Land-use legacies in ecosystems: impacts of historical land use on carbon storage and species composition in Quebec

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Anthropogenic land-use is the most pervasive and persistent driver of change in ecosystems. At the global scale, land-use is the second greatest source of net carbon dioxide emissions to the atmosphere and the most important driver of biodiversity loss. Moreover, land-use legacies can persist for thousands of years after direct use has ceased through altered nutrient cycling and species composition. Despite the importance of land-use legacies in ecosystems, many of the underlying mechanisms are still not well understood. The role of land-use history in driving the critical terrestrial carbon sink, for example, remains uncertain, as do the mechanisms by which land use history affects biodiversity.The long-term objective of my research program is thus to examine the extent and influence of historical land-use legacies on changes in ecosystem structure and function, with a view to demonstrating how this knowledge can enhance carbon and ecosystem management. In the short term, the research will be focused in Quebec, a region well suited to these issues given its 300+ years of varied land-use history. I will address the following questions: (1) How has historical land use affected forest extent, composition, and spatial pattern across Quebec since European settlement? (2) How has land-use history impacted forest carbon storage? Has forest regrowth provided a significant carbon sink? What is the potential for future forest sequestration? (3) What are the mechanisms driving changes in forest biodiversity and pathways of recovery? In particular, what is the role of historical and current landscape configuration and connectivity? The research has important policy applications for forest management in southern Canadian landscapes, including enhancing forest carbon sequestration to help meet climate mitigation targets and providing rules of thumb for prioritizing forest protection to enhance ecosystem functioning in agricultural landscapes.