Events & Media


A PhD Dissertation Defense

"Exposure and Sensitivity of Ponderosa Pine to Climate Change
in Mountainous Western North American Landscapes.

Ian McCullough
PhD Candidate
Bren School

Thursday, June 8, 2017
1:00 p.m.
Bren Hall 1414

Faculty Advisor: Frank Davis
Committee Members: James Frew, Christina Tague

My research focuses on responses of forests to climate change. In my first chapter, I developed a conceptual framework for climate change exposure, which I applied to a mountainous landscape at Tejon Ranch, CA. I found that high elevations are disproportionately exposed to future climate change due to projected losses in snowpack. In my second chapter, I examined long-term relationships between climate, particularly drought, and ponderosa pine tree rings at Tejon Ranch to place the recent multi-year California drought in an ecological, historical context. According to a range of climate change projections, there will likely be similar extreme droughts in the future, so this case study provides a possible window into future forest responses to climate change. In my final chapter, I examined the sensitivity of ponderosa pine to historical climate across the western United States, also using tree rings. Climate sensitivity is highly variable across the species' range as a function of local climate and adaptation. Therefore, future conservation efforts for ponderosa pine and other wide-ranging species should consider within-species variability in climate sensitivity.


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