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Establishing Fuelwood and Fire Crop Performance on the Highlands of : The case of globulus Labill.ssp. globulus

Amanuel Mehari

Institutionen for skogsskotsel Swedish University of Agricultural Sciences Rapporter 41 Department of Umea 1996 Reports, No. 41 Institutionen for skogsskotsel Department of Silviculture

Forteckning overutgivnaRAPPORTERfranochmed 1982: List of REPORTS from 1982 onwards:

1982 in June 1984). 7. Olsson, H.: Skogsodlingsresultat i ovre Norr- land. Beskri vning och analys av 24 skogsodlings- 15. Martinsson, O.: Markberedningens inlytande objekt. (Results of artificial regeneration in pa overlevnad, tillvaxt och rot-skottrelation i northern Sweden. Description and analysis of 24 foryngringar av tall, gran och contorta. (The regeneration areas). influence of site preparation on survival, growth and root/shoots ratio in young stands of Scots 1983 pine, Norway spruce and lodgepole pine). 8; Naslund, B-A.: T allsadders utveckling fram till forsta gallring. Resultat fran tre forsoksy termed 16. Ekd, P-M.: En produktionsmodell for skog i och utan enkelstallning. (Development of Scots Sverige, baserad pa bestand fran riksskogstax- pine seededplantations tofirst thinning. Results eringens provytor. (A growth simulator for Swe­ from three experimental plots with and without dish , based on data from the National release-cutting). Survey).

9. Bjorkroth, G.: Inverkan av hyggesavfall pa 17. Pehap, A. & Sahlen, K.: A literature review of kvavet och den organiska substansen i nagra 14- seed respiration. 18 ar gamla forsoksplanteringar med gran. (The influence from slash on nitrogen and organic 1986 matter in some 14- 18years old experiments with 18. Naslund, B.-A.: Simulering av skador och av- Norway spruce). gang i ungskog och deras betydelse for be- standsutvecklingen. (Simulation of damage and 10. Martinsson, O., Karlman, M. & Lundh, J-E.: mortality inyoung stands and associated stand Avgangar och skador i odlingsforsok av tall och development effects). contortatall 4-9 ar efter plantering. (Mortality and damage msemipnqctimlirml\ ofSflots p)he 19. Albrektson, A.,F rivold, H., Holstener-Jorgen­ and Lodgep ole pipe years after plmtiflions). f ' sen, H., & Malkonen, E.: Published and Unpublished Studies in the Nordic 11. Pehap, A.: A review of literature in the subject Countries. An annotated bibliography up to of some physiologically active substances in the 1982. seeds and pollen of forest, fruit and agricultural species. (En litteraturoversikt om nagrafysiolo- 20. Simak, M.: Chromosome aberrations in stored giska aktiva substanser i pollen och fron fran seeds of Pinus silvestris and Picea abies and the upptagnaarter). ; consequences on plant properties. 1987 12. Simak, M. & Sahlen, K.: Bibliography on x- 21. Pehap, A., Henriksson, G. & Sahlen, K.: radiography in seed research and testing. Respiration ofindividual, germiatingspruce seeds: Some investigations and measurements with the 1985 Warburg Direct Method. 13. Bergsten, U.: A study on the influence of seed predators at direct seeding of Finns sylvestris L. 22. Mellberg, I. & Naslund, B-A.: Barrotsplantors tillvaxt och overlevnad fram till ro jningstidpunkt. 14. Hagglund, B. & Peterson, G. (Editors).: - Resultat fran en forsoksserie med skildaplants- Broadleaves in Boreal Silviculture - an obstacle or orter. (Growth and survival for bare-root an asset? (The report contains seventeen papers seedlings until the time of cleaning. - Resultsfrom presented at the Kempe-symposium at the Swe­ experimental series with different types of dish University of Agricultural Sciences, Umea, seedlings). SiO'SSK~n_~ F4- 4/

Establishing Fuelwood plantation and Fire wood Tree Crop Performance on the Highlands of Ethiopia: The case of Eucalyptus globulus Labill.ssp. globulus

Amanuel Mehari

OF TW DOCUMENT » WNLMTED

Institutionen for skogsskotsel Swedish University of Agricultural Sciences Rapporter 41 Department of Silviculture Umea 1996 Reports, No. 41 ISSN 0348-896/ f ISRN SLU-SSKTL-R—41 -SE

Printed by SLU, Grafiska Enheten, Ume&, Sweden 1997 DISCLAIMER

Portions of this document may be illegible in electronic image products. Images are produced from the best available original document Preface

This study is divided into ten sections. The introductory part deals with the physiogeography, geology, and the application and limits of the soil and classification on the current programme of Ethiopia. Fuelwood is the chief energy source for Ethiopian households. Its present and future status is reviewed in the first section of this work. The socioeconomy and other sources of energy, and some data on and land degradation of the country are also included here. The fuelwood shortage in Ethiopia is beyond the energy problem. It has adversely affected the life of low income groups of the rural and urban areas, and the community development in the country. In order to alleviate the scarcity, its supply must be increased from man-made forests. Economic and ecological reasons for the establishment of fuelwood in Ethiopia are given in section two and three of this study. The two approaches of establishing a plantation and factors, which affect the selection of a tree species for a given site and purpose, are reviewed in section four. Eucalyptus globulus is popular among farmers on the highlands. The reasons for its cultivation are given in section five. Section six deals with the botanical attributes of E.globulus and its distribution in Ethiopia. However, the cultivation and distribu ­ tion of E.globulus is dependent on its silvicultural and ecological requirement, which are summarised in section seven. Depending on site quality, E.globulus performs differently on the highlands of Ethiopia. Section eight reviews the growthof E.globulus on four different site clas­ ses. Though E.globulus is fast growing and cultivated widely on the highlands, there are allegations that it harms the growing site. Section nine reviews the cultivation of E.globulus and its impact on the environment. Finally, a summary and a conclusion on the role of E.globulus in the country ’s future forestation programme are given in section ten.

Amanuel Mehari Uppsala, 1996. Abbreviations

CFSSCDD Community and Soil Conservation Development Department CSA Central Statistcs Authority EGA Economic Commission for EFAP Ethiopian Forestry Action Program EMA Ethiopian Mapping Authority FAQ Food and Agricultural Organization IFAD International Fund for Agricultural Development. MOA Minstry of Agriculture ONCCP Office of the National Commitee for Central Planning Twh Tera watt TJ Tera Joule UNSO United Nations Sudano-Sahelian Office Contents

Introduction, 6 Country Context, 6 Physiogeography, 6 Geology, 6 Soils, 9 Climate, 10 General pressure patterns and wind flow, 10 Climate classification, 11 Socioeconomy of Ethiopia and Energy Resources in the country, 15 Present and future status of fuelwood, 17 Some Data on Deforestation and Land degradation, 19,

Social and Economic Reasons for Fire Wood Use and Establishing Fuelwood Plantations, 21 Fire wood and rural and urban living condition in Ethiopia, 21 Why fire wood andfuelwood plantations? 22

Ecological and Economic Reasons for Establishing Fuelwood Plantations, 24

Establishment of forest plantations, 28 Two approaches of plantations establishment and choice of species, 28 The in Ethiopia, 28 The commercial plantation, 29 Choice of Species, 29

The rational to grow Eucalyptus globulus, 32

The Eucalyptus globulus Labill. subsp. globulus and its distribution in Ethiopia, 33

Silvicultural and Ecological Requirements of Eucalyptus globulus, 41 Silvicultural Requirement of Eucalyptus globulus, 41 Sowing and Transplanting, 41 Nursery soils, 41 Nursery soil analysis, 50 Ecological requirements of Eucalyptus globulus Labill., 52

Growth and yield of Eucalyptus globulus LabilLsubsp. globulus (Blue Gum), 53

Eucalyptus globulus and Environmental Concern, 56 Water and nutrient use, 56 Eucalyptus and soil erosion, 57

Summary and conclusion, 59

References, 60

Annex Introduction

Country Context

Physiogeography Relief influences climatic parameters, and pedogenic processes and it indirectly affects tree cultivation, plant growth and distribution. Therefore, an understanding of the present morphological features of the country would be important for the current forestation in Ethiopia. The morphological features of Ethiopia are of tectonic origin (Merla et al., 1979) and out come of two tectonic phenomenon in the past (Mohr 1962). One is the uplifting of the Abyssinian plateau in the north and the Somalian plateau in the south. The second is the subsequent formation of the System because the eastern lithospheric plate of Africa has spreaded apart (Mohr, 1962). The Abyssinian platueau is bounded by Rift System on the east and by the plain on the west. On the south the plateau declines gently to the low plains of northern Kenya. Regions on the Abyssynian plateau are drained to the west because the interior and the eastern parts of the plateaux are elevated higher than its western margins. Major rivers in the plateaux are the Abay, Baro and Tekeze. The Somalian platueau is bounded on the west by the Rift System and declines gently towards Southeast without clearly defined boundary. Close to the Rift Valley the plateau is uplifted higher and descends gradually down in Southeast direction through Somalia towards the Indian . Regions of the Somalian plateau are drained to Southeast because the elevation decreases gradually in Southeast direction. Important river basins in this area are the Genale and the Wabi Shebele. The Rift-Valley System, which is a downdropped fault block, separates the Abyssynian plateau almost to the west and the Somalian platueau to the east. It stretches from the Afar region on the north to the Borona region in the south. The tensional crustal forces, which pulled the lithospheric plate of Africa apart to east and west direction, are responsible for slipping down of the keystone between two neighbouring plateaux and for the formation of the Rift System (Press and Siever, 1977). The interior and eastern highlands, regions laying >1500 m.a.s.l., of the Abyssinian plateau, and the central high elevated regions of the Somalian plateau are cooler and receive relatively higher rainfall than the hot and dry lowlands of the Rift Valley. Due to favourable climate, many of the settlements are concentrated on the high­ lands and farmers are growing Eucalyptus globulus widely.

Geology Many and agriculturist in Ethiopia are interested in soils of the country, but not much in the parent material and its geology. Given the fact that the parent material is an important soil formation factor that determines the physical and chemical property of a given soil, an understanding of its geological formation would be necessary. Thus, an effort is made here to summarise the formation of the geological structure of Ethiopia.

6 The geological structure of Ethiopia is a result of various geological events at different time. In the Precambrian age, the basement rocks of the country, which are mainly composed of metamorphic rocks such as schists, quartzites, marble, mica- schists, amphibolites, para-genesis and granites of different ages, went under the process of deformation and metamorphism. This was followed by the deposition of Mesozoic marine strata and Tertiary traps over it. At present, the Ethiopian basement can clearly be seen on the periphery of the country and regions without Mesozoic sediments and the tertiary lava cover. During the Palaeozoic time, the land mass, which was uplifted in the Precambrain time, was subjected to denudation and near-peneplanation of the Precambrian moun ­ tain ranges where the deposition of the sediments are visible today in northern re­ gion of the country (Mohr, 1962; Merla et ah, 1979; EMA, 1988). In the early Mesozoic, because of a gentle epeirogenic movement regions of Ogaden, Tigray, and western Ethiopia sunk below level. Transgression of the sea took place over the Precambrian Basement Complex. This marine transgression caused the deposition of marine mud and sandstones over the Ogaden and Tigray regions. At the end of this era, the transgression was followed by regression of the sea due to epeirogenic uplift. The regression caused deposition of clay, silt, sand, and conglomerates in the western part of the country and ended with the precipitation of gypsum and anhydrides on Ogaden region (Merla et ah, 1979). Geologists distinguish three different types of rock formation in Mesozoic time. These are, namely, the Addigrat Sandstone, the Antalo Limestone and the Upper Sandstone. The Addigrat Sandstone is the oldest Mesozoic rock. It lies directly over the basement with varying thickness. It goes up to 500 meters in depth (Furon, 1963). The Addigrat Sandstone is mainly composed of grains from 0.5 to 4 millimetres in diameter and is mineralogical dominated by Quartz usually cemented by Silica or Kaoloinite or hematite (Mohr, 1962). Hematite is responsible for yellow, brown, red or violet colour seen in many sedimentary rocks and soils that are containing it (Mohr, 1962; Morton, 1978). The Addigrat Sandstone is overlain by the marine Antalo Limestone. The thickness of the Antalo Limestone ranges from zero to 1000 metres (Merla et ah ,1979). Its formation consists of many lithological types of limestone and contains marl, and silt, and occasionally arenaceous bands particularly, close to the top. The Upper Sandstones lies over the Antalo Limestone. Its thickness varies from 100 to 500 meters (Mohr, 1962). The Upper Sandstones is lithologically similar to the Addigrat Sandstone. Its composition is predominated by angular quartz grains cemented with Kaolin or Iron-Oxide (Mohr, 1962; Morton, 1978). In the early Tertiary, the region of Horn Africa was uplifted and this was accompanied by the fracture of the basement and Mesozoic rocks (Merla et ah, 1979). Through the fractures the lava flowed over the Mesozoic rocks and resulted in forming the plateau traps and especially, in north and central Ethiopia (Mohr, 1962; Furon, 1963; Merla etal., 1979). The extrusion of the Trap series, in most of the country, had ended in late Tertiary (Mohr, 1962; Merla et ah, 1979). The Trapic Series contains less calc-alkaline and is olivine deficient (Mohr, 1962). The younger deposits in Ethiopia were formed during the Quaternary period (EMA, 1988). The cause for the formation of the sediments were the cool and wet pluvial climate with heavy rainfall combined with the relief and continued tectonic uplift of the region (Mohr, 1962; Merla et al., 1979). Mohr (1962) distinguished two type of Quaternary deposits. These are the pluvial and interpluvial. The pluvial deposits include the glacial and glaciofluvial sediments on the highest mountains; the lacustrine deposits in the Rift System and basin and the fluviatile deposits and pebble beds on the plateaux. The sediments from aeolian sands and rubbles, loess, calcrete and ferrocrete weathering surfaces are grouped under interpluvial. During the pluvial period the highest mountains of the country were under ice. As the glacier moved over the bed rock floor, large quantities of material were eroded and shifted to the lower levels of these mountainous regions. After the ice melted, a morainic deposits (which are an accumulation of rocks, sand, and clay) were left in ravines, on lower slopes and the foot of the mountains. The low air temperature and high precipitation during the pluvial time associated with low evaporation rate caused the formation of deep and large lakes in the Rift System and other troughs of the country. As the lakes dried-up or diminished in size, the lake-beds remained covered by lacustrine deposits. Fluid agents during the pluvial time were the main causes for the formation of fluvial landforms in Ethiopia. These are : the erosional and depositional landforms. These fluvial landforms are shaped by geologic activities of erosion, transportation, and deposition. The removal of rocks by fluvial agents results in the formation of valleys and the crustal blocks such as the ridges, hills, and summits between them. Landform sequences that are developed gradually due to removal of the bed ­ rock mass are collectively known as erosional landforms. The ravine, canyon, peaks, spur and col on the highlands or mountainous region of the country are erosional landforms. Landforms that are formed from eroded fragments, regolith, and bedrocks due to sedimentation process are called depositional landforms. The fan, built of coarse sediments below the mouth of the ravine is a depositional landform. The floodplain in the Rift Valley and the alluvial depositions in valleys of the highlands and lowlands built of alluvium transported by rivers and streams, are also depositional landforms. On the highlands of the county, Quaternary deposits are common. These are formed during the arid interpluvial period from torrent and slope-wash gravel through calcification processes and ferruginisation where the gravels are cemented by carbonate or limonite and then converted to calcretes or ferrocretes. During the Quaternary there was active volcanism in Ethiopia. Most of these volcanoes occur in the Rift Valley. The rocks of these volcanic material are known as Aden Volcanic Series that are confined in their occurrence to the Rift Valley itself. According to Mohr (1962), the formation of the Aden Series started earlier than the formation of the Rift Valley, in the Tertiary and extended to the Quaternary. The rocks of these Series are mainly alkaline olive (Mohr, 1962). Recent volcanic structures in Ethiopia are restricted to the Rift System. The cones are rarely over 1000 meters high and much smaller than the older volcanoes of the Trap Series (Mohr, 1962). Secondary volcanic activity in the form of fumaroles and hot spring are abundant on the floor of the Ethiopian Rift System and are most commonly associated with recent volcanic phenomena. On the high plateaux hot springs may emerge through the Trap series, usually at the bottom of valleys, sometimes through the basement complex rocks.

