UPLAND BIRCHWOODS (UK BAP PRIORITY HABITAT) Summary This is woodland in which birch – whether silver birch Betula pendula, downy birch Betula pubescens or both – is dominant in the canopy. It occurs in places where the climate is too cold for oak Quercus spp. or ash Fraxinus excelsior to attain abundance or dominance. Other trees and shrubs can occur, especially rowan Sorbus aucuparia, aspen Populus tremula, hazel Corylus avellana, eared willow Salix aurita and juniper Juniperus communis. This woodland occurs on well-drained to rather poorly drained acidic soils in the Scottish Highlands and the Hebrides. The field layer is mostly grassy or heathy, but when very heavily grazed may be dominated by large bryophytes. Small herbs, bryophytes and ferns, including bracken Pteridium aquilinum, can be common, and on rocks, banks, trees and shrubs in the west there can be a rich flora of oceanic bryophytes including some uncommon species. Most examples of this priority habitat are on moderate to steep slopes below 400 m, with well-drained brown earth or podzol soils. This priority habitat can occur in mosaics with the Upland oakwood, Upland mixed ashwoods and Wet woodland priority habitats, as well as with open habitats including bracken, heath, cliffs, screes and acid grassland. Good management for conservation in this habitat generally aims towards maintaining a good diversity of species, sizes and age classes of trees and shrubs, encouraging diversity in the structure and species composition of the ground vegetation, maintaining rich bryophyte and lichen assemblages on rocks and trees especially in the west, maintaining good quantities of standing and fallen dead wood, and controlling the extent and spread of non-native trees and shrubs, especially Rhododendron ponticum. What is it? This is woodland in which downy birch or silver birch, or both, are dominant in the canopy. It generally occurs in places where the climate is too cold for oak or ash to attain abundance or dominance, although some small to medium-sized trees and shrubs can occur as associates of the birch, especially rowan, aspen, hazel, eared willow and juniper. These associates may themselves form large stands as part of this habitat. This woodland occurs on well-drained to rather poorly-drained acidic soils and is widespread in the Scottish Highlands and the Hebrides. Stands of birch further south are best regarded as cyclical or successional stages of other types of woodland, especially the Upland oakwood priority habitat. Most of the Upland birchwoods priority habitat has a field layer which is grassy or heathy. In grassy examples typical species include wavy hair grass Deschampsia flexuosa, common bent Agrostis capillaris, sweet vernal-grass Anthoxanthum odoratum, tormentil Potentilla erecta and heath bedstraw Galium saxatile. In heathy examples these species can also occur in small quantity but among a sward of heather Calluna vulgaris, bilberry Vaccinium myrtillus or, on some south-facing slopes, bell heather Erica cinerea. The heathy examples are generally on strongly acid soils, but moderate to heavy grazing in such places can lead to grassier – or even bryophyte dominated – field layers. On more mildly acid soils the ground flora is less heathy and small herbs are more common, including wood-sorrel Oxalis acetosella, common dog-violet Viola riviniana and primrose Primula vulgaris. In the damper examples of this priority habitat purple moor-grass Molinia caerulea can be abundant or dominant in the field layer. Bryophytes and ferns are generally common throughout. Typical bryophytes include the mosses Hylocomium splendens, Pleurozium schreberi, Pseudoscleropodium purum, Rhytidiadelphus loreus, R. triquetrus, R. squarrosus, Dicranum majus, D. scoparium, Polytrichastrum formosum and Leucobryum glaucum. Bryophytes are especially plentiful and diverse on the thinner, more acidic soils. Ferns typically include hard fern Blechnum spicant, Dryopteris spp. And bracken Pteridium aquilinum: this last species can be abundant to dominant in the field layer on deep brown-earth soils. Much of this woodland is on steep slopes where the ground vegetation is broken by rock outcrops and boulders. These rocks generally support an abundance of bryophytes and, in some places, lichens. Their bryophyte floras are especially luxuriant and varied in the wetter west, where they include several western species such as the mosses Dicranum scottianum and Sematophyllum micans and the liverworts Scapania gracilis, Plagiochila spinulosa, P. atlantica, P. bifaria, P. punctata, Saccogyna viticulosa, Bazzania trilobata, Adelanthus decipiens, Aphanolejeunea microscopica, Drepanolejeunea hamatifolia and Harpalejeunea molleri. The western filmy ferns Hymenophyllum wilsonii and H. tunbrigense also grow in these habitats. The epiphytic flora on birches can be rich and can include species of interest such as the uncommon western liverworts Plagiochila atlantica, Leptoscyphus cuneifolius and Douinia ovata, as well as lichens such as Menegazzia terebrata and Hypotrachyna taylorensis. The Lobarion lichen