'the use of the capital gain principle has. encouraged investments in private forestry and should be continued' (1446). In the Netherlands, though all income from wood growing is exempt from taxation, forestry is at present in the red- Unfortunately the losses cannot be deducted from other in­ come (178). In Finland, 25 % of the harvested gross stumpa9e value may be deducted as a compensation for silvicultural and exploitation costs; at present this percentage seems to A be somewhere between 31 and 52 (947). In England the forest owner can make his own choice (483)' he pays either for the occupation of his land, or for the 239

income. Death duties become due when the stands are cut down (1423). The owner who destinâtes his land forever to wood growing receives, under certain conditions, untaxed Slants (482). Recently objections have been raised against such tax exemptions for private afforestations, because social benefits are questionable (1256, 1725). In Australia, taxes are not considered an obstacle to forest investments, though death duties have to be paid on them, it has been proposed to drop them, as has been done in New Zealand (85, 1424). The farmer in Finland who inhe­ rits his forest commonly at the age of 34-39 years and stops forking at 67, is owner for about 30 years. Hence death duties have to be paid once in 30 to 35 years (792). If farm forests were exempt from death duties, the farmer would probably be more inclined to start tree growing. An inquiry in Australia on the growing of poplars (return 6 %, Station 8-18 years) has shown that 59 % of the farmers dislike the long periods, particularly among the older men (1415) who are afraid that at their death much will be lost taxation. In Canada, and in many tropical regions, payment on stan­ ding timber has been considered a kind of tax collection. ïn Canada, taxes are now deducted from market value minus SxPloitation costs (1708). Taxes calculated as percentages wood prices proportionally reduce the value of the stan­ ding timber but leave the culmination point in Faustmann s formula unchanged (1219). Taxes and annual costs exceeding the land rent will 'in the long run, drive forest land out of forest production' (l2l9). In the Netherlands this process is already far ad- v®nced, except for poplar. The annual costs e, in Faust- man n's formula capitalized as E, directly subtracted from t le ^ soil expectation value Se, have no influence on the ClJlmination of the financial rotation. 240

9.4 Wood growing and its possible integration

9.4.1 Co-operation in wood production

Forestry no longer semi-processes wood for industry, it just provides the raw material. Today even fence posts are treated in factories (708). Because of the competition from other materials, forest product laboratories have been esta" blished to promote the use of wood as raw material (910). If he is not too individualistic (313), or reluctant to give up his position as manager-owner (709) , the small fo­ rest-owner, feeling uncertain when faced with the well-or­ ganized wood trade and wood processing industry, tends to co-operate with colleagues for a better income, in a kind of horizontal integration (1579). Since 1934, the wood growers associations in Finland have exported their own round timber. They also pay much atten­ tion to (the vertical) integration in saw-milling and, since 1953, in pulp and paper making (1183, 1202). Norway has associations supervising wood measurements and management; they also organize the selling of wood (364, 903). In addition they own sawmills but do not consider wood processing one of their primary tasks (1787). Denmark has management associations, and special working groups for such activities as exploitation, and sales pro­ motion (509). Sweden has the best organized and most advanced associa­ tions, operating since 1920, to pool wood sales and to buy and establish wood industries (1181). Their main task is i*1 technical and economical development of forest production (1178). They possess the most modern plywood mill of Europe (1757). In 1971, their membership has reached 130 000, jointly possessing 7 million hectare production forest, one third of all in Sweden (1534). In England, the forest owners association are in the course of building up their own service (312), tackling 241

the problem of organized marketing 'to ensure a balanced output' so that big industries can be established (1599). To enlarge existing sawmills or to replace them by big­ ger ones, in Switzerland co-operation has been recommended to obtain large wood-delivery contracts (1658) by joining the mostly small (75 % less than one hectare) forest proper­ ties (856) and by introducing better management in more con­ centrated areas (573), aiming at vertical integration; al­ though here including the wood industry (307). Por Belgium, with 55 % of its forests in private hands, it has been proposed to allow the owners to form associa­ tions 'by law', to strengthen their financial position (891). Although the Dutch forest owners tried to join on a co­ operative base (1578, 180, 181, 628), it did not work sa- tisfactorely so that the government was asked for assis­ tance (166). Concentration of wood trade, or direct co- deration with wood industry have also been recommended (1°54), and re-allotment to enlarge stand sizes was proposed

(228, 112). the Swiss kanton Zürich, re-allotment resulted in an increase of the average forest parcel size from 0.26 to 0,83 ha (1376). In the past such re-allotments must have ta- ^en place regularly in combination with agriculture (1533), but no data are available. In the Netherlands, re-allotments have been proposed for 19 70 - 19 80; they should be success- ful if carried out in combination with the extension of re­ lation facilities (1258). Germany at present some 30 % of the total 527 000 ha forest area is jointly managed. The extension of this area ^as top priority at present in German forest policy (1724), integration with state-owned or communal forests into te9ional management units is being discussed seriously ^though the state refrains from participation in a possible Vertical integration with industry)(1464). In Italy, lack of co-operation hampers the development of 242

poplar growing (1635), though with half of the timber har­ vested from this tree species (2 750 000 m^ annually), con­ centration would certainly be beneficial for all involved parties (540). In New Zealand, where farm forests are gaining in impor­ tance, co-operation is considered a means of obtaining a continuous supply of raw material for the industry (1247)- In the USA, after the virgin forests had almost disappear' ed, wood industry had to turn to tree farming (1031). The resulting farm forests, assisted in their management by in­ dustry, are considered the best managed (475). At present, 31 000 farmers own some 28 million hectares,supervised and checked to receive the certificate 'Tree Farm1 (287). To be sponsored by wood industry is considered most effective and profitable for the owners (249). In Texas, however, still no great progress has been made; in 1964 the Forest Service started promoting aggregation of forests as appa­ rent from the Co-operation Act of 1944, also called the Sustained Yield Management Act (289, 845). After World War II, attention shifted from the state fo­ rests to the farm forests. In the USA, Canada and England they were considered badly treated, but all writers agreed that owner associations would be beneficial to the wood- grower and the wood working industry (87, 782, 767, 984, 966), though an American author remarked that their struc­ ture would probably have to change to that of a corpora­ tion (965).

9.4.2 Stimulation of wood growing and special forms of

co-operation

Private forest owners are inclined to raise quickly yielding species. In Japan, the farmers in their associa- * tions (including 57 % of the owners (481))are regularly ex~ perimenting with new varieties for this purpose (1169). However, in other regions due to the absence of a nearby 243

factory to buy the large quantities of mostly young timber, the farmer, often refrains from planting and the industry hestitates to start for lack of guaranteed supplies (1260).

