craig christensen march 5, 2009 development studies
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Craig ChristensenMarch 5, 2009Development Studies
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An ecotone A transitional zone between two different
ecosystems Areas where precipitation is high
enough to sustain grass, but (sometimes) only a few trees.
Occur between forested and desert areas.
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* All occur in temperate regions (beyond 23.5 degrees North or South of the Equator.)
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1.-1.- Central/North America - Plains and Central/North America - Plains and PrairiesPrairies
2.- 2.- Argentina - Argentina - PampasPampas 3.- 3.- Hungary - Hungary - PusztaPuszta 4.- 4.- Russia - Russia - SteppesSteppes 5.- 5.- Australia - Australia - DownsDowns 6.- 6.- New Zealand - New Zealand - DownsDowns 7.- 7.- South Africa - South Africa - VeldtsVeldts
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Continental climate due to location Hot summers, up to 30°C, below freezing
for up to six months continuous. Low ppt. (250-750mm annual)
convectional rain in summer, snow in winter
High evaporation rates in summer Periods of drought, and torrential rain can
occur
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Chernozem soils Thick humus layer Calcium carbonate
deposits Leaching during spring
(snowmelt), and capillary rise in summer
Deeps roots and flat relief minimize erosion
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Mainly grasses, with sparse bushes and trees Height of grass relates to amount of
precipitation Vegetation is xerophytic and pyrophytic NPP = 600g/m2/yr Biomass = 1.6kg/m (low due to lack of
trees)
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Considering harsher climate, and lower availability of energy from primary producers, zoo-diversity quite low.
Species include: Hoofed mammals (pronghorn,
bison) Ground rodents (prairie dogs) Small carnivores (coyote,
badgers, weasels) Decomposers crucial in mixing
soil.
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Largest reserve of nutrients is in Soil Very little lost to run-off and leaching Fire is important in returning nutrients
to the soil.
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Grass species include: Spear grass, wheat, barley, thread grass
Many small bushes: Saskatoon, choke cherry, aster
Being on the edge of the ecotone, isolated forest communities exist, especially in Northern and Eastern limits. Dedicious species : birch, willow, elder, aspen,
poplar Coniferous species : Spruce
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Local topography can affect ecosystem River valleys often have forest Occasional deserts in valleys (Badlands)
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Climactic Hazards Convectional summer rainfall can cause
damaging hail and occasional tornadoes Ex. Black Friday, summer ‘04 in Edmonton
Extreme winter cold (down to -40°C) troublesome for keeping livestock
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95% of original, natural prairie has been converted to agricultural land. Little natural prairie remains.
Hunting of bison left only 250 wood bison at the end of the 19th century
Extinction and extirpation of many native species. Swift fox
Introduction of pests Dandelion
Colony Collapse disorder and bees 30-70% losses reported in Winter
’06-’07 Bees add $15 billion to US
economy; similar impact could be felt
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http://www.runet.edu/~swoodwar/CLASSES/GEOG235/biomes/tempgrass/tempgras.html
http://www.eldoradocountyweather.com/canada/climate/medicinehatclimate.html
http://canadianbiodiversity.mcgill.ca/english/ecozones/prairies/prairies.htm#
http://www.srd.gov.ab.ca/fishwildlife/status/bison/index.html http://www2.canada.com/edmonton/edmontonjournal/news/
story.html?id=b9fa4403-a7f9-40b8-bcb9-f8a8f6966968 http://www.ars.usda.gov/News/docs.htm?docid=15572