Mixed forests management for enhancing adaptation to climate change

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Background In the face of unprecedented climate change impacts on forests and forest-dependent communities, new strategies to enhance resilience and reduce the impacts of climate change are urgently needed. Researchers and managers are turning their attention to mixed forests, as evidence shows that single- species forests, often used to maximize profit, are more prone to health problems resulting in reduced productivity. We can design specific mixtures of species to enhance ecological and economic benefits for adaptation- but how? Many long--term mixed- species experiments have been installed in BC since the 1970's. However, while such long-term data is necessary to begin to examine mixtures, true advances in understanding how forests react to drought events or insect attacks are severely limited by a lack of fine-scale spatial and temporal data. Objectives My long-term objective is to determine which silvicultural choices in species compositions and forest structures promote desired ecosystem functions. Within the next five years, 12 HQP will develop and apply novel monitoring tools to quantify how various mixtures, arrangement of species and site conditions affect:(1) Stand structure, specifically spatial complementarity in light use and wood quality;(2) Biomass allocation, carbon storage and temporal complementarity in resource use; and (3) Vulnerability to drought, insects and pathogens. To have maximum practical impact, the proposed work will focus on species mixtures that are common in western Canada, both in interior forests such as spruce mixed with lodgepole pine, and coastal forests such as Douglas-fir mixed with alder. Methods This program will use a novel combination of highly detailed spatial information of forest structure and high-resolution temporal growth and water-use data with process-based modelling. Crown and branch 3-D structure will be collected using terrestrial laser scanning, a non-destructive method, across a range of forest stands with varying species mixtures, which have been subject to a range of disturbance types and intensities. This data will be used in combination with a tree-level model to quantify the implications for light absorption and productivity. Tree cores and point dendrometers will provide growth data with yearly and hourly resolution respectively. Growth data will be coupled with water-use efficiency measurements obtained with sap-flow sensors and isotopes. Impact This research will establish novel silvicultural techniques designed to drive decisions around planting and management of future-ready mixed-species forests that meet the needs of the forest sector and society. My research team will develop new methodologies to quantify complementarity of resource use and resilience to drought, insects and pathogens in mixtures, that will be used by the international research community. This research will engage a large number of stakeholders including forest agencies and the forest industry.