Effects of Partial Harvest on the Carbon Stores in Douglas-fir/Western Hemlock Forests: A Simulation Study

The STANDCARB 2.0 model was used to examine the effects of partial harvest of trees within stands on forest-related carbon (C) stores in a typical Pacific Northwest Pseudotsuga/Tsuga forest. For harvest rotation intervals of 20 to 250 years the effect of completely dispersed (that is, a checkerboard) versus completely aggregated cutting patterns (that is, single blocks) was compared. The simulations indicated that forests with frequent, but partial removal of live trees can store as much C as those with complete tree harvest on less frequent intervals. Stores in forest products generally declined as the fraction of live trees harvested declined and as the interval between harvests increased. Although the proportion of total system stores in forest products increased as the frequency of harvests and proportion of trees removed increased, this did not offset the reduction in forest C stores these treatments caused. Spatial arrangement of harvest influenced tree species composition profoundly; however, the effects of aggregated versus dispersed cutting patterns on C stores were relatively small compared to the other treatments. This study indicates that there are multiple methods to increase C stores in the forest sector including either increasing the time between harvests or reducing the fraction of trees harvested during each harvest.