Cascading effects of insect outbreak on plant and fungal community structure and function

  • Author / Creator
    Pec, Gregory J
  • Western North American landscapes are rapidly being transformed by forest die- off caused by mountain pine beetle with implications for plant and soil communities. The mechanisms that drive changes in plant and soil community structure and function, particularly for understory vegetation and the highly prevalent ectomycorrhizal fungi in pine forests, are complex and intertwined. In this thesis, I use a recent bark beetle outbreak in lodgepole pine (Pinus contorta) forests of western Canada to disentangle the relative importance of beetle-induced tree mortality from changes in environmental conditions following tree death, and in turn, its effects on: (1) understory plant community diversity and productivity, (2) the richness and composition of soil fungal communities, (3) the spatial structuring of ectomycorrhizal and saprotrophic fungal communities, and (4) the functional importance of ectomycorrhizal fungal networks on tree seedling establishment. My results indicate that both deterministic and stochastic processes structure plant and soil fungal communities following landscape-level insect outbreak and reflect both the independent and shared roles tree mortality, soil chemistry, and spatial distance play in regulating both these communities. My results also demonstrate that ectomycorrhizal fungal networks seemed to not be degraded with stand level tree mortality, with access to these networks improving both the growth and nutrition of tree seedlings. Taken together, this thesis demonstrates the far-reaching effects of biotic disturbance and emphasizes the interconnectedness between understory vegetation, trees, soils, and soil fungi.

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  • Degree
    Doctor of Philosophy
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    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.