In countries with a state-directed economy this is no Problem: there forest utilization has always been subordi­ nated to industrialization (185). In a free-trade society, however, competition has to show the way, and often the in­ ternational wood market is involved (772). In western Europe the latter situation has never existed: there mostly the state has interfered to preserve the forests or to extend them to 'maintain their production and ensure their benefi­ cial effects' (1182). Recently it has been suggested that governments should also study the situation, to base their Policy on national inventories, timber-balances, etc., to direct, renew, or at least assess their 'far—reaching mea— Sur®s to promote timber production and to ensure efficient wood-supply1 (1456, 1014). This does not mean that all low-yielding forests can be changed into highly producing stands, or that changes to a9riculture should not be considered (291). Such an a prio- ri' standpoint, inherent to former forestry, should be aban­ doned. But after the decision 'forest' has been taken, one ^as to accept the principle 'that the whole operation of lowing, transportation and processing wood is one exercise in forest economics, certainly viewed from the regional and national viewpoints' (1125). self-supporting wood industries have understood this : they buy their own forests (mostly naturally grown) or woodlands change to mechanized plantation forestry to safeguard future supplies. So they become managers of capital, which sometimes profitable (by rising stumpage prices) , and sometimes a nuisance (more personnel, fire-protection, re- strictions on management dictated by law, etc.) (454, 973, ^•102, 1436 , 1065, 794, 310). In western Europe, with its ^a^celled stands, hilly or mountainous forest-country, and ^Sh land prices, mechanized plantation forestry is well- 244 nigh impossible (4). To protect a region, from the conservation point of view, it is possible to restrict or abolish wood exploitation. For industries this is impossible, without a revision of their working methods, relocation or terminating production (763). Changes in exploitation or transport can also put a heavy burden on wood industry. For example, during the pe­ riod 1970 - 1980, the Swedish pulp and board industry is being reorganized because river transport in summer has to be replaced by road transport throughout the year to safe­ guard a continuous supply of raw material (1392). Seen from the present general standpoint, it may be considered a draw­ back, that the combination wood processing industry and woodgrower can only exist if it can take full advantage of the earning capacity of its woodlands by 'making profits from yields reaped as thinnings (carried out mechanically) as well as crops reaped as clear fellings' (46). In large parts of Europe the tendency is in the entirely opposite direction: so much emphasis is put on the social function of the forest that the state, spending money earn­ ed by its citizens, has practically become the only plantet of trees, either directly, or by means of subsidies (1290, 6). The tendency to call in the help of the state is also ob' served in regions where the industries do not venture to supply the large capitals needed to start forestry (439). Exceptions are plantations of radiate pine (Pinus radiata) established in Chile by the mining industry, wattle (Acads decurrens) in South Africa for the tanning industry, slash pine (pinus elliottii)for the paper industry in the southed part of the USA; etc. (210). But they all involve species with short rotations and nobody is willing to invest money for profit in. the far future (65). As a solution, it has been suggested, in New Zealand, that planting by industry should be encouraged with voluntary taxation of its annual production, forming an (inter-industrial) afforestation 245

fund (577). Especially in developing countries, the inhabitants owning the land should participate in timber growing, first- because they dislike foreigners who occupy part of the iand (1084), secondly as an example to be followed by the inhabitants themselves.Unfortunately, in the past this type of farm forestry has received little attention (7) ,though it may provide much wood (in the USA half of the national pro­ duction (1602), in Europe practically all poplar wood). ïn the former colonial regions, farm or village forestry Was, as a rule, grossly neglected; exceptions were India and Burma, where nowadays even more attention is paid to it: (1252, 1277, 141 , 803, 1020, 480). Trees between crop fields or in shelterbelts can produce the fuel that otherwise has to be extracted from forest reserves. When adequately aPPüed, this system results in a balanced landuse and may even provide industrial bulk products, as has been suggest- ed for South America (898) and Australia (widely spaced t^ees with an undergrowth of grass for cattle, a kind of mixed farming ) (9 9 3). Another way to stimulate tree growing is to assist the farmer in planting, provided he sells the crop to the spon- s°r. Where labour is cheap and fast growing tree species raised, in a short time large new wood resources can be created (413).Share-cropping, outdated in the western w°rld, seems to be socially acceptable as long as property rights remain exclusive and transferable (278). In Japan, share-cropping which is often practised is con­ sidered the easiest way to encourage tree growing, as it dispenses with land transfers. Some 650 000 ha is managed in this way, including 300 000 ha owned by the government. the past, 40 % of the yield was for the owner, 60 % for the farmer; recently this ratio has changed to 30 : 70 (1405). •Trees can also be grown on leased agriculture land. In Prance the product may be harvested as annual growth, but 246

in England it is legally considered capital which the te­ nant cannot touch (mostly resulting in negligence) (566). In northern Italy, where agriculture and poplar growing (covering up to 20 % of the fields) are often combined without hampering food production, serious troubles have arisen on the question how the profits should be divided between land owner and tenant (263).

9.4.3 The aspects of integrated tree growing

The present forest enterprises are often in a difficult position: the State forests may be burdened with such high management costs that economic treatment is practically impossible (even if for the invested capitals no interest is taken into account). The private forest owner, willing to grow wood or forced to by Law, can only hope for a capi­ tal increase counterbalancing his annual low income or even loss. If taxes are high and not attuned to 'the long delay be­ tween establishment of woodlands and reaping its products' (25), planting can mean throwing away money. In France, practically no taxes are levied on waste lands, but as soon as trees have been planted the treasury is quick in asking payment for something that in future someone else will collect (1227). It is hardly surprising that under such circumstances the creation of new., forests by private owners not allied with industry or by an investment corpo­ ration is unfeasible. Still governments are often much in favour of establish­ ing forests. The motives vary. After World War I, England wanted to build up a strategic forest reserve, recently pa' raphrased as, 'the need to maintain an increased forest production for economic and social reasons' (1315). Brazil promotes afforestation with the outspoken purpose to indu­ strialize, and it allows private owners to invest half of 247

