Upland Calcareous Grassland
Upland calcareous grasslands are found on thin base-rich soils derived fromunderlying limestone rocks. Most examples occur at altitudes of 250 - 300 m, but the habitat is also found on unenclosed moorland at lower elevations. They are subject to a harsher climate than their lowland counterparts and so their vegetation has developed a slightly different character. While many of their characteristic species, such as thyme Thymus praecox and quaking grass Briza media, are shared with lowland grasslands, plants associated with acid grasslands, such as tormentil Potentilla erecta, flea sedge Carex pulicaris and mat grass Nardus stricta, can also be found. Upland calcareous grasslands typically occur as part of a habitat mosaic managed as rough grazing.
Upland calcareous grasslands are a relatively rare upland vegetation type which supports a particularly wide range of plants, including some very rare or specialised species such as spring gentian Gentiana verna and Teesdale violet Viola rupestris. The habitat is used by a number of breeding birds including skylark and lapwing, and is important for several invertebrate species.
There is estimated to be 10 000 ha of upland calcareous grassland in England. Little data is available on how the extent or quality of the habitat has changed in recent years. Within the UK the North Pennines, Cumbria and Breadalbane in Scotland are regarded as being particularly important areas for upland calcareous Grassland.
Upper Teesdale is the stronghold for upland calcareous grassland within the North East Region and supports a flora that is particularly rich in rarities, for example hair sedge Carex capillaris. Elsewhere, smaller areas of calcareous grassland are found on the Carboniferous Limestone and in association with outcrops of the Whin Sill.
The majority of upland limestone grasslands within the Region have been designated as SSSI. The important calcareous grasslands of Teesdale are within the Moor House - Upper Teesdale Special Area of Conservation (SAC), and form part of the Upper Teesdale NNR.
- Overgrazing can cause soil erosion and lead to a loss of species-richness and structural diversity within the grassland.
- Neglect and absence of grazing can lead to scrub encroachment or bracken invasion and loss of grassland areas.
- Agricultural intensification in the form of fertilizer use, herbicide application, ploughing and re-seeding has historically been a major source of losses of grassland sites and may still potentially be damaging and destroying some grasslands.
- The in-filling of abandoned limestone quarries (eg, by use as land-fill sites) where calcareous grasslands have become established is a threat in some localities.
- Acidification and nitrogen enrichment caused by atmospheric deposition may have a deleterious effect on calcareous grasslands, but potential impacts have not been fully assessed.
Opportunities for protection and enhancement
- Upland calcareous grassland is the principal target of the Tier 2B pasture option of the Pennine Dales ESA. The Environmental Stewardship Scheme has an option which makes payments for the appropriate management of upland calcareous grasslands.