366 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1960 



Under these circumstances soil moisture and nutrients are secured 

 from different levels, reducing the amount of competition among the 

 various species. There is considerable replacement of roots each 

 year — the dead roots increasing the supply of organic matter in the 

 soil. Under good range management even the litter and debris on 

 the surface gradually becomes incorporated into the soil. 



In addition to being a first-rate soil builder, a good cover of grass 

 also ranks near the top as a soil protector. As the raindrops strike 

 the prairie vegetation the force is broken, and the shattered raindrops 

 run down the blades and stems of the vegetation where the accumu- 

 lated water is held long enough for most of it to enter the soil. During 

 downpours the clear excess water slowly runs away leaving the soil 

 held firmly in place by the vegetation. 



There is a close relationship between the type of climate, vegetation, 

 and soil found in any region, and it appears safe to assume that to 

 understand our climate we must understand our vegetation and the 

 soils this plant growth produces. There is just one major reason 

 why the grasses invaded as far east as Ohio in past geologic ages — it 

 was climate. There is just one major reason why the forest did not 

 replace the grasses in the high plains — it was climate. Thus we may 

 study our native vegetation and predict with a considerable degree 

 of accuracy the type of climate that produced the vegetation and the 

 type of soil in which the vegetation is growing. 



The herbaceous type of vegetation in the Great Plains is best adapted 

 to the extremes in climate that occur. Cycles of drought, hot desic- 

 cating winds of high velocity, prairie fires, tornadoes, hail storms, and 

 severe winters are all common to the plains region, but through all 

 these, the prairies have prevailed. There are times each season, how- 

 ever, when prairie vegetation does not receive sufficient moisture for 

 growth, and, therefore, much of it is forced into dormancy. The 

 process of going into dormancy and out again may occur several times 

 in one season ; this is a common experience for the short grasses of the 

 high plains ( Albertson and Weaver, 1942) . During extreme adversity 

 in the past, our native prairie doubtless suffered greatly, but upon the 

 the advent of more favorable conditions replacement of the former 

 cover was rapid (Albertson and Weaver, 1944b) . Dust storms have 

 been known to occur earlier than those that visited us during the 

 thirties. The wind-formed soils extending from the Mississippi 

 Yalley westward and covering much of northwestern Kansas illustrate 

 this fact (Lyon and Buckman, 1943). Even during the last half of 

 the nineteenth century our early settlers reported numerous "dusters" 

 (Malin, 1946). 



"Wlien the early explorers came through the plains region they found 

 many of the plants that abound today in our native prairies; for 