their annual income taxes in their own plantations. Owing to this measure, in the period 1967 - 1969 an area of 300 000 ha forest was planted, to be increased by 123 000 ha Annually in the period 1970 - 1980 (1443). Obviously a wood industry does not simply want to have a forest area near at hand (299), but it also wants to have some (or a decisive) influence on the kind of wood grown. °nly then is an 'integrated wood industry' feasible, mana­ ged by the state, by private enterprises, or by an associa­ tion of wood growers (1500, 1485). Eastern Germany has such a full integration of forestry ®nd industry in the 'national management units' (1311). In Hungary, in 19 70, Forest Wood Working Corporations were formed on similar principles (831). In France, where almost wood production in controlled by the state, attempts a^e made to provide industry with long-term contracts esta­ blishing priority cutting on forest stands, a form of co­ operation between state and industry (1624). Such a co-ope­ ration could be substantially expanded in Europe, especial- 1y in view of the four million hectares of crop fields the Common Market has proposed to convert into forest. If this Proposal is carried out, planting has to be left to the farmers, subsidized by the governments (274). The govern­ ments could select areas on reasonably flat country to gua- r®ntee a suitable industrial wood production. is remarkable that, due to the promising aspects of w°od export, even in New Zealand the need is felt to assist the farmer in planting; there it is expected that the neces- sary legislation can be kept much less complicated than in Europe (1709, 1093). Ät first sight this all may seem rather simple. But the Realization of such plans encounters various difficulties. important problem to be solved is in how far industry maV interfer with forest management between planting and Cutting. Experience in America, and also in Europe, has shown that owners of economically well-located stands are 248 often not interested in forest management, in income from wood, or in taxes to be paid (they sometimes consider such stands more as a stamp collection) (985). Farmers, given a certain guidance, are most capable of caring for their own moderately sized stands (569). Industry willing to de­ pend on nearby wood supplies, however, has to be informed on the regional production potential. For the Netherlands it was remarked that this involves the co-operation between grower and industry, which eliminates traditional wood trade (1051). Such integrations not only need co-operation in wood gro­ wing and wood processing, but also in selling by regional 'compound working circles' (79), as prices depend on of­ fered quantities (in Austria, quantities of 1 to 20 m^ yielded 7 % less money than those of 700 to 1000 m^)(544)- For the Netherlands it has been suggested that the state should sell its wood per forest district, avoiding the se­ parate sale of small quantities (1052). Where co-operation between smaller forest owners and in­ dustry is not efficient, as in Germany, the rather awkward situation may occur that the farmer must leave his forest work to expensive hired labour (1462), and that (still in 1971) both farmer and management organization are taxed oveï the same income (1240). Consequently it was suggested to transfer ownership to a corporation or something similar (954). Some people are optimistic about integration on a regio­ nal base and consider it unavoidable to save European fo­ restry as long as wood wants to cope wit "Ersatz' (1486, 1582). Modern development in wood harvesting shows the way for such changes. In the USA, 'to offset steadily rising costs of obtaining and processing timber, emphasis has been placed on mechanization and on obtaining the highest value fibre of each log. Log-merchandizing centers which combine debarking, bucking/slashing, sorting, and chipping machine' ry, are gaining favour as a means of breaking down tree- 249

length material into a variety of end-uses' (1218). Such centers will be suited to work the products of the manage- ment units on a purely economic base, whereby the future has to teach who can best handle such places: the forest owners, the industry, or a combination of both (108). Such a center was established in 1970 in southern Germa­ ny, serving 39 000 ha forest, including 33 % state-owned stands. It is able to sort and debark incoming trees; chip- Pers to use the waste will be added (639). Probably the wish to promote the use of local wood (1142) has contributed in the Netherlands to the establishment of two comparable places: one with a capacity of 15 000 m3, the other with a capacity of 10 000 m3 (annex sawmill) where incoming tree-length wood is trimmed and debarked (178, 715). because of the flat country and the many good roads and wa­ terways no transport difficulties will arise so that a few Centers may be able to assist in curing the ailing Dutch Production forests.

9*5 Wood production outside the forest

•^n many regions substantial amounts of timber are grown al°ng roads, in parks, in orchards, etc. (953, 267). In l969, in Italy poplars covered the equivalent of 250 000 ha forest as against 145 000 ha in stands (442). In 1951, Swit- 2erland had about 1^ million apple trees and over 2\ million cherry trees (204); in addition there were some 585 000 wal- nut trees (Juglans regia) with half a million cubic metres W°°

To decide on future forest management, first an invento- rY has to be made, resulting in a number of alternatives for exploitation and wood growing. This means planning for a future, usually a distant future, and involves the study of historical trends with special attention to recent de­ velopment to be explained 'by a set of mathematical re­ lationships between economic variables to draw up long- term forecasts. Such forecasts contain many uncertainties (the most important related to changes in technology), so that it is essential to repeat studies on trends in timber- Use at fairly short intervals(575).The 'continuously perfor- inventories ' or CFI are the most suitable as a base ^°r this purpose.

l0-l The future of wood utilization

•^•t has to be proved, or at least made acceptable that Growing wood for the future is a necessity. This will be difficult. Prognoses will have to be based on national or r®gional statistics, including non—registered transactions ^out which only a well-informed district forest officer Can supply the necessary information (1317). The easiest forecast to make is most probably for veneer. W°od for high quality veneer will always find a market, be- Cause imitations generate an 'increased demand for the real thing I (442). Except for pulpwood, the tendency is a shift f r0m firewood to fossil fuel, and from timber to iron, alu- concrete and plastics. . Finland, wood consumption for own use has, since the 17th Century, Creased from 75 % to 20 %; the pulp industry, started around 1930, "°*adays uses one third (22). In Russia, the consumption of firewood nas dropped since 1913 from 59 % to 3 % of the wood harvest (1668). In Western Germany, the annual wood consumption amounted for 1959 to 46.5, for 1967 - 1969 to 54.2, and for 1969 to 59.9 million 252

m3 roundwood; extrapolation gave an estimate of 75.8 million m3 for 1980. As their own wood production in 1969 was only 26.6 million m3 (1179), the prospects are bright for the wood export of the northern European countries. In 1970, Japan consumed 127 million m3 wood of which 55 % was im­ ported. As its own production will probably not increase anymore (1038), this may stimulate wood growing in New Zealand, where in 1971 of the 8.2 million m3 wood produced, 3.4 million m3 was exported (for 84 % to Japan and Australia) (1238). Furthermore it is expected that up to 1990 Japanese paper and board production will increase three­ fold. This increase may be important for Australia where in 1970 (in Tasmania) chip production started, soon to be followed by Papua, New Guinea, where an annual production of 174 000 tons is expected (674). During the period 1960 - 1970 all wood processing indus­ tries have made great 'progress, in particular those produ­ cing plywood, chipboard, hardboard and fibreboard. The annual world production of chipboard has increased from 1.9 mil­ lion metric tons in 1960 to 7 million in 1970, that of plywood from 15 to 26 million cubic metres (788). In Russia the production of chip­ board increased from 116 000 m3 in 1960 to 1 650 000 m3 in 1970, with a planned production of 5 million m3 in 1975 (412). Germany, where the fabrication of chipboard started, produced in 1971 a quantity of 4.3 million m3 , and its industry has a capacity of almost 6 million m3 for 1972 - 1973 (1482). With the improved resins thinner sheets can be manufactured and mol­ ded to rounded forms, applied in furniture (408). The Forest Products Laboratory in Madison, USA, estimates for the year 2000 a doubling of the world consumption, distributed over some 5000 items, partly in combination with bark and plastics (860). The timber Committee of the European Economic Community admits that synthetic materials are sometimes better than wood, but it is con­ vinced that there will always be a market for a combination of both in the furniture industry (713). Because the demand for saw and vèTïeer logs between 19 80 and 2000 in Europe is expected to increase slowly, it is concluded that the over-mature forests will be large enough to satisfy future production and consumption, even in the distant future (71). At present, organo-chemical compounds can replace one of the most typical forest products: wooden fence posts (671)* As with the furniture, some people will reject them for aeS thetic reasons, but this will hardly influence the market (1371). For the production of plastic furniture the neces­ sary investments are still twice as high (per m3) as those for wood (706). Nevertheless some authors presume that 253

