Biome

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A biome is a climate and geographical area of ecologically similar communities of plants, animals, and soil organisms, often referred to as ecosystems. Biomes are defined based on factors such as plant structures (such as trees, shrubs, and grasses), leaf types (such as broadleaf and needleleaf), plant spacing (forest, woodland, savanna), and other factors like climate. Unlike ecozones, biomes are not defined by genetic, taxonomic, or historical similarities. Biomes are often identified with particular patterns of ecological succession and climax vegetation.

The biodiversity characteristic of each biome, especially the diversity of fauna and subdominant plant forms, is a function of abiotic factors and the biomass productivity of the dominant vegetation. Species diversity tends to be higher in terrestrial biomes with higher net primary productivity,eat out moisture availability, and temperature.^[1]

Ecoregions are grouped into both biomes and ecozones.

A fundamental classification of biomes is into:

Terrestrial (land) biomes and
Aquatic (water) biomes.

Biomes are often given local names. For example, a Temperate grassland or shrubland biome is known commonly as steppe in central Asia, savanna or veldt in southern Africa, prairie in North America, pampa in South America and outback or scrub in Australia. Sometimes an entire biome may be targeted for protection, especially under an individual nation's what evevrerereBiodiversity Action Plan.

Climate is a major factor determining the distribution of terrestrial biomes. Among the important climatic factors are:

latitude: arctic, boreal, temperate, subtropical, tropical.
humidity: humid, semi-humid, semi-arid, and arid.
- seasonal variation: rainfall may be distributed evenly throughout the year, or be marked by seasonal variations.
- dry summer, wet winter: most regions of the earth receive most of their rainfall during the summer months; Mediterranean climate regions receive their rainfall during the winter months.
elevation: increasing elevation causes a distribution of habitat types similar to that of increasing latitude.

Biodiversity generally increases away from the poles towards the equator, and increases with humidity.

The most widely used systems of classifying biomes correspond to latitude (or temperature zoning) and humidity.

Udvardy system[edit]

In 1975, Miklos Udvardy published a system of biogeographic provinces that were divided into 12 terrestrial biomes:

Tropical humid forests
Subtropical and temperate rainforests or woodlands
Temperate broad-leaf forests or woodlands and subpolar deciduous thickets
Temperate needle-leaf forests or woodlands
Evergreen sclerophyllous forests, scrub, or woodlands
Tropical dry or deciduous forests (including Monsoon forests) or woodlands
Temperate grasslands
Warm deserts and semideserts
Cold-winter (continental) deserts and semideserts
Tundra communities and barren Arctic deserts
Mixed mountain and highland systems with complex zonation
Mixed island systems

Bailey system[edit]

Robert G. Bailey developed a biogeographical classification system for the United States in a map published in 1975. Bailey subsequently expanded the system to include the rest of North America in 1981, and the world in 1989. The Bailey system is based on climate, and is divided into four domains (Polar, Humid Temperate, Dry, and Humid Tropical), with further divisions based on other climate characteristics (subarctic, warm temperate, hot temperate, and subtropical, marine and continental, lowland and mountain).

100 Polar Domain
- 120 Tundra Division
- M120 Tundra Division - Mountain Provinces
- 130 Subarctic Division
- M130 Subarctic Division - Mountain Provinces
200 Humid Temperate Domain
- 210 Warm Continental Division
- M210 Warm Continental Division - Mountain Provinces
- 220 Hot Continental Division
- M220 Hot Continental Division - Mountain Provinces
- 230 Subtropical Division
- M230 Subtropical Division - Mountain Provinces
- 240 Marine Division
- M240 Marine Division - Mountain Provinces
- 250 Prairie Division
- 260 Mediterranean Division
- M260 Mediterranean Division - Mountain Provinces
300 Dry Domain
- 310 Tropical/Subtropical Steppe Division
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WWF system[edit]

A team of biologists convened by the World Wildlife Fund (WWF) developed an ecological land classification system that identified 14 biomes, called major habitat types, and further divided the world's land area into 825 terrestrial ecoregions. This classification is used to define the Global 200 list of ecoregions identified by the (WWF) as priorities for conservation. The WWF major habitat types are as follows:

Tundra (arctic)
Boreal forests/taiga (subarctic, humid)
Temperate coniferous forests (temperate, humid to semi-humid)
Temperate broadleaf and mixed forests (temperate, humid)
Temperate grasslands, savannas, and shrublands (temperate, semi-arid)
Mediterranean forests, woodlands, and shrub (temperate warm, semi-humid to semi-arid with winter rainfall)
Tropical and subtropical coniferous forests (tropical and subtropical, semi-humid)
Tropical and subtropical moist broadleaf forests (tropical and subtropical, humid)
Tropical and subtropical dry broadleaf forests (tropical and subtropical, semi-humid)
Tropical and subtropical grasslands, savannas, and shrublands (tropical and subtropical, semi-arid)
Montane grasslands and shrublands (alpine or montane climate)
Deserts and xeric shrublands (temperate to tropical, arid)
Mangrove (subtropical and tropical, salt water inundated)
Flooded grasslands and savannas (temperate to tropical, fresh or brackish water inundated)

Freshwater biomes[edit]

WWF has several systems for classifying freshwater biomes, which vary somewhat:

Global 200 freshwater major habitat types[edit]

Large rivers
Large river headwaters
Large river deltas
Small rivers
Large lakes
Small lakes
Xeric basins

Freshwater major habitat types of Latin America and the Caribbean[edit]

For more information, see: List of freshwater ecoregions of Latin America and the Caribbean.

Large Rivers
Large River Deltas
Montane Rivers and Streams
Wet-Region Rivers and Streams
Xeric-Region Rivers and Streams
Xeric-Region Endorheic (closed) Basins
Flooded Grasslands and Savannas
Cold Streams, Bogs, Swamps, and Mires
Large Lakes

Freshwater major habitat types of Africa and Madagascar[edit]

For more information, see: List of freshwater ecoregions in Africa and Madagascar.

Closed basins and small lakes
Floodplains, swamps, and lakes
Moist forest rivers
Mediterranean systems
Highland and mountain systems
Island rivers and lakes
Large lakes
Large river deltas
Large river rapids
Savanna-dry forest rivers
Subterranean and spring systems
Xeric systems

Marine biomes[edit]

Global 200 marine major habitat types[edit]

Polar
Temperate shelves and seas
Temperate upwelling
Tropical upwelling
Tropical coral

Other marine habitat types[edit]

Other biomes[edit]

The Endolithic biome, consisting entirely of microscopic life in rock pores and cracks, kilometers beneath the surface, has only recently been discovered and does not fit well into most classification schemes.

Provenance[edit]

Some content on this page may previously have appeared on Wikipedia.

References[edit]

↑ Pidwirny, Michael (2006-10-16). Biomes. Encyclopedia of Earth. Ed. Sidney Draggan. Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment. Retrieved on 2006-11-16.

[1] Pidwirny, Michael (2006-10-16). Biomes. Encyclopedia of Earth. Ed. Sidney Draggan. Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment. Retrieved on 2006-11-16.

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