Common (Translated Scientific) Name: Tropical Open Rock Vegetation Subclass

Colloquial Name: Tropical Open Rock Vegetation

Hierarchy Level:  Subclass

Type Concept: Tropical Open Rock Vegetation is found on rocky habitats (such as cliffs, talus, scree, pavement, cobbles, lava, or boulderfields) in the tropical regional around the globe. Stands typically contain a covering of crustose lichens and/or sparse covering of vascular plants. Vascular and nonvascular plant cover, especially bryophytes, lichens, algae, or ferns, is >1%; vascular plant cover, including bromeliad growth forms, is largely determined by the rock fissures and is typically <10%, with irregular horizontal spacing. Stable rock surfaces (e.g., outcrops) prevent vascular plant roots from penetrating, and their presence is largely determined by the rock fissures. On unstable rocky surfaces (e.g., talus), the presence of vascular plants is largely determined by a degree of permanence. Vascular woody growth forms of either evergreen broad-leaved or drought-deciduous woody plants, including lianas, may be present. Tropical climates, where daily temperate changes are greater than the seasonal changes, are various and often less determinative than presence of open rock surfaces. Substrates are typically 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, with cover >1%; vascular vegetation (including clubmosses, etc.), bromeliads, and crevice-dwelling (rupicolous) vascular plants is typically <10% cover. Vascular cover may include either evergreen broad-leaved or drought-deciduous trees and shrubs or evergreen herbs. Vegetation structure may be patchy across the rocky surfaces.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: There is little information that has been comprehensively evaluated across the globe, making it difficult to describe the type concept. We suggest that cliff and slope sites with hardpacked sedimentary rocks and clays be included in this class. More work is needed to clarify the distinctions between Open 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.A.3. ~Tropical Scrub & Herb Coastal Vegetation Formation (F024)$$ where vegetation is patchy but may exceed 10%.

Currently all vascular plant cover is treated together. But cover of ferns (non-woody, including clubmosses, etc.), bromeliads, and crevice-dwelling (rupicolous) vascular plants may need to be considered separately from other vascular cover when deciding on cover thresholds for this class.

Further review may suggest that this subclass can be improved by distinguishing the less "rocklike" vegetation (including vegetation on scree, badlands, and pavement) from the true lithomorphic (solid rock) vegetation (C. Lea pers. comm. 2012).

Similar NVC Types: No Data Available

note: No Data Available