8240 - Pavements calcaires (Habitats d'intérêt communautaire (HIC))

8240 - Pavements calcaires

Limestone pavements

8230 - Roches siliceuses avec végétation pionnière du Sedo-Scleranthion ou du Sedo albi-Veronicion dillenii

Liste hiérarchisée et descriptifs des Habitats d'Intérêt Communautaire (HIC) de la directive "Habitats-Faune-Flore"

Définition EUR 28

Regular blocks of limestone known as ‘clints’ with loose flags separated by a network of vertical fissures known as ‘grykes’ or ‘shattered pavements’, containing more loose limestone rubble. The rock surface is almost devoid of overlying soils (considerably less than 50% cover) except for some patches of shallow skeletal or loessic soils, although more extensive areas of deeper soil occasionally occur; sometimes there is encroachment of peat. This morphology offers a variety of microclimates allowing the establishment of complex vegetation consisting of a mosaic of different communities. The fissures provide a cold humid microclimate where shade-tolerant vascular plants such as Geranium robertianum and Ceterach officinale occur, as well as formations of herbaceous species typical of calcareous woodland; the small pockets of soil are occupied by communities of Mesobromion (e.g. Seslerio-Mesobromenion); heath and scrub also occur (e.g. Corylo-Fraxinetum). Apart from areas of species rich scrub (generally Prunetalia spinosae), the ecosystem is maintained by grazing in some regions; this, combined with severe winds, means that isolated shrubs can only survive in prostrate growth form (e.g. Dryas octopetala); at the margins of ungrazed sites Geranium sanguineum occurs.
In Sweden, limestone blocks are larger and cracks are smaller. The species composition reflects a more continental, dryer and cooler climate. The pavements are mostly exposed with scattered cushions of bryophytes, more seldom covered by a thin layer of soil. The surface is covered by Sedum album, Cerastium pumilum, C. semidecandrum, lichens (Aspicilia calcarea, Thamnolia vermicularis, Verrucaria nigrescens) and bryophytes (Tortella tortuosa, Grimmia pulvinata). The vegetation in the cracks contains Gymnocarpium robertianum, Asplenium ruta-muraria, A. trichomanes ssp. quadrivalens and, occasionally, bushes of Prunus spinosa, Fraxinus excelsior, Cotoneaster spp., Rosa spp.
Some sites in Ireland host an open Taxus-Juniperus scrub of major interest; certain arctic alpine species such as Gentiana verna and Dryas octopetala are characteristic and in The Burren, these species occur with Atlantic-Mediterranean species such as Neotinea maculata.

Espèces caractéristiques

Plants: Britain and Ireland - Asplenium spp., Ceterach officinale, Cystopteris fragilis, Dryas octopetala, Dryopteris villarii, Epipactis atrorubens, Gentiana verna, Polygonatum odoratum, Ribes spicatum. Sweden - Sedum album, Cerastium pumilum, C. semidecandrum, Aspicilia calcarea, Thamnolia vermicularis, Verrucaria nigrescens, Tortella tortuosa, Grimmia pulvinata, Gymnocarpium robertianum, Asplenium ruta-muraria, A. trichomanes ssp. quadrivalens.

Correspondances avec la classification du Paléarctique

62.3

Correspondances avec d'autres classifications

United Kingdom classification : ‘W8 Fraxinus excelsior-Acer campestre-Mercurialis perennis woodland' and ‘W9 Fraxinus excelsior-Sorbus aucuparia-Mercurialis perennis woodland'. Very locally in the United Kingdom, ancient woodland containing Tilia cordata occurs which is of great conservation importance.
Nordic classification: ‘5151b Asplenium ruta-muraria-Asplenium trichomanes-Homalothecium sericeum-variant' variant of ‘5151 Sedum album-Tortella spp. typ'.

Bibliographie

Conseil de l'Union européenne, 2013. Directive 2013/17/UE du Conseil du 13 mai 2013 portant adaptation de certaines directives dans le domaine de l'environnement, du fait de l'adhésion de la République de Croatie. Annexes. Partie B Protection de la nature. Journal officiel de l'Union européenne, L 158 du 10/06/2013, p. : 195-203. (Source)

European Commission, 2013. Interpretation manual of European Union habitats. EUR 28. European Commission, DG Environment, 144 p. (Source)

Bobe, B. (1991). Gefässpflanzenvegetation und Mikroklima der Karstspalten des Grossen Alvars auf Öland, Schweden. Unpubl. diploma work, München.

Etherington, J.R. (1981). Limestone heaths in south-west Britain: their soils and the maintenance of their calcicole-calcifuge mixtures.

Kelly, D. et Kirby, E.N. (1982). Irish native woodlands over limestone. J, Life Sci. R. Dubl. Soc. 3, 181-198.

O' Sullivan, A.M. (1982). The lowland grasslands of Ireland. J. Life Sci. R. Dubl. Soc. 3, 131-142. Ward,S.D. et Evans,D.F.(1976).Conservation assessment of British limestone pavements based upon floristic criteria. Biological Conservation, 9, 217-233.