Upland Flushes, Fens and Swamps (Uk Bap Priority Habitat)
Total Page：16
File Type：pdf, Size：1020Kb
UPLAND FLUSHES, FENS AND SWAMPS (UK BAP PRIORITY HABITAT) Summary This priority habitat takes in a number of wetland communities in the uplands, from swamp vegetation at the margins of lochs or in the waters of sluggish streams, through tall fens with mixtures of herbs and rushes, to sedge-dominated mires and bryophyte springs. Each has a characteristic set of species. In the tall fens and swamps the dominant plants are large sedges, rushes and, on neutral soils, herbs. On more acid soils mosses and herbs are more common. The sedge mires can consist of any of many species either alone or in combination. Small herbs are common in these mires, depending on the base-status of the water. Bryophyte springs vary from the almost pure mats of a few specific mosses to intricate, brightly-coloured mixtures of species, dotted with small herbs. All these types of vegetation rely on a wet but not stagnant habitat where water flows laterally over or through the ground. Since all are more common where the climate is cool and wet, they are most widespread in the uplands. All of these communities are common throughout the uplands, though the montane flushes and springs are confined to the upper slopes of the higher hills. Swamps, fens and sedge mires can be found a few metres above sea level as well as on montane plateaux and hill tops. These communities add a great deal to the structural and floristic diversity of upland vegetation, and are also home to a great many rare species. Wetland communities of all types are host to large numbers of invertebrates, especially flies and spiders, and so are valuable feeding grounds for many insectivorous birds, including waders. Most of these Upland flushes, fens and swamps are open to grazing animals and probably need light grazing to maintain the structure and species diversity except at the very highest altitudes. What is it? The Upland flushes, fens and swamps priority habitat includes a very wide range of plant communities, from tall swards of herbs, rushes and sedges to mats and patches of bryophytes. What they all have in common is an association with water either in flooded ditches, channels or valley floors, or emerging from and flowing gently over the surface of the ground. For the purpose of description this varied priority habitat is split into 5 subdivisions related to NVC communities: Swamps Terrestrial swamp NVC communities – as opposed to those where the plants grow in deep water – are included in this priority habitat although they are also represented by the aquatic priority types where they form a very narrow waterside strip, or emergent stands in open water. They consist of species-poor, in some stands single-species, swards of bottle sedge Carex rostrata, bladder sedge C. vesicaria, great horsetail Equisetum fluviatile and common spike-rush Eleocharis palustris. In the more diverse examples there is an array of tall herbs such as bogbean Menyanthes trifoliata, marsh cinquefoil Potentilla palustris, bog pondweed Potamogeton polygonifolius, water mint Mentha aquatica, marsh marigold Caltha palustris and lesser spearwort Ranunculus flammula. Tall fen communities These are assemblages of plants such as soft rush Juncus effusus and sharp-flowered rush J. acutiflorus, purple moor-grass Molinia caerulea, flag iris Iris pseudacorus and herbs including meadowsweet Filipendula ulmaria, wild angelica Angelica sylvestris, meadow buttercup Ranunculus acris, R. flammula, Mentha aquatica, water avens Geum rivale, marsh bedstraw Galium palustre, ragged robin Lychnis flos-cuculi and common valerian Valeriana officinalis. The vegetation generally grows tall and lush. There is a sparse underlayer of bryophytes such as Calliergonella cuspidata, Rhizomnium punctatum and Brachythecium rutabulum. Sedge mires or flushes Shorter in stature than the tall fens, these are assemblages of sedges and other small species. Any of a number of sedges may dominate, including common sedge Carex nigra, star sedge C. echinata, carnation sedge C. panicea, common yellow sedge C. viridula ssp. oedocarpa, dioecious sedge C. dioica, C. rostrata, white sedge C. curta and russet sedge C. saxatilis. They vary from species-poor assemblages on acid substrates, with an underlayer of Sphagnum fallax, S. palustre and Polytrichum commune and a sparse interleaving of Ranunculus flammula, tormentil Potentilla erecta and marsh violet Viola palustris, to species- rich swards on base-rich soils with a flora including butterwort Pinguicula vulgaris, yellow saxifrage Saxifraga aizoides, purple saxifrage S. oppositifolia and alpine meadow-rue Thalictrum alpinum and a characteristic suite of bryophytes consisting of Campylium stellatum, Scorpidium scorpioides, Drepanocladus