LAND CLASSIFICATION. 245 



A SYSTEM OF LAND CLASSIFICATION. 



Bases. — As has been repeatedly emphasized, a system of land classification 

 which is both practically and scientifically adequate must ignore no source 

 of evidence. While indicator vegetation must be regarded as the chief tool, 

 the latter is valueless unless it is correlated with practical experience and 

 experiment on the one hand and with factor measurements on the other. 

 Some indicator values can be disclosed by the use of a single one of these 

 correlations, but all of them are necessary for complete certainty and accuracy. 

 They not only serve to check each other, but also to reveal additional and final 

 values. Furthermore, it must be recognized that all the climatic and hence 

 many of the soil factors vary considerably and sometimes critically from year 

 to year, and that this means a corresponding difference in crop production, 

 and often in tillage methods. As a consequence, the annual variations in 

 factors, indicators, and production must always be taken into account and 

 related, as far as possible, to an average or norm. The normal rainfall or mean 

 temperature is insufficient for this purpose, especially since it fails to disclose 

 the number and occurrence of the critical dry years. For this purpose the 

 use of climatic cycles is necessary, and in consequence they must be assigned 

 an important part in the classification of lands in arid and semi-arid regions. 

 The existence and effect of such cycles are established beyond a doubt, and the 

 chief task at present is to learn how to make the fullest possible use of them. 

 This naturally depends upon the certainty and accuracy with which the dry 

 and wet phases of the cycle can be predicted (Clements, 1917: 304, 1918: 295). 

 The nature and utilization of climatic cycles are discussed in the following 

 section. 



Classification and use. — The close relationship between classification and 

 use surveys and the importance of developing the one into the other can hardly 

 be emphasized too strongly. The vital connection between the two in the 

 proper development of the possibilities of the land may be seen from the 

 following (Clements, 1910:52): 



"The first step in determining the final possibilities of plant production is 

 to ascertain just what the conditions of soil and climate are from the stand- 

 point 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 decide 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 climatic differ- 

 ences of regions and fields, and of taking advantage of this 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. 



"A use survey is the logical outcome of the classification of land. Its 

 greatest importance is with agricultural lands, since grassland and forest 

 permit less specialization in crop production. The period of the one-crop 

 farm seems nearly closed; that of the special-crop farm is barely begun in 

 this country. As a method of conservation, diversified farming is a perma- 

 nent step in advance. It is the foundation upon which a distinctively success- 



