Ecosystem disturbances in the western United States are large-scale processes that are often driven by small-scale mechanisms. Previous research on drought, bark beetles, and fire has made significant progress connecting these mechanisms to their impact on landscapes. Macro-ecological approaches can apply knowledge of mechanisms across large spatial extents and over long periods of time in order to test the generality of mechanistic theory across highly variable natural systems. The goal of this dissertation is to examine patterns of drought, insect, and fire disturbance across the western United States and infer signals of their underlying mechanistic process. Chapter 1 begins with a brief introduction to disturbance ecology. Chapter 2 examines insect, disease, and drought mortality across forested ecosystems and determines pattern of tree mortality across species and regions. I find that mortality rates will likely increase in the future, although with high variability between species and ecosystems. This chapter excludes fire in order to focus on individual-tree mortality, and Chapter 3 therefore complements it by focusing on wildfire throughout interior drylands. In agreement with the literature, Chapter 3 finds that predicting wildfire occurrence across six interior drylands is dependent on climate, with smaller contributions from land cover. To connect mechanisms back to predictions, Chapter 4 looks at plant cover, soil cover, and biogeochemical differences between fires of varying age. It finds that changes to ecosystem structure and function are evident in the Great Basin and Colorado Plateau, with smaller effects in the Chihuahuan, Mojave, and Sonoran. Chapter 5 summarizes my findings and discusses the implications of my research in advancing the state of knowledge in disturbance ecology as well as directions for follow-up and future research. In addition, I discuss the methods I utilized in my research and implications for landscape conservation.
|Advisor:||Strand, Eva K.|
|Commitee:||Smith, Alistair M.S., Hudak, Andrew T., Reed, Sasha C.|
|School:||University of Idaho|
|School Location:||United States -- Idaho|
|Source:||DAI-B 82/8(E), Dissertation Abstracts International|
|Subjects:||Ecology, Natural Resource Management|
|Keywords:||Macro-ecological approaches, Western United States, Wildfires|
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