Plastics and dérivâtes of AlFeSiCa minerals will take over within the next half century (335) , notwithstanding the in­ volved 'substantial problems of pollution', which could e- ventually prevent such a development (1309).

In Japan, the shortage of raw material for paper has directed re­ search towards fossil organic material, perhaps to be combined with w°od fibres, that is workable in normal paper machines (714). This example demonstrates the unpredictability of the factors that may en- ter the picture. On the other hand it has been alleged that man feels m°re comfortable in wooden than in stone or metal houses due to their lower radioactivity (861), better isolation, better moisture regula­ tion, more favourable acoustics, etc. (30, 31). More to the point is that the railways in Germany have stopped replacing wooden sleepers by concrete ones, which has resulted in an increase in wood imported for that pur- Pose from 20 000 m3 in 1968 to 101 000 m3 in 1971(701,1180). Such facts, and the FAO prognoses, make it reasonable to ®xpect a growing demand for wood products. This demand can only be met if existing stands are better treated and new 0nes are planted. Especially for countries depending on wood export and w°od industries such trends are highly important. Finland a good example because wood and its products make up 60 % of its export. Recent inventories have shown how much forest production can be increased (765): in 1970, drain and allowable cut' almost balanced, but the north of the c°untry has good opportunities to enlarge production, as alternative land uses are absent (897). Sweden with 24 % its export consisting of forest products, in 1970, is steadily improving its wood processing industry; in the s°uthern part more efficient management may increase pro- action by 30 % in the next ten years to meet the increa- s ing demands, especially from western Europe (711). Countries like England, with few forests, focus their attention on regrouping woodlands to establish forest units at least 10 000 ha within a 30-mile radius of the in- dustry (700). Unfortunately, the English hardwood sawmill

^dustry is in a difficult position because of the poorly 254

formed logs and the prohibition to cut stands (for rea­ sons of amenity and environment). 'At the current rate of usage good stands will hardly be available for the next five years' (after 1972) (1083). Argentina, with much bare land and only a few accessible forests, is trying to find a solution by planting: in 1971 a forest area of 300 000 ha had been established (willows, poplars, eucalypts and pine) at a rate of 25 000 ha per year, to be increased to 50 000 ha (1659). In the period 1970 - 1980, the Netherlands expect to have f at their disposal a relatively large area of abandoned fields that produce insufficient crops of which about half will be available for afforestation, mainly for recreation (1259). As this country hardly produces any heavy wood, and because other countries increasingly dislike exporting raw material, it is forced to import large quantities of finish" ed and half-finished products. As a countermeasure, planting 300 000 ha new forest has been proposed (1054). Recent cal" culations have shown that, based on a land rent of ƒ 130 a year, the returns (excluding drainage charges) will amount to 4.5 % for poplar, 2.5 % for spruce, but less than 0.5 % for oak with its long rotation (174). In former sections much attention has been paid to fo­ restry in developing regions, especially to those in the subtropics and tropics where co-operation between research and surveying is necessary to promote utilization of still unknown wood species (1385, 658), especially those which may give high annual yields in man-made stands. Attempts in this direction were made immediately after World War II by the Organization for European Economic Co-operation (1171) and were continued by the Forestry Division of FAO. Remark" able, however, is that the United Nations in their general economic development planning based on international co­ operation, hardly mention wood growing (926, 1216, 1253)- Only in a recent study on utilization of tropical lowland forests sponsored by UNESCO, was it concluded that for 255

forestry 'authority in land-use should be given to ecolo- 9ists or ecologically trained field biologists who better than other professionals or scientists can arrive at a just utilization of wood and land' (1122). It may be feared fchat such 'naturalists', lacking sufficient practical in- sight, will always advise a hands-off policy.

*0.2 Future land-use

In remote regions wood may first be grown on practically w°rthless land. When population increases, the land value rises and the production of the forest becomes relatively insignificant. Industrialization speeds up this process and may put a heavy strain on decision making in product­ ion forestry. The complexity of such decision-making is obvious in the Netherlands, especially in its most densily populated wes­ tern areas, the 'megalopolis Holland'. Between 1955 and l965 13 % of the agricultural land, already a low percenta­ ge in this area, was set aside for other purposes (1615). such developments can lead to large-scale speculations in land and to agricultural and forest enterprises content With covering their running expenses and relying on future CaPital gain(212,155).Forest owners also expect a rise in Value of their land if wood growing can be combined with income from recreation(campings, weekend houses,etc.),or a higher expropriation value when the land is kept under forest. °n the other hand, industrialization may further wood lowing if it includes wood processing factories because the consumers are close at hand (1393). This is one of the reasons why a 1968 decree of the pre- sident of the Federal Forest Institute of Brazil forces Wo°d exploitation firms working in naturally grown forests to Plant four normally spaced trees for each extracted Cubic meter of roundwood in parcels of at least 5 ha in the v^cinity of markets (1087). 256

These examples show that decision making in forestry has become more and more complex, so that new tools are needed in planning. Mathematical models have to be constructed, and simulation programms including time and tree growth have to be drawn up. Uncertainties can be 'incorporated into the models by probability distributions and random number generators to give a realistic range of outcomes that may be encountered. This may assist the manager in coping with uncertainty' (609) , to protect himself against possible future misfortunes (392). Today for this purpose the computor is indispensable (1201).

