Prairie Ecosystem

The interaction of three factors maintains the Prairie as a grassland:

Drought:

  The periodic lack of rainfall is a very important factor in preventing the growth of trees in prairies. A drought is when the prairie receives no more than 10 inches of rain per year. In the picture below, you can see how a few trees are tenuously rooted in slight depressions where what little moisture there is gets concentrated.


photo M. Noonan

Grazing:

  Continuous grazing by bison, prairie dogs, and numerous other species, keeps the grass short. In a feedback cycle, the grazing also stimulates new shoots to grow which the grazing animals depend upon. As bison graze, their hoof-action also sows new seeds into the earth which helps to promote new vegetation.


photo M. Noonan

Fire:

  Every three to seven years, any given area of tall grass prairie is likely to burn due to fires started naturally by lightning. This too prevents long-lived species like trees from becoming established.


photo M. Noonan
 

 

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