FORESTRY COMMISSION BULLETIN No. 34 CHALK DOWNLAND AFFORESTATION By R. F. WOOD, B.A., B.Sc. and M. NIMMO FORESTRY COMMISSION LONDON: HER MAJESTY’S STATIONERY OFFICE 1EN SHILLINGS NET Forestry Commission ARCHIVE FORESTRY COMMISSION BULLETIN No. 34 CHALK DOWNLAND AFFORESTATION By R. F. WOOD, B.A., B.SC., AND M. NIMMO FORESTRY COMMISSION LONDON: HER MAJESTY’S STATIONERY OFFICE 1 9 6 2 FOREWORD The substantial areas of chalk downs and wolds ments into the best methods to use, and the most which are found in the south and east of England suitable kinds of trees to plant, on chalk downs and include many tracks of land well suited to afforesta­ wolds undergoing afforestation for the first time. tion. But the peculiar characters of the bedrock and its superficial soils present many problems, which These trials, most of which are centred on Friston have occupied the attention of the Forestry Com­ Forest, near Eastbourne in Sussex, and Queen mission’s staff since it made its first acquisition of a Elizabeth Forest near Petersfield in Hampshire, have chalk downland area, at Friston Forest in Sussex, been continued ever since, and the main purpose of in 1927. The Commission has now (1961) over 30 this Bulletin is to present the findings to date. It also forests situated wholly or partly on chalk formations, includes an account of the characteristics of the scattered over the southern and eastern counties chalk country, a historical review of planting practice from Dorset to Kent and north to Yorkshire, while since 1808, and a discussion of the future prospects. private estate owners are also engaged in the planting and management of extensive stretches of chalk It is written by Mr. R. F. Wood and Mr. M. Nimmo, down woodland. two Forest Officers in the Commission’s Research Branch, who have had many years experience of In 1927 the Commission began a series of experi­ the problems and methods discussed. FORESTRY COMMISSION, 25, Savile Row, London, W.l. August, 1961. CONTENTS Page CHAPTER 1. INTRODUCTORY 1 CHAPTER 6. PRO SPECTS O F CHALK CHAPTER 2. SPECIAL CHARACTERS OF DOWNLAND PLANTATIONS .. 36 CHALK DOWNLANDS ............................ 4 APPENDIX. GENERAL DESCRIPTION CHAPTER 3. HISTORICAL NOTES .. 11 AND SPECIAL FEATURES OF THE CHAPTER 4. PLANTING TECHNIQUES PRINCIPAL EXPERIMENTAL AREAS .. 41 WITH SPECIAL REFERENCE TO BEECH ........................................................................ 14 BIBLIOGRAPHY .. 45 CHAPTER 5. USES OF PIONEERS AND NURSES FOR BEECH, AND PHOTOGRAPHS ALTERNATIVE CROP SPECIES.. .. 23 Following pages .. .. .. 10 and 26 NOTES (1) Throughout this text, capitals as in “ Chalk”, are used to denote a specific geological for­ mation, and small initial letters, as in “chalk”, a type of soil or rock. (2) All the photographs are drawn from the Commission’s own collection. Chapter 1 INTRODUCTORY The area represented by the Chalk on a ‘solid’ makes it necessary to be very careful in defining the geological map is some 5,000 square miles, or about site. one tenth of the land surface of England. (Fig. 1). The Chalk is not a formation of the first impor­ Chalk does not occur in Wales or Scotland, except tance to foresters. Where the topography is favour­ for a tiny outcrop in the Isle of Mull. able and the soils deep enough, there is much Other calcareous rocks outcrop over a somewhat excellent arable land. The downs themselves are larger area, but though certain of the limestones give traditionally open grazing, and it seems likely that rise to soils similar to those derived from the Chalk, the greater part will remain under agriculture. There it is the latter formation which provides the best and has however always been a considerable area of most extensive examples of soils dominated or woodland on the Chalk, ranging from the extensive strongly influenced by calcareous materials. Chiltern woodlands to the small remnants of natural forest to be found on the downland valley slopes. Salisbury (1952) in comparing the chalk and lime­ In addition, plantations have been made for many stone habitats, observes that limestones (while ex­ reasons, for shelter, as game preserves, for profit, and tremely variable in this respect) generally contain a sometimes purely for ornament. Whatever the far greater proportion of insoluble residues than motive, a wood is a wood, and the beauties of does the Chalk, which is usually 95% or more mature chalk beechwoods are as frequently extolled calcium carbonate. Hence limestone-derived soils as fresh plantations on open downlands are con­ are usually deeper and moister than those derived demned (and often by the same critics). from the Chalk, and they are also much more The subject matter of this report is the afforesta­ variable in physical texture. Salisbury (ibid) also tion of chalk downland. Most of our experiments, comments