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WOODLAND VARIATION, NOW AND IN THE FUTURE: EVERY SITE IS DIFFERENT REITH KIRBY Variations in trees and woods contribute to our sense of place, to local distinctiveness; these variations also mean that the plants and animals found in woods differ from one to the next. Every wood is different but some are more alike than others. Classification provides a way of grouping woods, stands or plant lists from quadrats according to similarities in their structure, composition, history or current treatment (Table 1). Woods may end up in different groups depending on what type of Classification is used, which in turn depends on our objectives in carrying out the Classification exercise. There is no Single 'right' way.

Table 1. Examples of different types of woodland Classification a. By tree and shrub composition • Coppice types described by Rackham (1980) based on underwood composition.

• Stand Types (Peterken 1993) based on tree and shrub layer, plus some soil characteristics.

• Forestry Commission census data: woods classified by main tree crop species (Forestry Commission 1983a, b). b. By ground flora as well as woody Vegetation • Merlewood Plot Type Classification (Bunce 1982).

• The National Vegetation Classification (Rodwell 1991). c. By structure • Classifying woods according to whether they are coppice (± Standards), high forest, wood pastures is used both in Forestry Commission Censuses and in the selection of Sites of Special Scientific Interest. d. Historical breakdown of woods into ancient and recent sites and into seminatural stands or plantations as in the Ancient Woodland Inventories (Spencer & Kirby 1992).

Classification helps us in describing woodland and in communicating our descriptions of stands to others. It helps to put sites into context, to help us in their evaluation, whether from a landscape, timber production or nature conservation perspective. Finally classifications may help in the prediction of where particular species or groups of species may occur or how woods may respond to particular treatments. The results can then be used, for example, as a guide to what species to use in new planting schemes.

My aim in this paper is to show how Suffolk's woodland cover compares with that in England as a whole using different types of Classification and how understanding and describing the Variation in these woods contribute to the achievement of nature conservation aims.

Total woodland cover and extent of ancient woodland The total area of woodland in Suffolk was estimated to be 22,211 ha in the early 1980's (Table 2) (Forestry Commission, 1983a, b). The percentage cover

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Table 2. Summary statistics for Suffolk woodland (Forestry Commission 1983a, b; Spencer & Thomas 1992; Spencer & Kirby 1992; Thomas 1994) Suffolk England Feature 28211 947,688 Total woodland cover (ha) 7.4% 7.2% Total woodland % land surface 51% 58% Broadleaves as % of total woodland <1% 4% Coppice and coppice with Standards 4287 339,673 Ancient woodland cover (ha) 1.1% 2.6% Ancient woodland as % land surface 31% 41% % of ancient woodland replanted 12% 7% % of 1930's woodland cleared since 1504 49,137 Ancient woodland in SSSIs (ha) 35% 14% SSSI ancient woods as % of total of woodland at 7.4% is almost exactly the same as the national average for England; there is 51% cover of broadleaves, mainly oak, ash and birch. As in most of England outside the south-east very little of the woodland was still actively coppiced although that would have been the commonest form of treatment 200 years ago. The next census has just begun in England. It will probably not show a dramatic change in Suffolk's woodland cover overall, but the amount of coppice should have gone up as a result of the efforts of Suffolk County Council, the Wildlife Trust and others to promote a return to this traditional form of management. The history of Suffolk's woodland is one of the best described in the country (Rackham 1980). Based on this work and other recent surveys there are about 4,287 ha of ancient woodland (ie that arising before 1600AD) of which 31% has been replanted, largely with conifers, but in some cases with broadleaved trees. This is less than elsewhere in the country but on the other hand clearance particularly for agriculture has been higher over the last 60 years. The total cover of ancient woodland is below average.

Ancient woodland is not evenly distributed across the country. Suffolk has rather compact isolated woods, a quite distinct pattern when compared to the extensive blocks of the south-east or the elongated ancient woods found along valley sides and rivers in the uplands (Figure 1). Within the county ancient woodland is virtually absent from Breckland in the north-west and from large parts of the coastal belt. In contrast it is widely distributed through much of the central part of the county (Figure 2).

