18 CONCEPT AND HISTORY. 



disturbed and that the more important phases of the successional series are 

 properly understood. 



"The fundamental study of forest planting sites logically resolves itself into 

 three categories: (1) The empirical establishment of plantations and the 

 obeervation and study of their survival and subsequent development; (2) the 

 measurement and study of the most important physical factors of the site, 

 such as the available soil moisture or growth water and evaporation; and (3) 

 the indicator significance of the native vegetation occurring on the sites, imply- 

 ing a very careful correlation of all three phases. 



"It is readily conceivable that site studies of this character will be of the 

 utmost value in explaining the presence or absence of tree growth on certain 

 areas, in the judicious selection of the proper species and sites in the reforesta- 

 tion of much of the denuded forest land of the United States, and in establish- 

 ing a working basis for the classification of forest lands. Only after considering 

 the relative agricultural and forest productivity of the land on a combined 

 scientific and economic basis, can a positive conclusion be reached that its 

 greatest utility Ues in its use for forestry or for agricultural purposes." 



V GRAZING INDICATORS. 



Grazing has been recognized as a distinct field for investigation for scarcely 

 more than a decade. Complete recognition of grazing as a subject for experi- 

 ment should perhaps be dated from the establishment of the Utah Forest 

 Experiment Station for grazing in 1912. Three more or less marked steps in 

 advance had preceded this and had made it inevitable. The first was a 

 general study of the West with reference to the species, distribution, and value 

 of the native grasses and forage plants. The stimulus for this seems to have 

 been the work of Bessey in Nebraska, as indicated by the publication of many 

 reports dealing with grasses and forage plants from 1886 to 1907. Webber 

 (1890), Smith (1890), and Williams were associated with Bessey in some 

 of this work and the last two later carried on extensive grassland studies 

 over the Great Plains and the Rocky Mountain region (Smith, 1898; Williams, 

 1897, 1898). Similar studies were made by Shear and Clements in 1896, by 

 Rydberg and Shear in 1897, by Pammel in 1897, Nelson in 1898, and others (cf . 

 Shear, 1901). The second step was perhaps the most significant, inasmuch as 

 it introduced the quantitative study of grazing areas by means of the quadrat, 

 and provided an exact method of measuring carrying capacity and deter- 

 mining the degree of overgrazing or the amount of regeneration. This work 

 was begun by Griffiths and Thornber in 1901 and enlarged in 1903 on what is 

 now the Santa Rita Grazing Reserve of the Forest Service. It has been 

 carried on continuously since that time by Griffiths, Wooton, Thornber, Hurtt, 

 and Hensel in turn, and now constitutes the classic field for grazing study 

 anywhere in the world. It has yielded publications of primary importance 

 by Griffiths (1901, 1904, 1907, 1910), Thornber (1910), and Wooton (1916). 

 Somewhat similar lines of experiment were begun by Coville and Sampson in 

 1907 in the Wallowa National Forest in northeastern Oregon. The results 

 are recorded in a series of reports of unusual significance, namely, Sampson 

 (1908, 1909, 1913, 1917) and Jardine (1908). 



The third period of rapid development in grazing studies began with the 

 organization of grazing reconnaissance in the six districts of the Forest Service 

 in 1911. During the past seven years reconnoissances have been made on 

 practically all of the National Forests, and the grazing upon these has been 



