LOWLAND FENS (UK BAP PRIORITY HABITAT)

Summary The Lowland fens priority habitat encompasses a very wide range of wetlands on wet acid, neutral or basic soils in the enclosed agricultural lowlands. The Lowland fens priority habitat encompasses a very wide range of wetland communities including soligenous and topogenous sedge and rush mires, herb-rich soakways, stands of tall herb-dominated vegetation and swamps dominated by tall sedges, grasses or herbs. To some extent this is the lowland counterpart of the Upland flushes, fens and swamps priority habitat and many NVC communities are shared by both priority habitats.

Lowland fens are commonly associated with other wetland habitats including wet woodland, and can also occur among otherwise drier farmland landscapes. They are widespread throughout the lowland areas of Scotland but are scarcer in the drier east. They also occur within enclosed lower ground in upland areas of Scotland. They are important as relatively small patches of semi-natural wetland within much larger areas of more modified, intensively-managed and ecologically less diverse farmland. Ideal management for conservation varies according to the different types of Lowland fens, but commonly includes light or moderate grazing by stock such as sheep or cattle, and an avoidance of artificial drainage, peat-cutting, burning and afforestation. What is it? The Lowland fens priority habitat encompasses a very wide range of wetlands including soligenous and topogenous sedge and rush mires, herb-rich soakways, stands of tall herb-dominated vegetation and swamps dominated by tall sedges, grasses or herbs. To some extent this is the lowland counterpart of the Upland flushes, fens and swamps priority

habitat: many NVC communities are shared by both priority habitats. For the purpose of description this large and varied priority habitat is split into five subdivisions related to NVC communities: Swamps NVC swamp communities on very wet ground or in shallow water are included in this priority habitat, but where they form a very narrow waterside strip or emergent stands in open water, they belong in one of the aquatic priority habitats. The swamps included in this priority habitat consist of species-poor, in some stands single-species, swards of species such as great reedmace Typha latifolia, greater pond sedge Carex riparia, lesser pond sedge C. acutiformis and reed canary grass Phalaris arundinacea. The more floristically diverse examples include herbs such as marsh bedstraw Galium palustre, marsh cinquefoil Potentilla palustris, water mint Mentha aquatica, marsh marigold Caltha palustris and meadowsweet Filipendula ulmaria. Tall fen communities These are generally on wet neutral soils and consist of tall, lush assemblages of plants such as Filipendula ulmaria, flag Iris pseudacorus, wild angelica Angelica sylvestris, valerian Valeriana officinalis, ragged robin Lychnis flos-cuculi, marsh thistle Cirsium palustre, hemlock water-dropwort Oenanthe crocata, Mentha aquatica and Galium palustre. There is a sparse growth of bryophytes such as the mosses Calliergonella cuspidata, Kindbergia praelonga and Brachythecium rutabulum. Some M27 vegetation can be overwhelmingly dominated by F. ulmaria with only a very sparse associated flora. Sedge mires or flushes These communities have shorter vegetation than most of the swamps and fens, and their associated flora shows great variation according to the acidity of the soils. The most common sedges are common sedge Carex nigra, star sedge C. echinata, carnation sedge C. panicea, yellow sedges C. viridula (ssp. oedocarpa and ssp. brachyrrhyncha) and bottle sedge C. rostrata. Examples on acid soils typically have extensive ground carpets of mosses such as Sphagnum fallax, S. palustre and Polytrichum commune, and scattered herbs such as marsh violet Viola palustris. Those on neutral soils commonly have carpets of mosses such as Calliergonella cuspidata, Brachythecium rutabulum, B. rivulare and Kindbergia praelonga, and herbs such as Galium palustre, marsh pennywort Hydrocotyle vulgaris, marsh willowherb Epilobium palustre, Cirsium palustre, meadow buttercup Ranunculus acris and Caltha palustris. On strongly base-rich soils the flora can include carpets of ‘brown mosses’ such as Campylium stellatum, Scorpidium revolvens and S. scorpioides. Springs and soakways Springs feature much less here than in the Upland flushes, fens and swamps priority habitat, but some lowland examples are included: they contain mixtures of species such as opposite-leaved golden saxifrage Chrysosplenium oppositifolium, alternate-leaved golden saxifrage C. alternifolium, blinks Montia fontana, wavy bitter-cress Cardamine flexuosa, cuckoo flower C. pratensis, large bitter-cress C. amara and bryophytes such as the mosses Calliergonella cuspidata, Kindbergia praelonga and Brachythecium rutabulum, and the liverworts Pellia epiphylla and Conocephalum conicum. These lowland springs (M36) are still very incompletely described compared with those in the uplands (M31-M35). Lowland examples of herb-rich soakways (M29-30) belong here too: their flora includes species such as bog pondweed Potamogeton polygonifolius, marsh St. John’s-wort Hypericum elodes, many-

