Cause of loss Engelmann spruce Subalpine fir 



Windthrow 81 11 

 Windbroken 4 

 Root rot and 



windthrow 7 

 Insects 8 19 



Sunscalding -- 56 



Unknown - - 14 



Response of residual trees in relation to time. --One of the chief reasons for reserving 

 trees on a cutover area, besides providing a seed source, is to obtain additional growth on 

 quality trees. This concept implies that the remaining trees will increase their increment 

 when the stand is thinned by cutting. The residual trees responded significantly to logging 

 release with acceleration in diameter growth, beginning in the second 5-year period after log- 

 ging (fig. 2). The diameter increment remained high through the 6- to 30-year period after 

 logging but fell off slightly during the last 5-year period. Dejarnette* reported no evident in- 

 crease in diameter growth after an examination of the cutting in 1929; this confirms the lack of 

 response depicted in the first 5 -year period in the 1954 data. 



Changing climatic conditions as well as release by logging can bring about accelerated 

 diameter growth rates in trees. To help eliminate the effect of climatic factors and isolate the 

 effect of logging release in the analysis, growth rates in an adjacent uncut stand were compared 

 with those in the cutover residual stand. The trees in the cutover stand grew considerably more 

 than those in the uncut stand; and the substantial difference between the two represents the 

 response attributable to release. 



0-5 6-10 11-15 16-20 21-25 26-30 



FIVE-YEAR PERIODS AFTER LOGGING 



Figure 2. --Average diameter increment of trees in relation to time since cutting. 



^Ibid. 



4 