8 Table 1. Summary on major geological events and geological structure formation in Ethiopia

Era Age Period Major Geological event (million years)

Cenozoic 65 Quaternary Formation of recent deposits, volcanic activities in the Rift System, formation of Aden Volcanic Series etc.

Tertiary Regional uplift accompanied by Mesozoic rock and basement fracture, Trappic flow, formation of Ethiopian plataeux, faulting and formation of Rift System etc.

Mesozoic 225 Subsidence and Marine transgression over the peneplain,Marine retreat and formation of the three Mesozoic rocks.

Paleozoic 570 Denudation and near-panplantion of the Pre-cambrian mountain ranges.

Age (billion years) Precambrian 4.6-4.7 Formation of the Ethiopian basement rocks.

Soils Depending on the type of parent material, relief and climate, various kinds of soils occur on the highland of Ethiopia. Based on their origin, three types of soils are recognized : the red to reddish-brown clayey loam and the black soils from volcanic material (Huffnagel, 1971; Ahmad, 1986) and the sandy loams to loamy sands from limestone and sand stone (Ahmad, 1986). The soils of the Ethiopian highlands have been remarkably little studied regarding their influence on human settlement and agriculture. Much of the study on soils of the country is reconnaissance to semi-detailed in nature (Ahmad, 1986) which has little practical importance in agriculture and forestry. Murphy (1959, 1963), for example, in his report about the fertility status of some soils of Ethiopia, distinguis ­ hed the soils by their color and chemical properties. No soil classification has been included in his work. Lundgren (1971) also attempted to include the classification in his study on soils of montan forest of Ethiopia. His work was not complete, because it did not include information on clay mineral type, textural composition, Si02/Sesquioxide-quotient, soil structure and color.

9 Entisols are weakly developed soils

Alfisoils are soils of high base content

Vertisols

Figure 1. Lateral variability of soils along a hillslope in central highlands of Ethiopia (adapted based on information from Ahmad, 1986).

A study on the distribution of some soils of the central highland of Ethiopia, in the middle part of the Abyssinian plateaux, was carried out by Ahmad (1986) using the U.S. Soil Classification System. He studied the lateral sequence of soils related to relief change. The toposequence of the four common soil orders of the Ethiopian highland, where Eucalyptus globulus is widely cultivated, is given in Figure 1. Entisols are soils with a profile which is less than 15 cm of depth and occur on severely eroded steeper to less steeper slopes of the central highland, while the Alfisols develop on stable slopes with less or no human interference and no geologic erosion (Ahmad, 1986). The Mollisols are soils that are often found at the foot of a hillslope. The Vertisoils are common in valleys or on flat terrain where the slope does not exceed 5-8 % (Berhanu, 1983). These soils cover about 8 million ha of the Ethiopian highlands, which accounts for about 70% of all highland soils with slope 0 and 8 percent (Jutzi, 1988) and about 10% of the country ’s soils (EMA, 1988). Detailed soil properties are given by Birkland, P. W. (1984) “Soils and Geomorphology” and U.S. Department of Agriculture Soil Conservation Service (1984?) “Soil Taxonomy ”.

Climate General pressure patterns and wind flow The climate of Ethiopia is regulated by the development of low and high pressure systems over southern Asia and the north-south migration of the Intertropical Convergence Zone (ITCZ) (Griffiths, 1972; Mesfin, 1972;.EMA, 1988). When a cyclone over develops in June-September (longer growing pe­ riod), strong and persistence southwesterlies from regions of high pressure move

10 towards Asian low passing over Ethiopia. At the same time, the ITCZ reaches about latitude 20° N, thus the resulting convergence brings much rain to the country. The rainfall during this season is due to the relatively warm and moist equatorial westerlies from Gulf of and the southerly winds from . According Liljequist (1986), the rainfall in Ethiopia are three type: convective, frontal and orographic. The first is the common rainfall type in the country. The cloud of this rainfall type, the Cumulonimbus, is formed when the warm air over the heated surface rises and cools adiabatically. For the ascent of the air, the convective movement is responsible which results from the temperature and pressure differences between adjacent air masses. As the air rises, its temperature drops below the dew point and condensation starts. If the lifted air mass has a low temperature, condensation results in the formation of Cumulus instead of the Cumulonimbus clouds near the ’s surface. Therefore, the air mass must be warmer and be lifted higher and condensed at higher level to reach the dew point, in order to promote the formation of Cumulonimbus clouds whose rainfall showers are usually attended by thunderstorms. The second rainfall type occurs when warm air moves upslope against an oppo­ sing mass of colder air with sky becoming overcast with layer-like clouds. These clouds release slow and continuous rainfall. The frontal rain can also result from a rapidly moving stream of cold air against warm air mass. The latter is forced up quickly and dark towering clouds are formed which are followed by heavy rain of short duration, accompanied by thunderstorms. When the ITCZ shifts to south from October to January, and the are dominated by high pressure, and a low pressure develops in the . Unless there is no interruption by the effect of low-pressure centers from the Mediterranean (Griffiths, 1972), most of the country at this time comes under the influence of the northeasterlies. These winds are no moisture laden because they are cold and dry continental currents that have originated from West Asian and north African high pressure centers. In March-May (shorter growing period), low pressure cells over the Sudan lowlands and Ethiopia controls the air flow in the Horn Africa. The easterly winds from and the southeasterly winds from Indian Ocean high flow towards the Sudan and Ethiopian low In this season, as the ITCZ moves northward, it crosses south of Ethiopia. As a result, the easterlies and southeasterlies converge and brings much rain to the east central part of Ethiopia and little to the east central part of the northwestern highlands.

Climate classification Ethiopia stretches approximately from latitude 3° to 14° 52'N and longitude from 33° to 48°E. The country with an area of more than 1 million km2 shows a considerable variation in altitude. The altitude varies from about 100 m below sea level in Danakil Depression to more than 4000 m above sea level in the interior Abyssinian plateau. This altitudinal variation controls climatic elements, e.g. temperature. As the altitude increases, the air temperature falls, with an average lapse rate of about 0.7°C per 100m of vertical rise (Griffiths, 1972). In the wet

11 seasons, a rising air mass drops its temperature by about 0.6°C per every 100 m rise (Fiedler and Gebeyehu 1988). As temperature is a function of altitude, the climate of Ethiopia is classified into 5 different thermal climate zones, namely, the ‘Bereha’(Ffof), ‘Ko\affVarm temperate), ‘Weina Dega ’(Temperate), ‘Dega\Cool temperate) and ‘Kur’(CooZ). (Fig. 2).

Kur(Cool)

10 and less 3500 Dega (Cool temperate) 15 2500 Weina Dega (Temperate) 20 1500 Kola (Warm temperate) 25 and above 500 Berha(Hot) '

Temperature (Centigrade) Thermal Zone Altitude (m.a.s.l.)

Figure 2. Thermal climatic zones of Ethiopia based on the local classifications (Data taken from EMA, 1988).

However, the climate of a given locality or a given region is determined, not by just one climatic parameter, but by combination of various meteorological variables that make up the climate. Two places within one thermal zone may have very sim­ ilar temperatures and elevation, but different amount of rainfall. Thus, their climatic difference could be clear only if other climatic parameters are considered besides temperature. This situation is tried to show in Figure 3. Addigrat (14° 16' N and 39°27' E) at an altitude of 2457 m.a.s.l. and Asela (7°52' N and 39°08' E) at an altitude of 2450 m.a.s.l. are classified in the Weina Dega thermal zone, but the climate of the two towns is not similar(Fig. 3). The difference does not lie on the monthly rainfall distribution pattern, but on the amount of monthly rainfall and accumulated annual precipitation which determines the vegetation and land use type in both areas. The annual precipitation at Addigrat amounts about 550 mm, while rainfall at Asela is about 1300 mm. This shows clearly the possible significant climatic variation that may occur among different places within one thermal climate zone and the risk inherent in using the thermal climate classification in forestry. It is, therefore, very important to take into account the climatic differences and classify the climate in correlation to the needs of the human development, agricultural and forestry activities. This would be possible either by including other meteorological variables (e.g. rainfall) to the thermal classification system or using other classification systems which are developed based more than climatic variables.

12 T 250

.. 200 ADIGRAT PRECIPITATION

ASELA PRECIPITATION - 150 ADIGRAT TEMP. DAY

ASELA TEMP. DAY - 100 ADIGRAT TEMP. MIN

ASELA TEMP. MIN

Months of the year

Figure 3. Climatograph ofAddigrat andAsela in Ethiopia (datafrom FAO., Plant Production and Protection Series No. 22, 1984).

The second type of climate classification in Ethiopia is the Koppen system (EMA, 1988). Under this system, are defined based on major vegetation types and the annual or monthly average values of temperature and precipitation to designate their boundaries (Koppen, 1923). According to EMA (1988), based on this classification system, the country ’s climate is divided into eight principal zones and hese are presented below. In Koppen ’s system (Table 2.), the principal climate zone is derived from combinations of two or three alphabets. The first letter represents the climatic group and is designated by capital letter. Only three out of five major climatic groups on earth are represented in Ethiopia. These are A (Tropical rainy climate), B (Dry climate), and C (Mild, humid (mesothermal) climates).The A and C are defined thermal (by mean temperature), while the B is defined hygric (by rainfall/evapora ­ tion).

13 Table 2. Principal climate zones of Ethiopia and vegetation

Principal Climate Zones Vegetation Bwh Hot semi-arid climate with annual rainfall less than 450 mm. The climate is characterized Identifiable in altitudinal range between 250 & 1200 m.a.s.l.; by barren to sparse type of in Southeast Lowland & lower Rift Valley vegetation BSh Hot arid climate. Average annual rainfall varies between 410 The climate supports a steppe & 800 mm. It takes an intermediate position between the dessert type of vegetation. climate (BW) & the A major climate groups. It is represented in the Rift Valley, North western, Southern & South Eastern Low Plateau Bsk Cool semi-arid climate. The mean annual rainfall varies from 400 Regions of this climate are to 620mm. It is represented in North Eastern highlands of Tigray covered mainly by steppe where the elevation varies between 1800 & 3200 m.a.s.1 type of vegetation. Aw Winter-dry tropical rain climate. Mean annual rainfall is in a range Savanna woodland. of 680 to 2000 mm. Identifiable in western slopes and plateau, Rift Valley escarpment,eastern plateau. The climate prevails up to 1720 m.a.s.l. Am Tropical rainforest climate. The average annual rainfall varies Evergreen rainforests. between 1200 & 2800 mm . Identifiable in south western table land and Lake Tana Basin( 1500-2800 m.a.s.l). Cwb Winter dry, warm temperate climate. Mean annual precipitation Tropical montan forests. varies between 800 and 1200 mm. It is largely represented on the regions of the Abyssinian & Somalian plateaux (1750-3200 m.a.s.1.) Cfb Humid warm temperate climate. Wetter than Cwb. Identifiable in Tropical montan forests south & south western highlands of the Oromo region to evergreen forests (1750-3200 m.a.s.1.). Cwc Winter-dry cool highland climate. Mean annual rainfall 800 to Afro alpine vegetation 2000 mm. Recognizable on regions beyond 3200 m.a.s.l. (The Amhara & the Oromo highlands).

The second letter in a principal climate zone stands for climate subgroups. The subgroups are represented by capital and small letters. All the six universal subgroups that are represented in the Ethiopian climate, as shown below.

Symbol Definition S Semiarid (steppe) W Dry Winter. w Arid (desert) S Dry Summer. f Moist (enough precipitation in all seasons of the year). m Rainforest climate, short dry season in type of rainfall cycle.

14 The climate subgroups S, W, and m have very restricted application. The S and W apply only to dry B climatic group,while m applies only to A macroclimate (climate group). Both S and W measure the degree of dryness. Further, the climate of the country is divided into five different climate types. Each climate type is derived from the combination of two letters. The first letter represents the climatic group, while the second letter stands for subgroup climate. The main climate types of the country are given below.

Symbol Definition

BW Arid (Desert) climate. BS Semi-arid (Steppe) climate. Cw Tropical savanna climate. Cf Mild humid climate with a dry winter. Aw Mild humid climate with no dry season.

A third small letter is introduced in the system to show further variation between each climate type and then derive a principal climate type. The introduced small letter represents an average temperature of a season or some months in a year and these are:

Symbole Definition a Hot summer where the warmest month > 22°C; restricted to C climate. b Hot summer where the warmest month < 22°C; restricted to C climate. c Cool, short summer where the average temperature is > 10°C for < four months, restricted to C climate. h Dry hot where the annual mean temperature > 18°C; restricted to B climate. k Dry cold where the annual mean temperature < 18°C; restricted to B climate.

Finally, from a combination of two or three letters, different principal climate zones are derived. However, derivation of the principal climat zones without reliable meteorological data may lead to a wrong designation of the climate which might be true to the case of Ethiopia. Therefore, more information on climate elements is required to revise the climate classification in the country and improve their application in forestry.

