UPLAND CALCAREOUS GRASSLAND (UK BAP PRIORITY HABITAT)

Summary

This priority habitat includes herb-rich upland grasslands and mountain avens Dryas octopetala heaths. They share an array of base-tolerant and are notable for a large number of rare and scarce species

This habitat occurs in mosaics with other upland grasslands, more acid heaths, bogs and montane communities, generally marking out areas of mineral soil where the underlying rocks or irrigating water, or both, are moderately to strongly base-rich. The climate is the typical upland combination of short, cool summers, long cold winters and plentiful wind, rain and snow.

Herb-rich upland communities occur throughout the uplands of , but are most extensive and best-developed in regions where much of the underlying rock is base-rich, such as the Dalradian schists and limestones, the Durness limestone and basic exposures of Moine schist and Lewisian gneiss. The Upland calcareous grassland priority habitat can occur from a few metres above sea level to over 1000 m on the highest hills.

With the exception of the montane Dryas heath CG14, which occurs on inaccessible cliff ledges for the most part, this habitat has developed from and needs to be maintained by grazing. Some examples experience exceptionally heavy grazing so that the sward is less than 5 cm tall and although this may prevent the flowering and setting seed it is likely to maintain the high diversity of species. If there is no grazing or not enough, then species diversity can be lost as the larger grasses and herbs increase at the expense of smaller or less competitive herbs. Further, a layer of litter and humus can accumulate, reducing the influence of the base-rich soil so much that herb-rich swards can be transformed within a few years into acid grassland or heath. Agricultural improvement and recreational developments on the upland margins can also threaten vegetation of this type.

What is it?

Upland calcareous grassland is notable for the array of base-demanding herbs and shrubs that grow among the grasses. Wild thyme Thymus polytrichus is the species that more than any other separates the calcareous from the neutral and acid grasslands, and the sweet scent of its crushed and flowers is noticeable on still, warm days. The sward is made up of species such as sheep’s fescue ovina, viviparous sheep's-fescue F. vivipara, red fescue F. rubra, common bent Agrostis capillaris, velvet bent A. canina, sweet vernal- grass Anthoxanthum odoratum and, on damper soils, sedges such as carnation sedge Carex panicea, flea sedge C. pulicaris, spring sedge C. caryophyllea and glaucous sedge C. flacca. These give a distinct greyish look to the vegetation. Quaking grass Briza media and meadow oat-grass also occur on the richer soils.

In U5c the dominant grass is mat grass Nardus stricta. The relative proportions of graminoids and herbs varies between the communities: the Festuca-Agrostis-Thymus grassland CG10 can be entirely dominated by grasses; the Festuca-Agrostis-Alchemilla grassland CG11 has a more herb-rich sward in which the yellow flowers of alpine lady’s mantle Alchemilla alpina are conspicuous in summer; the Festuca-Alchemilla-Silene community CG12 is generally dominated by herbs and the patches are a much brighter green than the more grassy swards.

Typical herbs found in all of these swards include meadow buttercup Ranunculus acris, selfheal Prunella vulgaris, ribwort plantain Plantago lanceolata, yarrow Achillea millefolium, alpine lady’s mantle Alchemilla alpina and A. glabra. On damp or flushed soils these are joined by species such as water avens Geum rivale, lesser clubmoss Selaginella selaginoides, meadowsweet Filipendula ulmaria, fairy flax Linum catharticum and globeflower Trollius europaeus. At higher altitudes and in the far north these grasslands are home to more montane calcicoles such as alpine bistort Persicaria vivipara, hair sedge Carex capillaris, alpine meadow-rue Thalictrum alpinum, campion Silene acaulis and cyphel Minuartia sedoides. The mountain avens Dryas octopetala swards CG13 and CG14 share the species of the other calcareous grasslands, growing through a creeping mat of D. octopetala with its scalloped, glossy, dark green leaves and large cream flowers in, early summer.

The bryophyte element in all of these grasslands is similar, with species such as Hypnum lacunosum, Tortella tortuosa, Hylocomium splendens, Ctenidium molluscum and, at higher altitudes, Ditrichum flexicaule s.l., Orthothecium rufescens and the liverwort Herbertus stramineus.

