Light green : borealie Green : Prairies

Pronghorn American bison Rough-legged hawk Mule deer Burrowing owl Black-tailed prairie dog Sandhill crane

The prairie is an important biome within the Borealie, because it takes up a vast stretch of land in North America. Globally, the prairies occupy 24% of the surface of the continents. ¹  The biome is characterized by its cold winters, and periods of drought in the summer which themselves often give rise to fires. The prairies receive between 300 and 1000 mm (120 and 390 in.) of rain annually. In North America, we find tall grass prairies that receive an annual rainfall of between 700 to 1000 mm (27.5 to 39.4 in.) and short grass prairies that receive only 300 mm (approx. 12 in.) per year.  ^1,2,3

The wildlife representatives of this biome are large herbivores (American bison, pronghorn), significant rodent populations (black-tailed prairie dogs, amongst many others) and their predators (fox, birds of prey). ^1,2,3 And, of course, one should not forget insects, which are very numerous and are represented mainly by the Orthoptera (crickets, grasshoppers). ^1,3

There are different factors that contribute to making the prairies what they are and to prevent the establishment of bushes and trees: fires, large herbivores2 and the very dense root-system network. ³

This last factor also contributes to the fertility of the prairie soil, which contains large quantities of organic matter. ^2,3

However, human beings have seriously modified the biome by almost completely eliminating the large herbivores and by cultivating the huge expanses of fertile land. The American continental prairies have produced and continue to produce immense quantities of cereal grain. But how much longer will that last? Over the past 40 years of exploitation, the prairies as a whole have lost 35% to 40% of their organic matter. As a result, producers today are obliged to use more and more fertilizers. This raises questions, but no answers, as to the impact of the decrease in organic matter in the soil and as to the impact of the use of chemical products on the environment. The questions have been asked, but the jury is still out… ³

References

1. Borcard, Daniel.  Department of Biological Sciences.  University of Montreal. http://biol10.biol.umontreal.ca/BIO1803/Biomes.html  Consulted on April 16, 2003

2. Following reference: Dajoz, R.  1996.  Précis d'écologie.  6th edition. Dunod.  Paris.

3. Campbell, Neil A.  1995.  Chapter 46 : L’écologie : Distribution et adaptation des organismes.  IN  Biologie.  Éditions du Renouveau Pédagogique Inc. Quebec. Canada.

4. Molles, Manuel C. Jr.  1999.  Chapter 2: Life on land.  IN  Ecology : Concepts and Applications.  McGraw-Hill.  Toronto.  Canada.