Socioeconomy of Ethiopia and Energy Resources in the country Ethiopia, with an area over 1 million square kilometers and a population over 50 million, is the third populous country in Africa. Its population grows at the rate of 3% per annum. The population density of the country is estimated over at 50 people per km2. About 90% of the population lives in rural areas and agriculture is a domi ­ nant economy sector in the country (Briine, 1994). Agriculture constitutes 40% of the Gross Domesti Product (GDP) and gives employment opportunity to about 85% of the Ethiopian labour forces. Almost all the foreign exchange earnings of the country come from the export of agricultural products. Besides, it is an important

15 source of raw materials for the factories or industries in the country. Ethiopia is materially poor and technically backward, and thus belongs to the least developed countries of the world. Nearly 60% the Ethiopian population lives below the absolute poverty line and the country ’s agricultural development depends much on foreign technology (Briine, 1994). The agriculture in the country is subsistence. The large majority of families cultivate extremely small plots with an average size about 1-2 ha and the greater portion of the agricultural products are consumed by producers themselves (Dessalegn, 1984). Ethiopia has vast natural resources. The country ’s about 650 TWh per year of hydro-electric production potential, over 30 billion m3 of natural gas, more than 1000 MW of geothermal, and several hundred million tons of coal and Oil shale are energy potential that have been recently discovered in the country (Hailu, 1992). In spite of the huge energy resources that the country is endowed with, biomass fuels in form of firewood, dung and crop residues are the predominant sources of . They accounts for about 94% of the total 661445 TJ of energy used in 1988/89, but the contribution of petroleum and electricity to the supplied energy was less than 6% for the same year (Fig. 4a). Among the biomass fuels, fuelwood is an important source of energy in Ethiopia. It accounts for 70% of the total energy requirments of all sectors in the country (Fig.4a). However, it is scarce particularly, on highlands where the largest country ’s population live (MOA, 1992). For example, the total fuelwood consumption for 1992 was estimated up to 64 million m3 and only about 37% of the estimated value was supplied for the period (MOA, 1992).

0.60% ^ 9.60% ■ Electricity Z X ^ 5.1% □ Household 69.80% / ■ Animal energy 82% J 48% ■ Transport I 15% ■ Other biomass V X^# 4.4% ■ Agriculture ■ Petroleum ---- " X 3.7% ■ Industry □ Woodfuel ■ Service and Others

Figure 4. (a) Energy sources in Ethiopia 1988/89 (b) Energy consumption by different sectors in 1988/89 in Ethiopia (Data from MOA, 1992).

The country ’s natural forests and woodlands are the main sources of fire wood. For instance, about 40% of the total fire wood supply in 1992 was derived from their incremental yield (MOA, 1992), whereas the contribution of the country ’s 345817 ha of plantation to the total fuelwood supply was only about 10-12% for the same year (MOA, 1992). The rest of the demand deficit should have been bridged with wood from agricultural residues and other substitutes. According to some sources, Ethiopian households use annually about 8 million tones of dung and 5 million tones of crop residues. This is equal to 12.6 and 8.9 million m3 wood equivalent. The major consumers of energy in Ethiopia are the households and their consumption constitutes 82% of the total net energy of the country. The transport,

16 agriculture, industry and services consume 5.1% 4.8% 4.4% 3.7% of the net energy consumption respectively (Fig. 4b). Biomass fuels (fire wood, dung and crop residues) are the major energy type utilized by households, while commercial fuels like electricity and petroleum oils are mainly used by industry and transport. In Ethiopia, households spend a significant amount of money for energy. According to the Central Statistics Authority (1988), energy expenditure reaches in average up to 17% of the total household spending and about 86% of it is paid for fire wood.

Present and future status of fuelwood Fuelwood is scarce in Ethiopia especially, on highlands where the climate is cool, but adequate in warmer low lands of the country (MOA, 1992). According to the estimations made by Economic Commission for Africa (1993), the fuelwood dem ­ and for Ethiopian highland ranges from 1.2 to 1.8 m3 per person per year. Nevertheless, the available annual per capita supply still remains lower between 0.3 - 0.74 m3 per person per year (ECA, 1993).

Table 3. Projectedfuelwood demand (requirement) and supply 1980-2010

Population Per capita fire wood Fuelwood demand Projected supply Year in'000 consumption (m3) in ‘000 (m3) in ‘000 (m3) 1980 37684.70 “ 1.23" 46352.18 44402b 1990 49188.94 “ 1.23b 60502.39 43937 ” 2000 65339.63“ 1.23b 80367.74 43344" 2010 86969.00 “ 1.23" 106963.00 29480" Sources:

“Office of the Committee For central Planning : Conference on population issues in Ethiopia's natio­ nal Development: Report of conference proceedings, vol. 2 p.59 , 1989. bZerai Araya (1992): Farm Forestry Action plan, EFAP, MOA, Addis Ababa (Consultant report).

The demand for fuelwood is mainly regulated by the prices of its substitutes, its availability and retail price. Consumers reduce their consumption and shift to other cheaper alternatives, as fuelwood becomes scarce and expensive (Asmerom, 1991), which has influence on the per capita demand for firewood. It is, therefore, important to take into account the consumers reaction to market prices of any energy commodity, before estimations are made on fuelwood consumption of a given locality. However, because no rent is charged for fuelwood, the largest population (> 85%) in Ethiopia collects fire wood for free. Hence, price has little or no effect on the aggregate consumption of this energy commodity in the country. Therefore, the country ’s present and future fuelwood status given in Table 3 is projected based on the population growth rate (see Annex 1) and average per capita fuelwood consumption with the assumption that the agricultural residues are fully substituted with fire wood. According to Zerai (1992), the average per capita fuelwood need for Ethiopia was estimated at 1.23 m3 per annum. This is a value in the range of ECA’s estimation and used to project the country ’s future fuelwood consumption in this study (Table 3).

17 0 4------H------1------i------0 1980 1990 2000 2010 Year

Figure 5. Population growth, and Fuelwood demand (consumption need) and supply in Ethiopia between 1980-2010. (Note: Plantations are included in the statistics).

By the year 2000 (Table 3), the demand for fire wood will be about two times the available supply, i.e. the amount of fire wood from the existing forest stock including plantations. A decade after, the population grows by about 33%, and the gap between the demand and supply will be widened by more than 200%. For the widening of the gap two things are responsible. One is the continuous depletion of forests in the country that has reduced the stock by volume and the second is the decline of mean annual increment (MAI) proportional to the volume of the stock.

18 , 16 : □ demand 14 3 ■ supply 12 3 io i 8 1 «! I I 1 l l ::i] 1 0

O c” =3 " O to j» fed

Regions

Figure 6. Projected fuelwood demand (consumption need) and supply by regions in year 2000 (Data source: Zerai, 1992).

18 The present status and future trend of fuelwood need and supply is depicted in Fig. 5. The rapid drop of the supply curve from year 2000 to 2010 indicates an extreme depletion of the country ’s forests, woodlands and plantations in the coming fifteen years. As a result, use of animal dung and agriculture residues as source of household energy will be increasing. In year 2000, large population of the country will face the fuelwood shortage (Fig. 6) but in south and south western Ethiopia (Bale, Illibabor and Kefa), where the population density is low and the country ’s natural forests are not yet depleted, will have surplus. In some areas, the demand will be eight times more than the supply. In the future, the northern region (Gonder, Wello and Tigray), the central region (Gojam, Shewa and Wellega),and the eastern region (Harerge) will be seriou­ sly affected by the fuelwood shortage as compared to the Southern region (Arsi, Gamu Gofa and Sidamo).

Some Data onDeforestation and Land degradation The highland of Ethiopia covers about 46% of the country ’s total area and it is home for 88% of the country ’s total population (Hurni, 1988; Taddesse, 1989). Early human settlement, grass domestication and cultivation of principal crops such as teff, ensete etc. started on the highlands around 2500 BC (Palo & Salim, 1987 p. 33). Suitable climate and environmental conditions were factors that have encouraged earlier agriculture development and human settlement in the region (Hurni, 1988). At present, over 90% of the country ’s economy activity is also concentrated on the highlands. They support ninety five percent of the country ’s regularly cropped land, 2/3 of the livestock and the largest proportion of the country ’s population (Hurni, 1988; Taddesse, 1989). Agriculture on highlands is a mixed type. It includes both livestock and crop production. Because of favorable climate, farmers cultivate different types of crops. Some crops are produced for home consumption and others are for cash income. The Ethiopian highlands do not only have a climate which favors agricultural life, but it is also nearly free from environmental diseases like malaria etc. (Mesfin, 1992). The absence of environmental diseases has contributed to a relatively decline of the mortality rate in the region compared to regions where environmental diseases are epidemic and occur often. Between 1970 and 1988, the population of the highlands grew by 65% (Taddesse, 1989). The fast demographic growth in this pre-industrial society resulted in a growing imbalance between population and natural resource base. The rapid popu­ lation growth accelerates the clearing of natural forests for cultivation, fire and construction wood (Hurni & Messerli, 1981; Stahl, 1989; Tewolde Berhan, 1989). This has led to a rapid shrinkage of the of the country from 40% in 1900 to about 3% in 1985 (Pohjonen and Pukkalla, 1990). As deforestation practices increase and forests disappear, fire wood becomes scarce. In the absence of fuelwood, people use cow dung and crop residues. Use of these as fuel gradually reduces the utilization of dung as fertilizer and thus lead to a yield reduction (Camp­ bell, 1991).

19 Continued high population growth has also brought increased pressure on local resources. The size of land holding are reduced in small plots. Intensive cultivation of the fragmented land without fallowing leads to the depletion of the soil of nutrients which may finally result in yield reduction. Later on, yield reduction forces farmers to expand their cultivation land to marginal lands, i.e. from gently sloping land in the highlands onto steeper slopes of the neighboring mountains (Cross, 1983; Mer- sie, 1989; Mesfin, 1992). Because of forest loss and continuous use of the land for agricultural production, 75% of the Ethiopian highlands is significantly eroded and 4% of it is beyond recovery and no economic production could be sustained (Janssen, 1991). Recent studies have estimated that on the highlands, which covers some 54 million ha, erosion has left 14 million ha seriously degraded; 13 million ha moderately degraded and 2 million ha unproductive (Campbell, 1991). The rate of soil loss varies greatly between different agroclimatic zones, land use, relief and soil type. The highest rate of soil loss documented is in regions of high rainfall with temperate and cool temperate climate, and intensive crop cultivation (Hurni,1988). Soil loss from non-productive lands and cropland are found to be up to 70 t/ha/year and 40 t/ha/year respectively (Fig. 7).

70 'u s 60 1 50 MM

w 40 . MM MM I 30 _ •§ 0 20 - MM . 1C5 MMMM to 1 MMMM a MMM .0 -

=y m 1 1 3S c. Ml .S i 1 C. pa = "g £ 2V IE i •a <5 £ s3 «8 o ee = s 5P D 5■g Land Use Type

Figure 7. Soil loss from different land use type in Ethiopia (Data from Hurni, 1988).

20 The rugged topography of Ethiopia has a significant influence on rate of soil erosion. The hills and ridges associated with high intensity of rainfall accelerate the soil erosion rate. Consequently, the country is loosing its soil cover at a rate which is 6 times faster than the soil formation (Campbell, 1991). However, soil erodiblity varies much within different type of soils. The erodiblity in taxonomic order: Alfisols/ Aridisols > Mollisols/Vertisols > Inceptisols > Oxisols/Ultisols (El-Swaify and Fownes, 1989). The Oxisols and Ultisols are less erodible because of their good hydrologic (infiltration, drainage), mineralogical (aggregate and structural stabil­ ity) property which is caused by the presence of sesquioxides in these soils. Due to erosion, the top soil is losing large amount of nutrients and organic matter. In Ghana, for example, after a forest is converted to agricultural land, the annual rate of organic matter and cations loss in the upper layers of the soil was estimated to be up to 13% and 33% respectively. In Costa Rica, it is reported that the cropland lost 60% of their calcium (Ca) and 25% of their magnesium (Mg) after 22 years of consecutive agricultural practices (Mabbeerly, 1991 p. 239). As a consequence of land and biological degradation in Ethiopia, the crop yield has declined annually by 120,000 tons between 1983 and 1990 (Girina, 1992 p. 61). This amounts to about 13% of the 942,000 metric tons of estimated food deficit for 1990/91 (Briine, 1994). The decline in food production has in turn led to the decrease of the per capita calories intake in some parts of the country by 30 to 40% (Stahl, 1989).

Social and Economic Reasons for Fire Wood Use and Establishing Fuelwood Plantations

Firewood and the rural and urban living condition in Ethiopia In the food production process of subsistence agriculture, human labour is the chief energy source for operations like clearing, planting, weeding and harvesting. Thus, Ethiopian agriculture relies on the labour of the family members where women and children have an important role to play (Amare, 1978). As fire wood becomes scarce, it puts burden on the labour of the rural population. Women and children spend much time and travel longer distance to collect fuelwood. As a result, the on farm labour input decreases and timely operations are not often easily completed. Consequently, the productivity level of food producing process decreases because the labour input on cultivation field has declined. This leads to reduced food production in rural areas. As fire wood becomes scarce, its price increases and simultaneously, the nutritional status and health of the low income groups in rural and urban areas of the country will be severely affected. When fuel is short or expensive, people cook less and eat more raw or undercooked foods, and they reduce eating foods of higher nutritional or biological values which requires an intensive cooking (meat, beans, grains etc.). Especially, eating raw meats containing eggs or reproductive structures of intestinal parasites or pathogens can severely deteriorate the health of the population in the

21 rural area. Health debilitation can negatively influence the efficiency and performance of human labour in the agricultural development. Space heating is also limited due to fire wood shortage. Because of the increasing scarcity, the price of construction and fire wood in towns is raising very rapidly. Depending on the distance between the forests and the urban settlement areas, the price for a metric ton in 1992 has risen by 9% to 290% of the price in 1970 (MOA, 1992 p. 54). The price increase has strained on the income of the poor city dwellers. Therefore, here is necessary to control the prices by increasing the fuelwood supply to the market from established peri-urban fire wood plantation or village woodlots in the surrounding (Asmerom, 1991).

Why fire wood and fuelwood plantations? In spite of the growing scarcity and environmental degradation, why has fire wood remained as chief source of energy for rural and urban population of Ethiopia? What are the reasons that have hampered the population not to shift to other energy resources? Attempts will be made to answer to these and related questions in this section. The development of other energy potentials such as hydro-electric power etc. require huge investment of foreign currency which should be mainly generated through the export of agricultural commodities (credits). But, as Figure 8 shows, the aggregate exports are lower than the imports (debts) and this means that the credit items are not able to provide the country with the amount of required foreign currencies to finance large energy plants. Use of other energy resources, such as commercial fuels is usually accompanied by economic development and rise of income which is a long way for the country to achieve. In Ethiopia, the gross domestic products (GDP) per capita during 1975- 1991 has remained at Birr 215.1 and saving is very low due to low per capita income (Shibeshi, 1994). The rate of saving declined from 4.8 percent in the 1980s to 0.2 per cent in 1991 and investment declined from 15.8 per cent in 1987 to 9.1 per cent in 1991/92 (Getachew, 1994). Total Government expenditure was up to 30.8 per cent of the GDP in 1989/1990 with a growing overall deficit up to 17.1 per cent. This has led to the rise of arrears from Birr 391 million in 1989/90 to Birr 635 million in 1991/92 (Getachew, 1994). The GDP of the country has declined in 1989/ 90 and 1990/91 by 0.9 and 0.3 per cent respectively and in 1991/92 the GDP at constant prices declined from Birr 9,175.8 million to Birr 8,254.4 million. Consequently, Ethiopia with a population growth rate of 3 per cent had a negative rate of growth of GDP per capita of -3.7 per cent (Getachew, 1994). These all indicate the poor performance of the macroeconomy of the country. Because of poor macroeconomic performance, unequal income distribution and unemployment have prevailed in the country. As long as the performance of the macroeconomics is poor, the large population of the country have low income and live at a subsistence level, and the income distribution in the society is unequal, the low income groups in the country may not have the financial power to switch from wood to commercial energy sources. The foreign currency generated through exports is important to finance the country ’s imports like capital goods, commercial fuels, intermediate and basic goods.

