Biomes

• Definition: a major geographic region defined on the Definition: a major geographic region defined on the basis of dominant plant growth forms.basis of dominant plant growth forms.

• Determinants: 1) Climate- particularly temperature Determinants: 1) Climate- particularly temperature and rainfall patterns; 2) Topography (landforms) and and rainfall patterns; 2) Topography (landforms) and soils (edaphic factors): factors that secondarily soils (edaphic factors): factors that secondarily influence the local distribution of organisms within influence the local distribution of organisms within biomes.biomes.

• Climatic zones: 1) boreal (mean <5ºC), 2) temperate Climatic zones: 1) boreal (mean <5ºC), 2) temperate (mean >5, <20 ºC), 3) tropical (mean >20ºC).(mean >5, <20 ºC), 3) tropical (mean >20ºC).

• The biome concept applies best to terrestrial systems.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:1) Climate- polar

2) Vegetation- treeless, low evergreen shrubs, herbs and lichens

3) Limiting factor- permafrost

4) Distribution- far northern hemisphere and alpine zones

5) Animals- polar bear (right)

Principal Biomes

Boreal Forest (Taiga):1) Climate- cool summer,

long, cold winter

2) Vegetation- evergreen and deciduous conifers

3) Limiting factor- short growing season (10 weeks)

4) Distribution- northern hemisphere and alpine zones

5) Animals- blue-headed vireo (right).

Principal Biomes

Temperate Grassland (Prairie):1) Climate- hot summer, cold winter

(continental climate)

2) Vegetation- grasses and forbs; trees along rivers (riparian forest)

3) Limiting factor- annual rainfall about 10”

4) Distribution- centers of continents

5) Animals- bison (above), prairie dog (left)

Principal Biomes

Temperate Seasonal Forest:1) Climate- moderate; winter

mean >-20ºF

2) Vegetation- deciduous trees

3) Limiting factor- 17 week growing season

4) Distribution- eastern North America, western Europe, Korea

5) Animals- red-spotted newt (right)

Principal BiomesTemperate Rainforest:1) Climate- mild and wet

2) Vegetation- large conifers

3) Limiting factor- summer rain and fog

4) Distribution- Pacific northwest, New Zealand, S. South America

5) Animals- ruby-crowned kinglet

Principal Biomes

Shrubland (Chaparral):1) Climate- summer drought, rainy winter

2) Vegetation- waxy-leaved, evergreen shrubs

3) Limiting factor- frequent fires

4) Distribution- S. California, Mediterranean, S. Australia

5) Animals- western tanager (left)

Principal Biomes

Subtropical Desert:1) Climate- very dry, high daytime

temperature

2) Vegetation- sparse, with drought-resistant leaves

3) Limiting factor- heat, dryness

4) Distribution- southwestern North America, central Africa, central Asia

5) Animals- spadefoot toad (left)

Principal Biomes

Tropical Savannah:1) Climate- rainy summer, dry winter

2) Vegetation- grasslands with park-like stands of trees

3) Limiting factor- limited rainfall

4) Distribution- Mexico, S. Africa, SE Asia, N. Australia, E. S. America

5) Animals- burrowing owl (right)

Principal Biomes

Tropical Rainforest:1) Climate- uniform hot, wet

and dry seasons

2) Vegetation- diverse tropical hardwoods and vines

3) Limiting factor- heavy rainfall and uniform high temperatures

4) Distribution- N. S. America, W. Africa, SE Asia

5) 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.

Global Biome Distribution

Climatic Relationship of Biomes