2. On plots 3 and 4, trees were cut for a radius of 3 to 6 feet from the crown edge on at 

 least three sides of each crop tree. 



3. Plot 5 was left unthinned, but crop trees were marked for later comparison. 



Trees were removed in October 1949 by cutting, axe girdling, and poisoning. Those 

 smaller than 5 inches d.b.h. were cut with axes; those 5 inches and larger were girdled on 

 plots 2 and 4 , and poisoned on plots 1 and 3 . 



All larch and ponderosa pine crop trees were pruned with pole saws to a height of about 

 18 feet to include one log length. 



Pattee Canyon Plots ° 



These three plots were located in Pattee Canyon east of Missoula, Montana, on the Lolo 

 National Forest, at an elevation of about 4,600 feet. They were situated on a 15- to 20-percent 

 north -facing slope. The average site index of the area, determined by using Cummings ' site 

 classification curves, is 44 feet at 50 years, or site class IV. This stand also originated follow- 

 ing a bum and consists of nearly pure larch. Douglas-fir and ponderosa pine comprise less 

 than 5 percent of the total number of trees. The stand was about 30 years old when the treated 

 plot was thinned in 1932. 



1. Plot 1, one-fourth acre in size, was thinned from below by removing all of the sup- 

 pressed and part of the intermediate trees from the stand (grade B, low thinning). This left 876 

 of the original 2,468 trees per acre, at a spacing of approximately 7 by 7 feet. 



2. Plots 2 and 3, one-twentieth and one-fiftieth acre, respectively, were laid out and 

 trees were measured in 1949, because no control plots were established in 1932 when plot 1 was 

 thirmed. The locations of these plots in the stand had been considered in 1932, but no measure- 

 ments were taken then. Growth for the previous 17 years was determined from increment bor- 

 ings in green trees and by recording dead trees in the stand. The numbers and diameters of 

 trees on these unthinned plots in 1932 were calculated from the mortality, growth, and bark data 

 obtained in 1949. We believe that a reasonably reliable estimate of the 1932 stand resulted. 



Analysis 



Thinning in the West Fork study was aimed at favoring individual trees. Therefore , the 

 analysis was based upon records of individual crop trees. Multiple regression analysis was 

 used to adjust for individual tree growth responses by treatments represented on the plots . 



Analysis of the Pattee Canyon plots was based upon data from all trees because it was a 

 uniform thinning. 



The original thinning plot was established by Millard C. Evenson in 1932, while he was 

 a student at the Forestry School, Montana State University, and two small control plots were 

 established in 1949. 



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