Biomes

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Biomes are climatically and geographically defined areas of ecologically similar climatic conditions such as communities of plants, animals, and soil organisms that are often referred to as ecosystems. A biome is defined by several factors including, but always limited to, plant structures, leaf types, plant spacing, and climate. Biomes are often identified with particular patterns of ecological succession and climax vegetation. That is a pretty general definition that seems to confuse people somewhat, so I will clear things up with a few examples of what a biome is.

There are two ways to define biomes: the Holdridge scheme and Whittaker’s biome-type classification scheme. The Holdridge classification scheme was developed by L. R. Holdridge. It maps climates based on four categories: Average total precipitation in cm, potential evapotranspiration ratio(the potential evapotranspiration divided by the precipitation; the ratio increases from humid to arid regions), potential evapotranspiration, and mean annual biotemperature.

Whittaker, seeing the need for a simpler way to express the relationship of community structure to biomes, used what he called “gradient analysis” of ecocline patterns to relate communities to climate on a worldwide scale. Whittaker considered four main ecoclines in the terrestrial realm: Intertidal levels: The wetness gradient of areas that are exposed to alternating water and dryness with intensities that vary by location from high to low tide, climatic moisture gradient, temperature gradient by altitude,temperature gradient by latitude. When he applied these gradients, Whittaker noticed that he was able to qualitatively establish biomes. While the Holdride and Whitaker schemes may not clear up what biomes are, they help you understand how scientists have gone about establishing the many biomes of our planet.

Biomes are classified by their type: freshwater, terrestrial(land), marine, etc. The World Wide Fund for Nature has the simplest way of defining biomes. The WWF breaks them down into these categories that are fairly self-explanatory:

Tropical and subtropical dry broadleaf forests (tropical and subtropical, semi-humid)

Tropical and subtropical moist broadleaf forests (tropical and subtropical, humid)

Tropical and subtropical coniferous forests (tropical and subtropical, semi-humid)

Temperate broadleaf and mixed forests (temperate, humid)

Temperate coniferous forests (temperate, humid to semi-humid)

Boreal forests and tiaga (subarctic, humid)

Tropical and subtropical grasslands, savannahs, and shrublands (tropical and subtropical, semi-arid)

Temperate grasslands, savannahs, and shrublands (temperate, semi-arid)

Flooded grasslands and savannahs (temperate to tropical, fresh or brackish water inundated)

Montane grasslands and shrublands (alpine or montane climate)

Tundra (arctic)

Mediterranean forests, woodlands, and scrub or Sclerophyll forests (temperate warm, semi-humid to semi-arid with winter rainfall)

Deserts and xeric shrublands (temperate to tropical, arid)

Mangrove (subtropical and tropical, salt water inundated)

The biomes are further broken down and defined, but these make biomes are easier to understand for the average person. Here on Universe Today we have a couple of great articles about the Earth’s biosphere (biosphere definition). The first one is about the biosphere itself and the other is about the experiment to reproduce the biosphere in a dome. Astronomy Cast offers a good episode about the biology of the universe. You can find a lot of good information about biomes here.

Sources:
http://www.ucmp.berkeley.edu/exhibits/biomes/index.php
http://en.wikipedia.org/wiki/Biome
http://www.cotf.edu/ete/modules/msese/earthsysflr/biomes.html
http://www.radford.edu/swoodwar/CLASSES/GEOG235/biomes/intro.html

Tagged as: biome, biomes, ecosystems. ecosystem