The areas where ancient woodland in Suffolk is least have been those where the greatest afforestation this Century has occurred, for example around Mildenhall or at Rendlesham. There are also probably about 3,000 ha of broadleaved woodland that has grown up naturally in odd corners, where land has been abandoned over the last few hundred years. This can be important in adding variety to intensive farmland but is also a conservation problem where it consists of young birch on former heathland.

Thus classifying Suffolk woods according to their origin, treatment and size brings out some preliminary ideas as to their likely conservation value and also some of the issues that must be faced in their management. These include, for example, the abandonment (at least until recently) of traditional management Trans. Suffolk Nat. Soc. 32 (1996)

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c ?

jy

(a)

o

250

(b)

200 2

150 100 50 45 ha

610 ha

1120 ha

2150 ha

51100 ha

> 100 ha

Size class

/f (c)

Figure 1: Size distribution for ancient woods in Suffolk (a) and woodland patterns for typical 4 x 4 km squares in (b) Suffolk, (c) Cumbria and (d) Kent.

(where should it be restored?); the past losses of semi-natural stands to plantations (can these be reversed?); the isolation of many ancient woods (do we need to try to create links or stepping stone patches between them?); where do we want to keep or encourage new woods and where would it be better to clear them to restore the former Vegetation.

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Figure 2: Ancient woodland distribution in the Natural Areas of Suffolk.

Ancient Woodland Distribution hectares o 0 to 5 (12012) â&#x20AC;˘ 5 to 20 (11875) e 20 to 50 (3256) â&#x20AC;˘ 50 to 100 (968) % 100 to 800 (465)

NA Name Fenland Broadland Suffolk C&H E A Piain Breckland EA Southern Chalk

AW area 0 5 1084 2929 257 0

% Cover 0 0.1 1.2 1.3 0.6 0

Variations in woodland composition Plantations are not the same across the country - pines are much commoner in East Anglia than in western Britain where Sitka spruce predominates. However the composition of plantations tends to be quite uniform and reflect only the coarsest levels of local Variation in soil and climate compared to the patterns that are found in ancient semi-natural woods. Rackham (1980) describes these patterns in terms of his Classification based on the composition of the underwood. For the purposes of comparing Suffolk woods with those elsewhere in Britain, however, it is easier to use the Stand Type system of Peterken (1981) and the more recently adopted National Vegetation Classification (Rodwell, 1991).

Both these classifications highlight the pronounced trend in British woodland Vegetation from the south-east to the north-west, the difference between the

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Table 3. Distribution of woodland types by broad zones and their frequency in Suffolk, based on distributions recorded in Peterken (1993) and Rodwell (1991). ** = common * = scarce Type Suffolk 'South-east' 'Other lowland' 'Upland' 'Pine' Stand group * * ** ** 1. Wych elm woods ** ** * 2. Ash-maple woods ** ** ** * * 3. Ash-hazel woods * * * 4. Lime-ash woods * * * * 5. Lime-oak woods * ** ** 6. Lowland oakwood ** * Upland oakwood ** ** * ** * 7. Alderwoods * ** 8. Beechwoods ** ** 9. Hornbeam woods ** ** ** * 10. Suckering elms ** 11. Pinewoods * * * ** ** 12. Birchwoods Type NVC W1.

W2.

W3.

W4.

W5.

W6.

W7.

W8.

W9.

W10.

Wll. W12.

W14.

W15.

W16.

W17.

W18.

Suffolk 'South-east' 'Other lowland' 'Upland' 'Pint Community Sallow/bedstraw Sallow/reed Sallow/sedge Birch/Sphagnum Alder/sedge Alder/nettle Alder/pimpernel Ash/mercury Ash/rowan Oak/bramble Oak/grasses Beech/mercury Beech/bramble Beech/hairgrass Oak/hairgrass Oak/mosses Pinewoods

*

*

*

*

*

*

*

*

**

*

*

*

*

*

**

**

*

9

*

*

**

**

**

**

*

**

**

**

**

*

*

*

**

*

*

*

* **

*

**

*

**

*

**

**

*

**

* **

lowland and upland parts of the country, the Continental versus the Atlantic influences. As expected the types recorded from Suffolk in both systems are those from the south-east end of the spectrum (Table 3). Stand Types with lime and hornbeam are represented, but unlike counties further south beech is scarce as a native tree. Diffuse patches of alder, not obviously associated with streams or sumps, are a feature of some of these woods.

