/ 



THPUCLUN_ 

 ABGR/CLUN 



ABLA/CLUN 



PSME/PHMA 



— I ; r— 



5 10 15 



Years Since Last Disturbance 



20 



Figure 4 — The effect of habitat type and time on predicted probability 

 of stocking. 



but never achieves as high a stocking level. The Abies lasiocarpa series has 

 a lower rate of stocking than the ThujalTsuga and Abies grandis series and 

 also does not achieve as high a stocking level. The Pseudotsuga menziesii 

 series has the lowest stocking level and the lowest increases over time of all 

 the series. 



Elevation is another important independent variable. For the Abies grandis 

 and ThujalTsuga series, the effect of elevation on the probability of stocking 

 is quadratic (fig. 5). In the ThujalTsuga series, the optimum elevation is 

 about 3,500 feet. The optimum elevation in the Abies grandis series is near 

 4,500 feet. The quadratic effect of elevation in the Abies grandis series is less 

 than that in the ThujalTsuga series. In the Pseudotsuga menziesii series, 

 increasing elevation decreases the probability of stocking. Elevation was 

 not an important independent variable in the Abies lasiocarpa series. 



The effect of residual overstory basal area on the probability of stocking 

 changes with aspect and slope. The general trend of residual basal area on 

 the probability of stocking for the Abies grandis and ThujalTsuga series is 

 quadratic. On north aspects, optimtmi basal area decreases as slope increases 

 (fig. 6). This means that a steep north-facing slope does not need as much 

 shelter as a gentle north-facing slope. On south aspects, optimimi basal area 

 increases as slope increases (fig. 7). Steep south-facing slopes need more 

 shelter than gentle south-facing slopes. 



Residual basal area was not important in the equation for the Pseudotsuga 

 menziesii series. In the Abies lasiocarpa series, the natural log of residual 

 basal area was significant, meaning that the probability of stocking increases 

 rapidly as basal area increases at low densities, but there is Httle additional 

 effect as basal area gets progressively more dense. 



14 



