Abstract for S04

Temperate & Boreal Open Rock Vegetation
Végétation sur roc des zones tempérée et boréale (végétation mésomorphe de milieu ouvert – cryptogame)

Temperate & Boreal Open Rock Vegetation is found on rocky habitats (such as cliffs, talus, recent lava flows, or rock outcrops) in the Mediterranean, temperate and boreal regions around the globe. Stands typically contain a covering of saxicolous foliose and/or crustose lichens growing directly on rock surfaces and/or sparse covering of vascular plants growing in soil pockets. Vascular and nonvascular plant cover is >1%; vascular plant cover is typically <10%, with irregular horizontal spacing, and is typically exceeded by nonvascular cover, especially lichens, bryophytes, and/or algae. On stable rock surfaces (e.g., outcrops), vascular plant roots are prevented from penetrating most of the substrate, and their presence is largely determined by the rock fissures, where minimal soil development and more moisture occurs. On less stable rocky surfaces (e.g., talus), the presence of vascular plants is largely determined by a degree of permanence and depth to soil under the boulders. A sparse cover of vascular mesomorphic growth forms, including evergreen needle-leaved or cold-deciduous broad-leaved woody plants, may be present. Herbs are often seasonally green. Low-elevation temperate and boreal climates are various, often less determinative than presence of open rock surfaces. Substrates are typically very dry to moist, but occasionally wet and typically lack soil development of any kind. The climate is cool and warm temperate, Mediterranean, and to boreal, and even subarctic, where frosts occur regularly (except in part of the Mediterranean region), snow is not permanent, and there are strong daily and seasonal temperature changes.

Source: Faber-Langendoen, D., T. Keeler-Wolf, D. Meidinger, C. Josse, A. Weakley, D. Tart, G. Navarro, B. Hoagland, S. Ponomarenko, J.-P. Saucier, G. Fults, E. Helmer. 2014. Classification and description of world formation types. Part I (Introduction) and Part II (Description of world formations). Hierarchy Revisions Working Group, Federal Geographic Data Committee, FGDC Secretariat, U.S. Geological Survey. Reston, VA, and NatureServe, Arlington, VA.

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