The role of mycorrhizae and mycorrhizal networks in tree species range shifts with climate change nad disturbance

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Tree species ranges are predicted to shift dramatically in Canada with climate change, typically with northward migration at the leading edges and extensive mortality at the trailing edges. The ability of trees to migrate will depend not only on their genetic suitability, but also the hospitability of the new environment, including the presence of compatible ectomycorrhizal fungi (EMF) in soil, the severity of site disturbance, and the intensity of plant competition. Whereas previous research predicting tree species range shifts has focused on climatic and genetic factors, my program makes the novel contribution of examining the contributing biotic effects of EMF and mycorrhizal networks (MNs) in real species migration experiments using cutting edge techniques in isotope tracers, molecular biology (metagenomics, microsatellites, and DNA sequencing) and network analysis. Across a regional drought-stress gradient serving as a spatial proxy for climate change, I will study the roles of: (1) local EMF in facilitating migration of tree genotypes to new environments; (2) MNs formed by mature trees in facilitating natural regeneration, particularly of closely related (kin) genotypes; (3) disturbance severity in reorganizing the MN and affecting natural regeneration patterns; and (4) shifting interplant carbon source-sink gradients in transfer of carbon from dying to establishing trees. For (1), I will examine the role of EMF in establishment of non-local tree genotypes within assisted migration field and growth chamber experiments. For (2) and (3), I will plant kin and non-kin seed in mesh bag treatments (controlling for the formation and complexity ot MNs) either in natural gaps or within harvesting treatments that remove different levels of hub (highly connected) trees. For (4), I will manipulate seedling carbon source-sink gradients using defoliation treatments emulating natural tree senescence. The contributions of my program on the roles and mechanisms by which EMF and MNs facilitate tree range shifts, and how these affect plant community and soil carbon dynamics, will help scientists to predict forest ecosystem responses to climate change and managers to design practices for maintaining the resilience, carbon storage, and adaptive capacity of Canada's forests.