274 



Origin of Biomes and Succession 



Fig. 121. Native prairie under different grazing conditions. Above, with light 

 to moderate grazing on prairie ahnost entirely composed of A)uh()<i,opou grasses 

 and other climax plants. Below, with heavy grazing with the climax Andropogon 

 species replaced by blue grass Poa pratensis and ironweed Vernonia sp. (From 

 Weaver. ) 



