61 - Screes, gravel and boulder fields

Classification des habitats du Paléarctique (2001)

Description

Accumulations of boulders, stones, rock fragments, pebbles, gravels or finer material, of non-aeolian depositional origin, unvegetated, occupied by lichens or mosses, or colonized by sparse herb- or shrub-dominated communities. Included are screes and scree slopes produced by slope processes, moraines and drumlins originating from glacial deposition, sandar, eskers and kames resulting from fluvio-glacial deposition, block slopes, block streams and block fields constructed by periglacial depositional processes of downslope mass movement, ancient beach deposits constituted by former coastal constructional processes. Deposits originating from aeolian depositional processes (dunes) or from eruptive volcanic activity are not included, nor are those developed under desert climates; they are included in sections 64, 66 and 7, respectively. Accumulations of rock debris of erosional origin, resulting from frost weathering, heaving, thrusting or cracking, from aeolian denudation, erosion or abrasion processes, or from glacial erosion are also excluded and placed in unit 62. High mountain, boreal and mediterranean unstable screes are colonized by highly specialized plant communities. They or their constituting species may also inhabit moraines and other depositional debris accumulations in the same areas. A very few communities form in lowland areas elsewhere.

Correspondances phytosociologiques

Thlaspietea rotundifolii p., Drypetea spinosae i.a.

Bibliographie

Devillers P., Devillers-Terschuren J. & Vander Linden C., 2001. PHYSIS Palaearctic Habitat Classification Database. Updated to 10 December 2001. Institut Royal des Sciences Naturelles, Bruxelles. (Source)

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