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native prairie ecosystem with agricultural systems, particularly crop- 

 fallow, and to understand why the one has succeeded where the other 

 has failed. 



The undisturbed aboriginal prairie ecosystem covering the 

 glacial till of northeastern Montana represents an accumulated "wisdom" 



of about 15,000 years. Since the retreat of the last ice age glacier, 

 the plant community has been evolving, by trial and error selection 



and replacement of species, to the point of optimum environmental 

 adaptation. The grasses, forbs, and shrubs of the native prairie, 

 together with the fauna, geology, soils, and hydrology, and such ex- 

 trinsic factors as precipitation, temperature, solar radiation, and 

 their seasonality function in a finely tuned dynamic equilibrium that is 

 only remotely approached in the most diversified of man's agricultural 

 systems. The ecologic flexibility of the hundreds of native plant 

 species allows them to form communities adapted to a w^ide array of 

 environmental situations (including extreme natural fluctuations in 

 climate, such as very dry, wet, warm, or cold periods). The destiny 

 of a diverse native plant community is nnore predictable than that of a 

 homogeneous system such as a field of grain: patchy distribution plus 

 the inherent resistance of sonrve native species to insects and disease 

 make the diverse community nauch less susceptible than monoculture to 

 widespread devastation. 



The most innportant characteristics of natural systems in 

 preventing seeps appear to be efficient water use and restricted 



