560 JOURNAL OF FORESTRY 



Separating these regions in accordance with the grouping proposed, 

 we find that CaHfornia and Washington fall into Group B; Union 

 County, Oregon, into Group C ; Whitman, Montana, and Klamath, into 

 Group D, and the remainder fall into Group E. This grouping is 

 merely for illustration ; more and better data are needed before a final 

 classification can be done. 



The illustration indicates that this method of grouping is cosmo- 

 politan and perfectly adaptive. 



It is seen that the classification and grouping are merely a measure 

 for comparisons of tree growth in the various regions. It appears to 

 us to be as good and as handy a measure as is available. 



APPLICATION OF THE SYSTEMS AND METHODS OUTLINED 



The following description of the application of the methods out- 

 lined for the determination and classification of sites is based upon the 

 methods used by the United States Forest Service in its timber surveys : 



The first thing to be done is to group the area which is being cruised 

 according to the grouping system outlined. Usually there are available 

 growth tables which show the growth on at least the best sites of the 

 area. This is all that is required to accomplish the grouping, since it is 

 very doubtful if the growth on the poorest site will be less than that 

 which is indicated by the site classification. The sites intermediary 

 between the best and the poorest fall into their places mechanically, 

 according to the classification. But if there are no growth tables, or if 

 they are not considered satisfactory, then a dozen healthy, dominant 

 trees, approximately 100 years old, growing on representative sites. 

 may be cut, and they will give the data required for the grouping. 



After having determined the group to which the area belongs, the 

 next step is to construct curves of height growth based on age and 

 diameter for each species. The trees for analysis should not have 

 irregular butts, should be dominant or co-dominant, healthy and pre- 

 ferably neither overmature nor yet saplings. The trees used in the 

 determination of the grouping may be used. 



Draw a curve of the growth in height on Site I. The curves of the 

 growth in height on the other sites will follow it in general shape, but 

 as far distant below the first curve as the classification indicates. These 

 curves of growth do not need to be based on a great many measure- 

 ments ; it is very probable that entirely sufficiently accurate figures can 

 be obtained by the use of an increment borer and hypsometer, if the 

 trees are not too large. 



