Maritime Cliff and Slopes (Uk Bap Priority Habitat)
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MARITIME CLIFF AND SLOPES (UK BAP PRIORITY HABITAT) Summary This priority habitat takes in the vegetation that occurs on cliffs and sloping ground adjacent to the sea and includes communities specific to this habitat as well as others that also occur inland. They range from woodland through heathland to grasslands and tall herb assemblages. There is a range of small trees or large shrubs on these coastal slopes. Most of the heaths and grasslands are herb-rich as well as having some more strictly maritime plants. The cliff communities vary from grassy swards in locations enriched by the droppings of nesting seabirds to tall-herb. The habitat varies from hard, acid, near-vertical rocks to softer, more gently sloping, more basic substrates. The vegetation is exposed to salt spray, salt-laden wind and, on stormy occasions, washing with sea water, the extent and frequency of these events being greater on exposed coasts facing the prevailing wind and where waves are generally larger. The climate varies from mild in the south-west to cold in the north-east. These are near-natural communities possibly owing more to the extreme environment than to a low level of human intervention, and contain a number of uncommon plant species. Coastal cliffs in Scotland are important nesting habitats for birds such as gannet Morus bassanus, puffin Fratercula arctica, guillemot Uria aalge, razorbill Alca torda, kittiwake Rissa tridactyla, fulmar Fulmarus glacialis, shag Phalacrocorax aristotelis and Manx shearwater Puffinus puffinus, and in the treeless Outer Hebrides for grey heron Ardea cinerea. Much of the vegetation on cliffs and steep slopes is out of the reach of grazing animals – except goats, which occur in some places – and is difficult to burn. In general, light grazing will maintain the vegetation. Heavy grazing and burning can convert heaths and woodlands to grassland and also initiate soil erosion and landslips. What is it? This priority habitat contains terrestrial plant communities of cliffs and slopes near the sea, and encompasses a great range of vegetation types from scrub woodland to grassland, heath and bracken. Coastal scrub Several scrub communities occur on coastal slopes, with a canopy of tall shrubs or small trees such as hawthorn Crataegus monogyna, gorse Ulex europaeus, blackthorn Prunus spinosa, hazel Corylus avellana, bramble Rubus fruticosus or raspberry R. idaeus and an understorey of species such as bracken Pteridium aquilinum, ivy Hedera helix, red campion Silene dioica, nettle Urtica dioica, cleavers Galium aparine, ground ivy Glechoma hederacea, creeping soft-grass Holcus mollis and false oat-grass Arrhenatherum elatius. On richer soils wild hyacinth Hyacinthoides non-scripta and primrose Primula vulgaris are common. Maritime species such as sea campion Silene uniflora and thrift Armeria maritima may also occur. Patches of coastal scrub tend to be small, especially on the more exposed west coast, where they tend to be tucked into sheltered coves and gullies or pruned hard against the cliffs in a sort of near-vertical carpet. Coastal heath The H7 Calluna vulgaris-Scilla verna heath is a coastal community with a dark, dense sward of Calluna vulgaris and Erica cinerea dotted with small species such as wild thyme Thymus polytrichus, bird’s-foot trefoil Lotus corniculatus, Yorkshire fog Holcus lanatus, sheep’s fescue Festuca ovina, tormentil Potentilla erecta, kidney vetch Anthyllis vulneraria, ribwort plantain Plantago lanceolata and the maritime species spring squill Scilla verna, Armeria maritima, Silene uniflora and Plantago maritima. In addition, stands of the Scilla verna sub- community H8d of the Calluna vulgaris-Ulex gallii heath are also distinctly coastal. The sward of C. vulgaris, U. gallii and Erica cinerea is a dazzling sight in summer when the shrubs are in flower with the bright yellow of the gorse set off by the purple and magenta tones of the heathers. Again, the maritime plants Scilla verna, Armeria maritima and sea plantain Plantago maritima are common here, along with other small species such as Thymus polytrichus, Lotus corniculatus, Festuca ovina and cat’s-ear Hypochoeris radicata. Coastal grassland Short, hard-grazed, species-rich grasslands are common on coastal slopes. In the upland climate of the north and west the most common of these communities is the CG10 Festuca ovina-Agrostis capillaris-Thymus polytrichus grassland, with a sward made up of these species together with sweet vernal grass Anthoxanthum odoratum, common dog-violet Viola riviniana, selfheal Prunella vulgaris and Plantago lanceolata. The maritime species Armeria maritima and Plantago maritima are common. Where the soils are flushed the grasslands have a grey-green, sedge