APPLIED ECOLOGY 357 



narily would not be preferred, and, with this, accelerated ero- 

 sion. 249 It is also highly desirable that the slow successional changes 

 in species composition resulting from grazing under a certain 

 system be recognized. Usually if these are in the direction of 

 climax, they are advantageous. If they show an increase of forbs 

 or of unpalatable species, management practices must be corrected 

 before the trend becomes serious. 



In each grazing region, the significant indicators must be known 

 and interpreted. Often selected species can be used and checked 

 upon to simplify evaluations. Likewise, restricted areas, selected 

 on the basis of experience, may be used for observation as repre- 

 sentative of the general conditions on a range as a whole. 



Range management is obviously applied ecology in which indi- 

 cators play an important part. The more completely the ecology 

 of the species and communities is known under grazing condi- 

 tions, the more readily their responses can be interpreted and the 

 more effective management practices can be. 



Forest Site Indicators.— In forestry, as in agriculture, the indica- 

 tor significance of one group of plants must be interpreted and 

 applied to an entirely different group of plants. Since forest indi- 

 cators are commonly herbs or shrubs, there is often some diffi- 

 culty in translating their meaning to apply to trees. In the broad- 

 est sense, forest indicators are site indicators, but rarely do they 

 suggest more than a portion of the several factors that contribute 

 to site. Physical or chemical characteristics of soil, moisture rela- 

 tionships, aeration, or erosion may be indicated by some species. 

 With these and others the probable development of a particular 

 stand can be interpreted. Still others may indicate the past history 

 of vegetation on the site or the probable successional trend to be 

 anticipated in the future. 



It is fundamental to indicator interpretation that the succes- 

 sional trends of a region be thoroughly understood for every type 

 of habitat. Only when an indicator is considered in relation to the 

 stage of succession concerned can its meaning be at all clear. 



The use of subordinate or dependent species as indicators of 

 site quality has been attempted under various conditions since 

 Cajander 51 set up such a system for classifying forest types in 

 Finland. This system assumes that, since communities of similar 



