Ecology: Biomes

Biomes

The biome is a major terrestrial assemblage of plants, animals, and microorganisms that has a characteristic appearance and occurs over large geographical areas on the earth's surface.

Biomes are largely determined by combination of temperature (in term determined by latitude) and rainfall, as indicated by the following diagram:

Biome diagram from Environmental Biology - Grasslands page

for a geographical representation see the Holdridge Life-Zone map at the NPP Database

Biomes can be divided up in several ways, but it is most usual to list six or seven: (from tropical to polar): tropical rainforest, savanna, desert, grassland. temperate deciduous forest, taiga (boreal forest), tundra. These ecosystems differ dramatically from one another, largely because of climatic factors.

The ocean can be considered an eighth biome, or even a succession of biomes, determined by depth and proximity to the continental shelf. Sometimes freshwater ecosystems are also considered biomes.

The biomes mentioned above are those currently in existence on earth. However, some of them have not always been around. The first forests appeared during the late Devonian,  modern deciduous trees in the Cretaceous, and grasslands only in the Miocene epoch. Biomes during the Jurassic, the Permian or the Carboniferous were very different. Fern savannas for example seem have served as vast prairies which provided food for herds of grazing sauropod dinosaurs.

During the Holocene biomes have changed radically. Two artificial biomes could be added, the agricultural and the urban landscapes, as environments modified by man.

Links

World Wide Biome project

Biome Basics

Biome Resources

Biomes - annotated list of links

Biomes - huge list of links

Biomes - list of links

Modern Ecosystems - has material on Biomes

mapsGlobal land environments since the last interglacial by Jonathan Adams