22 But, because of the reduction in value and volume of the credit items (export commodities), export earnings have significantly decreased (Getachew, 1994) and the country ’s overall balance of payment shows a deficit since 1974 (Fig. 8). Export earnings decline from Birr 556.20 million in 1974 to Birr 448.39 million in 1992. So that the trade deficit widened from Birr 29.8 million in 1974 to Birr 1696.91 million in 1992.

Aggregate Import o Aggregate Export 2500

0 r't'-r-.ooooooooooovovXJ- OO O CN Tf VC OO O Cvt OvCvOvOvOvOvOvOvOvCTv

Year

Figure 8. Balance of Payment deficit from 1974-1992 (Datafrom The United Nations: 1993 International Trade Statistics Year Book. Trade by Country 1995, Vol. 1, p. 305). (* Birr is Ethiopian currency.)

The continuous increase in value of the debt items (imported goods) (Getachew, 1994) and growing imbalances between the export and import has let the economy of the country suffering from foreign exchanges shortages (Shibeshi, 1994) and finally weakened the purchasing power of the Government to import commercial fuels to ensure sufficient energy supply for all economic sectors. The population in the rural areas of Ethiopia is more than 85% of the country ’s total population and receives no more than 1 per cent of the electric supply in the country (Fig. 4b). This is among others due to the high investment requirments for extending the national electric grid to the rural area and small towns. The settlement style is a dispersed type and people live in scattered villages. Hence, the expense involved in establishing branch connections to villages from the main lines that run between generating station to towns will be very high (Hailu, 1992). Ethiopia is a country in the tropics. It receives about 2.3 TWh of solar radiation every year (Hailu, 1992). The greatest amount of solar radiation the country receives combined with its favorable climate and soil, the potential of growing for energy in Ethiopia is very high. Unlike commercial fuels, energy resources from energy forests are most economically exploited on small scale, decentralized bases, and are thus, well matched to the needs of population living in dispersed settlement areas of the country.

23 Ecological and Economic Reasons for Establishing Fuelwood plantations

According to FAQ statistics (Fig. 9), the population in 1990 has increased by more than 80%, when it is compared to 1965. In order to feed the increased population, enough food must be produced by increasing agricultural purchased production inputs, notably fertilizer, improved seeds, pesticides etc. But, because of low income and no access to credit (Gebrehiwote, 1992) and poor delivery infrastructures, subsistence farmers are not able to purchase and apply off-farm inputs on their cultivation fields (Singh, 1987). Besides, cow dung and crop residues (agricultural residues) are used by farmers as fuel in absence of fire wood. For example, between 1981-1982, the dung and crop residues used as domestic fuel is estimated at 5.1-7.9 million tons (Newcombe, 1989). The fertilization potential forgone due to use of cow dung as domestic fuels is presented in table 4 and 5 below. The use of cow dung as domestic fuel mitigates productivity potential while the use of cereal straw as fuel has depleted the soil of nutrients by removing a considerable amount of nutrients from crop and grazing lands. Depleting the soil of nutrients gradually leads to reduction of land productivity potential and yield fall which may finally result in widening the food deficit in the country. The food deficit that has been exacerbated by land degradation and recurring drought can be bridged either through food aid or food import. But, the question is how long the country could depend on food aid and imported food? Are there means to reduce at least the food deficit that has been caused by land degradation? Are there low cost inputs in the country that can be used by subsistence farmers to improve the nutrient status of the soil and increase the food production and ultimately reduce the gap between the food demand and supply? Of course, animal manure and crop residues with the exception of millet and sorghum stalks that have low fertilizer value and are difficult to recycle (Van de Larr, 1991 p.23) are the possible options. Fertilization of crop lands by adding animal manure improves the nutrient status of the soil because it is nutrient rich and its soil amelioration potential is very high (Table 4 & 5). According to the Office of the National Committee for Central Planing (1989 p. 55), using cow dung as fertilizer increases the country ’s grain harvest each year by about 1-1.5 millions tons.

24 Table 4. Nutrient composition of cow dung (Taken from Newcombe, 1989)

Moisture content fresh 87.00 per cent dry (as burnt) 15.00 per cent Nitrogen (N2) (by weight) wet 0.70 per cent dry 1.46 per cent Phosphorus(P) (by weight) wet 0.20 per cent dry 1.30 per cent

Note: For the most part, phosphorus is retained in the dry matter and is taken as conserved during drying. Nitrogen is readily volatilized (mainly as ammonical nitrogen) and is reduced almost fourfold during storage and processing. As stored, cow dung has been measured at 1.84 per cent nitrogen. When spread on fields another 20 pre cent loss of nitrogen occurs.

Table 5. Additional nutrients in fresh animal manure ( Taken from Newcombe, 1989)

Kilogram per Parts per million Major nutrients oven dry tonne Trace elements oven dry matter Potassium (K) 5.7 Boron (B) 20.2 Calcium (Ca) 1.4 Manganese(Mn) 201.1 Iron (Fe) 0.1 Cobalt (Co) 1.0 Sulphur (S) 1.0 Zinc (Zn) 96.2 Magnesium (Mg) 1.1 Molybdenum (Mo) 2.1

The advantages of cow dung as fertilizer over the use of commercial fertilizer are that it is locally available and costs very little. For application, it requires little technical advice from outside. A wide use of dung as fertilizer can be realized, if it is replaced by other energy sources such as wood. Thus, establishing farm and vil­ lage woodlots and peri-urban plantations and the supply at comparable prices would be necessary to ensure a switch from cow dung to fuelwood. Further, the use of dung and crop residues as fertilizers and soil conditioner gives a better economic return to farmers than when it is used as fuel. Newcombe (1989) found that use of dung as fertilizer in agricultural fields and growing trees in Ethiopia for fuel gives an internal rate of return between 35% to 70% in real terms. Therefore, there is a compelling reason to establish woodlots or multi-purpose forest plantations in order to use agricultural waste to its best use, i.e. as fertilizer.

25 £ S 10 i h Forest/wood land o 3 o in —a — Arable land 10 <6 -e— Population < 0 0 196519701975198019851990 Year

Figure 9. Population growth, expansion of Arable land and Deforestation in Ethiopia 1965- 1990 (Data from FAO (1991): Agrostat PC 1 & 3, Rome.).

The forests and woodlands of Ethiopia are dwindling at the rate of about 125 000 ha per year (Fig. 9). Until 1980 the arable land had been extended by 60 000 ha/ annum and about 65,000 ha of forests are cleared every year to get new land for settlement and wood for fuel and construction. Consequently, the country ’s present high forest is reduced to less than 3% of the total surface area. If the trend of deforestation in Ethiopia continues at this rate, the remaining few forested areas will disappear at the beginning of the next century. The establishment of forest plantations for fuelwood and construction purposes is, therefore, necessary in order to reduce the pressure on the few remaining natural forests of the country. As a result of deforestation, the forest products are becoming scarce. The past uncontrolled exploitation of forests, has increased the distance between the forests and human settlement. Because of the increased distance, absence of infrastructure, and physical barriers such as swamps, and steep mountainous terrain (Tewolde Berhan, 1989), access to the remaining few forest areas of the country is difficult. Because of the increased distance, women and children, who are responsible for fire wood collection, must travel a long distance and spend much time for fuelwood collection. Consequently, the labour input in subsistence agriculture is reduced. These all have finally affected the living condition and development of the society. Development and progress of wood based industries, such as small carpentry shops, tobacco drying, brick, pottery and tile backing and lime and steel in rural and urban areas is hampered by the shortage of wood supply. This means that the employment in the country has been strongly affected by shortage of forest products. It is, thus, essential to increase the local wood supply from man-made forests in order to improve the living condition, encourage employment and enhance the development of communities.

26 The remaining natural forests of Ethiopia are not attractive for investors. Like other African natural forests, the merchantable yields are low per hectare and are far from market centres (Evans, 1992 p. 17). Therefore, establishing plantation of fast growing trees species around centres of high demand is economically viable and highly profitable. Plantation stands have a significant influence on microclimates of neighbouring agricultural land (Rosenberg etal., 1983). Windbreaks and shelterbelts are valuable because they reduce soil erosion by decreasing surface wind-shear stress, trapping moving soil, and slowing soil drying. However, almost all cultivation and grazing lands in Ethiopia lack protective structures such as windbreaks and shelterbelts. They are exposed to strong wind. Increase in wind speed enhances the rate of soil loss from the cultivated fields and evapotranspiration with the attendant loss of soil moisture which is important for plant growth results in decline of the crop yield. Yield reduction due to soil and moisture losses can be effected by introducing practices which can improve the resource use (nutrients and water). Thus can be achieved by the establishment of properly designed shelter belts, for instance, on grazing lands and cultivated field. This increases the boundary layer resistance by reducing the wind speed; this leads to the decline of the evapotranspiration rate from soil surface and plant canopy (Jones, 1992). Due to slow rate of evapotranspiration, the soil dries slowly and generally moisture loss through non ­ productive processes from soil-plant system decreases. This may give the plant an opportunity to transpire efficiently and use the soil resources effectively and may finally result in improved plant and yield growth. Depending on climate, soil and crop type, protecting crop land from soil and moisture loss by establishing windbreaks or shelterbelts increases the gross farm incomes by 10 to 50 per cent (Anderson, 1989) and yield up to 23% (Leach and Robin p 154,1988; Nair, 1990 pp. 336-338). Establishing shelterbelts also increases the supply of woody bioamass (branches and leaves) in a community. In Ethiopia, the highlands are the most degraded landscape in the country. They are rugged topography with slopes more than 16 per cent of grade (Campbell, 1991). The potential risk of land degradation on slope is very high because it has a strong influence on forces that causes or aggravates erosion. The agriculture and settle­ ment activities here, therefore, requires a proper action of agricultural resource (soil, water etc.) conservation to reduce the risk of ecological instability and the consequences of land degradation in the region. Since the time that the peasants have been aware of the consequences of soil degradation and agricultural resource depletion, they are actively taking part in soil and water conservation programs that are supported by external donors. They construct erosion-control structures such as bench terraces (from soil and stone bunds) along grassed waterways on cultivated lands and hillside terraces on steep slopes. In spite of their vulnerability to water erosion, farmers construct preferably earth terraces than stone ones because the latter give shelter for farm pests like rodents (Stahl, 1990). Constructing earth terraces demands high labour input. In Ethiopia, 1 km of earth terrace requires 150 man/day (Cross, 1983). In order to protect the soil successfully from erosion and harvest enough water to support plant growth, earth terraces should be maintained every

27 year. But, farmers are not willing to do the maintenance job with out payment (IFAD, 1992 p. 50). Therefore, there is need for constructing less frequent maintenance demanding stable earth terraces at reasonable cost. Planting trees with careful de ­ sign would be the cheapest means of stabilizing erosion-control structures constructed from soil because the root system of trees stabilize earth structures on steeper slopes. In addition to their effect on stabilizing erosion-control structures, trees play major role in the nutrient cycle of farm ecosystem. They also serve to make productive use of the land, for example fire wood etc.

Establishment of Forest Plantations

Two approaches of establishing plantations in Ethiopia and choice of species For economic and environmental reasons plantation establishment must be encouraged in Ethiopia. In the year 2000, for example, the country requires to raise about 4 million ha of fire wood plantations in order to ensure the future fuelwood need of the population (Zerai, 1992 p. 31) and these are going to be implemented through two major approaches. One is the community forestry approach in which individuals or communities in rural and urban areas are taking the responsibility in raising and maintaining the fire wood and forestry plantation. The second approach is the commercial wood farming system for fuel and construction by the state and private sectors. The participation of the people is important for the implementation of the community forestry because they have labour and other resources (e.g. land etc.) which are needed for establishing and maintaining new plantations. To encourage popular participation in communal , material and technical support are distributed by responsible Governmental and Non-governmental agencies in the country. Nevertheless, the success of any project that has been initiated under the participation of a community members is mainly determined by their perception of the afforestation or project. It is, therefore, important to make people realize the significance of such plantation projects in community lands to which they have traditionally free access for grazing and wood gathering. If people do not perceive the aim of the project, they tend to look the project with suspicion. Hence, it is important to mobilize rural and urban organization at various levels in order to ensure people’s participation and guaranty the successful implementation of the plantation project. Through the second approach, new plantations of significant size are raised around urban centers where wood for fuel and construction is scarce.

The community forestry in Ethiopia Community forestry was launched in 1979 by Community Forests and Soil conservation Development Department (CFSCDD) of the Ministry of Agriculture. The main task of this Governmental agency is to encourage the participation of the urban and rural population in the reforestation and afforestation activities of the

28 country by giving technical advice and distributing material support such as seedlings or tools. Though no reliable statistics on its performance and achievements are available, until 1986 among the raised and distributed seedlings, nearly 70 per cent of them were Eucalyptus globulus and Eucalyptus camaldulencis (Zerai, 1992 p. 12). The community forestry is implemented in two programs: the supervised and the self-help . In the first program, land for tree planting and nursery establishment is acquired from rural and urban communities. The government or­ gan prepare the plan for plantation establishment and carry out the management of the forest until they reach the maturity for harvest. Then, the communities will be entitled to have the ownership right over the forest, immediately after they have refunded the costs that the state has invested on the plan, establishment and mana ­ gement of these forests. In the later one, new fire wood plantations are established on community land by mobilizing the labour from community members. Some incentives like seedlings or seeds and tools which are not available or could not produced locally (e.g. water cans, dig axes etc.) are distributed by Government and Non-government agencies to these groups, while costs for nursery and plantation maintenance and management are covered by the community.

The commercial plantations Establishing forest tree plantation is profitable particularly, on regions where wood for fuel and construction is scarce, (Pohjonen and Pukkala, 1988). Therefore, the forestry department assisted by foreign donor agencies started establishing peri­ urban plantation in regions where demand for fuelwood is very high. The two known projects of this type are the Nazerate- and Addis-Bahr Dar fuelwood projects. These two projects have been simultaneously planed to increase the supply of wood for construction to the citizens of major towns on the highland of Ethiopia. The former was started in 1984 and terminated in 1989 (Stiles et al, 1991). The later has been started in 1986.

Choice of species People, Governmental and Non-Governmental institutions in Ethiopia plant trees for various reasons. Some plant to meet their energy and construction material need, while others plant for environmental reasons or both. However, the success of tree growing is strongly determined by the decision on a tree type, because the selected species has influence on the future silvicultural practices, stand management and crop utilization (Evans, 1992 p. 99). Therefore, tree species for a particular purpose or combined objectives must be carefully selected based on factors like species availability, suitability for the plantation site, silvicultural attributes etc.(Fig. 10).

29 Figure 10. Factors which should be considered when species are selected for any type of afforestation project in Ethiopia.

