X 



0) 





 E 

 g 



b 



24 



20 



= 16 



12 



Site index 



75 Feet (Good) 



55 Feet (Medium) 

 35 Feet (Poor) 



A (Section of curve adjusted to S.i. 52. 



B (Section of curve adjusted to S.I. 44.) 



20 



40 



60 80 

 Age — Years 



100 



120 



140 



Figure 2. - -Potential diameter breast high for western larch 

 by age and site index, adjusted to optimum stocking. 



Table 5. --Relation of actual to potential crop-tree diameter growth 



Comparison 



: West Fork : 



Pattee Canyon 



of growth 



: 10-year 



: Percent of : 



27 -year 



: Percent of 



by treatments 



: growth 



: site potential : 



growth 



: site potential 





Inches 





Inches 





Potential growth 



1.8 



100 



4.9 



100 



Actual growth: 











D+4 



1.4 



78 







Crown 



1.2 



67 







Unthinned 



1.0 



56 







Low thinning, 











"B" grade 







2.8 



57 



Unthinned 







1.8 



37 



The low thinning in Pattee Canyon was too light. Only 57 percent of the goal was attained 

 over a 27-year growth period. However, this is 20 percent better than no treatment (unthinned) 

 More than twice the number of trees per acre were present in the thinned plot at the end of the 

 27 -year growth period than are desirable to obtain potential growth (fig. 3). 



7 



