NOTES FROM THE FIELD
Research Supports Operational Practice in Community Forests:
Reducing Climate Change-Related Risks to Timber Supply
Climate change is expected to increase the intensity and severity of both abiotic and biotic disturbances, alter forest productivity, and change the distribution of species in forest types across British Columbia Assisted migration, species diversification, and thinning have been suggested as options to potentially reduce these climate change-related risks. There is a renewed interest in commercial thinning (CT) specifically as an option to mitigate the mid-term timber supply shortage induced by the unbalanced age class distribution inherited from past mountain pine beetle (MPB) outbreaks and large wildfires. This potentially allows access to timber volume in immature stands or in areas managed for non-timber objectives, and shortens the time to merchantability.
Researchers at the University of BC and the BC Ministry of Forests recently published the results of a case study where they modelled the potential of combining CT and species diversification to mitigate the impacts to timber supply The study area is located in the Copper Pine Creek area within the Bulkley timber supply area. It covers approximately 96 000 ha, with abroad elevation range (from 460 to 2500 m) and is transitional between coastal and interior climates. The Copper Pine Creek area encompasses three main biogeoclimatic ecosystem classification zones and five variants (Figure 1).
For the baseline and no climate change scenarios, the study followed a classic approach to timber supply analyses in BC. Stand level growth and yield models were used to derive yield curves that were used as inputs for the forest estate model PatchworksTM. By allowing timber extraction from immature stands, CT increased harvest levels over the entire 250-year planning horizon and mitigated the projected reduction in timber supply.
Figure 1 Location of the Copper Pine Creek study area (a, in British Columbia; b, within Bulkley timber supply area and description of the biogeoclimatic zone variants (c) and land base (d) (Lafond, V et al 2024)
The effects of severe, hotter and drier weather on tree species productivity was incorporated in a novel approach by linking a process model with a growth and yield model. These simulations also showed that CT mitigated the timber supply shortage under climate change and had an even stronger positive effect on harvest levels in the short and long term Here, CT provides an opportunity to access volume early to mitigate both the MPB-induced mid-term shortage and partially, the future volume losses induced by climate change, as well as accessing volume in stands affected by model constraints (e.g. visual quality and watershed protection).
This study also showed the potential benefits of alternative planting regimes focusing on assisted migration and species diversification. The positive effect of species diversification on timber supply under climate change is the combined result of the LANDIS-II yield curves simulating (i) increased climatic fitness of the species mixture in this scenario and (ii) increased productivity in mixed-stands in general Combining both options allowed limiting negative climate change effects, allowing to maintain or even increase forest productivity and timber supply under climate change. Actively replacing the MPB-host lodgepole pine with a mix of species including Douglas-fir is advocated as a way to increase forest resilience. This case study showed that there is strong evidence of the combined benefits of thinning and species diversification.
Pre-treatment stand Burns Lake Community Forest Post treatment
Burn Lake Community Forest
Many Community Forests across BC have already completed thinning treatments as part of wildfire risk reduction whereas several others such as the Burns Lake Community Forest, Terrace Community Forest and the Wetzin’kwa Community Forest have or are planning to implement more intentional CT treatments in the next five years. They feel that CT can immediately help manage for multiple values including conserving and preserving Indigenous cultural values, maintaining continuous canopy cover, enable a more continuous fiber supply and potentially increasing stream flows and water availability in key watersheds.
Commercial thinning can also potentially improve the growth of residual trees, increase wood quality, or obtain certain species or sizes needed for specialty products. The Burns Lake Community forest completed and documented a thorough account of a recently completed commercial thinning operation. The increased implementation of commercial thinning on the ground presents an excellent opportunity for adaptive management. The Ministry of Forests intends to initiate a province wide monitoring of commercial thinning in 2025 pending funding.
Practitioners inspect the treated area post harvest
For more information contact:
Research - Greg.paradis@ubc.ca caren.dymond@gov.bc.ca verena griess@usys ethz ch
Community Forests Management – Sam Coggins management@wetzinkwa.ca
Ministry of Forests - Craig Wickland, Stand Management Team Lead Craig.Wickland@gov.bc.ca
If your Community Forest would like to be included in the next “Notes From The Field” series, please reach out to:
Deborah de Long at deborah delong@ubc ca