Date of this Version
When, in 1916, the writer came to the University of Nebraska as a young instructor, he came with a background that well fitted him for studies in the field. His research in the grassland and adjoining forests of southeastern Washington and adjacent Idaho had been completed and a fine acquaintance had been made with methods of examining the prairie both above and below ground level (Weaver, 1915, 1917). Similar studies in the area between the Missouri River and the Rocky Mountains were now to be made, and these have resulted in many new investigations that are of both scientific and practical value.
During 1914 the writer had investigated the root systems of the prairie plants of southeastern Washington, where an annual precipitation of only 21.6 inches occurred, mostly in the period of rest. After that he planned to make a comparative study of the roots of prairie plants in a more humid region, where the precipitation occurs mostly during the season of plant growth. The opportunity for such a study came during the fall of 1917, and the first publication of results appeared in "The Ecological Relations of Roots," in 1919. Here may be found descriptions of the character, depth, and distribution of the roots of about 140 species of grasses, shrubs, and forbs of prairie and plains. A companion work, "Root Development in the Grassland Formation "-also published by the Carnegie Institution of Washington -appeared in 1920. It includes the results of investigations at more than 25 stations in Kansas, Colorado, South Dakota, and Nebraska.
The climax plant community has integrated all of the environmental factors of its habitat; it is the fundamental response to the controlling conditions. The individual root habit and especially the community root habit, together with the more familiar above-ground parts, serve to interpret the environmental conditions. Both of these criteria are needed to reveal the "judgment" of the plants as to the fitness of the habitat in which they grow or in which crop plants are to be grown.