In selecting the species, especially for community forestry, it is important to consider the objective of tree growing by the participating people and give priority to the species of their own choice. For example, in northern Ethiopia the purpose of cultivating trees by farmers was different from that of the development workers in the region. The peasants were interested in an afforestation project which includes both soil conservation and the fuelwood production, whereas the interest of exten ­ sion workers was only the fuelwood production. As a result, a difference was created between the farmers and the “so-called ” experts in selecting the species that might have led to a conflict in implementing the whole tree cultivation program (Leach and Mearns, 1988 p. 183-184). Therefore, investigating the social factor that limits the reforestation and afforestation work is important, before any work is started. The selection of a species is also governed by other social factors. Some times people grow particular and available tree to promote employment or development in the community. Thus, by selecting a species and establishing a plantation, a priority must be given to these objectives of the community before others (Evans, 1992 p. 100). The lose of most of the forests from the highlands dates back to the 16th century (Horvath, 1968). But, the replanting of sites that had lost their natural forest cover due to uncontrolled exploitation started very late in the end of the 19th century (El­

30 lis, 1992). The objective of the planting programme was to increase the supply of fuelwood and construction wood which was scarce in the country ’s capital and its surroundings. However, because of little or no knowledge of the silviculture and ecological requirements of the indigenous trees (Tewolde Berhan, 1991), species selection was difficult. The only way of selecting a tree type at that time was by conducting an experiment in species trial (Orlander, 1986). For the trial, about 26 species of Eucalyptus were introduced (Ellis, 1992). Among the introduced non-indigenous trees Eucalyptus globulus Labill. subsp. globulus (blue-gum) was found to be promising (Orlander, 1986) and it was the most important species in forestry activities of the early years (Horvath, 1968). Currently, because of shortage of qualified personal and money, conducting an experiment in species trial are not easy in Ethiopia. Therefore, tree species are selected in cheapest ways, i.e. by evaluating relevant publications and by analyzing the performance of plantations that had been established in the past (Lamprecht, 1989) and thus summary lists of species suitable for different purposes, zones of agro­ climate, altitude and amount of annual rainfall were developed by Orlander (1986) Pohjonen (1989) CFSCDD (1989) and Zerai (1992). Due to lack of knowledge in the silviculture and ecological requirements of the indigenous tree species (Tewolde Berhan, 1991), the present forestation in Ethiopia is also dominated by non-indigenous tree species. With the help of the species summary lists, many different type of exotic trees spp. other than Eucalyptus globu­ lus Labill. subsp. globulus are introduced to serve the present afforestation and reforestation program in the country. Nevertheless, because Eucalyptus globulus fulfills many of the criteria of proper species selection, it has remained to be the most important tree species in the country ’s tree growing program (Leach and Meams, 1988 p. 135; CFSCDD, 1989, Pohjonen 1989; Stiles, 1991 p. 6; Kahurananga et al., 1993). For instance, from 1984 to 1989, in the state owned fuelwood plantation projects of Nazerate and Debre Birhan towns, more than 75% of the planted species were E. globulus (Stiles et al, 1991 p. 18, Table 5) and this species constitutes up to 100% of the new forest plantations of Addis-Bah fuelwood project near the Capital of the country (personal observation). It is cultivated on highlands particularly, for fuelwood and construction purposes (Pukkala and Pohjonen, 1990a; Pukkala and Pohjonen, 1990b), and soil conservation in some place on the highlands (FAO, 1981 p. 419; Fiedler and Gebeyehu, 1988). The Rationalto Grow Eucalyptus globulus

More than one third of the country ’s already total established plantations was constituted of this species (Pohjonen, 1989 p. 13) and currently, Eucalyptus globu­ lus dominates up to 100% of the tree growing program on the highlands. The main objective for its cultivation is the production of wood for energy and construction, and to arrest and reverse the deforestation process in the country. On the highlands, Eucalyptus globulus is usually grown around domestic compounds, on grazing land, as boundary and road side plantations, in woodlots etc.. Some of the reasons for its cultivation are the followings:

i. The tree species is easily available. ii. Afforestation activities in Ethiopia are mostly carried out by employed or volunteer unskilled people. Therefore, the current tree growing program in the country requires simple growing and insensitive species. E. globulus qualifies these criteria. Besides, it is a tolerant to dry climate and not palatable or have resistance to browsing and grazing (Pohjonen & Pukkala, 1990). iii. The species is fast growing. Its maximum growth rate culminates early at the age of 9 to II years (Fig. 21) and efficient to convert the solar energy (Pohjonen & Pukkala, 1990). iv. E. globulus has the ability to produce wood of high specific gravity and high wood calorific value, even when grown rapidly in short rotation (Davidson, 1987). v. E. globulus grows fast and yield high volume of biomass in short rotation of about 4-8 years in close tree spacing (Davidson, 1987). vi. The species has a good ability and many of its mature stands at present in the country are coppice regrowth (Fig. 11). vii. Planting E. globulus brings good economical gains (Pohjonen & Pukkala, 1988; Pukala & Pohjonen, 1990a). viii. About 70 % of the Ethiopian population is living in altitudinal range between 2000 and 3200 m.a.s.l. (Mesfin, 1992). Here, frost is frequent and the largest population is peasantry who don ’t have access to commercial energy sources. To supply this population with fuelwood and construction material, plantation must be established from species that are able to perform well in frost areas. Through 100 years of traditional forestry practice in the country, Eucalyptus globulus has proved itself to have resistance against frost. This and other attributes of the species have contributed to its popularity between farmers in the region.

32 Figure 11. Coppicing abilty of E.globulus and the the soil underneath one year after it is harvested. (Photo taken by A. Mehari).

The Eucalyptus globulus Labill. subsp. globulus and its distribution in Ethiopia

Eucalyptus globulus Labill. subsp. globulus occurs in naturally , and between latitudes 31 and 43°S. The species was introduced to Ethiopia by a French citizen called Mondon-Vidaillet in 1894-1895 (Huffnagel, 1961; Horvath, 1968) and for the first time it was this time that plantations of E. globulus was established around Addis Ababa, in order to replace the depleted na ­ tural forests around the city. Because of its successful early performance, extraordinary quick growth and non-palatability, the species has spreaded very fast and dominated the tree growing activities in the country during the early years (Huffnagel, 1961 p. 405; FAO, 198 lp. 76; Pohjonen, 1989 p. 56;). Currently, it is raised in regions with a range of altitude from 1500 to 3200 m.a.s.l. and rainfall from 800-1500 mm (CFSCDD, 1989 p. 75). Eucalyptus globulus Labill. subsp. globulus (blue-gum) belongs to the sub-family Leptospermoideae within the family of the Myrtaceae. The tree is easily distinguis ­ hed from other subspecies by its morphological attributes. Eucalyptus globulus Labill.

33 subsp. globulus shows different pattern of growth habit. Usually, it has tall tree habit with smooth bark, long adult leaves, large solitary glaucous buds and fruits, and with flowers which are important sources of honey (Chippendale, 1988 p. 354). But, sometimes it occurs also as a (“shrub”) (Fig. 13) which consists of several to many thin stems. The shrubby growth habit of E. globulus is associated with the formation of lignotuber (Beadle, 1981 p. 84; Bell, 1991 p. 237 Fig. 237d) at the cotyledonary nodes in the early growth stage of a seedling (Cattaway, 1958; FAO, 1979 p. 16-22). Lignotubers are swellings on the stem and occur above the group of axillary buds. They start to grow between the stem and concealed buds (accessory buds) which are tissues having merstematic origin. Later on, Lignotubers increase to grow in size towards the direction of the root encircling the stem and ultimately force the axillary shoots to take the lower position above the cotyledonary node of a seedling (Cattaway, 1958 p. 110 Fig. 7). Lignotubers of malle can grow up to a size of about 20 cm in diameter and sometimes larger (Beadle, 1981 p. 341). Lignotubers are woody structures and have basically similar woody elements like the stem on which they occur ( Cattaway, 1958). They contain vegetative buds, associated vascular tissues and also food reserves (Cattaway, 1958; Pryor, 1975 p. 10). If the aerial part of the seedling is destroyed by frost or browse (e.g. rodents) or trampling (e.g. domestic and wild animals), growth is renewed by the development of many new leading shoots from the vegetative buds of the lignotubers which finally leads to the formation of many stemmed shrub called mallee.

34 Figure 12. Mallee (Shrub) of Eucalyptus globulus Labill. subsp. globulus. (Photo taken by A. Mehari) .

The tree of E. globulus exhibits an excurrent type of branching or crown form where the stem or leader outgrows the lateral branches beneath, giving raise to cone shaped crowns and a clearly defined central bole (Fig. 13). This is probably due to the effect of the apical control (Zimmermann and Brown, 1980 pp. 130-134) that may lead the proximal branches to grow in the basitonic condition. Though E. globulus shows a pronounced morphological difference between the juvenile and adult stage, owing to its monpodial trunk which grows continuously, orthotropic monpodial branches, it is grouped to the model of Attims (Halle et al., 1978 pp. 228-232).

35 Figure. 13 Four years old Eucalyptus globulus Labill. ssp. globulus from Addis Ababa fuelwoodproject (09° 15'N 38° 45'E). (Photo taken by A. Mehari).

36 E. globulus is a heterophyllous plant (Figs. 13 &14). This means that the leaf forms at various times in the life cycle of the species are different. The primary leaves of the embryo, i.e. the cotyledons fairly deeply emarginate, the lobes asymmetrical, obviate-oblong and obtuse, cordate at base, purple on undersides, 0.9x0.3 (?), petiole 0.4 (?) (Hall, 1914). At seedling or sapling stage, the juvenile leaf form is morphologically different from the adult. They are opposite, sessile, highly glaucous, oblong-accuminate in shape and dorsiventral, 7 to 15 cm long and 4 to 8 cm wide (Fig. 14), while the adult leaves are alternate, petiolate, non-glaucous, falcate- lanceolate and isobilateral, 10 to 30 cm long and 2 to 6 cm wide (Chippendale, 1988 pp. 352-353, Pohjonen; 1989 p. 57). In the beginning the stem of a young seedling is glabourous, terete, purplish. Later it becomes quadraangular in shape. The stem of an adult tree is spherical with deciduous bark which means that the bark of the tree peels off in long strips regularly and the upper part of the tree becomes smooth. However, the lower part of the tree remains persistent The phylotaxis of the species is interesting. In the young stage the leaf arrange­ ment on the stem axis is opposite decussate. This means that the successive pairs are mutually arranged at right angels, whereas in the adult agethe leaves are alter­ nate on the opposite sides of the stem and have a spiral phyllotactic arrangements. For the phylotaxis change in mature trees the elongation and twisting of the intemo- des and intranodes of a growing shoot below the terminal bud combined together with the effect of light are responsible (Penfold and Willis, 1961 pp. 25-30; Brooker, 1968). In contrast to other Eucalyptus and species in the family of Myrtaceae, E. globu­ lus has single standing inflorescence, i.e. a reproductive shoot system bearing flowers, in the axil of a leaf. The flower develops within an envelope formed from two opposite bracteoles which are quickly deciduous and their presence can be only recognized from the scare left on the junction between the flower and the peducle (Carr and Carr, 1959). The flower bud of E. globulus consists of two distinct parts and these are separated by a line. The upper part is called the operculum, while the lower one is known as receptacle. Immediately after the bracts are opened, the buds are highly glaucous. This is because of the wax covering the rods or granules of particular physical character on the cuticular surface of the operculum (Pryor, 1976 p. 32).

37 Figure 14. Seedling of Eucalyptus globulus Labill. ssp. globulus from Addis Ababa fuelwood project (09° 15'N 38° 45' E). (Photo taken by A. Mehari).

38 Figure 15 Eucalyptus globulus labill subsp. globulus, showing a typical flower at anthesis. (Photo taken by A. Mehari).

39 The operculum is the cap which protects the reproductive organs before the anthesis. Within the genus Eucalyptus, there are two type of opercula. These are the single and double structured operculum. The former is developed from a whorl of corolla or a sepal whorl, if the petaline is totally suppressed, or it is a composite structure derived from both. The later is a combination of two separate caps, the outer and the inner. These are recognized as being calyx and corolla respectively of tetramerous flower in which the four separate sepals are fused to form a single cap and the separate petals to form the second inner cap. Based on the operculum type, the genus of Eucalyptus are classified into mono-operculate and di-operculate species (Carr and Carr, 1968; Pryor and Knok, 1971). The mono-operculate are species with single structured operculum, whereas the di-operculate are those having two separate opercula. According to Chippendale (1988 p. 4), E. globulus Labill. subsp. globulus is a di-operculate species and its operculum is boss-shaped, 7-15 mm long and 14-17 mm wide. Both caps are deciduous, the inner one probably before anthesis, the outer one before or also at anthesis (Carr and Carr, 1968). The development of both opercula is well decumented (Pryor and Knok, 1971). At a time when the stamens starts to stand upright, the operculum falls and a scar left on its original position which is known as the Calyciline ring which makes the outer rim of the seed capsule. After the end of fertilization process, the male organ of the flower will be abscised and a ring is formed on which the stamens were inserted. This ring is called the staminal ring. The inner part of Eucalyptus fruit whose development is not yet clearly described (FAO, 1979 p. 47), is known as floral disc. Inside the disc is the upper part the capsule which in due course breaks up into two or more valves. E. globulus Labill. subsp. E. globulus has 4 to 5 valves on its seed capsule (Chippendale, 1988 p. 353). Finally the seed capsule dries and the valves spread apart to disseminate the seeds which were contained by the ovary. The flower of E. globulus Labill. subsp. globulus has a large number of white stamens and a perigynous arrangement of the outer floral whorls (Fig. 15). After flowering a process of fertilization follows which is the prerequisite for the development a seed from the ovule and of fruit from the ovary. The Fruit of the E. globulus Labill. subsp. globulus is a hard woody capsule, obconical, tetra-angular, 10 to 21 mm long and 14-24 mm wide (Chippendale, 1988 p. 4; Pohjonen, 1989 p. 57) and consists of six parts. These are the hard woody receptacle, the inner capsule which arises from the ovary is surronded and protected by the receptacle and the four segments of the upper part of the fruit: the calyciline ring, the staminal ring, the disc and the valve. In the flower of E. globulus, the ovary is divided into 4 or more chambers (Cronquist, 1981 p. 642; Chippendale, 1988 p. 5). Each chamber contains two dif ­ ferent structures. These are the ovules and ovulodes (Pryor, 1975 p. 15). After fertilization the former develops into seeds, while the later become chaff. When the seed capsule dehisces, a mixture of seed and chaff are released out. Morphologically the seeds are different from the chaff. They are bigger and heavier. Because the seeds are making about 5% of the disseminated chaff by weight (Pryor, 1975) their separation from the unfertilized mature ovulodes isn ’t be simple. The number of viable and mature seeds per capsule are usually quite small. In a gramof commercial seed, including chaff, there are only about 75 viable seeds (FAO, 1985 p. 213, Table 9.1).

40 Silvicultural and Ecological Requirements of Eucalyptus globulus

Silvicultural Requirement of Eucalyptus globulus

Sowing and transplanting Nursery practice in Ethiopia is well documented in Pohjonen (1989). Eucalyptus globulus seedlings are regenerated artificially by sowing either in seed beds or directly in containers. But, usually it is done in container. The first step is, fill the container with fairly light and permeable soil and then water it. After the container become wet, few fertile seeds are sown directly on it and lightly covered with soil. The sowing time is usually between January and February. About one month after the sowing date or the third pair of leaves appears, one seedling is left on the container and the rest are pricked out and transplanted to the empty growing polythene con ­ tainer.

