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Chapter

BIOL 121 Chapter Notes -Yuma, Arizona, Konza Prairie Biological Station, Tropical Rainforest


Department
Biology
Course Code
BIOL 121
Professor
Carol Pollock

Page:
of 3
Ecology- Biomes (Lecture 4)
Jan. 11, 10
Terrestrial Biomes
Key Distinguishing Factors (location, temperature, ppt, vegetation, etc)
Tropical rainforest
-also called tropical wet forests
-found in equatorial regions around the world
-plants in this biome have broad leaves (opposed to narrow, needle-like leaves), and are evergreen
-older leaves are shed throughout year, but no complete seasonal loss of leaves
-in some rainforests, monthly temperatures tend to stay within 25 and 30 C throughout the year
almost no seasonal variation in temperature
-important because temperatures are high enough to support growth throughout the year
-even in the driest month Nov, region receives over 5 cm (50 mm) considerably more than the
annual rainfall of many deserts
-favorable year-round growing conditions produce riotous growth high productivity and above-
ground biomass
- species diversity(many arthropods and trees)
-diversity of plant sizes and growth forms creates extraordinary structural diversity
-few extremely large trees tower over a layer of large trees that form a distinctive canopy, creating a
wide array of habitat types for animals
(Subtropical) desert
-found in two distinctive locations: 30 degrees latitude, both N and S
-mean monthly temp vary more than in tropical wet climates, and in some deserts temp is freezing
at night on average fairly warm temp.
-low ppt, average annual ppt in Yuma, Arizona is 75 mm
-scarcity of water means productivity of desert is little
-individual plants are widely spaced this may reflect intense competition for water
-species adapt to extreme temp and aridity (dryness) in two ways: growing at a low rate year-round
or breaking dormancy and growing rapidly in response to any rainfall
Temperate grassland
-found throughout central North America and heartland of Eurasia
-known as prairies or steppes
-a region is temperate if it has pronounced annual fluctuations in temp-typically hot summers and
cold winters-but not the temp extremes recorded in the tropics/arctic
-temp variation dictates a well-defined growing season
-in temperate zone, plant growth possible during spring, summer, and some fall months
-ppt at Konza Prairie near Manhattan, Kansas is 4x than Yuma, Arizona
-but still quite dry, and low ppt in no month is there more than 50 mm ppt
Temperate forest
-in temperate areas with relatively high ppt, grasslands give way to forests found in eastern North
America, western Europe, east Asia, Chile, New Zealand
-temperate forests experience period where mean monthly temp falls below freezing and plant
growth stops
-compared to grassland climates, ppt is moderately high, relatively constant annually
-Chicago, Illinois has annual ppt 850 mm
-in N.A. and Europe, temperate forests dominated by deciduous species, which drop their leaves in
autumn and grow new ones in spring
-needle-leaved evergreens and in other places broad-leaved evergreens dominate
-temperate forests productivity level b/t rainforest and grassland
Ecology- Biomes (Lecture 4)
Jan. 11, 10
-diversity level is moderate
Boreal forest (taiga)
-stretches across most of Canada, Alaska, Russia, northern Europe
-referred to as subarctic
-cold winters and cool, short summers
-temp variation is extreme; may range of more than 70 C difference
-annual ppt low, but temp are so cold that evaporation is minimal; therefore moisture supports
some tree/plant growth
boreal forests have highly cold-tolerant conifers (pines, spruce, fir, larch)
-evergreen (except for larches)
-evergreens may be able to begin P/S early in spring
-since they do not shed their leaves, evergreens keep nitrogen that is not highly available in the soil
Arctic tundra
-poleward from the subarctic (in Northern Hemis and in Anarctica) that are not covered in ice
-growing season 6-8 weeks at most, remainder of year, temp is below freezing
-ppt is extremely low, sometimes even less than desert
-extremely low evap rate too, so arctic soils saturated year-round
-treeless possibly b/c growing season too short and cool
-woody shrubs common but usually short
-tall plants receive damage from wind-driven snow and ice crystals
-low species diversity, low productivity, low aboveground biomass
-permafrost is common
-low temp inhibits both release of nutrients from decaying organic matter and the uptake of
nutrients into live roots
-ground surface in tundra is completely covered w/ plants/lichens
-animal diversity also low, but insect abundance can be high
Aquatic Biomes
Key Distinguishing Factors (Water depth, flow and organisms)
Wetlands
-shallow-water habitats where soil is saturated with water for at least part of the year
-wetlands diff. from ponds for two reasons: only shallow water, and have emergent vegetation
plants that grow above the surface of water
-most/all water in wetlands receives sunlight, & emergent plants capture it before it strikes the
water
-freshwater marshes and swamps are wetland types = slow, steady water flow; bogs = water flow is
low/nonexistent
-if water = stagnant, oxygen is used up in decomposition of dead organic matter faster than it enters
via diffusion from the atmosphere
-as a result, bog water is oxygen poor or even anoxic
-once oxygen in water depleted, decomposition slows, and acids lower the pH, making nitrogen
unavailable to plants
-combination of acidity, lack of nitrogen and anoxic conditions makes bogs extremely unproductive
habitats
-marshes and swamps offer ample supplies of oxygenated water and sun and are extraordinarily
productive
-marshes lack trees and typically feature grasses
-swamps are dominated by trees and shrubs
-because their physical environments are so different, little overlap in types of species found in
Ecology- Biomes (Lecture 4)
Jan. 11, 10
bogs, marshes, swamps
Estuaries
-form where rivers meet ocean thus freshwater mixes w/ salt water
-estuary incl slightly saline marshes as well as body of water that moves in/out of these
environments
-salinity varies with changes in river flows, and with proximity to ocean
-mostly shallow enough that sunlight reaches substrate
-water depth may fluctuate dramatically in response to tides/floods
-water flow fluctuates daily and seasonally due to tides/floods
-this is important for changing salinity, which affects presence of organisms
-b/c water shallow and sunlit, and nutrients replenished by incoming river water, very productive
-packed with young fish, feeding on abundant vegetation and plankton