Figure 1-2. A plant with 

 wide ecological amplitude, 

 side-oats gramagrass {Boute- 

 loua curtipendula), is a 

 leafy, perennial bunchgrass 

 widely distributed from Cali- 

 fornia to Montana, Maine, 

 and South Carolina, being 

 most abundant in the Great 

 Plains. August, Texas. (U.S.- 

 D.A. Soil Conservation 

 Service.) 



species with lower requirements, points to mineral deficiency as a 

 cause. Areas in the vicinity of bird roosts and animal dens or bur- 

 rows may favor the persistence or the invasion of species with high 

 nitrogen requirements — for optimum growth many grasses need 

 more nitrate and phosphate than is naturally present in some 

 soils. Sufficient potash in relation to nitrogen has been found to 

 reduce the winterkilling of some grasses, while lime is often 

 needed in some soils to counteract acidity. The trace elements, 

 boron, copper, manganese, or zinc, may be required to remedy 

 soil deficiencies in some regions. 



Big sagebrush {Artemisia tridentata) and its common associates 

 are practically never found in soils developed from altered vol- 

 canic rocks in the western part of the Great Basin in the United 

 States. Apparently these plants are unable to secure some essen- 



12 



Species and Popi^latiozms 