The various mixtures found in the underwood of coppice woods in part reflect

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underlying soil differences but are also affected by the long history of treatment.

Species may have been favoured or lost at different times and places and these changes are frozen in the subsequent stool pattern. The ground flora has been similarly affected by past practices, particularly in the presence or absence of grazing, but it may, since it was rarely directly managed, be a truer reflection of the influence of soils and climate. What is clear is that variations in ground flora and underwood layers do not necessarily coincide (Kirby, 1984).

The National Vegetation Classification (NVC) (Rodwell, 1991; Kirby, Saunders & Whitbread, 1991; Whitbread & Kirby, 1992) takes more account of ground flora differences in its breakdown of British woodland than does Peterken's system. However in Suffolk much of the ancient semi-natural woodland falls into just two broad communities, the oak-bramble-bracken type (W10) and the ash-field maple-dog's mercury type (W8), with lesser amounts of other mainly southern types. Even when sub-communities are included it has been suggested that the Variation in East Anglian woods is poorly served by NVC. As with any Classification there is always some Variation that is missed, because the surveys on which the Classification is based are incomplete. Finer scales of Variation can also always be recognised. However the levels at which the divisions in the NVC have been made are broadly comparable across the country. This is not to imply that the other variations in both the ground flora and tree and shrub layers are unimportant; rather that their extra variety is part of the reason why Suffolk examples of these broad communities are valued more highly than woods on similar soils elsewhere.

These two major forms of botanical Classification are not sufficient to describe Suffolk's woodland because treatment may lead to woods that are of the same V e g e t a t i o n type having very different structures according to whether they had been coppices, wood pastures with many old trees or high forest stands.

Despite similarities in their botanical composition the animal communities in these different types will be very different (e.g. FĂźller, 1995; Warren & Key, 1991).

Variation within designated sites English Nature has taken account of these types and scales of Variation, revealed by different classifications in its guidelines for the selection of Sites of Special Scientific Interest. It is not feasible to designate all ancient woods, but the coverage in Suffolk is high compared to many other counties (35% of all ancient woodland, 45% of ancient semi-natural stands) reflecting the relative importance of such woodland for nature conservation in the county.

The woods selected reflect the main types covered in NVC; they include the important ränge of tree and shrub communities, with, for example, the lime stands in Groton Wood and hornbeam at Burgate Wood; and 'classic' examples of both worked coppice and wood-pasture traditions in the Bradfield Woods and at Staverton Park respectively. At Lineage Wood it is the rieh grassland ndes that form the main justification for its selection, while Iken Wood may be the only example of ancient coppice on blown sand in Britain.

Some sites (Staverton Park) have also been put forward as possible Special Areas of Conservation under the Habitats and Species Directive, but overall

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East Anglian woodland types are not well-represented among those covered by current European legislation. In part this should not be unexpected. Britain lies on the western edge of Europe so it is the most extreme 'Atlantic' features of our woodland, which are better represented in the west, that should attract attention in this first attempt to frame habitat protection at a European level.

There will, however, be opportunities to review what types and sites should be included in future. The National Vegetation Classification is very similar to the classifications that have been used to describe Continental forests. Hence it is a good starting point for tracing the similarities and more importantly the differences that should be stressed at a European level. In particular the importance of England's wood-pasture sites and other areas with veteran trees needs to be addressed.

Woodland Variation in future woods We inherit a particular set of landscapes rieh in historical and biological meaning: some aspects of these we will wish to maintain into the next Century; others we may not. Social and economic conditions are changing, so too (probably) is the climate. What about the woodland of Suffolk?

Table 4. Criteria for or against restoration of coppicing as a priority in ancient woods (from Kirby & Rush, 1994) For coppice restoration: a. Woods with a history of coppicing and which have been cut over this Century, preferably during the last 10 years. b. Woods in regions where coppice management has been common until recently. c. Woods likely to produce a diverse ground flora and/or food plants for open stage invertebrates. Woods on base-rich or poorly drained soils are more likely to produce a rieh response to coppicing than species-poor woods on acid soils. d. Woods with a wide variety of trees and shrubs or distinet patterns in their distribution and abundance. In many cases this diversity is likely to be best maintained by restoring coppice, rather than by allowing high forest to develop. e. Woods with large old coppice stools - a feature of interest in their own right. f. Woods with elements of open grassland, scrub or heath communities that have been largely lost from the surrounding landscapes.

