Retention forestry has been gaining increasing popularity for its ability to provide ecosystem services outside of timber. Recent research has highlighted that residual persistence is highest when large numbers of residuals are maintained and that intensity of silvicultural treatments postharvest is less important for residual tree persistence than differences in site condition. However, little research has been conducted on how silvicultural treatments postharvest affect residual tree growth. This is especially meaningful for high retention silviculture systems like shelterwoods where the retained overstorey can potentially be released from competition and increase growth in response, or potentially incur damages that may not result in mortality but may result in a loss of vigor that can lead to defects. Using a silviculture experiment fully replicated within two sites in Ontario’s temperate forest, we examine how a gradient of post-harvest silviculture treatments affects residual tree growth. Four intensities of silvicultural treatments (extensive, basic, intensive, and elite in increasing order of intensity) were compared to unharvested mature stands.
Results/Conclusions
Growth rates of residual trees increased as silvicultural treatment intensity increased, but the effect was site-specific. At North Bay (temperate hardwood), residual growth was highest in the elite treatments and lowest in the natural treatments. At Petawawa (temperate conifer), residual growth was lowest in natural and extensive treatments and higher in basic, intensive, and elite treatments. However, the effect of site and treatment were overall less important than the effect of size and species. Larger residual trees and temperate hardwood tree species grew faster than smaller residual trees and boreal conifer tree species. These results indicate that while high retention harvests are associated with more service provision, and may produce more on aggregate than harvested plots, individual tree growth is higher when shelterwood cuts are applied. Coupled with previous work that shows a decrease in residual tree mortality in harvested versus unharvested treatments at the same sites, these results indicate that post-harvest silvicultural operations do not risk increased mortality or loss of vigor in residual trees in Ontario’s shelterwood harvests.