10.3 The rotation

For a well-managed forest enterprise an adequate, perio­ dically revised plan is indispensable. It must contain de­ tails on silvicultural measures and other technical sub­ jects (which will not be considered here). But the most im­ portant point is that it has to be based on a rotation (or rotations, where more tree species are involved), the lapse of time between establishment and end harvest, that serves as the main directive in setting up a wood-growing enter­ prise. Its calculation, if sufficient statistics are avail­ able, is purely mathematical. But in its application other criteria may be involved be­ sides the interest rates discussed in 9.3.2, for instance in farm forestry the farm enterprise has to be considered as a whole (1007). A biological rotation can be used in some cases; it is based on the maximum age a stand can reach without deterio­ ration. It may be applied in even-aged protection and recXe~ ation forests, and it plays a role in tropical jungles wit*1 scattered, selective cutting (268). Another possibility is to apply the rotation of maximum annual production in vo­ lume and value (disregarding maximum rentability of invested capital). It is usually applied where continuity outweighs 257

Maximalization of (temporary) profits, as in publicy owned forests or large industrial wood-growing enterprises (1134). Ultimately, a technical rotation is applied when a special Product is grown, such as willow coppice in the Netherlands dotation 3-4 years) to produce saplings for building and Protecting dikes (1679).

10*4 Other aspects of decision making

The forest-manager looking for optimum investment oppor­ tunities in wood growing will have to apply dynamic program­ ing, based on the best technical assessment available, to Çfuide growth from seedling to end product (1379). All will become part of the forester's working life, provided he is not kept under constant surveillance or too strongly bound to the management plans (1310). the forester is free in making decisions, especially f°r investing capital in tree growing, he will mostly have to deal with alternatives for which the rates of return VarY with the invested amounts (the use of selected or Unselected seedlings, the application of tillage or ferti­ lization, pruning, etc.). It has always been common practi- Ce to look for the highest rate of return per compartment °r stand, but recently it was pointed out that levels of Investment established for all projects simultaneously will result in greater investments in the stands promising the highest rates of return (972). p°r return estimates, the forester can base his calcula­ tions on the growth patterns provided by yield tables (in­ king thinning yields) adjusted to local marketing condi­ tions and co-operation with neighbours (1336). The forest-manager is usually not free, however, to make loi>9-term decisions, as he has to follow the management plan with its fixed rotations, thinnning schedules, etc. ailtling at a normal age-class distribution based on sustain- ed yield corrected for local aberrations (1425). Thus he 258 has to focus his efforts for efficiency on short-term ameliorations, including the maximization of returns from prescribed end-cuts, thinnings, etc., by planning road- building, by securing wood-delivery contracts, etc. (487). To obtain the highest net profit from wood harvesting, me­ chanized cutting and adequate sorting (based on regional markt analysis) can be indispensable (692). Recently the forester-manager has to pay much attention to the multiple purpose function of his forests. Hereby the problem recreation versus production, the need to mo­ dify exploitation techniques (excluding clear-felling), and comparable subjects will call for great skills in predicting' assessing and explaining the nature of the benefits for so­ ciety (283). Lack of experience in forest management for other purposes than wood production may call for 'static' models*, probably being the most comprehensive, to explain and direct future management (272). Often the forester will have to deal with less tangible influences. Although it is hardly possible to assess them money or services rendered, he still will be obliged to eva" luate them. On this problem a Swiss writer complained that the public appreciation of the forest welfare functions, compensated solely by tax exemptions has become doutbful (150). A French colleague remarked that recreation forests are more susceptible to fire; the private owner can(perhaps insure himself against the ensuing damages, but the ques­ tion remains who is going to pay for it (918). About the various aspects of decision making an AustraliaJl author wrote that 'unless there is an economic analysis f°r the various combinations of products from the range of mul' tiple use systems, discussion .... will remain vague, con­ tradictory and emotive and of little value to forest mana­ gers' (969). Qow complicated forest assessment and its re­ sulting decision making can become if influences from out­ side are at work, is shown by a large system model made by Duerr for the USA. This model includes data on public com-

Whereby the creation of well-defined (static) landscapes is involve^' 259

munications, explaining and assessing general sentiments ar>d wants, and the results of administrative and congres­ sional hearings on these subjects (393). An example of multiple land-use quite different from those discussed above has been presented for Nigeria. There, the 1 taungya' system; translated as agri-forestry, Gmeli- arborea with a rotation of 10 years is used in combina­ tion with food crops, or other trees with a cash crop (such as cocoa, coffee and oil palm) (811)• To arrive here at a financially and sociologically justified solution both ^°r the agricultural crop, the tree crop and the farmer Wlll be most complicated.

^•0.5 The social function of forests

^^5•1 The forms of forest recreation

The social importance of forests increases with a growing Population density and decreases with the extension of the ^°rest area. For Western Germany, with its forests valued DM 70 000 million (1 DM = $ 0.38), the social and recre- ational functions have been appraised at DM 53 000 million, °r three times the wood production value. Other estimates for that country vary from one to four times that value. Of c°urse such money estimates are questionable, but clearly f°rests are highly appreciated (783). p°r the French the situation seems to be different: their prime interest is recreation near or in water, whereby fo- tests are often considered only as an agreeable setting (1220). The most typical feature of forest recreation, even in Ger*any, is that only some places are frequented by visi- tors whereas the other parts are neglected. In England only 9 few people use the forests for walking (and hunting) and th®y enjoy 'the rural landscape only as long as it remains s°lated from the noisy majority'. 260

The uninterested masses should be persuaded to visit fo­ rests. Part of the forester's duty is to educate the visi­ tors to look'beyond the limited margins of the silent and tranquil nature trail' (1309). People instinctively feel that forests are free to dwell in, though at the same time they are reluctant or afraid to enter them. Especially in crowded regions the forester must do as much as possible to remove this fear, giving the people more room for really valuable recreation. The study of the influence of recreation on forestry had advanced most in the USA. Already in 1899, in the Mineral Spring Act, the provision of recreational facilities was foreseen (63). At present the expected number of visitors to national parks and forests can be mathematically estima­ ted so that adequate facilities can be planned. This number depends on the per capita income, the mobility (distances travelled per car per passenger), the leisure time, and the population density per distance from the recreation place. For 1960 the number of visitors to all national forests a- mounted to 93 million, for 1980 it is estimated at 430 mil"" lion, for the year 2000 a number of 2010 has been calculate^' This makes it necessary to enlarge the national forests from 5.6 million hectares to 22.7 million (942). Even where the public prefers well-managed small private woodlands to public camping grounds, they have to be provi" ded with rather costly swimming and skiing facilities, but this is realizable only when the place houses at least 70 families (1672, 907). A private forest owner may combine wood growing and recreation, whereby (also in the USA) the leasing of summerhouses only on a annual basis is consider' ed profitable (1548). In France it was suggested that inha" bitants of cities form co-operatives to build such houses in private forests licensed by the state (200). The general public, influenced by people who do not want the forests disturbed by too many city dwellers seeking re" creation, may become opposed to such plans especially the 261

