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. Most sites are found below 400 m in altitude although it can extend well above this in places.

This priority habitat is restricted to the Scottish Highlands and the Hebrides where it is widespread and common. The Native Woodland Survey of Scotland (2014) gives the area of this priority habitat in Scotland as 91,235ha. For reference see the National Report at p22 Table 3 http://www.forestry.gov.uk/PDF/FCMS126.pdf/$FILE/FCMS126.pdf

What is special about it?

Some species of special conservation status recorded in this priority habitat are listed below.

Wildlife EC Scottish and UK BAP Habitats Bio- Red Country- Common priority Directive diversity Data side Act Group name Latin name list Annex II List List (1981) shining guest Formicoxenus ant y y ant nitidulus bird tree pipit Anthus trivialis y y bird lesser redpoll Carduelis cabaret y y common bird Cuculus canorus y y cuckoo eurasian bird Jynx torquilla y y y y wryneck spotted bird Muscicapa striata y y y flycatcher Tetrao tetrix subsp. bird black grouse y y britannicus bird song thrush Turdus philomelos y y y bird ring ouzel Turdus torquatus y y y pearl- butterfly bordered Boloria euphrosyne y y y fritillary small pearl- butterfly bordered Boloria selene y y fritillary chequered Carterocephalus butterfly y y y skipper palaemon flowering juniper Juniperus communis y y plant flowering small cow- Melampyrum y y y plant wheat sylvaticum flowering Arran Sorbus arranensis y y y plant whitebeam flowering Arran service- Sorbus y y y plant tree pseudofennica Hammerschmidtia fly aspen hoverfly y y ferruginea large birch fly Lonchaea ragnari y y lance fly Hydnellum fungus velvet tooth y y spongiosipes golden gilled fungus Phylloporus pelletieri y y bolete fungus a tooth fungus Sarcodon scabrosus y y orange fungus Cantharellus friesii y y chanterelle blackening Cantharellus fungus y y chanterelle melanoxeros fungus a tooth fungus Phellodon confluens y y forked hair- lichen Bryoria furcellata y y y y lichen lichen a lichen Buellia violaceofusca y y y lichen a lichen Caloplaca ahtii y y y Candelariella lichen a lichen y y y superdistans lichen a lichen Collema fasciculare y y y Diplotomma lichen a lichen y y y pharcidium Fuscopannaria lichen a lichen y y y y ignobilis Fuscopannaria lichen a lichen y y y sampaiana lichen elm gyalecta Gyalecta ulmi y y y Hypotrachyna lichen a lichen y taylorensis Lecanora lichen a lichen y y y cinereofusca lichen a lichen Leptogium brebissonii y y y Megalospora lichen a lichen y y y tuberculosa lichen a lichen Menegazzia terebrata y lichen a lichen Pyrenula dermatodes y y y lichen a lichen Schismatomma y y y Wildlife EC Scottish and UK BAP Habitats Bio- Red Country- Common priority Directive diversity Data side Act Group name Latin name list Annex II List List (1981) graphidioides lichen a lichen Sclerophora pallida y y lichen a lichen Vulpicida pinastri y y y Wilson's liverwort Acrobolbus wilsonii y y pouchwort turps liverwort Geocalyx graveolens y y y pouchwort mammal wildcat Felis silvestris y y y y mammal pine marten Martes martes y y y soprano mammal Pipistrellus pygmaeus y y y pipistrelle brown long- mammal Plecotus auritus y y y y eared bat mammal red squirrel Sciurus vulgaris y y y silky swan- moss Campylopus setifolius y neck moss moss Irish daltonia Daltonia splachnoides y y y dark-bordered moth Epione vespertaria y y beauty netted moth mountain Macaria carbonaria y y moth pied tineid moth Nemapogon picarella y y moth cousin moth Protolampra sobrina y y german argent and moth Rheumaptera hastata y y sable reptile common lizard Zootoca vivipara y Y broad groove- Monocephalus spider y y head spider castaneipes lichen-running Philodromus spider y y spider margaritatus

How do we manage it?

Good management for conservation should aim towards the following:

 Encourage regeneration to ensure a continued canopy and diversity of species, sizes and age classes of trees and shrubs.

If felling or thinning takes place this should ideally not reduce the variation in species, sizes and age classes of trees and shrubs. In many woods natural regeneration can be encouraged, generally by at least a temporary reduction or removal of grazing, as a means of increasing the numbers of young trees, thereby helping to maintain the woodland in the long term. Birch and rowan regeneration often develops more quickly and abundantly than that of oak, elm and hazel. The benefits of management for natural regeneration should of course be balanced against any possible detrimental effects. Enclosing woodlands to encourage regeneration can lead to dense thicket regeneration of birch, which can lead to loss of ground flora and epiphytes, at least temporarily. A very dense tree/shrub canopy can outshade light- demanding species such as many lichens. It can be good to keep some glades open, to provide general habitat diversity and because glades can be important for groups such as insects, birds and, on trees at edges of glades, lichens. However it may be the only option available to allow regeneration to take place effectively and retain woodland at a site.

