1. 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.

2. 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.

3. 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)

4. 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).

5. 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)

6. 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)

7. 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

8. 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)

9. 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)

10. 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)

11. 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)

12. 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.

13. Global Biome Distribution

14. Climatic Relationship of Biomes