Dissertation
HOW DOES VEGETATION INFLUENCE THE INTERACTION BETWEEN CLIMATE CHANGE, INSECT DISTURBANCE AND WILDFIRE?
Doctor of Philosophy (PhD), Washington State University
01/2020
Handle:
https://hdl.handle.net/2376/118132
Abstract
Forests are essential for ecosystem biodiversity and provide numerous ecological services to humans, such as water supply for irrigation and drinking. In recent decades, Bark beetle outbreak and wildfire have consumed millions of hectares of forest. Climate change is projected to increase the severity and frequency of these two disturbances. Many of recent studies that focused on understanding the interactions between climate and forest disturbances are field-based and therefore, controlled experiments are not always feasible. Furthermore, natural wildfires occur over complex terrain and rarely provide the set of conditions needed to understand and predict how wildfires interact with climate and insect outbreaks over space and time or how they influence ecosystem and watershed processes such as streamflow. Therefore, we need to complement field studies, which have the advantage of being realistic, with physically-based models (e.g., Regional Hydro-ecologic Simulation System) which enable researchers to manipulate and isolate the individual and combined effects of multiple drivers over a range of possible scenarios.
In the first chapter, we find that water yield during the red phase after beetle attack (i.e., when leaves turn red) is constrained by interactions among interannual climate variability, the extent of tree mortality, and local water deficit conditions (i.e., aridity). We also find beetle outbreak decreases water yield in most dry years, and in wet years there is an increase in water yield; the direction of water yield in dry years is also affected by the extent of mortality and local aridity. In the second chapter, we find fire activity (i.e., fire size, burn probability) exhibits a non-monotonic response to future climate change over time; fire activity is projected to increase in the 2040s and decrease in the 2070s. This non-monotonic response is driven by tradeoffs between increases in aridity/flammability and decreases in fuel load. In the third chapter, we find fire activity has a nonlinear relationship with the level of vegetation mortality caused by beetle outbreak. High mortality may decrease the fire sizes due to the competition between an increase of fuel load (e.g., fall of snag) and decrease of fuel aridity (e.g., decrease in Evapotranspiration).
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Details
- Title
- HOW DOES VEGETATION INFLUENCE THE INTERACTION BETWEEN CLIMATE CHANGE, INSECT DISTURBANCE AND WILDFIRE?
- Creators
- Jianning Ren
- Contributors
- Jennifer C. Adam (Advisor)Jan Boll (Committee Member)Nicholas Engdahl (Committee Member)Erin Hanan (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 198
- Identifiers
- 99900581609801842
- Language
- English
- Resource Type
- Dissertation