VII. FOREST INDICATORS. 



Nature. — Forest indicators are of three chief types, namely, (1) those that 

 have to do with existing forests; (2) those that indicate former forests; (3) 

 those that indicate the possibility of establishing new forests. A community 

 of trees is axiomatically an indicator of forest, but it carries with it indications 

 of habitat, structure, and development which are not so obvious. More- 

 over, it involves important indications as to use, such as lumbering, water 

 regulation, grazing, etc. Indicators of former forests are either actual re- 

 licts of the forest itself or serai communities which mark particular stages of 

 the successional reforestation. They may consist of the dominant trees as 

 individuals or communities, of the subdominant shrubs or herbs of the climax 

 forest, or of the dominants or subdominant s of any successional stage. Their 

 great value lies in the fact that they not only indicate the possibility of re- 

 forestation, but also the stage which has been reached and the further methods 

 to be employed. They are by far the most important and practical of all 

 forest indicators when the vast extent and significance of deforested areas are 

 taken into account. They pass more or less gradually into indicators of the 

 possibility of forest production in regions which have been repeatedly de- 

 forested and which show neither relicts nor serai stages of the original climax. 

 Such are the transition regions between forest and scrub or prairie, in which 

 the latter appear to be climax, but are really subclimax and will consequently 

 yield to forest when artificial regeneration is employed. In addition, chaparral 

 and grassland may also indicate afforestation in regions which have not borne 

 forest for hundreds or thousands of years. These are primarily edaphic areas 

 in which the indicator community owes its presence to a higher water-content 

 resulting from soil or topography. Such are the sandhills of Nebraska and 

 the river valleys throughout the prairie associations. 



Kinds of indicators. — Both the individual and the community may be used 

 as indicators. The latter is naturally more complete and definite, but in 

 many cases the change following clearing or fire is so complete that a single 

 relict individual gives information of great value as to the original climax. 

 This is true also of subclimax forests which have more or less completely 

 disappeared in the reestablishment of the climax forest. The forest formation 

 which is climax for a certain region is itself the indicator of the permanent 

 type of the region, and hence of the forest which will naturally develop or 

 redevelop in all bare or cleared areas. As a consequence, it is an indicator of 

 site and likewise of the type of management to be employed. Each associ- 

 ation is an indicator of climate, while the various groupings and alternations 

 of the consociations indicate different edaphic conditions as well. The 

 societies indicate variations in water-content or light primarily, but the layer 

 societies are especially related to light. Differences in the density and growth 

 of dominants and subdominants serve as indications of minor changes in the 

 factor complex. Indicator values may be derived from growth in height, 

 diameter, or volume. The former is the most convenient for use, but the 

 latter is probably the most accurate. Seedlings are among the best of domi- 

 nant indicators, especially when their growth, habit, and abundance are taken 

 into account. The minute structure of leaves is an excellent indicator of 



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