Nursery soils After transplanting, growth of seedling depends fully upon the growth and function of root, photosynthesis and seedling density. For the process of photosynthesis, seedlings require the atmospheric C02 and soil water. Through this process, seedlings convert solar energy to chemical energy. This chemical energy is a simple sugar (CH20)n which is an energy source for the seedling and simplest carbon compound to build tissues and organs of the juvenile plant. The function of root is to provide the seedling with water, nutrients and anchorage. To perform its function, the root must be healthy and establish itself well in the growing media. If the growth of the root is hindered, its function will be restricted and the shoot growth also will be retarded. Root growth restrictions are usually caused due to the absence of optimum growing environment in the growing media which is determined by soil physical properties and shortage of nutrients (Russell, 1973 pp. 520-554). While the later can be easily modified by fertilization and irri­ gation, it is not considered as an important problem in the nursery management, but creating optimum soil conditions for root growth by manipulating the physical properties of the soil is hard to impossible because moving or modifying large mas­ ses of soils is costly and impractical. The only solution will be, therefore, to select nursery site on soil with desirable physical properties. The desirable soil conditions for seedling production are: i) Well aerated and drained nursery soil:

Seedling root requires oxygen to function and the source is the soil air in the pores not filled with water. Soils which are badly drained are poorly aerated because aeration is largely dependent upon the volume fractions of air-filled pores. The volume fraction of air filled pores or porosity depends on soil texture (Kramer, 1944; Koorevaar et al., 1983 p. 6; Hillel, 1982 p. 137). For example at field capa­

41 city, more than 25% of sandy soil, 15 to 20% of loamy soil and below 10% of clayey soil by volume is filled with air (Hillel, 1982 p. 137). Because they are poorly drained, the fine-textured soils are badly aerated than coarse-textured ones and the average size of individual pores is smaller in the former than in the latter (Hillel, 1982 p. 9). The capacity of fine textured soils to retain much moisture against gravitational force than the coarse textured soils also contributes to poor drainage. The water held in side their pores obstructs the gas exchange between the atmosphere and soil which finally affects severely the growth and development of seedling because their root is restricted to absorb adequate 02 and release the C02 in the process of respiration (Kramer and Kozlowski, 1979 pp. 459-460; Russell, 1973 pp. 416-419; Hillel, 1982 pp. 135-136). Theodorou et al. (1991), for instance, noted that root growth of seedlings of Pines radiata was significantly retarded when the soil aeration fall below 10%. Poor drainage is not only impeding aeration, it could also create an opportunity for the out break of damping off which is a fungal disease that attacks root and stem of seedlings in the nursery. Soil aeration and drainage are optimum in loam soils (Hillel, 1982 pp. 29-30). When soils of this textural class is not available close to nursery sites, sandy to sandy loam local soils mixed with compost/manure are used for seedling production in Ethiopia (Pohjonen, 1989, pp. 198-200). The best seedling growth at the Germama nursery of the Addis Ababa fuelwood project was found on loam to clay loam soils mixed to six month old organic manure in a ratio 3:2 respectively (Zerai, 1992). Depending on particle size composition (texture) of the local nursery soil, amendments are traditionally carried out in Ethiopia, in order to improve the nutrient status, drainage and aeration of the growing media (Pohjonen, 1989 pp. 198-200). If the local soils are clayey, usually they are amended by adding off-site sand soils and organic manure. For example, adding organic matter to clayey soil improves the saturated hydraulic conductivity (Ohu et al., 1994) and thus improves the air exchange between the soil and atmosphere. The addition of sand to clay is also aimed at increasing the rate of water percolation by raising the average pore size of the nursery soil. However, adding sand to heavy clay soil generally may reduce the percolation below that of the soil alone, increase the bulk density and reduce the maximum moisture holding capacity of a soil (Fig. 16). This happens because particles of small size (clay) are filling the pores between larger grains (sand) (Ghildyal and Tripathi, 1987 p. 131 ) which may lead to slow water infiltration in the growing media and poor soil aeration.

42 Bulk density Moiture content - 0.45

i 0.42

-r 0.39

i. 0.36

Sand added to Clay loam soil in per cent

Figure 16. Changes in soil bulk density and moisture contents introduced by coarse textured soil amendments (Data taken from Hanan (1981)). (*moisture content of a 20 cm column after drainage had ceased.).

The application of organic matter in nursery soils is aimed at improving the soil structure and nutrient status of the soil. However, animal manure added to the soil is usually fresh or partly decomposed material. Using unrotten organic matter (Fig. 17) in the nursery soils has risks that oxygen could be deficient to the growing seedlings on container soils. Immediately after transplantation, the seedlings are often supplied with water which can encourage the biological activity in the pot- soil and start to decompose the fresh or unrooten added animal manure. In aerobic condition, because most of the microorganism in the soil have a very efficient enzyme system for absorbing free oxygen (Russell, 1973 p. 415), a considerable amount of oxygen is consumed by the process of decomposition. As a result, oxygen for the root of seedling become deficient. If the situation is anaerobic, because of poor drainage in the growing media or the partial pressure of oxygen is lower than 1 percent of its pressure in the free atmosphere, products of reduction such as nitrous oxide (N20) from nitrates (N03 ), methane (CH4) and ethylene (C2H4) from carbohydrates etc. can be created at toxic concentration to inhibit the root growth (Russell, 1973 p. 416; Larcher, 1995 p. 375). Therefore, when the question of root aeration arises, it is important also to consider the composting degree of the organic matter added to the nursery soil. Figure 17. Organic amendments, i.e. the adddition of animal manure (darker in photo) to local nursery soils (reddish in photo), at Germam nursery of the Addis Abeba fuelwood project. (Photo taken by A. Mehari).

ii) Nursery soils must have the potential to store high plant availabile water.

The moisture in a growing media, which is available for a growing seedling, lies theoretically between two arbitrary limits (Fig. 18). These are the field capacity (FC) (upper limit of available water) and the permanent wilting point (PWP) (lower limit) (Marshall and Holmes, 1988 pp. 255-257). Field capacity is defined as the volume of water retained by a soil two or three days after drainage due to gravity or the internal drainage stops (Kramer, 1944; Hillel, 1982 pp. 297-299). The perma­ nent wilting point is defined as root zone wetness at which a plant wilts and does not recover turgor at night when placed in a saturated atmosphere (Veihmyere and Hedrickson, 1931). In terms of water suction, the permanent wilting point for most of agricultural crops begins at about-15 bar and the field capacity at-0.1 bar (Mars­ hall and Holmes, 1988 pp. 255-257; Hillel, 1982 p. 299). Both permanent wilting point and field capacity are not fixed constants. Their values changes with plant and soils type. Despite of their variation, they are universally accepted because of their convenient to define the soil moisture condition related to plant growth (Hillel, 1982 p. 297). Traditionally, seedlings at the nursery are watered either in the early morning or in the late afternoon in order to reduce the water loss due to evaporation. However,

44 because neither the quantity of required water nor the interval between each watering is known, most of the time seedlings at nursery are watered in excess. The excess water in the context of this study means the amount of water lost due to gravitational forces, evaporation, and surface runoff over the growing media. To reduce the non productive water loss from nursery soils, including water control in the nursery management is important. This could be possible, if the field capacity and perma­ nent wilting point for different nursery soil and plant type are known. The knowledge of the field capacity and permanent wilting point combined with meteorological variables, which are directly or indirectly affecting the soil-plant water system, helps nursery managers to know the amount of water required to raise a seedling on a given soil and climate type and thus regulate the frequency of watering or irrigation in nursery. The water content of various soils at FC and PWP and the range of available water between theses two limits is depicted in Figure 18. Sandy soils have a narrow rage of available water between FC and PWP. This is due to their quick drainage at moisture potential below the field capacity (-0.1 bar) and high hydraulic conductivity when they are wet (Hillel, 1982 p. 113 Figure 7.5; Gardner, 1985; Marshall and Flolmes, 1988 p. 87 Figure 4.4). And this attribute of sand soils leads plants or seedlings to suffer from moisture stress, especially in regions where water is scarce and its transpiration requirement is high.

0.45 - Water Content at FC

o 0.35

Plant Available Water

O 0.15 X

Water Content at PWP

Sand Loam Silty Loam Soil Texture

Figure 18. The volumetric water content of different textural classes at field capacity (FC) and the permanent wilting point (PWP) and their available water capacity at two limits (Data taken from Rowell, 1994 p. 248).

45 The water holding capacity of sand soils could be improved by adding fine-textu ­ red soils and organic matter (Russel, 1988 p. 357). The addition of organic manure on these soils is aimed at improving their nutrient status (Table 3 & 4) and water retention capacity. Adding organic matter improves the moisture content of sand soil by 3 to 5 times of the weight of the applied manure (Scheffer and Schactscha- bel, 1984 p. 66). This property is significant for sand soils whose field capacity is dependent on their organic matter other than their silt and clay content. Not only on sand soils, addition of organic matter also improves the water retaining capacity of other soils. For example, in England, application of organic manure on clay loam soils raised the moisture holding capacity of the plough layer by 30% (Russell, 1944 Table 4) and in Nigeria, addition of organic manure improved water retention capacity of the sandy clay loam soil by 5 to 100% (Mbagwu, 1989). Similar actions are also taken in Ethiopian nursery practice to improve the physical and chemical properties of different local soils of various textural classes. However, no study has been carried out on the effect of off-site soils and organic matter amendments on physical and chemical property of the local soils and their ultimate influence on seedling growth are not also clearly and quantitatively known. Soils of texture class clay, in spite of its high capacity of water storage, the plant available water is less than the clay loam, silty loam and loam soils because at PWP about 64% its volumetric water content is strongly held by the capillary forces inside the micropores (Kramer, 1944). Besides, clayey soils, depending on the type of clay mineral they contain and their wetness, have high to low degree of swelling and shrinking characteristics. Due to shrinkage, cracks are created on growing me­ dia that may cause root damage on seedlings. Therefore, it is wise to reduce the use of these type of soils for seedlings production. At PWP, the water content of every texture class is affected by clay content. It increases as the clay content in the soil increases (Hillel, 1982 p. 76) because for each added 1 per cent clay, the non-plant available water increases linearly at rate of 0.66 per cent until the clay content reaches 20% of a given soil (Russell, 1988 p. 354). The water holding capacity in textural order: Clay > Clay loam > Silty loam > Loam > Sandy loam > Sand (Fig. 18). However, for root water uptake, it is not simply the water holding capacity of a soil important, but the plant available water and the rate at which the water is conducted through the soil to the root surface of the seedling which depends upon the rooting density and the water movement (Hillel, 1982 p. 293; Brady, 1984 pp. 104-105). The water movement to the root is governed by hydraulic conductivity of the soil and the gradient potential. The hydraulic conductivity is greatest in saturated soils. It increases as soil moisture or water potential increases (Ghildyal, 1979 p. 162 Figure 3.1) or as the matric suction dec ­ reases (Hillel, 1982 p. 101). Due to increased conductivity, water held at low suction is more readily available than water held at higher suction (Russell, 1988 p. 356). At lower suction, plant available water in sandy loam is larger than silty loam and clay (Russell, 1988 p. 356 Figure 11.8). This is probably due to its larger average pore size than the silty and clay soils which has encouraged root growth and contributed to increased hydrualic conductivity. However, seedlings of E. globulus

46 at Addis Ababa fuelwood project are raised on loam (35-45% sand, 34-42% silt and 19-21% clay) to clay loam (31% sand, 33% silt 36% clay) soils (Table 4). These soils contain high content of clay than sandy loam. The content of sand in loam to clay loam soils is lower by 20 to 50% than sandy loam, whereas their clay content is higher by 5-15%. The increase in clay content reduces the average pore size of the soil, but increases soil surface area. With reduced pore size, and increasd soil sur­ face area, the adsorbed water retained by forces of adhesion increases (Brady , 1984 pp. 79-83; Hillel, 1982 pp. 66-72) which may finally result in the decline of the range of plant available water of a given soil.

Hi) Nursery soils must be less compactible

In Ethiopia, seedlings are often raised in polythene tubes. They are open on both sides (upper and bottom) and have a diameter of 4-10 cm and a length of 10 to 25 cm. To make them ready for the transplants, the plastic containers are filled first with nursery soils up to 5 cm from the bottom and will be tightly compacted by hand. After it is proven to be stable and compact, the plastic container will be turned up and the remaining part of it will be loosely filled with soil. Depending on the length and diameter of the container, the compacted soil holds 25 to 50% of the growing media. Whenever a soil is compacted, the process is accompanied by increase in the bulk density, and the particles are tightly pressed together. Consequently, the pore space in the soil will be reduced and the rate of water infiltration in the soil and gas exchange between the soil and atmosphere will be hindered. Due to badly aeration and poorly drainage, root growth and function will be adversely affected (Eavis, 1972; Russell, 1973; McMichael and Quisenberry, 1993) and this may lead to poor early performance of the seedling. Compaction also increases soil strength, bulk density and resistance for root penetration (Veihmyere and Hendrickson, 1948; Hardy, 1974). An increase in bulk density causes a decrease of dry mass production in nursery. For example, Thithamer (1989) found a decline of dry mass production of Douglas fir seedlings up to 50% when the soil density was raised from 1.5g/cm3 to 1.6g/cm3. Soil strength also retardes the rate of root elongation by decreasing the rate of meristematic cell division and reducing the cell length (Bengough and Mullins, 1990). According to Eavis (1967), at 3.4 bar of mechanical resistance, the cell divi ­ sion rate of bean plant was found to decline by 40% which has contributed to root elongation decrease by 70%. Veen (1982) also found a decrease of 75% in root growth for maize at mechanical resistance of 0.40 bar. The resistance for root elongation leads to higher shoot/root ratio. The shoot/root ratio is a measurment of plant quality because it indicats future growth and survival potential of seedlings in the field (Lavender, 1984; Hahn, 1984). For a better seedling performance on plantation site, the optimum shoot/root ratio lies between 0.35-0.55 (Evans, 1992 p. 160). Seedlings with higher shoot/root ratio values than the optimum have low growth and survival potencial and thus perform very poor when they are planted out on the field. Though there is no study carried out on the physical properties of nursery soils and their influence on seedling growth, the risk of soil compaction during potting in

47 Ethiopian nursery practice is very high and inevitable. During potting, the degree of compaction is determined by particle size distribution and water content. In container seedling production, nursery soils are often dry. They must first become wet and then filled into containers. Because nursery managers are aiming at maxi­ mum number of stable soil filled pots per man-day, they allow the soil to be wet in order to facilitate the rate of pot filling work. The rate of potting and pot stability depends upon the compactibility of the soil which are determined by moisture con ­ tent and the magnitude of compressive force. As the soil wetness increases, the moisture between the surface of soil particles serves as a lubricant and leads the soil to be more workable and compcatible (Hillel, 1982). Such practice particularly, affects soils of different grain size. Because they are more susceptible for compaction than those containing predominantly one grain size (Marshall and Holmes, 1988 pp. 237-238). Figure 19 illustrates the increases of bulk density with increase of moisture content and compaction. To reduce the risk of compaction and its negative influence on the growth of seedlings at nursery and later in the plantation site, nursery mangers should reduce practices that are contributing to soil bulk density increase. Seedlings of E. globulus are raised on loam to clay loam soils (Table 6). And these soils having 20 to 40 % clay (depending on the clay type) are hypothetically susceptible to compaction because finer particles can easily fill up the gap between coarser ones. As the soil wetness increases, its lubrication effect between soil particles also increases. As a result, the fine particles slide over the surface of larger ones to fill up the gaps between them. With increased moisture content, the soil become more compatible. For example, under a given pressure, sandy loam soils are found to be more compatible at 11% moisture content than at 6% (Warkentin, 1984 Fig. 9). In order to reduce the soil compaction and its consequences in nursery practices, it is, therefore, important to determine the critical value of soil wetness at which the bulk density is optimum for seedling growth. Plant root growth occurs inside pores of soil matrices which are highly influenced by bulk density. As the bulk density increases due to compaction, the pores size become much smaller. Finally, the decline in pore size hinders root elongation. Because of this mechanical impedance, the seedlings are going to be restricted only to the upper part of the soil volume in the container which leads to inefficient seedling resource (nutrients, water etc.) utilization. In order to reduce such problems, nursery managers must avoid nursery practices which are contributing to soil compaction. Regulating the compressive force, i.e. the pressure exerted by hand, is not simple. But, the wetness of the soil can be regulated to the level where it is more resistance to soil compaction. In the future studies on soil physical properties and their effect on the growth of seedling should be carried out to improve the nursery practice in the country.

