Craig ChristensenMarch 5, 2009Development 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.-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

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

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/m2/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 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

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