Craig Christensen March 5, 2009 Development Studies

 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.

* All occur in temperate regions (beyond 23.5 degrees North or South of the Equator.)

 1.- Central/North America - Plains and Prairies  2.- Argentina - Pampas  3.- Hungary - Puszta  4.- Russia - Steppes  5.- Australia - Downs  6.- New Zealand - Downs  7.- South Africa - Veldts

 Continental climate due to location  Hot summers, up to 30°C, below freezing for up to six months continuous.  Low ppt. ( mm annual) convectional rain in summer, snow in winter  High evaporation rates in summer  Periods of drought, and torrential rain can occur

 Chernozem soils  Thick humus layer  Calcium carbonate deposits  Leaching during spring (snowmelt), and capillary rise in summer  Deeps roots and flat relief minimize erosion

 Mainly grasses, with sparse bushes and trees  Height of grass relates to amount of precipitation  Vegetation is xerophytic and pyrophytic  NPP = 600g/m 2 /yr  Biomass = 1.6kg/m (low due to lack of trees)

 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.

 Largest reserve of nutrients is in Soil  Very little lost to run-off and leaching  Fire is important in returning nutrients to the soil.

 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

 Local topography can affect ecosystem  River valleys often have forest  Occasional deserts in valleys (Badlands)

 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

 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 19 th 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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