Radial growth of Douglas-fir was similar to that of 

 pine in the thinned stand prior to the thinning until 

 about 1960 (fig. 4). Radial increment of both species 

 increased between 1935 and 1952 but decreased from 

 1952 to 1960. Subsequently, the trend for fir diverged 

 from that of pine from 1960 until 1973, about the date 

 of thinning. Radial increment of both species then 

 increased from 1973 until present (1983). Unlike the 

 unthinned (fig. 3), however, pine in the thinned stand 

 (fig. 4) maintained much better annual increment (about 



0.07 inch per year) than the fir (about 0.04 inch per year). 



The general presence of budworm in the two stands is 

 reflected in the radial growth of Douglas-fir as analyzed 

 according to the methods of Carlson and McCaughey 

 (1982). Budworm appears to have impacted the fir about 

 1960, indicated by the divergence of the host curve (fir) 

 from the nonhost (fig. 5). The cumulative curve for 

 Douglas-fir also dropped sharply in 1927, but because 

 the same inflection at the same date occurred for pine, 

 that drop is attributed to factors other than budworm. 



0.12 



Figure 4.— Mean annual radial increment of 

 Douglas-fir and ponderosa pine in the 

 thinned stand. The budworm was heavy 

 during the late 1950's through the 1970's, 

 and the pine released in the late 1960's, 

 presumably due to the biological thinning 

 done by the insect on the Douglas-fir. 



THINNED STAND 



1 \ 



« 1 i J 1 PONDEROSA PINE 



' 1 



DOUGLAS-FIR 



Figure 5.— Cumulative mean squared radial 

 increment of Douglas-fir and ponderosa pine 

 in the thinned stand. Budworm probably 

 caused the deflection of the Douglas-fir 

 curve from 1960 to 1973 (B), whereas other 

 factors, such as drought and/or stand den- 

 sity, caused the deflection beginning in 1927 

 (A). A similar trend was observed for the un- 

 thinned stand. 



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