Range of difference between 6-node Number 



span and height-age determination of plots 

 feet 



0-10 11 



11-20 8 



21-30 4 



Total 23 



Additional tests are contemplated. At present it does not appear that 

 internodal span can be used for precise estimates of site index. How- 

 ever, it may be a useful procedure for general management purposes where 

 broad productivity classes are used. 



Further Tests of Yield Tables 



The Southeast Alaska yield tables were checked in 1949 as to growth, pre- 

 dicted and actual, over a 25-year period.^' They were found to be reason- 

 ably accurate. During the past two years additional plots were measured 

 to compare actual volumes of the plots with those given in the tables for 

 the site indices and ages. These averaged 94 percent of the merchantable 

 cubic volume, and 106 percent of the basal area, given in the yield tables. 

 Complete volumes of plots and of strips to be run through bodies of second- 

 growth will give a firm answer as to yield table accuracy. 



The yield tables indicate in a general way that in 100 years on an average 

 site, second-growth stands will have almost twice the volume of the 

 average climax stand. This is a generalization of many complex factors. 

 For example, it is assumed that a second-growth stand should be old enough 

 to be composed mostly of trees 7 inches d.b.h. and larger before cutting, 

 to avoid waste. This varies tremendously by site index as shown by the 

 following table: 



Table 10. -- Age when basal area of 7" + trees 

 is 90 percent of total basal area 



Site index Age required - years 



70 132 



90 100 



110 74 



130 60 



150 55 



9_/ First records of growth for Southeast Alaska's young stands. Tech. 

 Note No. 1, Alaska Forest Research Center, March 1949. 



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