10 CONCEPT AND HISTORY. 



results have already been published (Bergman and Stallard, 1916; Stallard, 

 1916 ; Bergman, 1919; Stallard, 1919), while a part of the indicator findings are 

 discussed later (Chapter III). 



Shantz, 1911. — The study of the natural vegetation of the Great Plains 

 by Shantz is the classic work on indicator plants. It was the first avowed 

 investigation of indicators to be based upon the three cardinal points, namely, 

 instrumentation, succession, and quadrats, and will long serve as the model 

 for all thorough research in this field. Because of its great importance, the 

 original should be consulted for the details. Here it must suffice to quote 

 the author's general principles, (p. 9.) 



"Farmers and other persons who have occasion to examine new land in 

 order to form a judgment of its agricultural value depend largely upon the 

 natural vegetation, or plant covering, as an indicator of its crop-producing 

 qualities. But there are many possibilities of error in judging land upon this 

 basis. Species that are closely related botanically and very similar in appear- 

 ance may indicate quite different conditions of soil and climate. The popular 

 names of plants are likely to cause confusion. Thus, the farmer who has 

 learned in the Great Basin region that ' greasewood ' is an indicator of alkali 

 land and that 'sage-brush' usually grows on land free from alkali, will find if 

 he moves to southern Arizona or southeastern California that the scrub there 

 known as 'greasewood' indicates absence of alkali, while the so-called 'sage 

 bushes' of that region grow on strongly alkali land. Furthermore, there is a 

 general tendency to depend upon a single plant species as an indicator, while 

 the investigations set forth in this bulletin show that the composition of the 

 plant covering as a whole is a much more reliable basis for judging the crop- 

 producing capabilities of land. 



"The chief object of the present paper is to show how these sources of error 

 may be avoided and how new land may be classified readily and with reasona- 

 ble accuracy on the basis of its natural vegetation. This paper is not a report 

 of a land survey, but rather a discussion of methods which it is believed could 

 be utilized to advantage in making such a survey, the methods being illus- 

 trated by application to a limited territory in the Great Plains area. 



"Too much emphasis can not be laid upon certain facts that have been 

 clearly brought out in the course of these investigations: (1) Correlations 

 between the natural plant cover and the crop-producing capabilities of land in 

 a given area can be satisfactorily determined only after careful study of the 

 different types of vegetation of the area in relation to their physical environ- 

 ments; (2) such correlations, determined for some particular region, will need 

 to be modified to a greater or less extent before they can be applied in another 

 region where the physical conditions are different. When, as a result of suffi- 

 cient investigation, correlations of this nature are determined for a given area, 

 it is believed that they will afford a basis for classifying the land of that area 

 more readily and at least as accurately as by any other known method. 



" In order to test and perfect the methods here described, it was necessary to 

 make a detailed study of the vegetation of some particular area in relation to 

 the physical conditions, checking the observations by the study of such exam- 

 ples of actual crop production as exist on the different types of land. It was 

 decided to begin work in the Great Plains area, for this region contains the 

 largest body of land in the United States having possible agricultural value on 

 which the native plant covering is still undisturbed. A further advantage is 

 the comparative uniformity of the climate throughout the area from the 

 Canadian boundary on the north to the 'Panhandle' of Texas on the south. 

 The investigations thus far have been made chiefly in a portion of eastern 