This habitat is notable for a large number of rare and scarce species including false sedge Kobresia simpliciuscula, purple oxytropis Oxytropis halleri, alpine forget-me-not Myosotis alpestris, alpine milk-vetch Astragalus alpinus, alpine bartsia Bartsia alpina, alpine pearlwort saginoides, alpine gentian Gentiana nivalis, Scottish primrose Primula scotica, and bryophytes Timmia norvegica, T. austriaca, Ptychodium plicatum, Pseudoleskeela incurvata, Saelania glaucescens, Seligeria trifaria, Syntrichia princeps, S. norvegicum and Campylophyllum halleri.

How do I recognise it?

These are grasslands on base-rich soils in the uplands. They consist of mixtures of grasses such as Festuca ovina, Agrostis capillaris and Anthoxanthum growing with Thymus polytrichus and a rich array of small base-tolerant herbs. Dryas octopetala is the dominant species in some examples and these are really more calcareous heaths than calcareous grasslands. Examples below the tree-line are produced and maintained by grazing; those in the montane zone are possibly near-natural climax communities but probably still need at least low levels of grazing to keep the larger, more vigorous plants in check. These grasslands are home to many of our most rare and threatened plant species. They are an important food source for grazing mammals, invertebrates and upland birds.

Differentiation from other Priority Habitats

In most cases the NVC community separates Upland calcareous grassland and Lowland calcareous grassland priority habitats: CG1-CG8 are lowland communities and CG11-CG14 and U5c are upland ones. CG10 (and in England CG9) can occur in both lowland and upland priority habitats and should be divided according to whether it occurs above the upper limits of agricultural land (upland) or within enclosed fields (lowland). Examples on coastal cliffs are classed as lowland. Examples of CG10 and CG13 on limestone pavements belong to the Limestone pavements priority habitat.

Definition in relation to other habitat classifications

Classification Habitat types belonging to this UK BAP priority habitat CG10 (all upland examples except those on coastal cliffs or limestone pavements), CG11-12 (all examples), CG13-14 (where not on limestone pavement), U4c and other flushed, herb-rich NVC examples and U5c (all examples). In N. England this priority habitat also includes upland examples of CG9 (this NVC community is not recorded in Scotland). (CG10-14 are all included in the Scottish Biodiversity List.) Phase 1 B3 (all upland examples). Examples of this priority habitat conforming to NVC CG10-14, UK BAP broad U4c and related forms, and U5c, as described, belong to the habitat broad habitat – Calcareous grassland.

CG10 is the most widespread of the NVC grassland communities in this priority habitat, and it occurs over the greatest altitudinal range. It is also well represented in the uplands of England and Wales. CG11 is common at higher altitudes. It occurs in northern England but not Wales. CG12 and CG14 are confined to basic soils at high altitudes and are uncommon in Scotland and rare in Wales; CG13 is confined to limestone soils at low altitudes in the far north and west Highlands. U5c has been recorded in small stands throughout the British uplands. CG9 in upland habitats also belongs to this priority type, but does not occur in Scotland.

Definition in relation to legislative classifications

Classification Habitat types belonging to this UK BAP priority habitat Habitats H6170 (all occurrences - this Annex I type includes all of the Directive Annex I Upland calcareous grassland priority habitat in Scotland). Subalpine calcareous grassland and Alpine calcareous grassland SSSI feature types (CG10-11 and CG12-14 respectively). This SNH SSSI priority habitat can also be part of a mosaic of two or more SSSI habitat features habitat features classed together as the Upland assemblage SSSI habitat feature.

Where is it?

Upland calcareous grassland comprises communities of base-rich mineral soils derived from rocks such as limestone, basalt and calcareous schists. The base status of the soil tends to be between 5.3 and 7.5 (McVean and Ratcliffe 1962) and is maintained by physical and chemical weathering or by flushing with base-rich water. The grasslands occur on hillsides, on consolidated scree, along streamsides and in glens. They are common along cliff-bases, where they may have many species in common with the vegetation of the ungrazed ledges. The altitudinal range is from near sea-level to over 1000 m. The higher examples may be covered by snow for much of the winter. Stands vary in size from a few square metres to several hectares and occur in mosaics with a range of heaths and other grasslands. The Dryas-Silene community CG14 is confined to ungrazed ledges or otherwise inaccessible sites away from grazing animals.