stalked spike-rush Eleocharis multicaulis and lesser spearwort Ranunculus flammula. They are less common in the lowlands than in the uplands. Valley mire Examples of Narthecium-Sphagnum valley mire (M21) situated among the enclosed agricultural lowlands belong in this priority habitat. Their flora includes cross-leaved heath Erica tetralix, ling Calluna vulgaris, bog myrtle Myrica gale, white-beaked sedge Rhynchospora alba and peat-forming Sphagnum spp., and is therefore very different from that of other communities in the Lowland fens priority habitat. However what M21 shares with many other Lowland fens NVC communities is laterally moving water in a saturated soil. How do I recognise it? Differentiation from other Priority Habitats The most similar UK BAP Priority habitats are Upland flushes, fens and swamps which share many NVC types with Lowland fens but differ in that they occur in unenclosed upland areas. Coastal and floodplain grazing marsh is separated by being on coastal or floodplain ground which has ditches and is periodically inundated by fresh or brackish water, and it also includes some NVC types not belonging to Lowland fens. Reedbeds differ because they are dominated by common reed Phragmites australis. Purple moor grass and rush pastures (NVC types M22-26) are not part of the Lowland fens priority habitat. Eutrophic standing waters are more aquatic, though they can include fen vegetation where this forms only a very narrow waterside strip. Definition in relation to other habitat classifications

Classification Habitat types belonging to this UK BAP priority habitat

NVC

M1-3 (in lowland non-bog situations), M4-9 (in lowlands), M10 (in lowlands and not on limestone pavements), M13 (all examples), M14 (in lowlands), M21 (all lowland examples), M27 (in lowlands and not on limestone pavements), M28-29 (in lowlands), M30, M36, S1 and S2 (all examples), S3 (non-aquatic lowlands examples), S5-6 (examples which do not form just a very thin waterside strip and which are not in coastal or floodplain situations with ditches and periodic inundation by fresh or brackish water), S7 (examples not in coastal/floodplain situations with ditches and periodic inundation), S8 (non-aquatic examples), S9-10 (lowland examples), S11 (lowland and not aquifer-fed naturally fluctuating water body), S12-14 (non-aquatic examples), S15-18 (all examples), S19 (lowland and not aquifer-fed naturally fluctuating water body), S20 (not aquatic or coastal saltmarsh), S21 (inland), S22-23 (all examples), S24-25 and S27 (not dominated by Phragmites australis), S28 (non-aquatic examples) and non-NVC neutral small sedge flush (lowland examples).

M1-2, M4-10, M13, M21, M27, S2, S25 and S27-28 are included in the Scottish Biodiversity List.

Phase 1 E2, E3 and F1 (lowland examples of all of these).

UK BAP broad habitat

All examples of this priority habitat which conform to the NVC communities described above belong in the broad habitat - Fen, marsh and swamp.

Definition in relation to legislative classifications

Classification Habitat types belonging to this UK BAP priority habitat

Habitats Directive Annex I

H7140, H7220 and H7230 (lowland occurrences).

SNH SSSI habitat features

Basin fen (including schwingmoor type): examples of NVC M1-6, M9-10, M13-14, M21, M29, M36, S1-2 and S27 which are peat-forming wetlands in badly-drained depressions.

Flood-plain fen: examples of NVC M1-3, M5, M9-10, M13-14, M29, S1-3, S5-6, S8-10, S12-14, S24-25 and S27-28 forming patches surrounded by drained fields, mainly on coastal or river floodplains.

Open water transition fen: examples of NVC S1-7, S9, S11-14, S16-21, S24-28 and OV26 at sites where this emergent vegetation is a notified feature (not just a non-notified minor component of a site notified for other wetland interest).

Springs and Spring fen (Lowland springs and flushes): lowland examples of NVC M4, M6, M10, M13-14, M32 and M35-37 where water emerges from ground surface in lowland areas.

Valley fen: examples of NVC M1-6, M9-10, M13-14, M18, M21-23, M25, M29, S1-3, S6, S9-10, S13, S24 and S27 occupying linear depressions, typically drained by a stream flowing through the middle.

Fen woodland: examples of NVC W1-7 occurring in close association with open fens.

Hydromorphological mire range

Laggs of raised bog

Transition grassland, heathland, ombrotrophic mire, saltmarsh, sand dune

Fen meadow (Lowland Grassland SSSI feature type): examples of NVC M22-26 in lowlands: can be adjacent to or mixed with other types of fen; produced and maintained by grazing, mowing or burning (otherwise it would revert to woodland).

Where is it? Lowland fens occur on a wide range of soils types, on level to moderately sloping ground in enclosed agricultural lowlands. They rely on non-intensive management and are commonly associated with other wetland UK BAP priority habitats: Wet woodland, Reedbeds, Purple moor grass and rush pastures, Eutrophic standing waters, Mesotrophic lakes, Oligotrophic and dystrophic lakes, and Ponds. Together with Lowland fens these other priority habitats can form ecologically diverse habitat mosaics. Lowland fens can also occupy the wetter parts of otherwise drier habitat mosaics including the Lowland meadows, Lowland dry acid grassland, Lowland calcareous grassland and Lowland mixed deciduous woodland priority habitats. At other sites they occur with few or no other priority habitats, occupying patches of wetter neglected land among intensively farmed pastures and arable fields. Lowland fens are widespread throughout the lowland areas of Scotland, and indeed lowland Britain as a whole. They form a significant proportion of the wetland habitats in lowland Britain. In many areas, especially drier ones, they have a patchy, uneven distribution or

occur mainly as thinly scattered small areas of wetland. Important representations of them occur in the Western Isles as the so-called ‘machair fens’. There is no accurate estimate for the extent of this habitat in Scotland, or Britain as a whole. What is special about it? Lowland fens are important in being relatively small patches of semi-natural wetland within much larger areas of more modified, intensively-managed and ecologically less diverse farmland. Their ecological interest varies greatly, as can be expected for such a variable habitat, but they are important for many groups of species. Species of special conservation status recorded in this priority habitat in Scotland are listed below.

