Biome

In ecology, a biome is a major regional group of distinctive plant and animal communities best adapted to the region's physical natural environment, latitude, elevation, and terrain. A biome is made up of ecoregions or communities at stable steady state and all associated transitional, disturbed, or degraded, vegetation, fauna and soils, but can often be identified by the climax vegetation type.

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, moisture availability, and temperature.

A fundamental classification of biomes is into:

1. Terrestrial (land) biomes and
2. 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 veld 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 Biodiversity Action Plan.

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Terrestrial biomes

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. Mountainous regions often exhibit complex patterns of climate and rainfall, resulting in a diversity of habitat types.

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.

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

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).

• Polar Domain
  • Tundra Division
    • Tundra Division - Mountain Provinces
  • Subarctic Division
    • Subarctic Division - Mountain Provinces
• Humid Temperate Domain
  • Warm Continental Division
    • Warm Continental Division - Mountain Provinces
  • Hot Continental Division
    • Hot Continental Division - Mountain Provinces
  • Subtropical Division
    • Subtropical Division - Mountain Provinces
  • Marine Division
    • Marine Division - Mountain Provinces
  • Prairie Division
  • Mediterranean Division
    • Mediterranean Division - Mountain Provinces
• Dry Domain
  • Tropical/Subtropical Steppe Division
    • Tropical/Subtropical Steppe Division - Mountain Provinces
  • Tropical/Subtropical Desert Division
  • Temperate Steppe Division
    • Temperate Steppe Division - Mountain Provinces
  • Temperate Desert Division
    • Temperate Desert Division - Mountain Provinces
• Humid Tropical Domain
  • Savanna Division
    • Savanna Division - Mountain Provinces
  • Rainforest Division
    • Rainforest Division - Mountain Provinces

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 867 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)
• 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)

 

Aquatic biomes

• continental shelf
• littoral/intertidal zone
• riparian
• pond
• coral reef
• kelp forest
• pack ice
• hydrothermal vents
• cold seeps
• benthic zone
• pelagic zone
• neritic zone

 

Other biomes

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.

 

See also

• Ecoregion
• Ecotope
• Ecozone
• Habitat

 

 

External links

• Biomes of the world (Missouri Botanic Garden)
• Biomes Quiz