Calcareous grasslands are confined to soils or substrates which are alkaline in pH, and which are naturally low fertility and free draining. In the area covered by the Rhondda Cynon Taf LNP, most of our calcareous grasslands are associated with the quarries and road cuttings which lie on the Carboniferous limestone which runs along the southern edge of the South Wales coalfield and which outcrops around Llantrisant, Pontyclun and Llanharry. These are secondary calcareous grasslands, which have developed where land use has exposed the limestone bedrock, and where thin calcareous soils have developed. 

 

Secondary calcareous grassland can also develop away from the main carboniferous limestone areas and can be found on post-industrial land where lime-rich thin soils develop on concrete hardstanding’s or on limestone railway ballast.  Where broken up concrete occurs in colliery spoils calcacerous species can be often be found growing in complex mosaics with acid grassland and heath communities. 

 

Although secondary in occurrence, our calcareous grasslands are species and flower rich. They include a characteristic suite of species with red fescue, yellow oat-grass, quaking grass and sheep’s fescue together glaucous sedge and a characteristic herb rich flora with bird’s-foot trefoil, common knapweed, greater knapweed, cowslip, agrimony, lady’s-bedstraw, fairy flax, carline thistle, bee orchid, common- spotted orchid, pyramidal orchid, twayblade and kidney vetch. 

 

Partly because of their shear diversity of plants, and nectar sources, and partly because they are shallow soiled and warm, our calcareous grassland are important invertebrate habitats. Declining butterfly species such as the small blue butterfly and dingy skipper find food sources and basking places, the calcium rich substrate supports diverse snail populations, and in turn support glow worms (a voracious snail-predator). These sites are also excellent reptile habitats, and slow worms and common lizards are often very common. 

 

Recent declines in rabbit numbers have led to an increase in scrub invasion (often hawthorn, ash and dogwood) on many sites, and while these calcareous scrub communities are often species-rich, there is a need for long-term management if open calcareous grassland is to be retained. Conservation grazing and ‘cut and collect’ grassland management are ideal.