BIOGEOGRAPHY: Lecture 7

Major Biomes B & L Fig. 5.11, 5.12

 
1 Tropical Rain Forest
low latitudes; low elevations, , e.g. Ecuador
MAT ca. 18 C, low seasonal variation; MAP 180 cm
Latisols; fast turnover of mineral and Carbon nutrients
large evergreen trees; woody vines; epiphytes; epiphylls
with only 6% of land surface, harbors 50% of biodiversity
 
2 Tropical Deciduous Forest
10-30 degrees latitude, e.g. Paraguay
Hot; seasonal moisture (monsoonal); "rain-green"
open-canopy forests with leafless dry season
 
3 Thorn Woodland
10-30 degrees latitude; e.g. Paraguay
drier, e.g. 30 cm MAP all in 6 months
Acacia; Cactaceae; others with spines and thorns
 
4 Tropical Savanna
25N to 25S; e.g. Africa
in intertropical convergence zone (in N&S trade winds)
dense grass and sedge layer in open fire-resistant forest
MAP = 30-160 in 1-2 rainy seasons; intense droughts
maintained by fire and seasonal grazing
Equus; many artiodactyls; baboons & humans
 
5 Desert and Semi-Desert; e.g., Africa; Nevada
west sides and internal of continents at 30-40 N&S
MAT >0; MAP 0 to 50cm: less than evaporation
small sclerophyllous shrubs; some succulents
small mammals, lizards, snakes; birds
 
6 Sclerophyllous Woodland; e.g. California
Temperate: Hot, dry summers; 60-120 cm winter precipitation
woody, evergreen leaves; e.g. Chaparral; Fynbos
pine barrens; pinion-Juniper, scrub oak;
eucalyptus woodlands (Austr);
often maintained by fire
 
7 Subtropical Evergreen Forest
intermediate elevations on subtropical mountains
frost free; moist equable rainfall
southern Appalachians; southern continents
Oak, magnolia, beeches, laurels

8 Temperate Broad Leaf Deciduous Forest "summer-green"
Temperate Zone: e.g. eastern U.S.; europe; China
and along rivers in drier climates
MAT = 3-18C MAP = 100-250 cm; seasonal Temp and Precip
Large Trees; good soils (Podzols)
 
9 Temperate Rain Forest e.g., WA OR, AL, BC
limited; west sides of continents
where moist >200cm; and cool-equable (no hard freeze)
large, old spruce, pine, fir; abundant mosses
slow growing; huge biomass
southern hemisphere trees are ancient:
Eucalyptus, Nothofagus, Podocarpus, and large tree ferns
 
10 Temperate Grassland
30-60 latitude; e.g. Great Plains
climatically between deserts and temperate forests
Prairie; Steppe; Pampas; Veldt
grasses may be 90% of biomass; but 25% of species
up to 90%+ of biomass may be underground
Rich soils and soil biodiversity
 
11 Boreal Forest "Taiga" or Swamp Forest
Siberia, Canada, So Alaska
MAT = -5 to +4 (cold); MAP = 50 to 200 (moist)
Spruce, Fir, Larch, Cedar
Humic, acid, Peat soils
 
12 Tundra and Ice
Arctic and Antarctic, with permafrost; no trees
MAT < -5C (below freezing for 7 months); MAP < 100 cm!
Alpine Tundra in N Rockies, Andes (Paramo), Alps, Himalayas
low Productivity (except short growing season) and Biomass
dwarf shrubs, willows, sedges, grasses, moss, lichens
caribou, muskox, Dall Sheep, Ptarmigan
 

Questions: Lecture 6
Discuss the concept of communities.
Explain the extreme definitions as a function of stability over geological time.