building of summerhouses. However if the authorities pro­ hibit these plans, the forest owner can confront them with fche financial losses involved (966). Opinion polls among forest visitors may give an impression of their wishes (1400), but investigations have shown that not only they, but everybody must be given the opportunity to express his °Pinion on such matters (638). !n the Netherlands wooded strips along the forest borders, °r tree strips are recommended to hide the visitors from the outside world and to protect them against the wind (1688). The Dutch seem to prefer, next to their national Parks, landscape parks characterized by forests and typical firitis. Here the old landscapes have to be maintained (820, 1313). In North America a special form of recreation is 'hiking', m°stly by small groups of experienced people from the upper and middle classes (1509). Among the other forms of outdoor recreation, one day visits predominate (in 1956 in the USA ^•5 million recristered people, one fourth fishing, many other photographing) (288). Fishing and hunting are all OVer the world favourite forms of recreation: in 1955 in the USA one in eleven women fished/ one in 128 hunted, one in every five people over 12 years fished or hunted (280).

^•5.2 Costs of forest recreation

these forms of recreation ask for protection and va- ri°us facilities (1774), involving costs. In 1961 the USA f°rest service spent $ 1.08 per family per camping day, * °-72 per picnic day; based on these data a licence would c°st only a few dollars a year per family(1410). It may be Cresting to compare these costs with those calculated f°r visitors to the city park of Amsterdam (946): in 1966, With about three million people, the annual maintenance Costs per head amounted to $ 0.23. But admission costs are levied either in the Netherlands, or in any other European 262 country (except some special properties). The maintenance costs mainly depend on the behaviour of the public: better guidance and education can considerably reduce these costs (1395). Unlike forest products, recreation cannot be imported:_ the demand has to be met on a national basis (859) , except for very small countries where people can easily visit their neighbours. Here enters the modern nomad in his car. He often regards roadside trees and forests more an obsta­ cle than necessary components of the landscape. He will pro bably admit their importance for such 'sedentary elements as farmers and villagers' who still consider trees as essen tial shelter for their living space which, ecologically speaking, they indeed are (1388). In Germany, the costs of recreation have been expressed in working hours: 100 hours per year for parks, 8-10 for forests (574). Expressed in DM per year per hectare they amounted for parks to DM 700, for extended forests to DM as an average to DM 29. Of these amounts 5 % was for clea­ ning, 9 % for policing, 8 % for making wood exploitation more complicated, 59 % for facilities, and the rest (19 %) to compensate for decreasing wood production (1045).Some­ times more personnel was needed; all did their jobs with pleasure, making the forestry profession more attractive to them (1681). Near towns some of these costs can often be covered by harvesting such minor products as Christmas trees, branches with coloured leaves, crooked pieces of wood or roots for ornamental purposes, etc. (1041, 213).

10.5.3 The outlook for forest recreation

In industrialized countries the number of working hours (see Table 11) tends to decrease and the salaries increase» giving more room for all 'to pursue both their material well-being and their spiritual development' (427). In the 263

Table li Number of working hours per year for various countries

country : Belgium Prance Germany Italy Luxembourg year . 1966*"^^ 1966*^"^ 1966^^ 1966*332 1966*332

number of hours: 1908 2072 1860 1877 2019

country . Netherlands USA forest service year . iqjq^^ 1966*332 19691®9 19751^°2 2000 (expected)

number of hours: 3556 1983 2019 1820 15601602 or 16007 78

n°t too distant future, the working schedule may be four days work followed by four days leisure. With 9-10 wor­ king hours a day this amounts to 1640 or 1825 hours per ^ear• A leisure of half the number of days in the year will Certainly stimulate outdoor life, for which the authorities "»ust be prepared (1387). Fees for housing and camping will be unavoidable to maintain the areas involved (175). That clear cutting and monotonous conifer stands do not fit in here is obvious: a more attractive vegetation will have to be established where people want to spend their "»any outdoor days (1257). In western Europe, and probably in the Netherlands»especially the ensuing changes in the f°rests, in wooded strips along roads, etc., will lead to a decrease in wood production and an increase in annual c°sts that will have to be paid for.

^•0.6 Conclusions

Whatever the main principles of decision-making are for forestry and the implements to realize them, all activities •"'Ust kg unobtrusive, so as not to hurt the public s aesthe­ tic feelings or its desire for a restful environment in which to relax. Nevertheless, foresters remain managers of a Part of the biosphere that also has to be used for the material well-being of society. This duality may place then> in conflict, especially nowadays. Outsiders should tealize this and understand that a compromise has to be te*ched between the feelings of the public (of which the 264

forester is also a member!) and the economic basis on which forest enterprises have to be run. This basis is, essentially, the exploitation of a number of natural laws resulting in an accumulation of organic matter (wood) suitable for a great number of purposes. When adequately managed, the forest (the 'factory' that provides this material) can produce an endless stream of it. In addi' tion, the forest assists in combatting air pollution, in preventing erosion, and in regulating the water-supply for various purposes. Forestry is even able to increase the stream of raw ma­ terial. The primeval forest, in its climax (equilibrium) stage, shows a very low wood increase due to the age of the trees and their heavy mutual competition. In managed stands, both factors can be corrected, especially when the primeval forest is changed into even-aged, regularly thin­ ned pure stands with a relatively short rotation. Again this may be a thorn in the flesh of 'naturalists', those who consider that 'nature must be left alone', or who want to return to the times in which mankind consisted solely of 'collectors'. In a way this feeling is understandable, but it is based on a false notion of what forestry aims at, on a lack of communication between good-willing people on both sides who love their environment and want to keep it in good shape. But the question is whether vast jungle-covered landscapes should be reserved for the few amateur and professional biologists and for hunters in view of the great majority of industrial workers and city-dwellers and their children» so much in need of outdoor life, and often condemned to seek their recreation on the verges of our highways. Furthermore it should be kept in mind that neither the general publie, nor the forester, want to decrease forest coverage or tree planting, either for production purposes/ or for recreation. On the contrary: all want an increase for which, at present, in many regions new opportunities 265

