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Predicting the growth responses to climate change among co-occurring, ecologically distinct tree species in BC
Miyamoto, Yumiko
Project Objective: Tree improvement programs in British Columbia have resulted in significant gains in the productive potential of key commercial species used in current stand regeneration. But, there remains considerable uncertainty about how regeneration and growth from both improved and wild seedlots may respond to future climate change in B.C. While tree migration may occur in response to climate change, the primary forest responses to climate change in coming decades will be seen in the capacity of trees to 'adapt' on site to fluctuating climates. Responses among tree species will not be uniform. Some species will likely be favored more than others under warming (or cooling) conditions, which will result in shifts in abundance, dominance and productivity among co-occurring tree species. Such differences may have significant implications for management decisions and harvesting quotas, yet the biology underlying these distinctions is poorly understood. The study proposed here (Timber Growth and Value Program: Proponent-Driven Priority) will address this critical knowledge gap by comparing the growth responses to climate change in mature populations of major co-occurring, ecologically distinct tree species in the central interior of B.C. This information will directly contribute to our understanding of the impacts of management decisions on timber outputs (funding priority 3.3  Estimating Impacts). Scientific Background: In temperate and cold-limited regions, numerous scientists (2,4,5,6,8,9) have observed that the adaptation of trees to their local environments entails a tradeoff between competitive ability (often characterized as height growth) and cold tolerance. In the adaptive process, links between the environment and plant response traits that favor one strategy (i.e., competitive ability or cold tolerance) generally entail a cost to the other strategy (4,5,7,1). For instance, variation in the timing of growth initiation/cessation mediates a tradeoff between the length of the growing period (competitive capacity) and protection from early or late frosts (cold tolerance). Ecologically distinct species (e.g., early vs. late succession, deciduous vs. evergreen habit) may express different tradeoffs in such adaptive traits that will result in unique responses to future climate change. Such species-specific differences in ecological tradeoffs in response to climate change may effect the future regeneration and productivity of managed and unmanaged forests in B.C. Such ecological tradeoffs have been observed in seedlings of three major B.C. conifers in a controlled study conducted by Dr. Green (4). In this study, different tradeoffs observed in key adaptive traits (e.g., growth rate, phenology, biomass allocation) in seedlings of ecologically distinct species would likely result in unique regeneration responses to future climate change. However, populations of mature trees might express different responses to climate fluctuations than seedlings among these distinct species. Project Approach: Different tradeoffs in key adaptive traits will likely translate into different growth responses to climate change among populations of mature trees. Consequently, growth-ring analyses will be conducted in mature populations of four major co-occurring and distinct tree species in central B.C. (lodgepole pine, interior spruce, subalpine fir and trembling aspen) at three ecologically different sites (warm/moist, warm/dry, cool/moist). Populations of each species will be sampled across a climate gradient (i.e., elevation) at each site to characterize the growth responses of each species to increasingly warmer climates that occur moving from high to low elevation. Annual growth (based on growth-ring analyses) in each species and population will be compared to annual variation in key climate variables (calculated from local climate data and climate models) to examine sensitivity to climate fluctuations within and between tree species. ...
Report Number
Executive Summary
Extension Note
Technical Report
Growth Responses Report
Climate Responses Report

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