Biomes
Terrestrial biomes
 Biomes - Areas sharing similar climate, topographic and soil conditions, and
roughly comparable communities
 Terrestrial biomes are identified by the dominant plants
Biomes
 Temperature and precipitation are the most important determinants in biome
distribution

Productivity also varies with temperature and precipitation
Do you remember what affects temperature and precipitation?
Tropical rain forests
 Humid tropical regions support one of most complex and biologically rich
biomes
 Ample rainfall and uniform temperatures
 90% nutrients tied up in living organisms
 Thin soil cannot support continued cropping and cannot resist erosion
 Subjected to clearing for settlements and farming, and to intense logging
Temperate rain forest
 Wettest portion of coniferous forests of Pacific Northwest
 Mild temperatures and very abundant precipitation
Temperate rain forest
Tropical seasonal forests
 Semi-evergreen and partly deciduous forests tending toward open woodlands
and grassy savannas
– Characterized by distinct wet and dry seasons with hot temperatures yearround
– Less than 1 percent remain undisturbed
Tropical monsoon forest (sort of)
Savannas
 Open with widely spaced trees
 Subtropical with seasonal (75 to 125 cm) rainfall
 Impacted by agricultural use, especially grazing
Deserts
 Characterized by low moisture levels and precipitation that is infrequent and
unpredictable
 Wide daily and seasonal temperature fluctuations
 Plants and animals exhibit water conservation characteristics
 Soils are easily disturbed by human activities, such as grazing, and slow to
recover


Hot desert
Cold desert
Grasslands
 Communities of grasses and seasonal herbaceous flowering plants in
temperate areas
 No trees due to inadequate rainfall
 Frequent grass fires
 Historic grazing by roaming herds of large ungulates
 Historic conversion to farmland
Broad-Leaved Deciduous Forest
 Temperate regions support lush summer plant growth when water is plentiful
– Deciduous leaves are an adaptation to freezing temperatures
 Eastern half of US was covered with broad-leaf deciduous forest when
European settlers arrived
Conifer forests
 Cone-bearing
 Plants reduce water loss by evolving thin, needle-like evergreen leaves with
thick waxy coating
 Fire often plays role in maintenance
 Humans rely on conifer forests for forest products
Conifer Forests
 Boreal Forest - Northern Conifer Forest
– Broad band of mixed coniferous and deciduous trees between 45° and 60°
N latitude
– Moist and cool climate with abundant streams and wetlands
 Taiga - Northernmost edge of boreal forest
– Species-poor
– Harsh climate limits productivity
Tundra
 Treeless
 Very short growing season, with cold harsh winters
 Damage slow to heal
 Low diversity and productivity
 Global warming and air pollution threaten tundras
 Oil and gas drilling
Mediterranean (A regional biome)
 Characterized by warm, dry summers and cool, moist winters
 Fires are a major factor in plant succession
– Referred to as chaparral in California
 Biodiversity hotspot threatened by human development
– Referred to as thorn scrub in Africa