are offered due to the abandonment of submarginal agricul­ tural fields. Obviously the forester wants to guide tree growth and to Us© the forest products, but his most extreme opponents (not the general public.') want the trees to die a natural death or even try to postpone this with the help of tree s"rgeons. Long experience has taught the forester that to Maintain a healthy growth, felling must be used as a tool, ev®n if this looks less pleasant, temporarily. Basically he follows nature in this respect and only modifies destruc­ tion caused by fire or storms, not leaving restoration to nature, as in real jungles, but by removing all 'rubbish'. doing so, he demonstrates his aversion to wilderness and his preference for neatly kept park-like landscapes. for state-owned forests, the 'save and protect' tendency w°uld mean more expenses which would have to be paid by the *-ax payer. Extra costs would hamper the private owner in his management and force him to ask for financial aid; °therwise he would be forced to use his lands for another purpose. Unfortunately, because of the present difficult economic Position of West-European forestry tree stands are often left unthinned, forest roads are neglected, and fire pro- action is often inefficient.This results in a forest land- ScaPe that looks like a disagreeable wilderness and so sup- P°rts the idea,especially among the many new recreationists, that this is a normal situation. The only solution for the economic problems is in more efficient methods, management and mechanization. However Europe this seems to be very difficult partly because forest areas lend themselves badly to mechanization and Partly because European state-oriented forestry has al- had a certain disdain for applied economics. Hence Practically nowhere are the financially most profitable ro­ dions applied, and almost nobody minds financial results forgetting about interests for the immense capitals in­ 266 volved)as long as annual or periodical output exceeds input. Plantation forestry, entirely dedicated to wood growing» with mechanized tree raising from planting (or sowing) and thinning to end cut, meets much resistance, except for pop­ lar and some other tree species with short rotations. Many do not even consider the latter real forestry, perhaps be­ cause it has too much in common with agriculture: it is too 'artificial', and the stands differ too much from naturally grown forests of old, heavy trees. To meet the growing demands for wood products, tree rai­ sing is being shifted to less developed regions. This trend is supported by public pressure and the attitude of 'clas­ sical' forestry. Many people consider the far-northern co­ nifer forests as hardly interesting because their growth is too slow, they are difficult to manage, and the area in which they grow has a rather disagreeable climate. In the tropics, however, with their fast growing trees, con­ ditions are considered much more favourable so that at­ tempts are being made to follow shifting cultivation or to cut rain forests. But because communications are poor and there is a lack of technical personnel willing to work there, especially in the less populated parts in the hearts of these regions, tree raising has not yet been attempted on a large scale. On the other handt plantation forestry in subtropical regions, with annual wood productions of 15 - 30 per hectare, is being steadily extended. It can be expected that these regions, and the tropics, in the not too distant future, will be able to take over part of the wood production for the countries in the temperate zo­ nes of the northern hemisphere. This is a logical develop­ ment and should be a blessing for some less-developed a- reas, especially when wood production is followed by semi- processing in* local factories. However it involves the establishment of wood-working industries for which the assistance and the 'know-how' of the internationally orientated corporations is needed. Al' 267

So here, a change from manual labour to full mechanization "ill be unavoidable, especially when besides logs, wood chips become valuable. Then there will be good prospects f°r a more complete exploitation of forests up to now only used for widely dispersed selective cutting. Today it is technically possible to use wood of both broadleaved spe­ cies and conifers, for the fabrication of pulp and paper, chipboard and fibreboard. It is hoped that during the de­ cade 1970 - 1980, a way of using a mixture of bark and w°od for these purposes will be discovered (447). Unfortu­ nately the economical application of wood mixtures from tropical broadleaved tree species is not yet clear. Such a technical development can also have a great impact °n forestry and tree-raising in more densely populated de- Veloped countries, where trees grow well. Trees predomi­ nantly planted or maintained not for producing wood, never­ theless produce wood; their continued presence requires Periodical removals or clearing of waste. As indicated f°r the forests of tropical countries, the »waste* can be turned into chips, which can either be used to improve the soil condition, or depending on the price and the e- t3uipm0n^ available, for the manufacture of industrial pro­ ducts. Considered from this standpoint, the parks and forest landscapes, frequented and loved so much by so many people, also need some kind of maintenance; they have to be kept clean, open, and agreeable. In view of the future need for Material, it is 'imprudent, at least, if not downright ^travagant' (490), to write off this 'accidental' wood Production amidst nearby consumers. Forestry has to adapt itself to new circumstances. This is Possible, provided the recent words of a Dutch forester are kept in mind: the invention of our technical institu- tions has supported the spectacular growth of our agn- Culture production; why can these institutions not develop 268 equipment suitable for a fully mechanized harvesting of our comparably small forests (or even our roadside trees), so that we do not have to depend on working with a chainsaw, a horse, and a truck? Indeed, with the present wood scarcity at hand, increa­ singly obvious in some regions where prices are rising steeply, it may be hoped that, especially in the temperate zones of western Europe, forestry will start paying more attention to the modernization of its activities. In this way it must be possible to offer the wood processing in­ dustries a solid base;for their future wood supplies, so that they can compete with northern Europe and other re­ gions. Then the community will make better use of its renewable natural resources.

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accessibility 11,16,24,29,77,79 area (forest) 81 ,218,233,235,237,254 delineation 76 aerial photographs 28-29,70,74, dot grids 76-77 164 estimates 74,76 black-and-white 29,78,80 line grids 76 coloured 15,80 associations crown measurements 212,213 plant 69,158,164 false coloured 80 forest 29,153-156 infra-red 79 forest owners 240-242,247 interpretation 74-76,80-81, assessment 5,6-7,17-18,24,26, 205-206, 212 29-30,34-36,46,53,108 maps and costs 83 maps or mosaics 82 balance obliques 70 water 25,90,161 panchromatic 79 wood production 243,253 sampling 204-205 bamboo 216 scale 78 bark 31,216,267 survey 28,74,196,203 removal (machines) 192,214 tree height 188 tanning 60,215,222 trimetrogon 70 weight 182,216 vertical 71 Brandis 44 volume tables 204-205 burning 3-4,20,22,38,40-41,44- air movement, see wind 45,50,58,85,87,122,138 air pollution, see forest damage controlled 20-21,42,58,139- afforestation 17,23,26-27,30,54, 140 60,96,145,164,167-168,212,236, 244,246,254 Cajander 150-152 agriculture calcium 128-130 fire 22 capital 35,221-223,230,238,244, primitive or shifting cultiva­ 246,255-256,265 tion or shag 3-4,22,37 carbon dioxide 3-4,24-25,87,94, 41-43,46,169,266 96,102,125 tree-raising 43-44,259 carrying capacity amenity in forestry 12-14,16, animals 31,47,170-171 168,254 recreationists 31 animals climate 24-25,161 buffaloes 45 changes 51,85-88 elephants 45 classification 84,89-91 goats 47,51-52,69,119 forest influences 24-25,91-92 grazing 22, 44-47,5Î,55,56,117, macro 84,88 119,142,148 micro 85,93-104,161 husbandry 4,37-38,45 collectors 38-40,63,264 pigs 42,46,222 Colliers 49 annual costs 226,237,263 cultivation costs 227, 235-236 apiculture 48 347

