ponderosa pine in the unthinned stand is 61 and 39, 

 respectively, similar to the thinned stand (table 1). 



Three circular 0.10-acre plots were systematically 

 located in each stand. Within each plot in the thinned 

 stand, tree density, species, d.b.h., height, crown ratios, 

 and budworm defoliation were recorded. On the control 

 plots, tree density and species composition were based 

 on all trees present on the plot, whereas d.b.h., height, 

 crown ratios, and defoliation were recorded for those 

 trees that would have been retained had the plot been 

 thinned. 



A whole-crown ocular estimate, which included all 

 crown levels and ages of foliage, of budworm defoliation 

 was made and classed for each host tree. The classes 



were: 



Rating 

 class 



1 



2 

 3 

 4 



Percent 

 defoliation 



0-25 

 26-50 

 51-75 

 76-100 



This rating was done from the ground— no branch sam- 

 ples were taken. 



In addition to the whole-tree estimate, current defolia- 

 tion was assessed on four midcrown branches of each of 

 three trees on each plot. Sample trees had to be climbed 

 because the branch sampling was nondestructive (fig. 2). 

 Four branches were permanently tagged for future refer- 

 ence, and defoliation on each branch was estimated and 

 recorded according to the method of Carlson and others 

 (1982). Twenty-five new shoots were observed and each 

 was rated as follows: 



Rating 

 class 





 1 

 2 

 3 

 4 

 5 



Percent 

 defoliation 







1-25 

 26-50 

 51-75 

 76-99 

 100 



Classes and 5 were included here because, unlike the 

 ground-based estimates of whole-tree defoliation, it was 

 possible to distinguish and 100 percent defoliation. 



Increment cores were taken to assess the response of 

 radial stem growth to thinning, budworm defoliation, or 

 a combination of the two. Two 0.197-inch-diameter cores 

 were extracted at d.b.h. from opposite sides of each sam- 

 ple tree parallel to the topographic contour. Five sample 

 trees of each species, Douglas-fir and ponderosa pine, 

 were randomly selected from the list of plot trees. If five 

 trees were not present, then the nearest tree similar to 

 the plot trees, but outside the plot, was selected. Cores 

 were labeled and sealed in plastic straws to prevent 

 moisture loss, returned to the laboratory, and frozen 

 until measurements were made. 



In the laboratory, annual increment was measured to 

 the nearest 0.003 inch and recorded for each core, using 

 a Bannister Incremental Measuring Machine. Annual 



Figure 2. — Inspecting midcrown 

 branches for defoliation caused by 

 budworm. 



increment was averaged by year for the two cores from 

 a sample tree and this average value was used in subse- 

 quent analyses. Our null hypotheses were: 



1. Defoliation (whole-tree and current-measured) on 

 Douglas-fir was not different between the thinned and 

 unthinned stand. 



2. Radial growth of Douglas-fir (a) has not changed 

 since thinning, (b) is not different from radial growth of 

 ponderosa pine, and (c) is not different between the 

 thinned and unthinned stands. 



Four variables were selected to test these hypotheses, 

 using the "t" statistic for an unpaired design (Sokal and 

 Rohlf 1969). Whole-tree defoliation (ground-based visual 

 estimate) and measured current defoliation (four-branch 

 midcrown sample) on Douglas-fir were tested between 

 stands. Two growth ratios were computed— one to repre- 

 sent growth since thinning, the other to depict growth 

 prior to thinning: 



Ratio 1— Radial growth since thinning 10-year 

 radial growth just prior to thinning. 



Ratio 2— 10-year radial growth immediately prior to 

 the date of thinning -i- 10-year radial growth 11 to 20 

 years previous to thinning. 



These radial growth ratios were tested (1) between 

 treatments (thinned and unthinned) by species, (2) 

 between species (Douglas-fir and ponderosa pine) by 

 treatment, and (3) between growth periods (before and 

 after thinning) by treatment by species. 



3 



