Recovery Across a Gradient of Disturbance Novelties: Patterns and Drivers of Understory Plant Community Dynamics in Northern Lodgepole Pine Forests

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Millions of hectares of Canada's northern forests are impacted each year by both natural and anthropogenic disturbance agents. Novel disturbances are pushing northern forests beyond their historical natural ranges of variability; these forests are experiencing unprecedented types and severities of disturbance. The changes in disturbance regimes are in turn are leading to changes in forest structure, function, and long-term successional trajectories, with unknown ecological consequences. The relative impacts of these disturbances on the forest canopy, understory plant community, and below-ground properties will play an important role in determining succession, biodiversity and conservation of these forests. Given that understory plant communities are integral to the ecological functioning and biodiversity of forests, gaining an understanding of impacts of disturbance on these plant communities and their linkages with other ecosystem properties and processes will help us to better understand the complex responses that forests may have to shifting disturbance regimes. Lodgepole pine (Pinus contorta) forests provide natural laboratories for assessing the effects of varying novelties of disturbance on understory plant communities. In western Canada, climate change has contributed to an unprecedented mountain pine beetle (MPB) outbreak, and the impacts of ongoing range expansion of MPB into new habitats on understory plant communities remain unknown. MPB selectively kills larger and older trees, leaving the understory intact, whereas salvage harvest of attacked trees has immediate direct effects on the understory. Direct effects are even more dramatic in logged areas that are subsequently used for oil and gas extraction, and then reclaimed to new forest. When pine trees are introduced to other regions of the world, they may themselves be considered as the primary disturbance agent. My research program focuses on understanding both how and why understory plant community responses differ among these disturbances compared with historical disturbance agents (stand-replacing fire). My proposed research examines plant community structural and functional responses of a single forest ecosystem type, lodgepole pine, across a gradient of novelties of disturbance types. My research activities will set the stage for development of a framework that will allow us to better predict: i) long-term impacts of varied disturbances on plant biodiversity and function, and ii) the successional trajectories of pine forests under changing disturbance regimes. Further, it will provide the empirical basis to inform conservation and restoration practices in northern forests, including advancing development of a provincial long-term monitoring program to assess ecological recovery of reclaimed forests in Alberta. It simultaneously provides transformative research experience and training for 11 next generation UG, MSc, PhD and PDF scientists in an inclusive brave space.