community, including distinctive foliose species such as Lobaria spp., Sticta spp., Nephroma laevigatum and Pseudocyphellaria spp., is rare on birches but can occur in this priority habitat on the bark of other trees such as rowan. How do I recognise it? Differentiation from other Priority Habitats Upland oakwood is similar in terms of its habitat and ground vegetation, but has a canopy in which oak is at least common and in many cases dominant. Birch-dominated stands similar to the Upland birchwoods priority habitat but situated south of the Highlands are best regarded as cyclical or successional stages of the Upland oakwood priority habitat. Lowland mixed deciduous woodland can have similar ground vegetation and in some cases a birch-dominated canopy, but is distinguished largely by NVC type. The only NVC overlap between Lowland mixed deciduous woodland and Upland birchwoods is the W16 community: birch-dominated stands of W16 in the lowlands are treated as Lowland mixed deciduous woodland, and those on the fringes of the Highlands are regarded as Upland birchwoods. The NVC separates Upland mixed ashwoods (W9 and certain examples of W7 and W8) from Upland birchwoods which does not include W7-9. The Upland birchwoods and Wet woodland priority habitats are largely separable by NVC type, but the W4 community occurs in both. The W4c sub-community is restricted to Wet woodland. The drier W4a sub-community occurs in the Upland birchwoods and Upland oakwood habitats but not in the Wet woodland habitat. In previously published priority habitat definitions, some of the less wet examples of W4b, and those which are in mosaics with drier W10e, W11, W16 and W17 woodland, are considered to be best placed in the Upland birchwoods and Upland oakwood priority habitats depending on location and canopy as described above. However, typical W4b is as wet as many other NVC communities in the Wet woodland priority habitat and is clearly different from the drier W10, W11 and W17 communities: this might suggest keeping it within the Wet woodland habitat. Using patch size as a guide is a useful approach such that a small area of W4b within a larger area of W11 would classify as Upland birchwood; whereas if the W4b is largely associated with W4c then it would classify as Wet woodland. Definition in relation to other habitat classifications Classification Habitat types belonging to this UK BAP priority habitat All examples of W4a, W10e, W11 and W17 in which oak forms <30% of the canopy cover. Upland fringe examples of W16 in which oak forms <30% of the canopy cover. NVC Examples of non-NVC ‘WLz’ (with very species-poor Luzula sylvatica ground vegetation) in upland or upland fringe situations, in which oak forms <30% of the canopy cover. (All of the above NVC communities are included in the Scottish Biodiversity List.) A1: birchwood examples of W4a, W10e, W11, W17 and WLz with oak <30% of canopy cover; total canopy cover >30% Phase 1 A2: birch scrub forms of W4a, W10e, W11, W17 and WLz with oak <30% of canopy cover A3: birchwood examples of W4a, W10e, W11, W17 and WLz with oak <30% of canopy cover; total canopy cover <30% A4: recently felled W4a, W10e, W11, W17 and WLz birchwood with oak <30% of canopy cover UK BAP broad All examples of this priority habitat belong to the broad habitat - habitat Broadleaved, mixed and yew woodland NVC communities W11 and W17 account for most of the Upland birchwoods in Scotland. The sub-communities W8e/f/g and W10e, and examples of W16 and W8d in the upland fringe, have historically been assigned to Upland priority woodland habitats. However, W8, W10 and W16 are generally lowland communities, and their flora and distribution reflect the influence of a warmer and/or drier lowland climate compared with that of their upland counterparts W9, W11 and W17. It may be preferable to consider all examples of W8/10/16 woodland in lowland Scotland as part of the Lowland Mixed Deciduous woodland habitat. The Native Woodland Survey of Scotland classified woodland to community level only, and included all examples of W8, W10 and W16 within the Lowland mixed deciduous woodland priority habitat. Definition in relation to legislative classifications Classification Habitat types belonging to this UK BAP priority habitat Habitats Directive The Upland birchwoods priority habitat does not include any Annex I Annex I habitats. SNH SSSI habitat All examples of the Upland birchwoods priority habitat belong features within the Upland birch woodland SSSI feature type. Where is it? Most examples of this priority habitat are on moderate to steep slopes with well-drained brown earth or podzol soils. Within larger areas of woodland this priority habitat can occur in mosaics with the Upland oakwood priority habitat, more flushed areas with the Upland mixed ashwoods priority habitat or wetter areas with the Wet woodland priority habitat. It can also occur in mosaics with open habitats including bracken, heath of the Upland heathland priority habitat, cliffs and screes of the Inland rock outcrop and scree habitats priority habitat, and acid grassland.