sward with glaucous sedge Carex flacca, flea sedge C. pulicaris and carnation sedge C. panicea. In the far north and west, montane plants such as hair sedge C. capillaris, alpine bistort Persicaria vivipara and alpine meadow-rue Thalictrum alpinum grow close to sea-level in this type of grassland. In the south and east of Scotland much of the short, herb-rich coastal grassland belongs to the CG2 Festuca ovina-Avenula pratensis grassland. This has a sward of grasses such as F. ovina, crested hair-grass Koeleria macrantha, early hair-grass Aira praecox and meadow oat-grass Avenula pratensis, with some Carex flacca and spring sedge C. caryophyllea and an array of small plants such as Thymus polytrichus, Plantago lanceolata, P. maritima, lady’s bedstraw Galium verum, mouse-ear hawkweed Pilosella officinarum, harebell Campanula rotundifolia, Anthyllis vulneraria, Armeria maritima and black medick Medicago lupulina. U4 Festuca-Agrostis-Galium grasslands occur on acid soils near the sea. They have a short, bright green, species-poor sward of Festuca ovina, F. rubra, Agrostis capillaris, Anthoxanthum odoratum, Potentilla erecta and Galium saxatile. The mesotrophic grasslands MG1 and MG5 can also clothe coastal slopes where grazing is light or absent. MG1 has a tall and rank sward of Arrhenatherum elatius, Dactylis glomerata and Hocus lanatus, scattered with large herbs such as hogweed Heracleum sphondylium, yarrow Achillea millefolium and ragwort Senecio jacobaea. MG5 has a sward of crested dog’s-tail Cynosurus cristatus, Festuca rubra, Agrostis capillaris, Anthoxanthum odoratum, Holcus lanatus and cock’s-foot Dactylis glomerata, and a rich array of herbs such as Trifolium pratense, T. repens, Galium verum, Achillea millefolium, black knapweed Centaurea nigra, yellow rattle Rhinanthus minor and Lotus corniculatus. Maritime cliff communities The vegetation of maritime cliff ledges is distinctive and is represented in Scotland by eleven NVC communities. Some of these such as the MC1 Crithmum maritimum-Spergularia rupestris, MC2 Armeria maritima-Ligusticum scoticum and MC4 Brassica oleracea crevice communities are open assemblages dominated by a particular large maritime species. Others are more diverse, such as the MC5 Armeria-Cerastium diffusum community that consists of a great array of small herbs such as Anthyllis vulneraria, Armeria maritima, Plantago maritima, buck’s-horn plantain P. coronopus, sea mouse-ear Cerastium diffusum, Achillea millefolium and biting stonecrop Sedum acre. The MC3 Sedum rosea-Armeria maritima ledge community can have a rich and luxuriant sward of tall herbs such as roseroot Sedum rosea, Silene uniflora, S. dioica, wild angelica Angelica sylvestris and Scot’s lovage Ligusticum scoticum. There are distinctive assemblages that develop on bird cliffs: the MC6 Atriplex prostrata- Beta uniflora community (which can also occur in the Coastal vegetated shingle priority habitat) and the MC7 Stellaria media-Rumex acetosa community. The remaining communites are maritime grasslands generally dominated by Festuca rubra. The MC8 Festuca rubra-Armeria maritima grassland has a bulky sward of F. rubra; MC9 F. rubra-Holcus lanatus grassland has a rank tussocky sward of these two species and Dactylis glomerata; MC10 F. rubra-Plantago maritima grassland has a short, close-grazed sward of these species; and MC12 F. rubra-Hyacinthoides non-scripta community is a lush sward dominated by H. non-scripta. The maritime species Plantago maritima, Armeria maritima and Scilla verna can occur in all these grasslands. In general the flora of maritime cliffs indicates that the soils are mostly neutral to basic as shown by the presence of species such as Thymus polytrichus, Holcus lanatus, Sedum rosea and Angelica sylvestris. Strongly acidic soils and markedly acidophilous plant communities are uncommon here, possibly because of enrichment of soils from mineral salts brought in with sea spray. In some western areas the cliffs are constantly wet because of the high rainfall, and can have wetland communities on ledges and in crevices with species such as black bog-rush Schoenus nigricans, hemp-agrimony Eupatorium cannabinum, royal fern Osmunda regalis and marsh pennywort Hydrocotyle vulgaris. How do I recognise it? Differentiation from other priority habitats The specifically coastal heaths, grasslands and cliff communities can be distinguished from terrestrial forms of the same types of vegetation by the presence of maritime species such as Armeria maritima, Plantago maritima, P. coronopus, Scilla verna, Silene uniflora and common scurvy-grass Cochlearia officinalis. Communities such as woodland and scrub and a range of other NVC types are assigned to this priority type where they occur in this habitat – steep cliffs and slopes running down to the sea. Definition in relation