HISTORICAL. 11 



Colorado, a region which is considered representative because of its central 

 position and because its climatic conditions are almost as severe as anywhere 

 in the Great Plains. But enough data have been gathered in other portions of 

 the Great Plains to make it fairly certain that with comparatively little modi- 

 fication the correlations shown will hold throughout the area. 



"The work so far accomplished has brought out clearly that in this area the 

 general conditions, whether favorable or unfavorable to crop production, are 

 indicated by the character of the native plant cover." (plate 1.) 



Kearney, Briggs, Shantz, McLane, and Piemeisel, 1914.— The first quanti- 

 tative study of plant communities as indicators of alkaline soils was made by 

 Kearney and his associates in the Tooele Valley of Utah. This was essen- 

 tially an application of Shantz's methods to a saline basin and met with 

 similarly important results, as the following indicates: 



"In the arid portion of the United States the different types of native vege- 

 tation are often very sharply delimited, the transitions being so abrupt that 

 they can not be attributed to climatic factors; this has suggested the possi- 

 bility of correlating the distribution of the vegetation with the physical and 

 chemical properties of the soil. If such correlations can be made, they may be 

 utilized in the classification of land with respect to its agricultural capabilities. 



"One of the writers has described the correlations which exist in the Great 

 Plains between the different types of vegetation and the physical characteris- 

 tics of the corresponding types of land, and has pointed out how the native 

 growth may be used in that region to determine the suitability of the land for 

 dry-farming. 



"The results obtained in the Great Plains made it desirable to undertake 

 similar investigations in the Great Basin region. The problems to be solved 

 were: First, what types of vegetation indicate conditions of soil moisture 

 favorable or unfavorable to dry farming, and second, what types indicate the 

 presence or absence of alkali salts in quantities likely to injure cultivated crops. 

 For the purpose of this investigation it was necessary to find a locality where 

 both dry farming and irrigation farming are practiced, where much of the soil 

 is still covered with the original native growth, and where some of the soils 

 contain an excess of alkali salts. 



"After a reconnoissance trip through portions of Wyoming, Utah, Idaho, 

 and Oregon in August, 1911, the Tooele Valley in central Utah was selected for 

 the following reasons: (1) Several very distinct types of vegetation are found 

 in a small area, (2) the soils show a great diversity in their moisture conditions 

 and salt content, (3) the greater part of the area retains its original plant cover, 

 while examples of crop production, both with and without irrigation, exist on 

 different types of land. 



"Detailed studies of the vegetation of Tooele Valley in relation to the mois- 

 ture conditions and salt content of the soil were carried on in 1912. The work 

 was begun near the close of the rainy season (end of May) and was terminated 

 during the first week of August, when the summer drought had reached its 

 height. Additional data were obtained during a third visit to the valley in the 

 latter part of August 1913. 



"The distribution of the native vegetation was found to depend in a marked 

 degree upon the physical and chemical properties of the soils, factors which also 

 influence crop production. So far as this particular area is concerned, the 

 vegetation unquestionably can be used with advantage in classifying land with 

 respect to its agricultural value. To what extent the correlations established 

 in the Tooele Valley hold good in other parts of the Great Basin region remains 

 to be determined by future investigation." (p. 365.) 



