PURPLE MOOR GRASS AND RUSH PASTURES (UK BAP PRIORITY HABITAT)

Summary

This priority habitat consists of vegetation dominated by tall swards of purple moor grass Molinia caerulea and rushes Juncus spp. on moist to wet, acidic to slightly basic peaty or mineral soils in the enclosed agricultural lowlands. Some examples are rush-dominated, with an associated flora including mesotrophic herbs. The examples dominated by purple moor grass (M24-26) have a flora generally associated with more acidic soils and, where soils are less acidic, mesotrophic herbs as in the M23 rush mires. This priority habitat is widespread at low altitudes in Scotland and it is most common in the south and west where it accounts for a significant proportion of the semi-natural wetland vegetation in the enclosed agricultural lowlands.

There are several plant species of note in this priority habitat in Scotland. This is an important breeding and feeding habitat for birds such as snipe Gallinago gallinago, curlew Numenius arquata, redshank Tringa totanus, lapwing Vanellus vanellus, barn owl Tyto alba, kestrel Falco tinnunculus and skylark Alauda arvensis, and is also important for many invertebrates.

The most common types of land management here are draining, grazing and afforestation. Draining can make conditions too dry so that wetland plants are lost at the expense of more common and more vigorous species. Overgrazing can reduce flowering and seed setting of palatable wetland herbs, but undergrazing or removal of grazing can allow stands of Molinia and Juncus to grow so tall and thick as to outcompete smaller wetland plants, leading to a reduction in botanical diversity. Some trampling associated with grazing can encourage a rich and varied flora.

What is it?

The Purple moor grass and rush pastures priority habitat consists of vegetation dominated by tall swards of Molinia caerulea, soft rush Juncus effusus, sharp-flowered rush J. acutiflorus or blunt-flowered rush J. subnodulosus on moist to wet, acidic to slightly basic soils in the enclosed agricultural lowlands. The soils can be mineral soil or peat. If it is peat, it is less than 50 cm deep and has at least some lateral ground flow of water and this separates the habitat from the Molinia vegetation on rain-fed ombrotrophic peat, which belongs in the Blanket bog and Lowland raised bog priority habitats.

The rush-dominated examples of this priority habitat (NVC communities M22-23) are all on more or less neutral soils, contrasting with more acidic rush mires (M6c and d) which belong in the Lowland fens and Upland flushes, fens and swamps priority habitats. Almost all of these neutral rush pastures are dominated by Juncus acutiflorus (M23a) or J. effusus (M23b). Examples with abundant J. subnodulosus (M22) are rare in Scotland, with only one example of this NVC community noted by MacKintosh et al. (2004) in the Borders; others could be present in Galloway, Islay or south Argyll. The associated floras of these neutral rush mires typically include mesotrophic herbs such as marsh bedstraw Galium palustre, marsh thistle Cirsium palustre, meadowsweet Filipendula ulmaria, wild angelica Angelica sylvestris, water avens Geum rivale, common valerian Valeriana officinalis, ragged robin Lychnis flos-cuculi, marsh marigold Caltha palustris and water mint Mentha aquatica, mosses such as Calliergonella cuspidata, Brachythecium rivulare, B. rutabulum and Kindbergia praelonga, and liverworts such as Lophocolea bidentata.

The Molinia-dominated examples (M24-26) have a tussocky structure owing to the growth form of Molinia, plants of which can over many years develop large raised basal stools separated by wet runnels. The associated flora in these vegetation types typically includes species such as tormentil Potentilla erecta, marsh violet Viola palustris, devil’s-bit scabious Succisa pratensis, cross-leaved heath Erica tetralix, bog myrtle Myrica gale, velvet bent Agrostis canina on acidic to neutral soils and, where soils are neutral to slightly basic, Filipendula ulmaria, Angelica sylvestris, Geum rivale, Valeriana officinalis and marsh hawk’s- beard Crepis paludosa. Almost all of this Molinia vegetation belongs to NVC type M25, but a few examples are M24 with meadow thistle Cirsium dissectum – in Scotland known only from Islay, Jura and south Argyll – and M26 including great burnet Sanguisorba officinalis, marsh valerian Valeriana dioica and quaking grass Briza media.

Scottish examples of this priority habitat include localities for plant species which are more common in England and Wales: Cirsium dissectum, Juncus subnodulosus, whorled caraway Carum verticillatum, marsh stitchwort Stellaria palustris, Sanguisorba officinalis and Valeriana dioica.

How do I recognise it?

Differentiation from other Priority Habitats

Coastal and floodplain grazing marsh has a similar set of NVC communities but differs in its location being on coastal or floodplain ground which has ditches and is periodically inundated by fresh or brackish water. That priority habitat is within the Improved grassland broad habitat.

The Blanket bog and Lowland raised bog priority habitats share some Molinia dominated vegetation (NVC M25) with this priority habitat but differ in being on deep (>50 cm) peat which is entirely rain-fed or ombrotrophic, with no groundwater flow. The Molinia-dominated M25 vegetation found very commonly and extensively on shallow (<50 cm) peat in unenclosed upland areas of Britain, especially in the west, does not belong in this or any other priority habitat. Lowland fens and Lowland meadows have no NVC overlap with Purple moor grass and rush pastures and lack vegetation dominated by Molinia.

Rush-dominated vegetation of NVC type M23, as found in this priority habitat, also occurs in unenclosed upland areas where it belongs in the Upland flushes, fens and swamps priority habitat if it is the M23a sub-community but does not belong to any priority habitat if it is M23b. Superficially similar M6c or d rush mire has a more acidophilous flora including the mosses Sphagnum spp. and Polytrichum commune, and belongs in the Lowland fens and Upland flushes, fens and swamps priority habitats for lowland and upland examples respectively.

