Limestone Pavement

Limestone pavement

This habitat is made of outcrops of limestone rock. Although a few examples are on steep slopes, most are more-or-less horizontal. Characteristically, the limestone rock surface has been weathered over millions of years into paving blocks (known as ‘clints’), which have a complex pattern of crevices between them (known as ‘grikes’).

 

It is widely scattered across the uplands of Wales, northern England, Northern Ireland, and Scotland. The largest areas occur on Carboniferous limestone in North Yorkshire and Cumbria, with smaller areas in Lancashire and Wales. It also occurs in Scotland, on the more ancient Dalradian and Durness limestones.

 

Limestone pavement supports a very wide range of vegetation communities and characteristic species – see below. The vegetation is characteristically rich in vascular plants, bryophytes and lichens. It varies according to geographical location, altitude, rock type, drainage, and the presence of grazing animals. It often contains an unusual combination of plants. On the clint surfaces or upper walls of the grikes there are plants of rocky habitats, such as wall-rue Asplenium ruta-muraria and maidenhair spleenwort Asplenium trichomanes. In contrast, the grikes provide a shady, humid environment, which favours woodland or wood-edge plants, such as hart’s-tongue fern Phyllitis scolopendrium and dog’s mercury Mercurialis perennis. In the absence of grazing, shrubs and trees may develop within the grykes to create various forms of ‘wooded pavement’. In oceanic areas, scrub over limestone pavement is an important habitat for epiphytes.

 

Vegetation types

Characteristic species

Calcareous grassland/heath

 

Blue moor-grass Sesleria caerulea [Sesleria albicans], common bent Agrostis capillaris, common knapweed Centaurea nigra, crested dog’s tail Cynosurus cristatus, glaucous sedge Carex flacca, limestone bedstraw Galium sterneri, mountain avens Dryas octopetala, sheep’s-fescue Festuca ovina, wild thyme Thymus praecox

Mire

 

Common butterwort Pinguicula vulgaris, dioecious sedge Carex dioica, marsh hawksbeard Crepis paludosa, meadowsweet Filipendula ulmaria, purple moor grass Molinia caerulea, wild angelica Angelica sylvestris

Open vegetation

 

Brittle bladder-fern Cystopteris fragilis, false oat-grass Arrhenatherum elatius, green spleenwort Asplenium viride, limestone fern Gymnocarpium robertianum, maidenhair spleenwort Asplenium Trichomanes, wall-rue Asplenium ruta-mutaria

Scrub and woodland

 

Ash Fraxinus excelsior, dog’s mercury Mercurialis perennis, field maple Acer campestre, hawthorn Crataegus monogyna, ivy Hedera helix, juniper Juniperus communis, rowan Sorbus aucuparia, wood sorrel Oxalis acetosella, yew Taxus baccata