HISTORICAL. 9 



alkali lands. While the author ascribes primary importance to the presence 

 of lime, he does not fail to assign great value to water, especially in the West. 

 He not only recognizes the indicator value of the presence of a particular 

 species or group of species, but also takes into account the size, form, and 

 development of the indicators. Significant tables and lists of indicators are 

 given on pages 490, 497, 514-516, 518-519, and 536. In so far as these con- 

 cern the West, they are considered in Chapters V, VI, and VII. 



Clements, 1910. — In 1908, the work of the Botanical Survey of Minnesota 

 was reorganized upon an ecological basis, for the purpose of making a classifica- 

 tion and use survey of the lands of the State. The objectives of the survey were 

 defined as follows (Clements, 1910:52): 



"The first step in determining the final possibilities of Minnesota in plant 

 production is to ascertain just what the conditions of soil and climate are from 

 the standpoint of the plant. This must be determined separately for the two 

 great groups of lands, those still unoccupied and those now in use. For the 

 former, a knowledge of soil and climate and of the plant's relation to them is 

 necessary to determine what primary crop, grain, forage, or forest is best. 

 For the farms of the State, the best use is a matter of knowing the soil and cli- 

 mate differences of regions and fields, and of taking advantage of these in crop 

 production. For the unoccupied lands of Minnesota, we need a classification 

 survey to determine the best use of different areas, to prevent the waste of 

 human effort and happiness involved in trying to secure from the land what it 

 can not give and yet to insure that the land will reach as quickly as possible 

 its maximum permanent return. For occupied lands, the study and mapping 

 of soil and climatic conditions would constitute a use survey of the greatest 

 value in adjusting plant production to the conditions which control it. 



"The chief object of a classification survey is to group the unoccupied lands 

 of the State as accurately as possible into three great divisions: (1) agricul- 

 tural land, for crop production; (2) pasture land, for dairying and stock raising; 

 (3) forest land, for lumbering, water regulation, and recreation parks. Such a 

 division would be determined primarily by studies of soil and climate, neces- 

 sarily supplemented by the evidence of native vegetation itself and of such 

 cultivation as has been tried. The value of classification depends upon its 

 accuracy, but the study of an area from these three standpoints neglects no 

 source of evidence, and discloses practically all that can be learned of the 

 possibilities." 



The survey method was based upon the instrumental and quadrat study of 

 habitats and communities, cultural as well as natural. The main divisions 

 were vegetation mapping, the determination of indicators, and the study of 

 succession. Vegetation and physiography were recorded on maps in which 

 each division of 40 acres was represented by a square decimeter. Quadrat 

 and transect charts were made of typical communities in each section of the 

 township, and determinations of physical factors in all charted quadrats. 

 The indicator work was devoted to the recognition of indicator species and 

 communities so closely dependent upon water-content, soil, acidity, or light 

 that they could always be used as indicating a certain set of conditions. 

 Especial attention was given to the correlation of indicators with crop plants 

 and with the secondary successions in burns, cutovers, fallow fields, pastures, 

 roadsides, etc. Four townships were mapped upon this basis in 1912. and a 

 large number of successional areas from 1913 to 1916. Some of the general 



