Vegetation

Vegetation is a general term for the plant life of an area; it refers to the ground cover provided by plants, and is by far the most abundant biotic element of the biosphere. The term is general: it does not, by itself, imply anything regarding species composition, life forms, structure, spatial extent, "naturalness" or any other more specific botanical or geographic characteristics. It is related to, but not synonymous with, flora but is broader in that it is not limited to information on species composition alone. Perhaps the closest synonym is plant community. Primeval redwood forests, coastal mangrove stands, sphagnum bogs, desert soil crusts, roadside weed patches, wheat fields, cultivated gardens and lawns; all are encompassed by the term.

Related Topics:
Plant - Biosphere - Flora - Plant community

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Vegetation serves several critical functions in the biosphere, at all possible spatial scales. First, vegetation regulates the flow of several biogeochemical cycles, most critically those of water, carbon, and nitrogen; it is also of great importance in the global energy balance. Such cycles are important not only for global patterns of vegetation but also for those of climate. Second, vegetation strongly affects soil characteristics, including soil volume, chemistry and texture, which feed back to affect various vegetational characteristics, including productivity and structure. Third, vegetation serves as wildlife habitat and the energy source for the vast array of animal species on the planet. Vegetation is also critically important to the world economy, particularly in the use of fossil fuels as an energy source, but also in the global production of food and other materials.

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Classification of vegetation (in North America) into vegetation types is based on a combination of climate pattern, plant habit, phenology and/or growth form, and species composition. In Europe, classification relies more heavily on floristic composition alone. In the current US standard adopted by the Federal Geographic Data Committee (FGDC), and originally developed by UNESCO and The Nature Conservancy, the classification is hierarchical and incorporates the non-floristic criteria just mentioned into the upper five levels and floristic criteria into its lower two levels. The hierarchy levels, from most general to most specific are referred to as: system, class, subclass, group, formation, alliance and association. The lowest level, or association, is thus the most precisely defined, and incoporates the names of the dominant one to three (usually two) species of the type. An example of a vegetation type defined at the level of class might be "Forest, canopy cover > 60%", at the level of a formation as "Winter-rain, broad-leaved, evergreen, scleophyllous, closed-canopy forest", at the level of alliance as "Arbutus menziesii forest" and at the level of association as "Arbutus menziesii-Lithocarpus densiflora forest". The levels of the alliance or association are most often used, particularly in vegetation mapping.

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Vegetation scientists study the causes of the patterns and processes observed in vegetation at various scales of distance and time. Of particular interest and importance is the question of the relative roles of climate, soil, topography and history on vegetation characteristics, including both species composition and structure. Because such questions are generally large scale, they usually cannot be addressed by experimentation in a meaningful way, and thus observational studies supplemented by knowledge of botany, paleobotany, ecology, soil science etc, are the rule.

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