revolvens and Blindia acuta. Mesotrophic Carex rostrata mires may include tall herb species such as Mentha aquatica, Lychnis flos- cuculi, Filipendula ulmaria, Menyanthes trifoliata and Potentilla palustris. Potamogeton polygonifolius soakways, with or without marsh St. John’s wort Hypericum elodes, and Ranunculus omiophyllus-Montia fontana rill communities also belong here. Springs Springs mark out the sites where water actually emerges from the ground. They almost all consist of mats and patches of brightly-coloured bryophytes dotted with small vascular plants. Characteristic bryophytes of this habitat include the mosses Philonotis fontana, Bryum pseudotriquetrum, Dicranella palustris and Sphagnum denticulatum, and the liverwort Scapania undulata. Where the irrigating water is base-rich the most common species is the moss Palustriella commutata. Associated vascular plants include blinks Montia fontana, opposite-leaved golden saxifrage Chrysosplenium oppositifolium, starry saxifrage Saxifraga stellaris and Viola palustris. At high altitudes where snow lies late in spring, Anthelia julacea forms patches of its tiny, silvery shoots, and Pohlia wahlenbergii var. glacialis grows in spreads of apple-green leaves which have a waxy bloom. Valley mire The M21 Narthecium-Sphagnum valley mire is also partly within this priority type where it occurs in the unenclosed uplands. Its flora, with cross-leaved heath Erica tetralix, ling Calluna vulgaris, bog myrtle Myrica gale, white beak-sedge Rhynchospora alba and peat- forming Sphagnum mosses, is very different from that of the other flush, fen and swamp communities, but it shares the habitat of laterally moving water in a saturated soil. How do I recognise it? This priority type encompasses a wide range of plant communities, united by their need for a constantly wet habitat. They vary from valley mires and rushy pastures to herb-rich swards, sedge mires and montane springs and flushes. Sedges, rushes and bryophytes are the predominant species. This priority type includes some of our most species-rich vegetation and is home to some of our rarest species. These communities are also a valuable habitat for upland invertebrates and birds. For the most part they are maintained by light grazing. Differentiation from other Priority Habitats The flushes that occur only in the uplands: M7, M8, M11, M12 and M31-M38 belong by definition to this priority habitat. Those with a wider altitudinal range belong to this priority habitat where they occur in the unenclosed uplands (but not on limestone pavement) and in the Lowland fens priority habitat where they occur in enclosed agricultural lowlands. Definition in relation to other habitat classifications Classification Habitat types belonging to this UK BAP priority habitat M4-6 (examples in unenclosed uplands), M7-8 (all examples), M9 (examples in unenclosed uplands), M10 (examples in unenclosed uplands but not on limestone pavements), M11-12 (all examples), M14 (in unenclosed uplands), M21, M23a, M25c (in unenclosed uplands), M27 (in unenclosed uplands but not on limestone pavements), M28-29 (in unenclosed uplands), M31-38 (all examples), S3 (upland examples not very closely associated with NVC aquatic habitats), S9-10 (in unenclosed uplands), S11, S19 (upland examples not very closely associated with aquatic habitats), S27 (upland examples not dominated by Phragmites), U6 (flushed, herb-rich forms – no NVC sub-community exists to accommodate these), and non-NVC Neutral small sedge flush (examples in unenclosed upland areas). M4-12, 21, 23, 27, 31-34, 37-38, S27 and U6 are included in the Scottish Biodiversity List. Phase 1 E2, E3 and F1 (examples in unenclosed upland areas). All examples of this priority habitat which conform to the NVC UK BAP broad communities described above belong in the broad habitat - Fen, habitat marsh and swamp. Definition in relation to legislative classifications Classification Habitat types belonging to this UK BAP priority habitat H7140 (upland examples), H7150 (examples which are not on Habitats Directive deep peat in bog ombrotrophic habitats), H7220 (all examples) Annex I and H7230 (upland examples). Alkaline fen Alpine flush Sub-alpine flushes SNH SSSI habitat Ladder fen features Spring-head, rill and flush This priority habitat can also be part of a mosaic of two or more SSSI habitat features classed together as the Upland assemblage SSSI habitat feature. Where is it? The Upland flushes, fens and swamps are communities of wet habitats. These vary from: springs, where water emerges from the ground at varying speeds from a slow trickle to a powerful gush, to stony and soily flushes where water seeps or runs over the surface of the ground, to fens and swamps where the water moves slowly, if at all, through deep soil. As surface water is a product of a cool and