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Biomes. Definition: a major geographic region defined on the basis of dominant plant growth forms.
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Biomes • Definition: a major geographic region defined on the basis of dominant plant growth forms. • Determinants: 1) Climate- particularly temperature and rainfall patterns; 2) Topography (landforms) and soils (edaphic factors): factors that secondarily influence the local distribution of organisms within biomes. • Climatic zones: 1) boreal (mean <5ºC), 2) temperate (mean >5, <20 ºC), 3) tropical (mean >20ºC). • The biome concept applies best to terrestrial systems.
Grouping Characteristics • Plants and animals from different parts of the world often show similar characteristics if they are part of the same biome (character convergence). • The catbird (upper right) of North America and the reed-warbler (lower right) of southeast Asia are ecologically equivalent species. • They also show similar physiological adaptations. • Plants further show similar growth forms.
Principal Biomes Tundra: • Climate- polar • Vegetation- treeless, low evergreen shrubs, herbs and lichens • Limiting factor- permafrost • Distribution- far northern hemisphere and alpine zones • Animals- polar bear (right)
Principal Biomes Boreal Forest (Taiga): • Climate- cool summer, long, cold winter • Vegetation- evergreen and deciduous conifers • Limiting factor- short growing season (10 weeks) • Distribution- northern hemisphere and alpine zones • Animals- blue-headed vireo (right).
Principal Biomes Temperate Grassland (Prairie): • Climate- hot summer, cold winter (continental climate) • Vegetation- grasses and forbs; trees along rivers (riparian forest) • Limiting factor- annual rainfall about 10” • Distribution- centers of continents • Animals- bison (above), prairie dog (left)
Principal Biomes Temperate Seasonal Forest: • Climate- moderate; winter mean >-20ºF • Vegetation- deciduous trees • Limiting factor- 17 week growing season • Distribution- eastern North America, western Europe, Korea • Animals- red-spotted newt (right)
Principal Biomes Temperate Rainforest: • Climate- mild and wet • Vegetation- large conifers • Limiting factor- summer rain and fog • Distribution- Pacific northwest, New Zealand, S. South America • Animals- ruby-crowned kinglet
Principal Biomes Shrubland (Chaparral): • Climate- summer drought, rainy winter • Vegetation- waxy-leaved, evergreen shrubs • Limiting factor- frequent fires • Distribution- S. California, Mediterranean, S. Australia • Animals- western tanager (left)
Principal Biomes Subtropical Desert: • Climate- very dry, high daytime temperature • Vegetation- sparse, with drought-resistant leaves • Limiting factor- heat, dryness • Distribution- southwestern North America, central Africa, central Asia • Animals- spadefoot toad (left)
Principal Biomes Tropical Savannah: • Climate- rainy summer, dry winter • Vegetation- grasslands with park-like stands of trees • Limiting factor- limited rainfall • Distribution- Mexico, S. Africa, SE Asia, N. Australia, E. S. America • Animals- burrowing owl (right)
Principal Biomes Tropical Rainforest: • Climate- uniform hot, wet and dry seasons • Vegetation- diverse tropical hardwoods and vines • Limiting factor- heavy rainfall and uniform high temperatures • Distribution- N. S. America, W. Africa, SE Asia • Animals- fruit dove (right)
Alpine Zonation • Increasing altitude mimics the effects of increasing latitude. • At higher altitudes in mountains, more northerly associated biomes are found. • In the northeast, the lowest elevations of mountains have temperate seasonal forest, which is replaced by boreal forest at higher elevations, which is in turn replaced by alpine tundra. • Near tree line (the highest elevation of tree growth), a stunted boreal forest called krummholz develops. • Alpine biomes differ from latitudinal biomes in factors like day length and temperature variation.