These grasslands generally form mosaics with upland acid grasslands or heaths or, at higher altitudes, with montane habitats. They can be dissected with base-rich springs and flushes where water reaches the surface of the ground. They can occur on river banks and vegetated river shingle adjacent to stands of blanket bog. They are common too around exposures of limestone pavement. Bands of calcicolous grassland along cliff bases may have many species in common with the vegetation of the ungrazed ledges above. They may also occur on the margins of grazed woodland.

Upland calcareous grassland is most common and widespread in the Scottish highlands, where all the communities occur. CG10 is the least exacting and occurs throughout the southern uplands and on smaller areas of hill ground within the more lowland areas of Fife and the Central Belt. CG13 is confined to the limestone areas in the far north and west of Scotland from Lismore in the south-west to Durness and along the north coast to Invernaver. CG10 is common throughout the British uplands. CG11 occurs in the Scottish highlands and in northern England; CG12 and CG14 occur in the Scottish highlands and North Wales but all three are far more common in Scotland than they are further south, and CG13 is confined to Scotland. The total extent of this type of vegetation in Scotland is estimated to be around 7000 ha (SNH BAP Review), but may be as much as 10,000 – 13,000 ha (UK BAP Priority Habitat Descriptions).

Upland examples of the Sesleria-Galium grassland CG9 belong to this priority habitat. Though extensive on Carboniferous limestone soils in northern England, CG9 does not occur in Scotland.

There are similar upland calcareous grassland communities in mainland Europe and in the Faroe Islands.

What is special about it?

Some species of special conservation status recorded in this Priority Habitat are listed below.

Wildlife EC Scottish and UK BAP Habitats Bio- Red Country- Common priority Directive diversity Data side Act Group name Latin name list Annex II List List (1981) bees, ruby-tailed Chrysura hirsuta y y wasps and wasp ants bees, northern Osmia inermis y y wasps and osmia ants bees, wall mason Osmia parietina y y Wildlife EC Scottish and UK BAP Habitats Bio- Red Country- Common priority Directive diversity Data side Act Group name Latin name list Annex II List List (1981) wasps and bee ants beetles violet oil- Meloe violaceus y y beetle bird lapwing Vanellus vanellus y y y bird golden plover Pluvialis apricaria y bird ring ouzel Turdus torquatus y y y birds skylark Alauda arvensis y y y subsp. arvensis/scotica butterflies small blue Cupido minimus y y y butterflies northern Aricia artaxerxes y y y brown argus butterflies Coenonympha y y pamphilus flowering close-headed Carex norvegica y y plant alpine-sedge flowering simple bog Kobresia y y plant sedge simpliciuscula flowering purple Oxytropis halleri y y plant oxytropis flowering alpine forget- Myosotis alpestris y y plant me-not flowering alpine Sagina saginoides y y plant pearlwort flowering alpine bartsia Bartsia alpina y y plant flowering alpine gentian Gentiana nivalis y y y plant flowering Scottish Primula scotica y plant primrose flowering field gentian Gentianella y y y plants campestris flowering small-white Pseudorchis albida y y y plants orchid flowering a hawkweed Hieracium sect. y y plants Alpestria flowering arctic norvegica y y y y plants sandwort subsp. norvegica flowering alpine milk- Astragalus alpinus y y y plants vetch flowering purple milk- Astragalus danicus y y y plants vetch flowering frog orchid Coeloglossum viride y y y plants flowering cyphel Minuartia sedoides y y y plants fungi stalked Tulostoma niveum y y puffball fungi date coloured Hygrocybe spadicea y y waxcap fungi big blue Entoloma bloxamii y y pinkgill fungi dark-purple Geoglossum y y earthtongue atropurpureum fungi spignel rust Nyssopsora echinata y y fungi alpine rust Puccinia y y septentrionalis mammals red deer Cervus elaphus y moss revolute plait- Hypnum revolutum y y moss moss Timmia norvegica y y timmia moss brown Pseudoleskea y y y mountain incurvata leskea moss plaited leskea Ptychodium plicatum y y moss blue dew- Saelania glaucescens y y y Wildlife EC Scottish and UK BAP Habitats Bio- Red Country- Common priority Directive diversity Data side Act Group name Latin name list Annex II List List (1981) moss moss trifid rock- Seligeria trifaria y bristle moss brown screw- Syntrichia princeps y moss moss Norway Syntrichia norvegica y y screw-moss moss haller’s Campylophyllum y y feather-moss halleri sheathed Timmia austriaca y y y timmia reptiles common lizard Zootoca vivipara y y y

