Different approaches to ecological classifications have been developed in terrestrial, freshwater and marine disciplines. Traditionally these approaches have focused on biotic components (
vegetation classification), abiotic components (
environmental approaches) or implied ecological and
evolutionary processes (
biogeographical approaches).
Ecosystem classifications are specific kinds of ecological classifications that consider all four elements of the definition of
ecosystems: a
biotic component, an
abiotic complex, the interactions between and within them, and the physical space they occupy (
ecotope).
Many schemes of vegetation classification are in use by the land, resource and environmental management agencies of different national and state jurisdictions. The International Vegetation Classification (IVC or EcoVeg) has been recently proposed but has not been yet widely adopted. Vegetation classifications have limited use in aquatic systems, since only a handful of freshwater or marine habitats are dominated by plants (e.g.
kelp forests or
seagrass meadows). Also, some extreme terrestrial environments, like
subterranean or
cryogenic ecosystems, are not properly described in vegetation classifications.
Biogeographical approach The disciplines of
phytogeography and
biogeography study the geographic distribution of
plant communities and
faunal communities. Common patterns of distribution of several
taxonomic groups are generalised into
bioregions,
floristic provinces or
zoogeographic regions.
Environmental approach Climate classifications are used in terrestrial disciplines due to the major influence of
climate on biological life in a region. The most popular classification scheme is probably the
Köppen climate classification scheme. Similarly
geological and
soil properties can affect terrestrial vegetation. In marine disciplines, the
stratification of water layers discriminate types based on the availability of light and nutrient, or changes in
biogeochemical properties.
Ecosystem classifications Global Ecosystem Typology Bailey outlined five different methods for identifying ecosystems:
gestalt ("a whole that is not derived through considerable of its parts"), in which regions are recognized and boundaries drawn intuitively; a map overlay system where different layers like
geology,
landforms and soil types are overlain to identify ecosystems;
multivariate clustering of site attributes;
digital image processing of
remotely sensed data grouping areas based on their appearance or other
spectral properties; or by a "controlling factors method" where a subset of factors (like soils, climate, vegetation
physiognomy or the
distribution of plant or animal species) are selected from a large array of possible ones are used to delineate ecosystems. The
International Union for The Conservation of Nature (IUCN) developed a global ecosystem
typology that conforms to the definition of ecosystems as ecological units that comprise a
biotic component, an
abiotic complex, the interactions between and within them, and occupy a finite physical space or
ecotope. This typology is based on six design principles: representation of
ecological processes, representation of
biota, conceptual consistency throughout the
biosphere, scalable structure, spatially explicit units, parsimony and utility. This approach has led to a dual representation of ecosystem functionality and composition within a flexible hierarchical structure that can be built from a top-down approach (subdivision of upper units by function) and a bottom-up approach (representation of compositional variation within functional units). ==See also==