Tree population responses to climatic extremes

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Background Increasingly severe climatic events significantly impact forest ecosystems. In 2021, for example, a record-breaking heat-drought event in western Canada led to significant tree mortality and will impact long-term forest health. At the same time, warmer winters cause trees to grow too early in spring and too late into the fall, increasing risk of frost damage. However, the capacity of tree species and populations to cope with extreme conditions varies widely and is often under high genetic control due to strong selective pressures. Investigating genetic adaptation to climatic extremes is key for predicting forest responses and mitigating impacts. Objectives & HQP The long-term objective of my research program is to discover and model the adaptive capacity of keystone tree species in Canada's western forests to climate extremes. To that end, I will build an inclusive and diverse team of 2 PhD, 2 MSc and 4 BSc students, who will have equitable access to training and research opportunities. Over 5 years, these HQP will test genetic variation across tree populations of a widespread conifer, lodgepole pine, and further examine variation within tree breeding populations for two iconic, co-occurring coastal conifers - western redcedar and Douglas-fir. We will: 1) Quantify genetic control of growth responses to heat-drought events; 2) establish links with physiology; 3) reveal genetic architecture behind changes in phenology; and 4) create population-specific climate niche models that incorporate this new knowledge of genetic adaptation to climatic extremes. This inter-disciplinary research involves partnerships across sectors, offering HQP networking opportunities. Methods New approaches to phenotyping trees will be combined with mature forest genetics experiments. Progeny and provenance trials can be used to decode patterns of inheritance or genetic variation across tree populations. To retrospectively assess resilience and to infer physiological mechanisms, we will use tree-rings, functional wood anatomy and stable isotope analyses. To assess tree responses in near real time, we will obtain remotely-sensed data from a novel assemblage of drone-mounted sensors, never before applied to progeny trials. These proxy data will be ground-truthed with foliar properties and further validated with independent tree-ring data. Resulting data will guide niche modeling. Impact Forest genetics programs supply the majority of material for tree planting initiatives in British Columbia, with millions of seedlings planted annually. By working with government partners, research results can guide these programs to select trees with climate-adaptive traits. Planting seedlings resilient to climate extremes will help newly established forests maintain long-term health and productivity to support a suite of ecological and economic values. Training of HQPs in this program will further increase capacity to address effects of climate warming and extremes.