Group Common name Latin name

UK BAP priority

list

EC Habitats Directive Annex II

Scottish Bio-

diversity List

Red Data List

Wildlife and

Country-side Act (1981)

beetles zircon reed beetle

Donacia aquatica y y

beetles oxbow diving beetle

Hydroporus rufifrons y y

birds marsh harrier Circus aerufinosus y

birds barn owl Tyto alba y y

birds grasshopper warbler

Locustella naevia y y y

birds starling Sturnus vulgaris y y y

birds reed bunting Emberiza schoeniclus y y

ferns marsh fern Thelypteris palustris y

flowering plants

narrow small-reed

Calamagrostis stricta y y y

flowering plants

Scottish small-reed

Calamagrostis scotica y y y

flowering plants

Scandinavian small-reed

Calamagrostis purpurea

y y

flowering plants

fibrous tussock-sedge

Carex appropinquata y y

flowering plants

lesser tussock-sedge

Carex diandra y

flowering plants tufted sedge Carex elata y

flowering plants Scottish dock Rumex aquaticus y y y

flowering plants

marsh stitchwort

Stellaria palustris y y y

mammals water vole Arvicola amphibius y y y

mammals otter Lutra lutra y y y y

mammals roe deer Capreolus capreolus y

moths Haworth’s minor

Celaena haworthii y y

moths forester Adscita statices y y

reptiles great crested newt

Triturus cristatus y y y y

spiders a money spider

Notioscopus sarcinatus

y y

spiders a money spider

Saaristoa firma y y

How do we manage it? The most common types of land management which affect Lowland fens in Scotland are draining, grazing and afforestation.

This is such a varied priority habitat that ideal management for conservation can vary according to the different types of vegetation. For example grazing can be especially important in vegetation which includes many small, low grown species of interest. For example many of the less excessively wet non-swamp plant communities. In other places the habitat can be so wet that this alone limits grazing and the ecological interest of the taller swampy vegetation reflects this. Good management commonly includes light or moderate grazing by stock such as sheep or cattle, but heavy grazing should be avoided as it can cause a reduction in the height, cover and flowering of large, palatable wetland plants such as Filipendula ulmaria and various Carex species. In Lowland fens vegetation types which are naturally low-grown or quite open (for example M10 flushes) avoiding heavy grazing and associated excessive trampling helps to keep soil and vegetation cover intact and to maintain populations of small plants of interest. On the other hand, grazing helps to prevent the dominance of a few large species at the expense of smaller ones. In many places there is therefore an optimum level of grazing which is intensive enough to prevent such over-dominance of tall species but not so intensive as to make the vegetation too short, with too little flowering and too much trampling. Generally the only way to discover this optimum level is by trial and error. In general, management should not include artificial drainage which, by lowering the water table, has a drying effect which can lead to increases of some common, vigorous species such as tufted hair-grass Deschampsia cespitosa, soft rush Juncus effusus, bracken Pteridium aquilinum, bramble Rubus fruticosus and various trees and shrubs, and corresponding losses of some specialist wetland plants. Ideally peat-cutting, burning and afforestation should also be avoided, because of the detrimental effects which they can have on the ecological interest and diversity of the habitat. References, links and further reading 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 Rodwell, J.S. (Ed.) (1991b). British Plant Communities. Volume 2 - Mires and Heaths. Cambridge, Cambridge University Press. Rodwell, J.S. (Ed.) (1995). British Plant Communities. Volume 4 - Aquatic communities, swamps and tall-herb fens. 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. 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. The Fen Management Handbook (2011), Editors A. McBride, I. Diack, N Droy, B. Hamill, P.Jones, J. Schutten, A. Skinner, and M. Street. Scottish Natural Heritage, Perth. http://www.snh.gov.uk/about-scotlands-nature/habitats-and-ecosystems/lochs-rivers-and-wetlands/fen/ UKBAP 2008: http://jncc.defra.gov.uk/pdf/UKBAP_BAPHabitats-27-LowlandFens.pdf

Common Standards Monitoring guidance http://www.jncc.gov.uk/page-2199 Countryside Survey: http://www.countrysidesurvey.org.uk National Biodiversity Network (NBN) Gateway https://data.nbn.org.uk/ Scottish Natural Heritage website: http://www.nature.scot UKBAP information on JNCC website: http://jncc.defra.gov.uk/default.aspx?page=5155