COS 91-5 - CANCELLED - Dynamics of natural regeneration following Douglas-fir beetle sanitation in a southern interior British Columbia forest

Background/Question/Methods

In British Columbia, Canada, dry interior Douglas-fir forests are managed to meet multiple, sometimes conflicting objectives such as timber production, visual quality, and wildlife habitat. Disturbances like fires, drought and insect outbreaks drive the dynamics of these forests. The intensity, severity and frequency of these events are expected to increase as the climate changes. Douglas-fir beetle (Dendroctonus pseudotsugae), a native defoliator has been at epidemic populations since 2002. Beginning in 2013, sanitation harvests were implemented in the UBC Alex Fraser research forest to control the spread of Douglas-fir beetle. Sanitation harvests are often planted post-harvest; however, little is known about the dynamics of natural regeneration in these dry forests. To understand future stand composition and ensure resilient stand structures, we investigated the establishment and growth of natural regeneration over a temporal gradient post-sanitation harvesting. Using fixed area plots and hemispherical photographs, we examined the interaction between harvest implementation, resource limitation and the silvics of Douglas-fir forests.

Results/Conclusions

The findings of the study revealed that approximately 70% of the gaps assessed did not meet stocking requirements, out of which about 40% had no regeneration. Based on the findings of the study, we do not accept the hypothesis that the establishment and growth of interior Douglas-fir will increase with increasing available growing space in the gaps of regenerating Douglas-fir stands, and that growing space availability will have an influence on the establishment and growth of naturally regenerating seedlings. This research provides insight into the conversation surrounding growing space availability and influence on naturally regenerating species. We recommend that additional research is needed to fully understand the dynamics of interior Douglas-fir regeneration and growth in gaps over temporal and spatial scales. This will enable management to make more informed ecological decisions on post-disturbance silvicultural prescriptions to maintain stand structure and functions within these dry forests.