Graduation Date
Spring 2021
Document Type
Thesis
Program
Master of Science degree with a major in Natural Resources, option Forestry, Watershed, & Wildland Sciences
Committee Chair Name
Dr. Rosemary Sherriff
Committee Chair Affiliation
HSU Faculty or Staff
Second Committee Member Name
Dr. Phillip van Mantgem
Second Committee Member Affiliation
Community Member or Outside Professional
Third Committee Member Name
Dr. Harold Zald
Third Committee Member Affiliation
Community Member or Outside Professional
Subject Categories
Natural Resources
Abstract
Forests throughout much of the western United States are experiencing increasing climatic variability, often resulting in decreased forest productivity and elevated likelihood of tree mortality. Severe drought, such California’s recent 2012-2015 drought, are projected to increase in intensity, frequency, and severity throughout much of this region in coming years. Forest management has long relied on prescribed fire and mechanical thinning to reduce fuel loads and ameliorate potential fire hazards. These treatments may also have the ability to reduce stand density, alleviate competitive pressures, and allow residual trees access to critical resources during periods of extreme stress. Utilizing a long-term National Park Service fire monitoring program allowed us to analyze the effects of prescribed fire treatments on radial growth response in a mixed-conifer forest of northern California.
Tree core samples were collected and analyzed from 136 yellow pine (ponderosa pine (Pinus ponderosa) and Jeffrey pine (Pinus jeffreyi)) and 136 white fir (Abies concolor) trees within Lassen Volcanic National Park. Tree-ring data was used to describe factors that influenced tree growth during the locally identified low moisture period (2007 - 2015), as well the potential ability of treatments to improve tree drought resistance and subsequent recovery.
Radial growth was positively associated with crown ratio and annual precipitation totals, and negatively associated with localized competitive pressures. Within treatment sites, where stand density was effectively reduced, trees showed improved annual radial growth rates. This appeared to be generally driven by overall treatment intensity and its ability to alter forest density. White fir exhibited a stronger growth response to competitive pressures compared to yellow pine; however, radial growth rates were generally driven by the same factors. Drought resistance did not appear to be strongly correlated with competitive pressures, though drought recovery was slightly associated with increased competitive levels. Findings suggests future forest management techniques, such as prescribed fire and thinning, may be beneficial in terms of reducing competitive pressures and improving radial tree growth among residual trees during future more severe drought.
Citation Style
APA
Recommended Citation
Wenderott, Zachary J., "Effects of prescribed fire on drought resistance and recovery in mixed conifer forests of Lassen Volcanic National Park, California" (2021). Cal Poly Humboldt theses and projects. 460.
https://digitalcommons.humboldt.edu/etd/460