Graduation Date
Summer 2019
Document Type
Thesis
Program
Master of Science degree with a major in Natural Resources, option Forestry, Watershed, & Wildland Sciences
Committee Chair Name
Harold Zald
Committee Chair Affiliation
HSU Faculty or Staff
Second Committee Member Name
Lucy Kerhoulas
Second Committee Member Affiliation
HSU Faculty or Staff
Third Committee Member Name
Phil van Matngem
Third Committee Member Affiliation
Community Member or Outside Professional
Keywords
Forestry, Sierra Nevada, Prescribed fire, Mechanical thinning, Forest ecology, Experimental forestry, Natural resources, Mixed-conifer
Subject Categories
Forestry
Abstract
Drought-induced tree mortality can drastically alter forest composition, structure, carbon dynamics, and ecosystem function. Increasingly, forest policy and management focuses on how to improve forest resistance and resilience to drought stress. This study used tree ring data at Teakettle Experimental Forest (TEF), a historically frequent fire mixed-conifer forest in the California Sierra Nevada, to quantify how prescribed fire and mechanical thinning conducted in 2001-2002 influenced stand and tree-level growth responses to the extreme California drought of 2012-2016. Overstory thinning and understory thinning significantly enhanced growth responses to treatments alone and treatments during the drought at the stand-level. In each year of the drought, distinct tree species were the only significant predictors of drought resistance at the stand-level. As drought persisted, shade-intolerant pine species yielded greater drought resistance values than shade-tolerant white fir and incense cedar. No prescribed burn effects were found, likely due low fire intensity. At the tree-level, tree diameter (DBH), tree height (HT), crown ratio (CRNR), topographic position index (TPI), and change in growing space over time (competition) were the most important predictors of growth responses to treatments and drought resistance. Mechanical thinning, in both understory and overstory thinning can enhance mixed-conifer forests ability to resist drought by reducing competition and increasing resource availability. This study suggests forest managers have flexibility in prescribing various thinning intensities to promote drought resistance. Prescribed burn effects were not found in this study, but further research is needed to understand long-term burn effects for promoting drought resistance in Sierra Nevada mixed-conifer forests.
Citation Style
Forest Ecology and Management
Recommended Citation
Callahan, Chance C., "Effects of thinning and prescribed burning on tree resistance to extreme drought in a Sierra Nevada mixed-conifer forest, California USA" (2019). Cal Poly Humboldt theses and projects. 298.
https://digitalcommons.humboldt.edu/etd/298