THE ECOLOGICAL EELATIONS OF EOOTS. 



INTRODUCTION. 



Although considerable progress has been made in the study of root 

 systems of desert plants (Cannon, 1911, 1913; Markle, 1917), very 

 little information is available concerning the roots of other native 

 species. During 1914 the writer investigated the root systems of the 

 prairie plants of southeastern Washington, where the annual pre- 

 cipitation is only 21.6 inches and occurs mostly in the period of rest. 

 Since that time it has been planned to make a comparative study of 

 the roots of prairie plants growing in a more humid region and where 

 the precipitation occurs mostly during the season of plant growth. 

 The opportunity for such study came during the fall of 1917 and work 

 was carried on vigorously until the soil became frozen in December. 

 The study was resumed early in the following spring. In June 1918 

 the field of investigation was extended to the Great Plains and sand- 

 hill region of Colorado, while later in the summer a large number of 

 plants were excavated and examined in various habitats about Pike's 

 Peak in the Rocky Mountains. 



A knowledge of root distribution and root competition under dif- 

 ferent natural conditions is not only of much scientific value, but it 

 also finds practical application in a better understanding of the value 

 of plants as indicators for distinguishing lands of grazing value only 

 from those with possibilities of crop production. It will result in a 

 more intelligent solution of the ecological problems of grazing and will 

 likewise be of great aid to the forester in selecting sites for afforesta- 

 tion. Moreover, a knowledge of root distribution will throw a flood 

 of light upon many of the problems of plant succession. Indeed, the 

 phenomena of ecesis, competition, and reaction can not be completely, 

 if indeed correctly, interpreted without a knowledge of the extent, 

 position, and relation of the root systems of the plants. 



Shantz has given us an excellent example of the value of a knowl- 

 edge of root distribution in his study of the natural vegetation of the 

 Great Plains as an indicator of the capabilities of land for crop produc- 

 tion (1911). Sampson (1914, 1917) has made a study of root systems 

 of many range plants in considering their life history, forage value, 

 and the natural re vegetation of range lands; while foresters are just 

 beginning to study the roots of plants as indicators of conditions of 

 soil moisture on various sites (Korstian, 1917). 



This paper contains descriptions of the character, depth, and dis- 

 tribution of the roots of about 140 species of plants. These include 

 shrubs, grasses, and other herbs, a few of the latter being noxious 



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