48 o "E £ 2

Soil compressed 1 day g after saturation Q) T3 Soil compressed 2 days after saturation 3 CO soil compressed 3 days after saturation

q— Soil compressed 7 days after saturation

6.7 10.0 13.3 Pressure (kg/cm2)

Figure 19. The effect of soil wetness and compaction on the bulk densit of sandy pot-soil (Data taken from Atta et al., 1989).

Adding organic matter to nursery soils improves its physical and chemical attributes. It increases their strength and decreases compaction. For example three samples of sand soil with 0, 1 and 2% farmyard manure (FYM) or organic matter content were tested for their compactibility at 0,3.3,6.7,10, and 13.3 kg per cm2 levels of pressure and the results are demonstrated in figure 20. However, excess application of organic matter on nursery soils could be disadvantageous. For example, Thihatmer (1989) found that height growth of Douglas firs (Pseudotsuga menziesii (Mirb.) Franco.) was reduced up to 75% when the organic content of the nursery soil exceeded 3.6%. This is probably because of the oxygen deficiency in the soil. As the organic matter in the soil increases and optimum conditions for its decomposition exists, the soil biological activity also increases. Due to increased soil biological activities, organic matter decomposing agents consume a substantial amount of 02 in the soil. As a result, oxygen will be deficient for plant roots which is important for its respiration (Hakasson and Von Polgar, 1979; Aldhous and Mason, 1994). 1.65 -

1.55 _ 0% FYM 1% FYM 2% FYM 1.45 -

Pressure (kg/cm)

Figure 20. Effect of organic matter on soil compaction (Data takenfromAtta et al., 1989).

iv) Soils must have low shear strength, otherwise harvesting bare seedling root may not be easy.

v) Soils must not be adhesive to the seedling root, or else separating the bareroot seedlings from the nursery soil will be very difficult.

Nursery soil analysis In nursery, E. globulus is raised in pot soils of various age.To investigate their texture and nutritional status, a laboratory analysis on 0,3 and 12 months old pot-soil was carried out at the soil laboratory of the Ministry of Agriculture (MO A). For the analysis a standard procedures were used (Allen, 1989). For the determina ­ tion of soil texture a hydrometer method; available phosphorous (ppm) Bray method No. II; total nitrogen (meq/lOOg) Kjeldahl method; organic matter content (mass/ mass) a Walky-Black oxidation method; calcium (meq/lOOg) and magnesium (meq/ lOOg) atomic absorption method; sodium (meq/lOOg) and potassium (meq/lOOg) flame photometry were used. The average results of the laboratory analysis on texture and chemical property of the pot soil for raising E. globulus at nursery of the Addis Ababa fuelwood project is given in Table 5. The soil acidity is commonly defined as the concentration of hydrogen ions in a solution. It is measured as the pH value which is - log [H+]. The pH is determined electrically in water and potassium chloride (KC1) solutions. The pH measured in solutions of KC1 is lower in the range of 0.62 to 1.18 units than in aqueous-solution. Generally, seedlings are raised in acid to slight acidic media. Organic amendment is common in traditional nursery practice in Ethiopian. At Germama, 2 unit of animal manure is added to 3 units of local soils. However, the laboratory result in Table 6 shows that the organic matter (OM) content (mass/ mass) of the pot soils of various age was found to be different in the following order: 12 months < 3 month < fresh soil. This is probably due to loss of carbon

50 compounds through leaching and volatilization of gases from aerobically and anaerobically decomposed organic matter in the soil. In contrast to the intermountain nursery (Table 5), the fresh and the three month old soil from Germama contain up to 14% more OM than the upper level laid for the former nursery.

Table 6. Chemical properties of the pot-soil at Germama nursery

Pot-Soil Age (months) Adequate 0 (L) 3(CL) 12(E) levels 1 Mechanical composition * Sand (%) 45 31 39 Silt (%) 34 33 42 Clay (%) 21 36 19 pH 1:1“ h 2o 5.760 5.960 6.290 Kcl 5.080 4.950 5.210 EC (mmhos/cm) “ 0.541 0.643 0.459 <4 Organic matter (%) * 5.742 5.078 4.125 2 to 5 CaC03 %" 3.400 3.800 4.600 0 Na(meq/100g)“ 1.050 0.940 0.830 n.d. K (meq/100g)“ 2.810 2.180 1.580 0.26 to 0.52 Ca (meq/lOOg)0 20.420 20.850 22.490 2.5 to 5 Mg (meq/100g)’ 8.220 9.160 8.200 1 to 2 N(%y 0.364 0.385 0.333 0.1 to 0.2 P(ppm)“ 99.450 90.160 91.430 30 to 60 CEC (meq/100g)“ 23.960 26.450 47.820 7 to 12

Note 1 Values recommended for intermountain nurseries that are producing seedlings of hard wood species (Youngberg, 1984). a The methods used to determine the chemical property of the soils from Germama nursery are summarized in Allen (1989). n.d.= not determined; L= Loam soil; CL= Clay Loam soil

Managers or foresters must consider the quality of the water and local soils when they are selecting their site for their nursery. The water and soils should not be saline. The salinity of a soil solution is determined by measuring its electrical conductivity (mmhos/cm). The electrical conductivity (EC) value of the nursery soil ranged between 0.359 to 0.35 mmhos/cm. These values are very low to cause an osmotic stress to the seedling. The cation exchange capacity (CEC) of a given soil is defined as the sum total of exchangeable cations that a soil can absorb (Brady, 1984 p. 175) and is measured in milliequivalent (meq) per lOOg of soil. In the laboratory, the CEC was determined at pH 7 using ammonium acetate as extractant. The CEC of a soil is influenced by its texture, organic matter content, pH and the amount and kind of clay minerals it contains. As the pH increases, the CEC increases (Brady, 1984 p. 197). This is true for the results obtained in water solution and the corresponding cation exchange capacity. The 0, 3 and 12 months old pot-soils with 5.76, 5.96 and 6.23 pH value have a CEC of 23.96, 26.45 and 47.82 meq/lOOg respectively. From the results on Table 5, the organic matter content seems to have no influence on the CEC of the

51 soil. Despite of low organic matter content in the 3 month and one years old soil, the CEC of these soils were higher than the fresh soil mixture. The variation in CEC to the largest extent is caused probably not due to the amount, but the type of clay minerals that the soil contains. In spite of their high clay content, the fresh and 3 month old pot-soils were observed to have lower CEC The nutrient requirement of E globulus is similar to those of temperate hardwood spp. (e.g. Betula spp.) (Ericsson, 1994) and an evalution on nutrient level of Germama nursery, where E.globulus is raised, was made by comparing to that suggested for the intermountain nurseries in America (Table 5). The values for macronutrients at Germama nursery were found to be higher than the recommended levels for raising hardwood seedlings at intermountain nurseries. The calcite (CaC03) content at the nursery of the Addis Ababa fuelwood project was also higher than the latter. E. globulus is known as a calcifuges plant type. It does not grow well in calcareous soils (Kirkpatrick, 1975). Therefore, it is important to know the tolerable limit of CaC03 for E. globulus, in order to reduce the risk of plant growth retardation or any kind of disease (e.g. a chlorosis, i.e. a disease caused by iron deficiency) at the nursery. In soils containing CaC03, exchangeable Ca2+ is too high (Hendershot etal., 1993) and this has led to low CEC of all soils of different age at Germama nursery when it is compared to the sum total of exchangeable cations that they can adsorb (Table 5). This is due to the dissolution of CaC03 which results in an excess of Ca2+ being extracted by NH4+ and decrease in the amount of NH4+ retained due to competition between Ca2+ and NH4+ during equilibration in saturating step (Hendershot et al., 1993). For accurate determination of CEC of soils containing CaC03, use of other extractants than the ammonium acetate is recommended.

Ecological requirements of Eucalyptus globulus Labill. Plantations of globulus Labill. subsp. globulus in Ethiopia are artificially regenerated forests. They are raised in wide range of climate and altitude. They grow on regions lying above 2000 m.a.s.l. (Pohjonen, 1989). This is an altitudinal range where commercially valuable indigenous trees such as , Hagenia abyssinca and gracilior are occuring. Most of the time, forests of E. globulus are moncultures. But, sometimes few remnant indigenous trees are observed inside them. Good examples are the forest in valleys that are intercepting the Entoto mountain around Addis Ababa and the Eucalyptus forest around Debre Sina, a small town about 200 kms north east of the country ’s Capital. The few indigenous trees that are rarely found mixed with globulus stands are: Juniperousprocera and Hagenia abyssinca. These indigenous trees are self established plants. Originally, Eucalyptus globulus ssp. globulus labill. is a subtropical to midlatitude (regions between 25° to 55°S) tree type. It grows in Cfb climate of the Koppen- Geiger classification on elevations lower than where it now cultivated in Ethiopia, and on a wide edaphic range (Kirkpatrick, 1975). It occurs from alkaline to acidic soils, coarse to medium coarse textured top soils that are originated predominantly from granite and granodiorite (Turnbull and Pryor, 1978). However, on calcareous soils, globulus performs very poor (Kirkpatrick, 1975). E. globulus in Ethiopia is cultivated on the ecotope of Podocarpus gracilior,

52 Juniperous procera, and Hagenia abyssinca , and on elevations beyond the tree up­ per limit which is generally located between 3200 and 3500 m.a.s.l. (Uhlig, 1988). The three indigenous spp. occur in montan to altimontan vegetation belt of the country and grow on soil which is originated from volcanic parent material, mainly from basalt of the Tertiary Trappean Lava Formation (Weinert and Mazurek, 1984), and in Cwb, Cfb and Cwc climates of the Koppen-Geiger classification. On the highlands, globulus grows also on well drained coarse textured soils ranging from sandy to silty loam soils with good chemical and physical properties. The vegetational association and the nutrient cycle in E. globulus stand in Ethiopia are fields that are not well investigated. However, a moss plant and some grass types are observed covering the forest floor. Studying the role of the ground vegeta­ tion and their interaction with Eucalyptus tree on the highlands may bring additional information to understand the plantation ecosystem. These information may also contribute to improved plantation management in the country. On high altitudes, frost is common in Ethiopia (EMA, 1988). Regions that are lying > 2000 m.a.s.l. experience a sever frost up to -10°C (Daniel, 1988; Sakai and Larcher, 1987 p. 4 Fig. 1.1). Though Eucalyptus globulus is a frost resistance spe­ cies, the mature trees cannot survive in temperature below -8°C and particularly, the seedlings are vulnerable to frost (Kirkpatrick, 1975). Therefore, planting seedlings of globulus on higher altitudes may require a special silvicultural practice in order to increase the survival rate and thus avoid a risk of project failure. E. globulus grows on soils of widely varying fertility (Kirkpatrick, 1975). None ­ theless, if planting Eucalyptus is aiming at economical gain, it should be raised in optimum conditions of soil and climate. It must be cultivated on deep soils of mode ­ rate fertility and good structure (FAO, 1979 p. 339). For an optimum to maximum growth rate, seedling of E. globulus requires a supply of nutrients at the following proportions, N = 100, K = 64, P = 13, Ca = 9, Mg = 9, S = 8 (Ericsson, 1994).

Growth and yield of Eucalyptus globulus Labill. subsp. globulus (Blue Gum)

Eucalyptus globulus labill. is a tree species which is cultivated for energy and construction purpose on sites of different climate, soil etc. in Ethiopia. Within dif ­ ferent growing site, E. globulus exhibits variation in growth and yield (Fig. 21). For the variation two things are responsible: the stand density, i.e. number of trees per ha. and the productive capacity of the growing site which is dependent upon environmental factors that directly (e.g. nutrient availability) or indirectly (e.g. topography) influence the survival and growth of planted blue gum seedlings. Therefore, before describing and predicting the growth of a tree species, it is important to know the density of the stand and the yield potential of the growing site where the

53 stand is established. In Ethiopia growth prediction on E. globulus is made using yield table or yield model. For the country both tools were developed by Pukkala and Pohjonen (1989) with the support obtained from the Unite Nations Sudano Sahalian Officce (UNSO). These prediction tools were established based on site productivity potential and the assumption that the initial and final stand density are about 2000 and 800 trees per ha respectively. The productive capacity or productivity potential of a growing site for a certain species is known as site quality. Site quality may be evaluated directly using vegetative characteristic such as plant indicators, plant sociological features and tree parameters (e.g., volume, basal area, mean height top or dominant height) or indirectly from environmental factors. However, because it is difficult to quantify the effect of site factors and no study is carried out on plant indicators or plant sociological feature related to site quality in the country, the tree parameters are preferred and used for evaluating the productivity potential of a growing site. They are simple to measure and also reflect the effect of the site quality. Among other tree measurements, the height of dominant and coodominant trees, at a given age, is the most commonly used site quality measurement in timber management. This is not only because it reflects the effect of site quality, but also because the dominant stand height is insensitive to stand density differences and wide range of thinning compared to other parameters like volume, basal area and mean height. The dominant height attained at a given age is called site index and growth poten ­ tial variations between different sites can be demonstrated by site index curves which can be further classified in an ascending order into site classes starting from the highest site index to the smallest one or the upper site index curve to the lower one in a height-age graph (Fig. 21a). Eucalyptus globulus is a fast growing tree species. Annually it grows by 20-40 m3/ha until it reaches turning point (TP) (Fig. 21). For example, at a reference age of 20 years, it reaches up to a height of 44, 40, 33 and 25 meter and gives a yield of stem wood volume up to 890, 695,470 and 245 m3 ha ' in site class I, II, III and IV respectively. The mean annual increment (MAI) culminates, when the current annual increment (CAI) is equal to the mean annual increment. The maximum MAI is obtained at the culmination point where the curves of the CAI and MAI cross each other (Fig. 21e, f, i,j). The culmination point is also a theoretical harvesting age of stand (THA). At this age trees are felled and replanting of the site would be started. The knowledge of THA is important because it helps forest mangers to avoid the yield loss which may be caused due to crop harvest earlier or later than the MAI culmination age. For E. globulus, the MAI culmination age in all site classes is reached between the age of 17 to 19 (Fig. 21e,f, i&j). The current annual increment (CAI) culminates at a time when the S-shaped curve of the total stem volume reaches its turning point (TP), i.e. between the age of 10 to 12 years (Fig. 21 c, d g & h). After a turning point, the slope of the curve, i.e. the increment, diminishes. However, figure 21e, f, i & j depict that the volume growth culminates in best sites earlier, when it is compared to the poorest sites.

