Biomes (main)
From The Encyclopedia of Earth
Biomes
Biomes are the composite of all species within a large scale ecological community. In the natural environment, these assemblies have typically co-evolved, so that they have a natural arrangement in terms of their positioning to compete for sunlight, water and nutrient resources; in some cases these associations are symbiotic, but in most cases they are simply optimal spatial arrangements to take advantage of all the resources available in a given habitat. For example, there is typically a vertical tiering, where plants of differing light requirements can occupy canopy, mid-level or forest floor niches; the same theory applies even in a grassland, where the canopy is simply the tallest of the grasses or herbs.
In the case of water competition, depth of rooting and tolerance to arid soils are chief determinants for spatial arrangement; as far as nutrient competition, plants will compete to determine the most robust competitor for a given edaphic niche. While the outcome geometry for the plant palette usually appears random, there is a complex network of ecological theory at work that determines the layout of the assembled community. The same concept applies to aquatic communities as to terrestrial systems, with some plants having immersed roots and others, either macrophytes or phytoplankton, floating or immersed at varying levels suitable for their sunlight needs.
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Kalahari xeric savanna Last Updated on 2015-07-10 18:01:28 WWF Terrestrial Ecoregions Collection The Kalahari xeric savanna is an ecoregion in southern Africa characterized by a harsh climate, where temperatures may vary by 44°C from night to day, and rainfall is infrequent. Rain appears only during the austral summer on the reddish-brown Kalahari sands , pelting the savanna with violent, localized storms. Although this area is semi-arid, there is an impressive diversity of migratory birds and large mammals, both herbivorous and carnivorous; in fact, 550 different vertebrates have been observed in the Kalahari xeric savanna. This ecoregion is classified within the Deserts and Xeric Shrublands biome. A considerable fraction (approximately 18 percent) of the Kalahari xeric savanna is protected. Where lands are not protected, overgrazing has often severely degraded habitat. Fences are a significant... More » 
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Madagascar dry deciduous forests Last Updated on 2015-06-02 11:51:21 WWF Terrestrial Ecoregions Collection The Madagascar dry deciduous forests of western Madagascar are some of the world’s most species rich and most distinctive tropical dry forests. They are characterized by very high local plant and animal endemism at the species, genera and family levels. A significant fraction of these dry forests have been previously cleared, and the remaining forests are fragmented and critically threatened by uncontrolled burning and cuttining for charcoal production, grazing and agriculture. Since human settlement of this region during the Holocene, an estimated 97 percent of the island’s dry deciduous western forests have been destroyed, and those remaining are extremely localized and fragmented. This ecoregion also contains spectacular limestone karst formations, known as tsingy, and their associated forests,... More » 