Against coppice restoration: g. Woods with communities of epiphytic lichens and bryophytes that may not tolerate the sudden changes in light and humidity associated with coppicing. h. Long-neglected woods that have developed a mature high forest strueture with much dead wood and many veteran trees.

We must maintain ancient woods and restore others that have been replanted with inappropriate species. In places this is already happening, for example at Arger Fen in Sulfolk and Chalkney Wood (Essex), not least because on some

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clay soils conifers have not grown well. Where conifers have been more suited to the conditions to what extent does the ground flora recover when the trees are removed; what sorts of tree and shrub communities come back? They may not be the same as existed in the past. There is a need for more research in this area.

The area of ancient semi-natural woodland under worked coppice should be expanded - nationally English Nature would like to see at least a doubling of the area of worked stands. Many Suffolk woods fit the criteria we have suggested for where re-coppicing would be a priority (Table 4), if it can be achieved. If it is to be successful, affordable and effective ways of managing coppice woods in the face of the expanding lowland deer populations need to be found. Otherwise much of the small-scale Variation that we value, particularly in the shrub and ground flora layers, will be lost. Clear quantitative evidence for this comes from English Nature's monitoring work at Monks Wood and Wytham Woods where even formerly common species such as dog's mercury and bramble respectively have been almost eliminated from large areas (Cooke et alâ&#x20AC;&#x17E; 1995; Kirby, Thomas & Dawkins, 1995).

Where coppicing cannot be restored, what new patterns in species distribution and abundance will have developed in 60 years time under high forest conditions? What practices should be encouraged to try to carry forward the flora and fauna that depend on open conditions? Wide rides and glades help (Warren & FĂźller, 1990), but are unlikely to be sufficient.

Similarly what is the future for former wood pasture sites, particularly those which are no longer grazed. Many of the species of high conservation value found in such sites presumably once occurred in or on the old trees and rotting logs that are believed to have been common through much of the wildwood.

Can such conditions be recreated? A series of ancient woods through the country should be left as undisturbed as possible to allow natural processes to operate as best they can under modern conditions. Changes in the structure of such woods compared to how they have been in the past will certainly occur in the Short term; but there will eventually be greater variety in the forest floor communities. As trees blow over pit and mound structures develop, each with their own suite of species; a line of nettles may come to indicate not some past human disturbance, but an almost disintegrated log. What sites in Suffolk should be considered for such minimum Intervention treatment? Table 5 suggests some criteria that might be used to select areas.

Woodland clearance and hedgerow removal over the last 50 years has left many ancient woods, including those in Suffolk, more isolated than ever before.

If we wish to encourage more woods in the landscape, where should we do this; how do we ensure they are not developed on land of high nature conservation value in its open State? Should they be large, small or a mixture of sizes? What plants and animals can be expected to colonise them? Near Stanstead in Essex oxlip spread from an ancient wood into the new oak-hazel coppice planted on fields next to it only 100 years ago (Webster & Kirby, 1988). The same might not happen in fields abandoned or planted now however, because of the soil changes brought about by recent agricultural practice. Should we expect to find in new broadleaved woodland patterns of the past, if the soils, the climate and the silvicultural treatments under which they develop are going to be different?

What is the place for new conifer plantations? It is, I suggest, unrealistic to

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presume that in the next 60 years consumption of paper and wood products will be reduced to that which can be met without any increase in the area of such stands. If new conifer plantations are not to go into the uplands and they are to be removed from ancient woodland sites, former heathland etc, then it is the agicultural land in Suffolk and other lowland counties which will have to take them. At present such a policy is not economic, but if it does Start to happen then again new patterns will emerge within the developing forests. New divisions may be needed in our Classification system to describe these new Community types.

Table 5. Desirable characteristics for woods that are to be put into minimum Intervention (from Kirby & Rush, 1994) Large area.

Compact shape.

Little recent treatment or unnatural disturbance.

Few introduced species and no highly invasive ones.

No major external deleterious factors operating, eg spray drift from neighbouring agricultural land.

Not noted for rare or unusual species that depend on management for their survival on site.