on the distribution of the chalk and lime­ and all our experimental results, have been obtained stone formations. The various limestone formations on southern chalk sites, but some generality may be are to be found to the west and north of the Chalk, claimed, since the shallower chalk soils present and thus generally lie in somewhat moister and/or similar problems whenever they are encountered. cooler climates. He notes that ‘a line drawn from the Wash to the Bristol Channel. has been shown It is somewhat difficult to draw a line which will to mark roughly the northern limit of many southern separate sites which are ‘specially’ chalk from sites species even though not associated with calcareous which are on the Chalk, but reflect chalk character­ soils’, and further, ‘it may be said that in this region istics and problems to a much lesser degree. Our soil conditions and climate combine to reinforce concern is plainly with soils which are shallow their respective influence’. enough for the chalk to have an early and significant influence. This condition is not of course confined The Chalk outcrops are well known features of to the Downs or Wolds, but it is more common here the south and east of England, forming the North than in the chalk country of lesser relief. Important and South Downs, the Chiltern Hills and the problems of calcareous subsoils are also to be met Lincolnshire and Yorkshire Wolds. In addition the with in East Anglia on the soils delivered from the Chalk underlies considerable areas of less elevated Chalky Boulder Tills, but these are less pure and or more gently rolling terrain, such as Salisbury normally have greater depths of lime-free material Plain or the Breckland of Norfolk and Suffolk. As at the surface. A number of useful analogies can be with other rocks, by no means all of the outcrop is drawn between the Breckland, where extensive represented by soils derived directly from the Chalk; afforestation has been carried out in the Thetford deposits of one sort or another varying greatly in area, and the Downlands, but the topography and depth cover much of the Chalk, and at the extreme microclimate of the Breckland are sufficiently the chalk may have little or no influence on con­ distinct to make the afforestation of this type of ditions at the surface. It is of course this fact which country a subject in itself. 1 CHALK DOWNLAND AFFORESTATION Key to Numbers and Letters on Mop Fo rests Climatic Stations 1.Wolds A.Bridlington 2.Burwel B.Harpenden 3.T hetfo rd C.Penn 4.Andover D.Marlborough 5.Crawley E. Dorchester 6.Queen Elizabeth F .R e ig a te 7.Friston G .Se a fo rd Q.Brighstone H.Ashford 9.Blandford Fig. 1. Distribution of the Chalk in England. INTRODUCTORY 3 The soils we are concerned with are special in that lands have all been the subjects of much study, and much of the root growth of trees growing on them reference will be made to a number of such basic lies in a highly calcareous medium, and it must be studies without any pretence at adding to the funda­ emphasised at the outset that there can be no greater mental knowledge of this environment. There is error than to assume that, because the underlying probably no site on which it is more important for rock happens to be chalk, the trees can be said to be the forester to pay close attention to the ecological growing in a chalk soil. Such assumptions lie behind aspects of his work, and it is fortunate that the down­ a number of unfortunate records of species ‘doing well lands have attracted the interest of some very able on chalk’, which have often led to disappointing ecologists. results when the species really have been planted on The material for this report has been collected it. Later investigations may reveal that the trees from several sources; the Forestry Commission’s concerned were growing happily on some two or own experimental work at Queen Elizabeth and more feet of Clay-with-flints. It is necessary to be Friston forests, mainly undertaken between 1927 and specially careful in interpreting the behaviour of 1939; the Forestry Commission’s general experiences young trees, since it is not only the depth of rootable at these and other chalk areas (Troup (1954) has soil over the chalk which is of importance, but the already covered much of this ground in a very con­ presence or absence of free lime in the top few cise account); published experiences by private inches. This is of special significance for most woodland owners; and surveys of chalk woodlands conifers, since the nutritional disorder known as undertaken in connection with the publication Studies lime-induced chlorosis may be delayed by the on British Beechwoods (Brown 1953). Mr. D. Fourt presence of quite small amounts of lime-free has been of particular assistance on all questions material.