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UBC Theses and Dissertations

Going underground : patterns of fine-root and mycorrhizal fungal trait variation across a biogeographic gradient in western Canada Defrenne, Camille Emilie


Understanding fine-root adjustments to the environment and identifying factors that shape mycorrhizal fungal communities is a prerequisite for predicting the response and feedbacks of plants to global changes. As a consequence, trait-based plant ecology, which has mostly focused on above-ground traits, is increasingly placing the emphasis below-ground. To improve our functional understanding of fine roots, we first quantified root morphological, chemical and architectural trait variation in interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) forests across a biogeographic gradient in Western Canada. We found substantial within-population root trait variation, which may enable acclimation of trees to future environmental conditions. Yet, we also identified moderate but consistent trait-environment linkages across populations of Douglas-fir. We provided evidence for decoupled variation in fine-root morphological and chemical traits. Our results highlight the existence of multiple axes of within-species fine-root adjustments that were consistent with a potential increase in fine-root acquisitive capacity with environmental limitations. Next, to better integrate mycorrhizal symbiosis into trait-based plant ecology, we combined trait measurements of fine roots and ectomycorrhizal fungi with next-generation sequencing. We found temperature, precipitation and soil C:N ratio affected ectomycorrhizal community similarities and exploration type abundance but had no effect on fungal richness and diversity. We did not provide evidence for a functional connection between root traits and fungal exploration types within Douglas-fir populations. Our study clarifies ectomycorrhizal taxonomic and functional responses to environmental factors but warrants further research to broaden root trait frameworks and evaluate the role of mycorrhizal fungi in mediating ecosystem responses to environmental changes. This line of inquiry will be particularly important to better manage existing forests and to ensure that well-adapted forest tree populations are regenerated in the future.

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