Upland calcareous grassland forms patches of very high diversity within larger areas of less species-rich heath and acid grassland, so much of the nature conservation interest in any particular area can be concentrated into these (along with some of the mires q. v.). Some examples are extremely species-rich with over 60 species in a 2m x 2m plot. These grasslands are among the main habitats in Scotland for the uncommon upland plants Alchemilla wichurae, rock sedge Carex rupestris, black alpine-sedge C. atrata, sheathed sedge C. vaginata, bearded couch Elymus caninus var. donianus, dark-red helleborine Epipactis atrorubens, rock whitlowgrass Draba norvegica, spring sandwort Minuartia verna, alpine cinquefoil crantzii, alpine mouse-ear Cerastium alpinum, alpine speedwell Veronica alpina, rock speedwell V. fruticans, alpine saxifrage Saxifraga nivalis and the bryophytes turgidum, Hypnum hamulosum, Conardia compacta, Rhytidium rugosum, Schistidium robustum, S. trichodon, Hylocomium pyrenaicum and Herbertus stramineus as well those listed in the table above.

Spring gentian Gentiana verna, Teesdale violet Viola rupestris and bird’s foot-sedge Carex ornithopoda are notable rarities in the northern English examples of this priority type.

The Dryas heaths CG13 and CG14 are surviving remnants of the sort of shrubby, flowery vegetation that is thought to have been widespread throughout Britain during the last glacial period and the immediate post-glacial times.

The flowering shrubs and herbs are a valuable nectar source for upland insects such as bumblebees.

CG11 and U5c are important habitats for the scarce Mountain Ringlet butterfly Erebia epiphron. The insects drawn to the flowering herbs and shrubs are fed upon by upland birds such as lapwing Vanellus vanellus, golden plover Pluvialis apricaria, ring ousel Turdus torquata, meadow pipit Anthus pratensis, skylark Alauda arvensis and wheatear Oenanthe oenanthe.

The grasslands are grazed by sheep, red deer, roe deer and sika deer, rabbits, mountain hares and field voles.

How do we manage it?

Almost all examples of Upland calcareous grasslandis produced and maintained by grazing, the exception being the Dryas-Silene community CG14 which is confined to inaccessible sites. Some examples are grazed to within 2 cm of the ground without losing their diversity, but too little grazing can be damaging as the larger plants and more robust grasses increase at the expense of the smaller and less-competitive species. Grazing herbivores naturally seek out and preferentially graze these patches of grassland, so it is common to find very short swards of Upland calcareous grassland set in a matrix of tall Calluna heath, for example. However, very heavy grazing tends to extend the areas of grassland by eliminating the dwarf shrubs in heaths. In some protected areas, it can be a challenge to find a level of grazing that will maintain the rich open swards of these grasslands without damaging the surrounding bogs and heaths where these are also of interest. Dryas octopetala cannot tolerate excessively heavy grazing. The Dryas-Carex community CG13 can be converted to CG10 grassland by excessive grazing, and it seems possible that CG14 was once more widespread in the Scottish hills.

CG10 swards at low altitudes may be converted to improved agricultural grassland by reseeding and fertilisation. Some examples of CG10 might revert to scrub and eventually to upland woodland in the absence of grazing, though the more montane CG11, CG12 and CG14 are likely to be near-natural climax communities. Even these may depend on light to moderate grazing to keep the more vigorous species in check.

Moderate grazing by a diversity of wild and domestic animals is probably the best way to maintain this habitat.

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

Rodwell, J.S., ed. 1991a 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-58-UplandCalcGrass.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.

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

UK BAP information on JNCC website: http://jncc.defra.gov.uk/default.aspx?page=5155