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News FAR NORTH WOODLAND BIODIVERSITY PROJECTNEW MEMBERS OF NHFT TEAM -WOODLAND BIODIVERSITY OFFICER - Pat RaePROJECT SUPPORT OFFICER - Sasha Saundersmore....NORTHERN ASPEN PROJECT AND ANCIENT WOOD PASTURE PROJECT - |
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Guide to National Vegetation
Classification (NVC) Woodland Types Ê Printer friendly version There are thirty-odd native British trees: some are widespread, while some are found only in certain areas. Few of them (beech and yew are obvious exceptions) grow in single-species stands, but instead are usually found in characteristic mixtures. The composition of these woodlands and their structure are determined by climate, soil conditions and biotic influence: chiefly the impact of humans. Foresters and ecologists recognise around 20 "woodland types" - each can be recognised by distinctive mixtures of trees and shrubs, and has a characteristic associated flora of flowering plants, ferns, mosses, etc., and each is limited to certain types of soil within a particular climatic zone. When planning new native woodlands it is important to ensure that the trees planted are appropriate for the climate, soil, drainage, etc, and identifying the appropriate NVC type(s) for the site is an essential part of the woodland design process. Not all the NVC Woodland types are found in the northern highlands - the following is a brief guide to the 6 most common. W4: Birch woodland with purple moorgrass. This woodland type is typically found on the margins of blanket mires, valley bogs, and hillslope and valley-side flushes. The soils at these sites are usually flushed and unflushed acid peats, or peaty surface water gleys. Downy birch is usually the dominant tree, forming a generally open and often rather decrepit canopy, with a field layer of purple moorgrass and various sphagnum moss species. Various willow species colonise sites too wet for birch, and common alder is often present beside streams and flushes where the nutrient status is higher. W7: Alder - ash woodland. This woodland type, like W4 above, is found on very wet soils, such as surface water gleys, but where nutrient enrichment has allowed alder to become more dominant, and ash to appear. Downy birch and willows will still be common, joined by hazel, hawthorn, rowan and even sessile oak. W9: Upland mixed-broadleaved woodland. This woodland type is found on the most fertile soils in the region, and consequently has been much reduced in extent by agriculture. Ash, alder, wych elm, hazel, downy birch, sessile oak, rowan, hawthorn, aspen, bird-cherry and holly will all be found, over a rich and varied ground flora, although the mixture at any site will usually reflect past management practices. W11: Upland oak-birch woodland with bluebell. On less fertile soils than W9, ash and elm disappear and sessile oak assumes dominance, with birch, rowan, hazel, hawthorn and holly in the understorey. These woodlands have often become overrun by bracken, though bluebells may provide a spring carpet. W17: Upland oak-birch woodland with blaeberry. This type is similar to W11 above, but is found on more acid, less fertile soils than W11, and has a very different ground flora. Sessile oak and downy birch are again the main species, with holly and rowan common and hazel and hawthorn found on pockets of better soils, and juniper in open spaces,The heathy field layer contains an abundance of mosses and liverworts, especially in rocky terrain or sunless gorges. Wood sorrel often carpets the ground. Both W11 and W17 can be found with greatly varying relative proportions of oak and birch. In the far north of Scotland, oak is often absent, further south, management to favour oak may have all but removed the birch. W18: Scots pine woodland. This woodland type is only found in Scotland, on poor, usually thin and well drained soils in the Grampians and western highlands. Downy birch (in the west and north) and silver birch (in the east) are usually an important component of the woodland, with juniper common. The ground flora is usually heather, with bilberry, cowberry and often extensive carpets of mosses. Non-native species Over the millennia, humans have greatly reduced the scale and diversity of Scotland's forests, either by removing tree cover completely or by managing woodlands, deliberately or otherwise, to favour certain species at the expense of others. Contemporaneously, many new species have been introduced, either from southern England (beech, and possibly sycamore), continental Europe (larch, sweet and horse chestnut, norway maple, norway spruce) or more recently, from America (sitka spruce, douglas fir, lodgepole pine). All of these species have become naturalised here - part of our ecology - and all can play a valuable role in the future forestry of the region.
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