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Vegetation is an assemblage of and the ground cover they provide.
It is a general term, without specific reference to particular Taxon, life forms, structure, Spatial ecology extent, or any other specific Botany or geographic characteristics. It is broader than the term flora which refers to species richness. Perhaps the closest synonym is plant community, but "vegetation" can, and often does, refer to a wider range of than that term does, including scales as large as the global. Primeval , coastal mangrove stands, , desert , Road verge weed patches, wheat fields, cultivated and lawns; all are encompassed by the term "vegetation".The vegetation type is defined by characteristic dominant species, or a common aspect of the assemblage, such as an elevation range or environmental commonality.Introduction to California Plant Life; Robert Ornduff, Phyllis M. Faber, Todd Keeler-Wolf; 2003 ed.; p. 112 The contemporary use of "vegetation" approximates that of ecologist Frederic Clements' term earth cover, an expression still used by the Bureau of Land Management.
Other concepts similar to vegetation are "physiognomy of vegetation" (Humboldt, 1805, 1807) and "formation" (August Grisebach, 1838, derived from " Vegetationsform", Martius, 1824).Martius, C. F. P. von. 1824. Die Physiognomie des Pflanzenreiches in Brasilien. Eine Rede, gelesen in der am 14. Febr. 1824 gehaltnen Sitzung der Königlichen Bayerischen Akademie der Wissenschaften. München, Lindauer, [1] .
Departing from Linnean taxonomy, Humboldt established a new science, dividing plant geography between taxonomists who studied plants as taxa and geographers who studied plants as vegetation.Ebach, M.C. (2015). Origins of biogeography. The role of biological classification in early plant and animal geography. Dordrecht: Springer, p. 89, [2]. The physiognomic approach in the study of vegetation is common among biogeographers working on vegetation on a world scale, or when there is a lack of taxonomic knowledge of someplace (e.g., in the tropics, where biodiversity is commonly high).
The concept of "vegetation type" is more ambiguous. The definition of a specific vegetation type may include not only physiognomy but also floristic and habitat aspects.Walter, B. M. T. (2006). Fitofisionomias do bioma Cerrado: síntese terminológica e relações florísticas. Doctoral dissertation, Universidade de Brasília, p. 10, . Furthermore, the phytosociology approach in the study of vegetation relies upon a fundamental unit, the plant association, which is defined upon flora.Rizzini, C.T. 1997. Tratado de fitogeografia do Brasil: aspectos ecológicos, sociológicos e florísticos. 2 ed. Rio de Janeiro: Âmbito Cultural Edições, p. 7-11.
An influential, clear and simple classification scheme for types of vegetation was produced by Wagner & von Sydow (1888).
Other important works with a physiognomic approach includes Grisebach (1872), Eugenius Warming (1895, 1909), Schimper (1898), Arthur Tansley and Chipp (1926), Rübel (1930), Burtt Davy (1938), Beard (1944, 1955), André Aubréville (1956, 1957), Trochain (1955, 1957), Küchler (1967), Heinz Ellenberg and Mueller-Dombois (1967) (see vegetation classification).
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There are many approaches for the classification of vegetation (physiognomy, flora, ecology, etc.).de Laubenfels, D. J. 1975. Mapping the World's Vegetation: Regionalization of Formation and Flora. Syracuse University Press: Syracuse, NY.
Much of the work on vegetation classification comes from European and North American ecologists, and they have fundamentally different approaches. In North America, vegetation types are based on a combination of the following criteria: climate pattern, plant habit, phenology and/or growth form, and dominant species. 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 hierarchy and incorporates the non-floristic criteria into the upper (most general) five levels and limited floristic criteria only into the lower (most specific) two levels. In Europe, classification often relies much more heavily, sometimes entirely, on floristic (species) composition alone, without explicit reference to climate, phenology or growth forms. It often emphasizes Indicator value which may distinguish one classification from another.In the FGDC standard, the hierarchy levels, from most general to most specific, are: system, class, subclass, group, formation, alliance, and association. The lowest level, or association, is thus the most precisely defined, and incorporates the names of the dominant one to three (usually two) species of a 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, sclerophyllous, closed-canopy forest"; at the level of alliance as " Arbutus menziesii forest"; and at the level of association as " Arbutus menziesii-Lithocarpus dense flora forest", referring to Pacific madrone-tanoak forests which occur in California and Oregon, US. In practice, the levels of the alliance and/or an association are the most often used, particularly in vegetation mapping, just as the Latin binomial is most often used in discussing particular species in taxonomy and in general communication.
Temporal change at a slower pace is ubiquitous; it comprises the ecological succession field. Succession is the relatively gradual structure and taxonomic composition change that arises as the vegetation modifies various environmental variables over time, including light, water, and nutrient levels. These modifications change the suite of species most adapted to grow, survive, and reproduce in an area, causing floristic changes. These floristic changes contribute to structural changes inherent in plant growth even in the absence of species changes (especially where plants have a large maximum size, i.e., trees), causing slow and broadly predictable changes in the vegetation. Succession can be interrupted at any time by disturbance, setting the system back to a previous state or off on another trajectory altogether. Because of this, successional processes may or may not lead to some static, climax community. Moreover, accurately predicting the characteristics of such a state, even if it does arise, is not always possible. In short, vegetative communities are subject to many variables that set limits on future conditions' predictability.
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