Common (Translated Scientific) Name: Temperate & Boreal Cliff, Scree & Other Rock Vegetation Formation

Colloquial Name: Temperate & Boreal Cliff, Scree & Other Rock Vegetation

Hierarchy Level:  Formation

Type Concept: Temperate & Boreal Cliff, Scree & Other Rock Vegetation is found on rocky habitats (such as cliffs, talus, scree, pavement, cobbles, lava, or large rock outcrops, such as boulderfields) in the 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. Stable rock surfaces (e.g., outcrops) prevent vascular plant roots 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. The vascular woody growth forms are a mix of evergreen needle-leaved or cold-deciduous broad-leaved trees and shrubs. The low-elevation climates are temperate or boreal (excluding Mediterranean ones), where there are strong daily temperate changes and even greater seasonal variations. These climates, though, are 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.

Diagnostic Characteristics: Rocky or rocklike substrates dominated by lithomorphic growth forms, including lichen (especially foliose and crustose lichens), bryophyte, and alga, and lithophilic or rupicolous vascular plants, often with a strong component of ferns and other pteridophytes. Vascular vegetation is typically <10% cover, and may include either evergreen needle-leaved or cold-deciduous broad-leaved trees or shrubs. Vegetation structure may be patchy.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: Mediterranean rock vegetation is included here with temperate rock vegetation. We suggest that cliff and slope sites with hardpacked sedimentary rocks and clays (badlands) be included in this class. More work is needed to clarify the distinctions between rock vegetation and other sparsely vegetated habitats where rocky substrates are dominant and lichen vegetation is absent. For example, many rocky river and lake shoreline types may be placed in 2.B.4 ~Temperate to Polar Scrub & Herb Coastal Vegetation Formation (F005)$$ where vegetation is patchy but may exceed 10%.

The term scree is used broadly to include talus. Talus may be the preferred term for lower elevation habitats, where a variety of geological factors are at work, whereas scree may be the preferred term for high elevation or polar habitats where frost action is the driving factor in producing the rocky habitat. Colloquially, in the western United States, and as used here, scree generally refers to smaller particle, looser, rock debris, and is often mixed with soil, whereas talus generally refers to larger, more stable particles, with little surface soil. Scree may be somewhat more abundant in high montane settings (perhaps because of more pronounced freeze-thaw cycles and weathering of rock), but both can be found at all elevations and latitudes.

Currently, vascular plant cover includes ferns (non-woody, including clubmosses, etc.) and crevice-dwelling (rupicolous) vascular plants. Consideration could be given to excluding these from the vascular species cover estimates.

More work is needed to separate rock vegetation from very sparsely vegetated habitats dominated by rocky substrates where lichen vegetation is absent. Placement of rocky river and lake shoreline types needs review.

Similar NVC Types: No Data Available

note: No Data Available