Date of Award

Spring 1-1-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Joel Hartter

Second Advisor

Carol Wessman

Third Advisor

Tom Veblen

Fourth Advisor

Carson Farmer

Fifth Advisor

Lawrence Hamilton

Abstract

Shifting climate and wildfire regimes are changing forest structure and function globally. In the western US, future forest structure will be determined by interactions between climate change and disturbance, including increasingly frequent large wildfires, as well as the forest management actions of landowners and managers. While research on the ecological impacts of these changes is rapidly expanding, there is limited focus on how forest vulnerability may vary across land ownerships, which may have varying capacities for climate-adaptive forest management. In this dissertation, I explored how coniferous forests in the Blue Mountains of eastern Oregon are vulnerable to climate and wildfire interactions across land ownerships, and investigated the adaptive capacity of private forest owners. First, I used LANDIS-II, a dynamic forest landscape model, to simulate potential impacts of climate change and wildfire on tree species establishment, abundance, and growth. I found that, despite establishment declines in moisture-limited areas, drought- and fire-tolerant ponderosa pine and Douglas-fir expanded their distributions under high wildfire activity and climate change scenarios, while less tolerant species such as subalpine fir declined. Second, I surveyed 184 sites across eight burned areas 15-21 years post-fire to understand how topography, climate, and post-fire legacies influence juvenile conifer abundance. One-third of sites contained no juvenile conifers, potentially indicating regeneration failure on warm slopes at low elevations far from a post-fire seed source. However, juvenile conifer abundance in most high elevation sites exceeded recommended stocking levels, suggesting forest resilience in high elevation forest types. Finally, I interviewed 50 private landowners to gauge their capacity for climate change adaptation. Very few landowners adapted to climate change intentionally, in part due to climate change skepticism. However, many forest owners implemented incidental adaptation actions, including fuels reductions, motivated by factors such as wildfire risk mitigation. Ultimately, private forest owners require educational, financial, and operational support to engage in climate-adaptive forest management. Just as the impacts of climate change and wildfire vary by forest type in the Blue Mountains, adaptation recommendations must reflect the varying adaptive capacities of local landowners and managers.

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