Topic 31 Flashcards
Biomes
basic community types occurring in particaunaular region, typically defined by the type of vegetation
Flora
plant species of the region
Fauna
animal species of the region
Convergence
evolution of similar growth forms among distantly related species in response to similar selection pressures
Terrestrial biome characterized by
climate (average annual precipitation vs average temp)
Biomes don’t function in
isolation
We focus on how many biomes
7
Tropical rainforest
from equator to 20 degrees. high stable temp (25-27C) high annual rainfall (2000-4000 mm). immense diversity (250-300 species) 882000 biomass/hectare growing to 75m
Tropical rainforest vegetation
high degree of vertical structure in vegetation, soil is thin and low in nutrients, carbon is trapped in living organisms. large leaves (evergreen)
Tropical rainforest plant order
emergent trees, canopy, epiphytes and vines, understory, scrubs and forbs
Plants in rainforest have access to plenty of water that may leech…
valuable nutrients (but compete for light)
Epiphyte
plants that use another plant as a substrate (buttress roots that grow above ground in tall trees.
Many prescription drugs are..
derived from tropical plants
Tropical rainforest vegetation is a major
carbon sink (37% of the terrestrial carbon pool) and removal contributes to atmospheric carbon and global warming
Tropical savannah
20-30 degrees N and S. high temp year round. seasonal variation in precipitation. periodic fires, annual draught/flood, grazing by animals favours growth of bunched grass species. spread out deciduous trees lead to microhabitats, migratory bands of animals.
Relatively nutrient rich soils in tropical savannah lead to early man..
colonizing savannah and converting to agricultural practices
Desert
2 distinct bands around 30 degrees N and S. 20% of land surface. characterized typically by high temp during the day but mostly by low levels of annual precipitation (highest 300mm) and evaporation exceeds precipitation
Vegetation in desert
sparse, algal, fungal or lichen mats can bind it in a fragile layer
Soil in desert is
gravel, sand, rock or alkaline
Though abundance is low in desert diversity can be..
high due to high fluctuations in abiotic conditions
Plants in desert
high degree of convergence in plant species, cacti of the west, euphorbs of the east. stem succulence, reduction or loss of leaves, hairy leaves, dormant seeds/annual habit. reduced pigmentation
Desertification
long term droughts in association with unsustainable grazing practices that results in loss of plant cover and soil erosion
Temperate shrub land
30-40 degrees. erred Chaparral in North America. (not in antarctica) dry summers and winter rain.
Plant species in temperate shrub land
highly adapted for fires in dry summer climate, contain flammable oils, underground storage organs, quick dispersal and germination (helps to prevent succession to fester landscape). limited agriculture capacity cause converted to urban area all over the world
Sclerophyllous leaves
tough, leathery and stiff *temperate shrub land”
Temperate grassland
30-50 degrees. strong seasonality in temperature and precipitation (highest in summer) period fires and grazing wildlife promote grass and for spices similar to savannahs.
Meristems located
undergoing as an adaptation for grazers in temper-ate grasslands
Temperate forests
cold winter temps results in deciduous forests. coastally temperate rainforests exist with evergreen trees. same vertical vegetation structure as rainforests without epiphytes. soil in deciduous forests is enriched by decomposition of leaf litter. not much of this biome remains (harvested for wood and paper, cleared for agricultural land)
Evergreen rainforests have
nutrient poor acidic soils
Deep roots in temperate grasslands ..
stabilize and enrich soil (breadbasket)
Level of moisture in temperate grasslands determines heigh so..
- short grass prairie (5 cm)
- tall grass parries (300m)
Boreal forest
50 degrees N. insufficient land mass in the south to support this biome. largest biome in area (1/3 Earths forests land) precipitation stable but long cold winters (6 months) highest temp ranges (siberia -70 to 30 C) cone shaped trees adapted to snow cover. same species occur across northern hemisphere. thin, relatively infertile soils with slow decomposition rates
Boreal forest dominated by ..
evergreen coniferous trees with needle like leaves (and birch)
Taiga
transition zone to tundra where eventually trees can no longer take root
Permafrost
layer under the soil that stays frozen year round. precipitation levels are low, drainage of water is prevented by permafrost layer, soil become saturated and period fires can melt permafrost and create peat bogs (harvest for limber and paper products)
Tundra
mostly in arctic circle (Antarctica peninsula). beyond 65 degrees. extreme seasonal variations (24 hours of light in summer) low precipitation (200-600 cm) but exceeds evaporation.
Vegetation in tundra
low perennial grasses, sedges, scrubs, mosses and lichens. ensure fierce winds and annual freezing temps. heliotropic flowers, hairy leaves and stems, permafrost prevents drainage. constant freeze/thaw and contraction of soil creates polygons and separates soil particle size creating growth ridges. largest remaining natural habitat (global warming melts permafrost)