 Encouraging diversity in the structure and species composition of the ground vegetation

If grazing is only light to moderate this can allow some tree and shrub regeneration to take place and also allow good flowering and seed-setting of ground flora plants including dwarf shrubs. Heavy grazing can lead to extensive carpets of mosses becoming dominant or co-dominant on the ground, as vascular cover becomes shorter and sparser. This has led some people to think that moderate to heavy grazing is needed in order to maintain bryophyte abundance and diversity, but the main bryological interest in these woods is not on the ground but on rocks and trees.

 Maintaining rich assemblages of bryophytes and lichens on rocks and trees, especially in the west

To a large extent this means maintaining shaded conditions so that shade- and humidity-demanding bryophytes and lichens, including many uncommon species, do not suffer from too much exposure to sunlight and wind. However, this also means guarding against overshading because many of these species are intolerant of heavy shade. Where felling or thinning is planned in western woods it is best to assess the richness of the trees and shrubs concerned, and that of nearby rocks, and to carry out the planned management only where these epiphytic and saxicolous floras are not especially rich or do not include species of special interest.

 Maintaining good quantities of standing and fallen dead wood

Dead wood is best left in the woodland because it is an important habitat for birds and insects and, on fallen rotting logs, bryophytes, especially liverworts. Fallen dead wood also helps to provide variety in habitat structure on the ground, and the additional shade and shelter close to fallen timber helps to maintain the humid conditions needed by some woodland species.

 Controlling the extent and spread of non-native trees and shrubs, especially Rhododendron ponticum

Non-native trees and shrubs can occur in this habitat as a result of deliberate under- or inter-planting, or by seeding in from nearby sources. The commonest of such species here are conifers such as spruces, firs, pines, larches and western hemlock, together with rhododendron. All of these except larch have the potential to grow thickly and cast such heavy shade and leaf litter as to impoverish the native woodland ecosystem. Control of these species is desirable in order to prevent ecological impoverishment of the habitat. Rhododendron ponticum is the most serious of these alien woody species because it can invade an area in a relatively short time, forming such dense thickets that almost all plant life is overshaded and smothered by leaf litter. Worst of all, rhododendron is especially common and invasive in the types of humid western woodland, including many belonging to this priority habitat, which are of international importance for the oceanic bryophyte, lichen and fern floras. Removal of rhododendron is therefore desirable from such woods and their surroundings. Sycamore is generally uncommon in Upland birchwoods, and where it occurs it is generally less competitive with native tree species and can actually be of conservation value in providing a neutral to basic bark habitat for certain lichens of interest which would otherwise be rare or absent on the more acidic bark of birch.

References, links and further reading

Averis, A., Averis, B., Birks, J., Horsfield, D., Thompson, D., & Yeo, M. 2004. An Illustrated Guide to British Upland Vegetation. Peterborough, JNCC http://jncc.defra.gov.uk/page-2463

Ellis, N.E. and Munro, K. 2004. A preliminary review of the distribution and extent of BAP priority habitats across Scotland. Scottish Natural Heritage Commissioned Report No.044 (ROAME No. F00NA02). https://www.nature.scot/information-library-data-and-research/information-library

Forestry Commission. 2003. The management of semi-natural woodlands. Practice Guide series of seven booklets (one for each woodland UK BAP priority habitat). Edinburgh, Forestry Commission.

Rodwell, J.S., ed. 1991a British plant communities Volume 1: Woodlands and scrub. Cambridge, Cambridge University Press

Rodwell, J.S., Dring, J.C., Averis, A.B.G., Proctor, M.C.F., Malloch, A.J.C., Schaminee, J.H.J. & Dargie, T.C.D. 1998. Review of coverage of the National Vegetation Classification. Joint Nature Conservation Committee contract report F76-01-170. Coordinated by the Unit of Vegetation Science, Lancaster University.

UK BAP 2008 http://jncc.defra.gov.uk/pdf/UKBAP_BAPHabitats-57-UplandBirchwoods.pdf

Usher, M.B., Bain, C. and Kerr, A. eds. 2000. Action for Scotland's Biodiversity. Scottish Biodiversity Group. Edinburgh, The Scottish Executive and The Stationery Office.

Common Standards Monitoring guidance http://www.jncc.gov.uk/page-2199

Native Woodland Survey of Scotland http://scotland.forestry.gov.uk/supporting/strategy- policy-guidance/native-woodland-survey-of-scotland-nwss

Managing native woodlands http://scotland.forestry.gov.uk/supporting/strategy-policy- guidance/biodiversity/native-woodlands

Managing invasive rhododendron http://www.forestry.gov.uk/fr/rhododendroncontrol

National Biodiversity Network (NBN) Gateway https://data.nbn.org.uk/

Scottish Natural Heritage website: http://www.nature.scot

UK BAP information on JNCC website: http://jncc.defra.gov.uk/default.aspx?page=5155