54 12 : I 10 i h ! E IV : 8 6

= • THA TP ------1 2 ...V-'" 0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 I 3 9 11 13 15 17 19 21 23 25 27 29 Age Age

•• -MAli CAI ! I

CAImax

13 15 17 19 21 23 25 27 29

Figure 21. Ten graphs on growth ofE.globulus labil. (blue gum) constracted based on yield table developed by Pukkala and Pohjonen (1989).

55 Eucalyptus globulus and Environmental Concern

Waterand nutrient use E. globulus is the most widely planted tree species on Ethiopian highlands. However, since 1900 its popularity among foresters, experts and extension agents of the Minis ­ try of Agriculture in the country is decreasing. For example, in 1913 the then Minis ­ try of Agriculture gave order for the uproot of the planted seedlings in the Capital because of the allegation that Eucalyptus dries up water supplies (Ellis, 1992). Lat­ ter, Hofmann (1989) wrote the irrelevance of Eucalyptus in the country ’s afforestation program because he believed that the tree depletes the soil moisture. Tewolde Ber- hane (1991) also mentioned similarly that water supplies were dried up due to Eu­ calyptus trees that are planted near them. These are fears that have arisen probably from earlier documentation on use of Eucalyptus to drain marshes near Rome in the 18th or 19th century (Ghosh et al., 1978) and in Uganda (see Nshubemuki and Somi, 1979) and in Israel (Saltiel, 1965). In present century the species is also used deliberately to lower water tables in that are experiencing salinity problems (Calder, 1986). The question is not how these fears develop, but does Eucalyptus really dry up water supplies or environments in Ethiopia? To understand these things, knowledge of the water use characteristics of Eucalyptus, in terms of transpiration and interception loss is important. Transpiration is a physiological process in which water is lost through the stomatal cavity. Whereas interception loss is a physical process in which water retained by the canopy of a vegetation is lost by evapora­ tion. Transpiration is affected by plant and external factors (Jarvia and Stewart, 1978). The external factors are the vapour deficit of the air, temperature, radiation and wind speed. The plant factor is the stomatal conductance of the leaves. The intensity of water loss through transpiration is also dependent on availability of soil water for the root, and the structural characteristics of the canopy which influences the boundary layer conductance beside to the wind speed. According Calder (1986) transpiration rates from Eucalyptus spp. is similar to other tree spp. Therefore, the speculation that Eucalyptus spp. consumes much water than other tree spp. is far from the truth. The size of the loss by interception depends upon canopy water retaining capa­ city, density of the plant cover and upon the metreological conditions prevailing during and after precipitation. Because Eucalyptus spp have smaller leaf area index comparing to other species (Andreson, 1981), the capacity their canopy to retain rain water is relatively low (Calder, 1986). Therefore, the intercepted water loss from Eucalyptus is relatively low than other tree species.However, because meteorological parameters are varying from one locality to another, extrapolating results on evapotranspiration rate of one vegetation cover from one locality and draw a conclusion for another is misleading. Therefore, it is important to conduct a research to determine the comparative water use and the mechanisms which control the use of water in different agro-climate of the country and soil from main vegeta­ tion types; these must include the commonly planted Eucalyptus and other tree species, naturally and degraded forests and agricultural crops.

56 In Ethiopia, Eucalyptus is also blamed for its high nutrient consumption. But, studies from India show that Eucalyptus is a low nutrient demanding species (Bargali and Singh, 1991). The low nutrient demand nature of Eucalyptus is advantageous and disadvantageous. If the present afforestation program are looked from land use perspective, planting Eucalyptus has an advantage. Because it grows on nutrient poor and degraded sites, the unproductive and waste lands of the country can be transfered to productive land by planting Eucalyptus. But, if things are considered from the side of nutrient cycle particularly, in moist and nutrient reach sites, plan ­ ting Eucalyptus might be disadvantageous. Because of its inefficient and low nutrient uptake capacity, loss of nutrients might occur from the plantation site through leaching.

Eucalyptus and soil erosion In Ethiopia, there is a dispute between people of different opinion on Eucalyptus. Some are against Eucalyptus planting in a belief that it suppresses the ground vege­ tation and enhances soil erosion (Fig. 22). Others believe that Eucalyptus is equally harmful like other indigenous and exotic fast growing species and thus recommend its cultivation further. For example, Fiedler and Gebeyehu (1988) reported that people on the Ethiopian highlands are planting Eucalyptus for soil conservation purpose and here will be tried to investigate, if Eucalyptus is an optimum tree species to conserve soils of the country. The investigations are based on literature studies . In Poore and Fries (1985), it is documented that less litter production and the absence of herbaceous vegetation under the canopy of the stand are causes for soil erosion on sites that are planted by Eucalyptus. However, de Moral and Muller (1969) showed that light, moisture and minerals under canopy of Eucalyptus are adequate to support other growth. They concluded that the lack of understory vege­ tation was due to allelopatic substances, not competition (del Moral and Muller 1969; A1 Mousawi and ALNaib, 1976; Kohli etal, 1987). The effect of the allelopatic chemicals is a function of their concentration which is dependent on the rainfall and moisture regimes, and decay of the source material (May and Ash, 1990). For example, del Moral and Muller (1970) observed concentration decline of allelochemicals in wet than dry seasons and May and Ash (1990) also noted reduction of allelopatic effects due to decay. This implies that in wet and warmer sites with high microbial activity, sufficient runoff and deep drainage, allelopatic suppression of understory vegetation is minimal. On highlands of Ethiopia, Eucalyptus stands are established on steeper hills and mountains. The Addis Ababa fuelwood plantation, the Entoto Eucalyptus forest, the Eucalyptus stand surrounding towns such as Dessie, Debre Berhane and Debre Sina are few examples among many. Because of extreme surface runoff and high rate of deep drainage on steep slopes, the sites are drier than sites on the foot of a hill or a mountain. Because of the dryness, trees grow slow and thus produce less litter. Under dry condition, the concentration of the allelopatic substance increases and thus suppresses the growth of underground vegetation. Less litter production and insufficient undersotry cover, exposes the soil to erosion agents. In addition, the collection of tree litters for household energy purpose on highlands make the situation sever.

57 Figure 22 Soil Erosion under the stand of E. globulus at Entoto, north east of Addis Ababa (slope > 70 %). (Photo taken by A. Mehari).

Leaves of Eucalyptus stands modify the drop-size of rainfall and can contribute to increased soil erosion (Calder el al., 1993). This happens because the size and mass of the drops are increased before they drip from the canopy. An increase in mass means an increase in kinetic energy which is also an increase in force that causes the detachment of soil particles from the uncovered soil surface of a forest stand. The potential for splash erosion under Eucalyptus forest depends also on tree height (Calder el al., 1993). The higher the tree is, the force exerted by a drop against the soil surface will be grater. The use of tree litter as fuel and the suppression of understory plants due to allelopatic chemicals and the drop-size modification by Eucalyptus lead to sever erosion on plantation site particularly, those established on drier sites. Particles that are detached due to splash erosion are transported by surface runoff and finally these small particles clog surface micropores and macropores leading to an impermeable crust which reduces infiltration and enhances the production of sur­ face runoff (Calder el al., 1993). The impermeable soil surface impedes root growth of the herbaceous plants and remains bare. This may also negatively affect the natu ­ ral regeneration of Eucalyptus from its seeds.

58 Summary and conclusion

This study reviews reasons for the establishment of fuelwood plantation and use of fuelwood in Ethiopia. The present and future status of fire wood and the environmental degradation and related consequences are also reviewed. On the highlands, fuelwood is the basic necessity. It is an energy source for 90% of the households in the region. However, the gap between the demand (consumption need) and supply is widening at the rate of 200% by year 2010. To bridge this gap, the supply of fire wood must be increased from plantations of fast growing species, for example, Eucalyptus globulus Labill. subsp. globulus which is fast growing tree species and widely planted on the Ethiopian highlands. But, because of the allegations that Eucalyptus harms the growing site, suppresses the ground vegetation and depletes water supply and soils of nutrient, it popularity is declining and the number of the antagonists against Eucalyptus cultivation are increasing. The other objective of this study is to investigate, if these criticism on Eucalyptus are true or not and draw a conclusion on its future service in the county ’s tree growing program. For this purpose a literature study was carried out and no prove have been found to agree with the antagonists, those against Eucalyptus planting. However, Eucalyptus can be like a knife in the hand of a murderer which take a life, if it is planted at wrong sites and cultivated under poor management. Therefore, with improved silvicultural management and proper site selection, Eucalyptus will not be disastrous to the environment and should continue to serve the future tree growing program on the highlands. Growing monoculture plantation of Eucalyptus must be reduced on drier, steeper, poorly drained sites and regions with narrow annual rainfall distribution in Ethiopia. On the highlands, if the objective is to conserve the soil on steeper moun ­ tains, establishing a mixed polyculture plantation from Eucalyptus and other indigenous species is advantageous. As Eucalyptus is fast growing, it provides the conserver with wood for fuel and construction, whereas the slow growing indigenous tree conserve the soil. Besides, owing to its coppicing ability, Eucalyptus establish itself very fast after harvest. Due to this attribute of the species, costs in seedling production and planting would be reduced, if forest regeneration is planned on sites of harvested mature stand. On the other hand, while the indigenous is left untouched, it would get an opportunity to grow and occupy the site and thus can the lost indigenous forest of the country be returned. Because of their influence on future performance of the outplanted seedlings, emphasis is also given to the traditional nursery practice on the highlands. Nursery soil amendment with organic manure and off-site soils is one of the traditional nursery practice on Ethiopian highlands. Based on literature and results of the laboratory analysis on soils from the nursery of Addis Ababa fuel wood project, the possible risks of failure accompanied with nursery soil amendments are discussed in this study. Nevertheless, these study is no a conclusive one. Further research is necessary on the nursery soil amendments, in order to improve the nursery practice of the country and reduce the consequences on seedling performance inside the nursery and latter outside on the field.

59 References

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67 Annex 1

Year Populaion( ‘000) Growth rate(%) 1980 37684.7" 2.6- 1990 49188.94 2.8 a 2000 65339.63 2.9" 2010 86969 2.9" For Sources see Tabel 2.

68 1988 hogskarm. {Shelterwoodregeneration of spruce 23. Simak, M. & Bergsten, B.: Databas over skogs- forests on productive peatlands). frolitteratur publicerad i Sverige fram till 1975. {Data base on forest seed literaturepublished in 33. Orlander, G., Gemmel, P. & Wilhelmsson, Swedenupto 1975). C.: Markberedningsmetodens, planterings- djupets och planteringspunktens betydelse for 24. Pehap, A., Henriksson, G. & Sahlen, K.: planters etablering i ettomrade med l&g humiditet Respiration ofgerminating spruce seeds: Further i sddra Sverige. {Effects of scarification, planting investigations and measurements with the depthandplantingspotonseedlingestablishment Warburg direct method. in alow humidity area in southern Sweden).

1989 1992 25. Jeansson, E., Bergman, F., Elfving, B., Falck, 34. Hanell, B : Skogsfornyelse pa hogproduktiva J. & Lundqvist, L.: Natural regeneration of pine torvmarker - plantering av gran pakalhygge och and spruce. - Proposal for a research program. under skarm trad .{Forest renewal on productive Faculty of Forestry. Swedish University of peatlands: Planting ofNorway spruce onclearcuts Agricultural Sciences. and inshelterwoods).

1990 35. Silvicultural alternatives. Proceedings from 26. Orlander, G., Hallsby, G. & Sundkvist, H.: an intemordic workshop June22 -251992. Editor: Overlevnad och tillvaxthos tall (Pmus sylvestris) Mats Hagner. och gran (Piceaabies ) samt naringsforhallanden 23 ar efter plantering pa helplojd resp brand 1993 tallhedsmark. 36. Andersson, B.: Lovtradens inverkan pa sma tallars (Pinus sylvestris) overlevnad, hojd och 27. Gemmel, P. & Nilsson, U.: Competition dimeter. (The influence ofbroad-leaved trees on between originally planted and beeted seedlings survival, height anddiameter of.small Scots pine in stands ofNorway spruce and Scots pine. (Pinus sylvestris L.) trees).

28. Lundqvist, L.: Bladningsytan i Gammels-torp - 1994 en demonstrationsyta skott med stamvis blad- 37. Valinger, E. & Lundqvist, L.: Reducing wind ning. {The selection plot in Gammelstorp - a and snow induces damage in forestry. permanent plot with single tree selection). 1995 29. Martinsson, O.: Den ryska larkens hojd- 38. Putenikhin, V.P. & Martinsson,O. Present utveckling och volymproduktion i norra Sverige. distribution of Larix sukaczewii Dyl. in Russia {Height growth andvolume production of Russ­ ian larch (Larix sukaczewii Dyl.) in northern 39. Larch genetics and breeding. Research findings Sweden). and ecological-silvicultural demands. Proceedings. IUFRO WORKING PARTY S2.02-07. July 30. Fries, C.: Utveckling hos bestandsforyngrad 31 -August 4,1995. Remningstorp and Siljans- gran och kompletteringsplanterade granar och fors. tallar i ett karvt klimatlage. {Developement of advance growth of Norway spruce and 40. Petursson, J.G. Direct seeding of Sitka spruce supplementary planted spruce and Scots pine in {Picea sitchensis (Bong.) Carr.), lodgepole pine a harsch climate). {Pinus contorta Dougl. v. contorta) and Siberian larch (Larix sibirica Ledeb.), on scarified seed 31. Sugg, A.: Seedling establishment results from a spots in southern , using various methods. site preparation study in southern Sweden: The first four years survival and growht of Scots pine {Pinus sylvestris L.) and Norway spruce {Picea abies (L.) Karst.)

1991 32. Hanell,B.: F omyelse av gransumpskog pa bor- digatorvmarkergenomnaturligforyngringunder DISTRIBUTION: Pris: 200:- Sveriges lantbruksuniversitet Institutionen for skogsskotsel 901 83 UMEA, Sweden Tel: 090-16 62 74 ISSN 0348-8969 Fax:090-16 76 69 ISRN SLU-SSKTL-R—41—SE