Stable ownership.

Diversity of age structure.

Conclusions The quirks of decisions by individuals - kings and queens, farmers, politicians and foresters - over centuries shaped the landscapes that we value, even though those same decision processes destroyed much during the last few decades.

Classification systems should not be seen as a way of cataloguing woods so that we can control where each plant, each tree, each wood should be. The future distribution, composition and management of Suffolk's woodland will not and should not be the product of some 'grand master plan', however well-intentioned those devising it. Instead let us use Classification as a way of celebrating just how variable our woods are.

Summary Every wood is different. Classification systems however group the variations in structure, composition, history and management in ways that enable us to describe and evaluate woods in a consistent way and to make predictions as to how they will respond to change. Suffolk's ancient woods (4,287 ha) tend to be isolated among farmland, are dominated by mixed deciduous communities (NVC types W10, W8) with lime and hornbeam stands well represented. The modern plantations are mainly of pine. The ancient woods are concentrated through the centre of the county, the plantations more in the north-west and in the coastal belt. Ancient woodland forms the bulk of that included within Sites of Special Scientific Interest and Special Areas of Conservation under the Habitats and Species Directive. Woods are dynamic, their composition and structure changes with time under both managed and unmanaged conditions; Classification systems will help us to identify and describe such changes in

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existing woods. They will also provide a way of comparing the similarities and differences between the communities found in ancient woods and those of new woods and plantations developing on ex-farmland.

References Bunce, R. G. H. (1982). Afield keyfor classifying British woodland Vegetation.

London, HMSO. Cooke, A. S„ Farrell, L„ Kirby, K. J. & Thomas, R. C. (1995). Changes in abundance and size of dog's mercury apparently associated with grazing by muntjac. Deer, 9, 429^433.

Forestry Commission (1983a). Census of woodland and trees: Suffolk. Forestry Commission, Edinburgh.

Forestry Commission (1983b). Census of woodlands and trees: England.

Forestry Commission, Edinburgh.

Forestry Commission (1994). The management of semi-natural woodland.

Forestry Commission (Forestry Practice Guides), Edinburgh.

Füller, R. J. Birdlife of woodland and forest. Cambridge University Press, Cambridge. ..

Kirby, K. J. (1984). A comparison of two methods of classifying British broadleaved woodland. Field Studies, 6, 103-116.

Kirby, K. J. & Rush, A. Sustainable forestry and nature conservation - slow steps in the right direction? English Nature (Research Report 122), Peterborough. , ,, T .

Kirby, K. J„ Saunders, G.R. & Whitbread, A.M. (1991). The National Vegetation Classification in nature conservation surveys - a guide to the use of the woodland section. British Wildlife, 3, 70-80.

Kirby K J , Thomas, R. C. & Dawkins, H. C. (1995). Changes in the composition and structure of the tree and shrub layers in Wytham Woods (Oxfordshire), 1974-1991. English Nature (Research Report 143), Peterborough.

Peterken, G. F. (1993). Woodland conservation and management (second edition). Chapman & Hall, London.

Rackham, O. (1980). Ancient woodland. Arnold, London.

Rodwell, J. (1991). British plant communities, 1. woodlands and scrub. Cambridge University Press, Cambridge.

Spencer, J. W. & Kirby, K. J. (1992). An ancient woodland inventory for England and Wales. Biological Conservation, 62, 77-93.

Spencer, J. W. & Thomas, R. C. (1992). Suffolk inventory of ancient woodland.

Nature Conservancy Council, Peterborough.

Thomas, R. C. (1994). Ancient woodland inventory. Amendment report. English Nature (Research Report 72), Peterborough.

Warren, M. S. & Füller, R. J. (1990). Rides and glades: their management for conservation. Joint Nature Conservation Committee, Peterborough.

Webster, S. D. & Kirby, K. J. (1988). A comparison of the structure and composition of an ancient and an adjacent recent woodland in Essex. London Naturalist, 67,33^15. „ . , „ .

Whitbread A M. & Kirby, K.J. (1992). Summaries of National Vegetation Classification woodland descriptions. Joint Nature Conservation Committee (UK Report 4), Peterborough.

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Keith Kirby, English Nature, Northminster House, Peterborough PE1 1UA

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