Knobcone pine response to shading from competing chaparral shrubs following stand-replacing wildfire

Author

Sean T. Lindley, Humboldt State UniversityFollow

Graduation Date

Spring 2023

Document Type

Thesis

Program

Master of Science degree with a major in Natural Resources, option Forestry, Watershed, & Wildland Sciences

Committee Chair Name

David Greene

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Buddhika Madurapperuma

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Jeffrey Kane

Third Committee Member Affiliation

HSU Faculty or Staff

Keywords

Northern California, Fire ecology, Knobcone pine, Cover type change, Ecosystem resilience, Fire resilience, Forest regeneration, Whiskeytown National Recreation Area, Stand development, Serotinous conifer, Chaparral

Subject Categories

Forestry

Abstract

In northern California, fire regimes are shifting towards more frequent and larger severe wildfire. There is growing concern that this shift poses a threat to biodiversity in the form of cover type change at the landscape scale, resulting in the extirpation of some species in favor of +AD617:AD649well-adapted ones. In northern California, mature serotinous conifers, such as knobcone pine (Pinus attenuata), and resprouting shrub species easily regenerate in severe patches of any size. There is no general consensus regarding the effects of shrub competition on conifer recruitment; conifer response varies with shade tolerance and other abiotic factors. Knobcone pine and chaparral shrubs are universally shade intolerant, and we expect shading to be the main driver of inter-species competition.

We examined knobcone pine regeneration on lower slopes within the 2018 Carr and Delta fires at the third and fourth post-fire years, as well as the 2008 Motion Fire at the 14th post-fire year, focusing on two measurements of shrub shading: inter-shrub porosity (% shrub cover) and intra-shrub porosity (species-specific crown density). Our response variables included recruitment success (recruits per ovulate cone) and growth (height). We found (1) there were few pine recruits under shrubs, with the bulk of the shrub-induced morality of knobcone pine occurring before the third growing season; (2) knobcone pine averaged about 6 established recruits per burned parent tree; and (3) the recruits were expected to persist despite limited growth and reach the shrub canopy by about the seventh year after fire. We conclude that competition with shrubs on lower slopes in northern California does not sufficiently impede the post-fire increase in serotinous pine density to limit subtle expansion into chaparral.

Citation Style

APA

Recommended Citation

Lindley, Sean T., "Knobcone pine response to shading from competing chaparral shrubs following stand-replacing wildfire" (2023). Cal Poly Humboldt theses and projects. 663.
https://digitalcommons.humboldt.edu/etd/663