Master of Science degree with a major in Natural Resources, option Forestry, Watershed, & Wildland Sciences
Committee Chair Name
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HSU Faculty or Staff
Second Committee Member Name
Phillip van Mantgem
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Community Member or Outside Professional
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HSU Faculty or Staff
Environmental Science and Management
Climate change is predicted to increase the frequency, duration, and severity of drought events across many bioregions. Forest managers have two active management techniques to promote resistance and resilience to drought: prescribed fire and mechanical thinning. Generally applied to reduce fuels and fire hazard, treated areas may also reduce competition for resources that may improve tree-growth during drought and reduce mortality. The recent severe and prolonged drought in California allowed me to investigate the effects of climate stress and fuel treatments on tree growth responses in a dry mixed-conifer forest ecosystem.
To assess tree-growth responses to fuel treatments during severe drought I collected and analyzed tree core samples from 300 ponderosa pine (Pinus ponderosa) and Douglas-fir (Pseudotsuga menziesii) trees in the mixed-conifer forests of Whiskeytown National Recreation Area in northern California. Tree-ring data was used to investigate factors that influenced tree-growth during the study period (2008-2015). Growth was positively associated with crown ratio and negatively associated with local competition and climate water deficit (1-yr lag). Douglas-fir generally had higher annual growth than ponderosa pine, though factors affecting growth were the same for both species. Overall, trees in thinning treatments had higher drought resistance compared to untreated stands. Drought resistance was significantly higher in treated stands compared to untreated stands during both years of extreme drought (2014-2015) for ponderosa pine but only one year (2014) for Douglas-fir. This information can help land managers decide on forest management practices that may enhance forest resistance to future drought events.
Vernon, Michael, "In the face of drought: Do fuel treatments promote resistance to multi-year drought in a mixed-conifer forest of northern California?" (2017). Theses and projects. 70.