RH2D Angelica sylvestris – Breutelia chrysocoma ledge community
Vegetation
The field layer of this variable community usually contains Festuca vivipara and Viola riviniana/reichenbachiana. Frequently there are also some tufts of Carex viridula and Carex pulicaris plus Anthoxanthum odoratum, Thymus polytrichus, Euphrasia officinalis agg., Galium saxatile, Agrostis capillaris and the non-native forb Epilobium brunnescens. Angelica sylvestris is occasional. Calluna vulgaris may provide some dwarf shrub cover. Breutelia chrysocoma and Hylocomium splendens are the main bryophytes with Ctenidium molluscum also frequent. There are a large number of occasional species, including some species typically associated with lowland grassland such as Primula vulgaris, Hypericum pulchrum and Succisa pratensis. Festuca rubra, when present, can form dense mats. The deep cushions of Amphidium mougeotii and Anoectangium aestivum may also be found on the rock face here.
Ecology
This is a community of wet ledges and crevices on cliff faces, or less frequently scree slopes or stony grassland, in the uplands (mean extent of bare rock = 17.1%, n = 47; mean altitude = 471 m, n = 47; mean slope = 52.3°, n = 47). The geology may be calcareous or siliceous, but if the latter there tends to be some base-rich seepage present that raises the pH levels. Soils are thin (mean soil depth = 3.7 cm, n = 26), mildly acidic, quite moist and infertile.
Sub-communities
Two sub-communities have been described for this community, but they are rather tentative due to the small sample sizes. The Festuca rubra – Diplophyllum albicans sub-community (RH2Di) represents more acidic conditions, whereas the Campanula rotundifolia – Selaginella selaginoides sub-community (RH2Dii) represents more basic conditions.
Similar communities
This community is rather intermediate between the calcareous RH1A Asplenium trichomanes – Ctenidium molluscum crevice community and the RH2A Saxifraga spathularis – Isothecium myosuroides crevice community, but is wetter than either. Ferns are less frequent here than those two assemblages and there are several more grassland species present.
Conservation value
Examples of this very species-rich community from cliff faces with ferns, saxifrages or arctic-alpine species are likely to qualify as EU HD Annex I habitats 8210 Calcareous rocky slopes or 8220 Siliceous rocky slopes. Instances from scree slopes will qualify as 8110 Siliceous scree (or, very rarely, 8120 Calcareous scree). Instances from upland ledges may represent habitat 6430 Hydrophilous tall-herb swamp. Species/4 m2 = 39.2, n = 22.
Management
Some more accessible areas of this vegetation may be sheep-grazed but it is essentially unmanaged. The impact of the non-native Epilobium brunnescens has not been investigated and hitherto no known management action has been taken. Climate change threatens arctic-alpine species which are restricted to such upland sites.