debris, see organic matter 56-58,67-68,245-246 decision-making 34,36,146,168, survey 27,66-68,72,176,178, 230,251-268 196 deforestation 3-4,50-52 types and formations 134,153 dendrochronology 86 utilization 37-38 density or specific gravity 176- forestry 181 classical 4,225,266 diameters plantataion 4,266 crowns 212-213 production 35,226-228 DBH 187 protection 5,9-10,15,27,35,38, Dokuchaev 108 51,54,115,169 drainage 144,167-168, 171-172 form Duerr 233,258 factor or taper for trees 184, 188 end harvest 218,233-235,244,256, factor for stands .196 258 Elliot 86 genetics 177,180-181,219 erosion 3,11,14,37,52,54,58-59, growth 33,148,161,208 109,112-113,116-117 annual, tree growth 208-209 water 26,113-116,165 diameter 179,208 wind 26,61,117-119,143 height 209 evaporation 25,85,89,94,110,122 history, see dendrochronology évapotranspiration 25,89,101, rings 33,85-87 104,141-142 stands 209 potential (PE) 89-91 yield measurement 210-212 exotics 17,24-26,58,60-62,84, ground 106,159,164,219 man-made 168 or minor vegetation 150-151 FAO 223,253-254 or terrestrial survey 28-29, Faustaman formula 229,231,233, 66,68,71-73,78 235-236,239 fertilization 17,22,26,42,46,111, Hoogendorp, van 57 126,145-148,157,166,219 Huber formula 184 fire 14,20-21,37,40-41,50,112, humidity 170,258 air 103 lightning 20-21,40-41,122 wood 181 man-made 21,40-41 humus, see organic matter forest conservation preservation 9,17, interest rates 229-233 52,56-57,59-61,169,243 interception of rain, see rain damages (incl. air pollution) inventory 27,29-32,35,151,196 5,14-15,25,31,34,122,131 procedures, see sampling exploitation 16,23-24,29,37-38, continuous or repeated 33,206- 50,58,234 207,251 inventory, see inventory irrigation 27,143,167 laws 6-7,9-10,51-54,57,59-60 litter or debris, see organic labour and working hours 4-5,22, matter 192,218,227,233,245,262-263 man-made 17,35,60-61,254 land-use 8,259 minor products 31,215-216,262 changes 8 qualification, see site future 255 reserves 4,11-12,38,43,48,54, valuation 229 348

water supply 142 weight 121,135 light intensity 88,93-96 orthophotomaps 29,82-83 tree growth 96-97 litter, see organic matter pedology, see soil Loetsch 205 phosphor 124-125 Lowdermilk 49 photogrammetry 71-72,78 photomaps or mosaics, see aerial magnesium 130-131 photographs management 4,7,9-12,15,18-19,27, potassium 126-127 29,33,47,52-58,72,81,83,105,108, precipitation, see rain 137,143,149,207,210,242,248,251, productivity 35,155-156,162,173, 265 211 ,220-222 ,232,249-250 adjustment 16-17 natural 155-156 normal or 'normalcy' 30,34, 149,211 ,233 radar pictures 77,80 site 163-165 radiation-solar 94-96,101 man-forest relationship 19-20 rain 24-25,84-85,88,91-92,108- Mantel 54 109,113,161 maps 27-28,63-66 interception 91-92 forest-types 75,81 recreation 3,6-7,9,11,13,15,31, reproduction 81 35-36,61,254,259-260,264 scale 81 costs 261-262 site-classification, see site future 262-263 vegetation 69,77 reforestation 52-56,157 mapping remote sensing 79-80 contour-lines 77 rentability, rate of return, see forest-borders 64-67 interest rates inside forest borders 28,67- roots 90,103,107,109-112,118, 68,75 12 3,125,148,152,176,182,213 property borders 28,73-74 rotation 4,9,11-12,14,17,19,35, mechanization 4,7,35,192,194- 43-44,58,149,207,222-225, 195,218,225,234,248,265,267 228,256-2.57 micro elements (or other elements) 132-133 sample plot 33,200-202,204,206- multiple use in forestry 3,18 207,210 mycorrhiza 123-124 line transect 203 mythology 48-49 size 33,203 sampling 32,200 natural resources density 203-204 renewable 10,268 list 205-206 conservation 49,156,169,171 point or angle count 197-199 naval stores 59,217 random 32-33,199-201,203 nitrogen 120-124,157 systematic 32-33,202-203 Schermerhorm 72 organic matter or humujs 15,21 — shag, see agricultural primitive 23,25,41,107-108,112,114-115, shelterbelts 104-105,117,119- 127-129,133-136,164 120 mor or raw humus 26,115,134, shipbuilding, see wood 145-146,150,154 site 29-31,90,149 mull or mild humus 115,134 assessment 149,157-158,163-165, removal 26,138 168,170-171 349

class tables 151,158,209-211 stand 32,34,195-197,199 classification 29-30,149-152 , stacked wood 31,185-186,189, 154 194 mapping 29-30,159-160,164 tables 32,189-190,195-197 soil 107-108 chemical properties 26,114, waste or slash 169,191-192,214 120 267 manipulation 137-138 water 109 maps 137,162 balance, see balance physical properties 26,107, content in wood, see humidity 110-112 forest soil 141 survey 136-137,157 streamflow 142,144-145,159 specific gravity, see density weight Spurr 72 scaling 31,176-180,214 sulphur 131-132 tree tables 182 surveys (see also forest) 27,63, wilderness 13-15,265 66,173,175-176,178 wildlife 9,15,47,58,170-171 national 207 wind 101-102 sustained yield 9-11,16,18,33, damage 15,102 54,57,153,221,257 wood world-wide 11,18 chips 170,176,186,191-192,214 248-249,252,267 taungya 44,259 (future) utilization 190-191, taxes 237,239,246,248 251 property 237-238 grown outside the forest 13- succession or death duties 239 14,249-250 temperature 24,84-85,88-89,98- shipbuilding 50-57,60,65 101,108 working industries 4,11-12, terrestrial survey, see ground- 17-18,23,33,243-244,247,252, survey 255,266,268 thinnings 33,47,55,96,189 218,223-224,233-235,244,264 yield 153,160,180,221,233 Thornthwaite 89-90 predictions 149,211,219,258 Thünen, von 234 site class tables 209-212, tillage 145-147,166-167 233,257 tree complete utilization 31,169, 177, 185-186,190-191,213,219 counts 193-195 height 188,190,197 naming 173-176

valuation, see assessment vegetation natural 29,157 semi-natural or reconstructed 29 vernacular names 174-175 volumes logs 32,183-185,189 measurements wood 183-186,214 measurements tree 186