Human-induced climate change is anticipated to cause major shifts in biome boundaries. Projections of vegetation responses to climate change typically assume that vegetation is in equilibrium with climate; i.e., that the distribution of vegetation types is a direct result of climate conditions. This doctoral dissertation research project will use a paleoecological approach to test whether the dominant forest type in Alaska (black spruce muskeg) is in climatic equilibrium. The investigators of this project have collected preliminary data that challenge long-standing ideas about how boreal-forest ecosystems responded to past climatic change. Specifically, the establishment of black spruce (a moisture-demanding tree) ~5000 years ago did not correspond to an increase in moisture availability, and the subsequent black spruce communities exhibited great stability despite pronounced moisture fluctuations. The goal of this project is to examine whether a climatic cooling resulted in permafrost accretion, which in turn increased soil moisture and led to the establishment of black spruce. The investigators will reconstruct Holocene changes in soil moisture, permafrost, and vegetation using peat cores from two permafrost-underlain bogs. The proposed study promises to enhance our understanding of the role of permafrost in boreal-forest dynamics. Evidence supporting the putative climate-permafrost-vegetation linkages would imply rapid and irreversible change in ecosystem state upon local loss of permafrost in response to warming. This project, which is a key to the completion of a doctoral dissertation, will also involve research training for an undergraduate student.
