THE EED SPRUCE. 



41 



Hampshire would undoubtedly show somewhat better general de- 

 velopment there than in Maine. 



The growth in volume of trees in even-aged stands may be deter- 

 mined in a manner similar to that just described. In this case, how- 

 ever, the diameter growth instead of being calculated by arbitrary 

 periods, such as 10 or 20 years, would be expressed in terms of total 

 age. If the rate of volume growth is to be determined for natural 

 stands undisturbed by thinnings or other treatment which would 

 tend to interfere with the process of elimination by natural competi- 

 tion, the diameter growth should be based on the average growth of 

 all green trees of the even-aged normal stands of different ages. If, 

 however, thinnings are contemplated which will enable the trees com- 

 posing a stand to grow at their maximum rate with the minumum 

 of competition, the basis for growth should be the mean average of 

 the dominant and intermediate (Table 12) or, under the most favor- 

 able conditions, the dominant trees only of the even-aged normal 

 stands of different ages. 



STANDS AND YIELDS. 



The yield of virgin or selection growth spruce, both present and 

 future, varies widely from one type to the other and within the same 

 type hi different regions. It is not possible under the circumstances 

 to discuss the subject in such detail as to cover the full range of 

 conditions which local variations impose, nor are the data available 

 for such discussion. Given certain fundamental data, the range of 

 reliability of which is less restricted than would be yield tables based 

 on the widely variable conditions existing in our present- virgin and 

 cull spruce selection forests, the yield for any particular tract can 

 be readily computed. 



Aside from that already presented for the various regions under the 

 headings of growth in height, diameter, and volume, the only infor- 

 mation needed is the enumeration of the stands 1 the yield of which is 

 to be determined and their average composition as to size and species 

 calculated and tabulated for use in the following convenient form: 



Diam- 

 eter, 



breast 

 high. 



Average number of trees. 



Spruce 



left to 



grow 



(average 



number). 



Spruce. 



Other 

 species. 



Total. 



1 



2 



3 



i 



5 



Inches. 











1 In the appendix (Tables 50-53, inclusive, on pp. 94-97), will be found stand tables prepared from such 

 enumerations in virgin forest growth of the spruce slope type. The associated species are included as a 

 matter of comparison. Incidentally, these tables show in a broad general way the relative production 

 per unit of area of the different regions which they represent. It must not be understood, however, that 

 any claim is made that they show exact average conditions throughout their respective regions. 