Reedbeds differ very clearly in the dominance of common reed Phragmites australis.

Definition in relation to other habitat classifications

Classification Habitat types belonging to this UK BAP priority habitat M22-24 (examples in agricultural lowlands but not in coastal or floodplain situations with ditches and periodic inundation by fresh or brackish water), M25 (examples in agricultural lowlands but not NVC on peat >50 cm deep and not in coastal or floodplain situations with ditches and periodic inundation by fresh or brackish water) and M26 (examples which are not on limestone pavement). M23 and M26 are included in the Scottish Biodiversity List. A2 (patches of scrub within this priority habitat), B5, E3 Phase 1 (examples with M22-26 in agricultural lowlands) and F1 (according to JNCC table, but this would be swamp and therefore too wet to be M22-26). 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.

NVC communities M23 and M25 account for most of this priority habitat in Scotland. M26 is scarce and mainly in southern Scotland. M22 and M24 are rare in Scotland, where they are restricted to a few places in the south.

Definition in relation to legislative classifications

Classification Habitat types belonging to this UK BAP priority habitat Habitats Directive H6410 (all occurrences). Annex I Fen meadow (examples in agricultural lowlands but not in SNH SSSI habitat coastal or floodplain situations with ditches and periodic features inundation by fresh or brackish water).

Where is it?

Purple moor grass and rush pastures occur on moist to wet, acidic to slightly basic peaty or mineral soils on level to moderately sloping ground in the enclosed agricultural lowlands. At most of their Scottish sites they occur in mosaics with other wetland UK BAP priority habitats, especially Wet woodlands and Lowland fens, or as patches marking out damper ground along flush lines or in hollows among more intensively managed pastures of improved or unimproved neutral grassland (NVC MG6-7 and MG9-10).

This priority habitat is widespread at low altitudes in Scotland, where it is most common in the south and west. It also occurs widely in Wales and western England (total at least 29000 ha) and in Northern Ireland (at least 24,600 ha) (UK BAP 2008). The total extent in Scotland is at least 4514 ha (Ellis and Munro 2004).

What is special about it?

This priority habitat is important in that it accounts for a significant proportion of the semi- natural wetland vegetation in the enclosed agricultural lowlands, especially in the south-west of Scotland and in the west of the UK as a whole.

Species of special conservation status recorded in this priority habitat in Scotland are listed below.

EC Scottish UK BAP Habitats Bio- Red Wildlife and Common priority Directive diversity Data Country-side Act Group name Latin name list Annex II List List (1981) red-shanked bee Bombus ruderarius y y carder-bee bird kestrel Falco tinnunculus y bird curlew Numenius arquata y y bird lapwing Vanellus vanellus y y y bird barn owl Tyto alba y y bird skylark Alauda arvensis y y y bird starling Sturnus vulgaris y y bird reed bunting Emberiza schoeniclus y y grasshopper bird Locustella naevia y y warbler butterfly marsh fritillary Euphydryas aurinia y y y y flowering narrow small- Calamagrostis stricta y y y plant reed flowering marsh Stellaria palustris y y plant stitchwort mammal water vole Arvicola amphibius y y y mammal otter Lutra lutra y y y y mammal roe deer Capreolus capreolus y narrow- moth bordered bee Hemaris tityus y y hawk-moth moth forester Adscita statices y y Haworth’s moth Celaena haworthii y y minor

How do we manage it?

The most common types of land management which affect this priority habitat in Scotland are draining, grazing and afforestation.

Ideal management for conservation typically includes light to moderate grazing by stock such as sheep or cattle. This keeps the height and density of the vegetation in a state whereby large, palatable wetland plants such as Filipendula ulmaria, Angelica sylvestris, Valeriana officinalis, Lychnis flos-cuculi and Crepis paludosa can flourish but potentially vigorous swards of Molinia and Juncus are prevented from growing so tall and thick as to outcompete smaller plants. This balance maintains high botanical diversity. A lack of grazing would allow Molinia and Juncus to become over-dominant.

Some degree of trampling or poaching, especially by cattle, can be beneficial to the botanical interest. As long as it is not excessive it can produce varied soil surfaces with drier raised areas, wetter depressions and patchworks of variably grazed vegetation broken up by small areas of barer ground where small plants can colonise and grow without being swamped out by larger ones.

Management should not include draining because the drying effect of this makes the habitat less suitable for specialist wetland plants such as Molinia, Juncus spp., Angelica, Filipendula and Caltha, and more suitable for a denser, competing growth of common, vigorous species such as Yorkshire fog Holcus lanatus, Festuca rubra, tufted hair-grass Deschampsia cespitosa and various trees and shrubs.

Tree-planting in this habitat is best kept to a minimum in order to maintain the characteristic ground flora, though this can persist among an open cover of trees and shrubs. If tree planting is associated with a removal of grazing, this can of course lead to an over- dominance of Molinia or Juncus.

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

MacKintosh, J., Hawker, D., Munro, K. & Smith, M. 2004. The distribution and extent of lowland grassland National Vegetation Classification (NVC) types and Biodiversity Action Plan (BAP) habitats in Scotland. Scottish Natural Heritage Commissioned Report No. 009 (ROAME No. F97AA100).

Rodwell, J.S. (Ed.) (1991b). British Plant Communities. Volume 2 - Mires and Heaths. Cambridge, Cambridge University Press.

Rodwell, J.S. (Ed.) (1992). British Plant Communities. Volume 3 - Grasslands and montane communities. 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-43-PurpleMoorGrass.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.

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/

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