Graduation Date
Spring 2022
Document Type
Thesis
Program
Master of Science degree with a major in Natural Resources, option Forestry, Watershed, & Wildland Sciences
Committee Chair Name
Jeffrey Kane
Committee Chair Affiliation
HSU Faculty or Staff
Second Committee Member Name
David Greene
Second Committee Member Affiliation
HSU Faculty or Staff
Third Committee Member Name
Erik Jules
Third Committee Member Affiliation
HSU Faculty or Staff
Subject Categories
Forestry
Abstract
Climate warming and associated dry conditions are contributing to increased fire frequency, severity, and size, for many regions in western North America. These changes in fire activity have prompted concern over the long-term persistence of some conifer species, specifically those not adapted to withstand high-severity fire. However, regeneration of non-serotinous conifer species is possible if the timing of fire occurs following seed maturation, and within a heat range that seeds can withstand, in a regenerative mechanism termed “facultative serotiny.” To address this mechanism, I determined the timing of conifer seed maturation using viability testing for four California conifer species: ponderosa pine (Pinus ponderosa), Sierra lodgepole pine (Pinus contorta var. murryana), incense cedar (Calocedrus decurrens), and Douglas-fir (Pseudotsuga menziesii). The unopened conifer cones were collected for these non-serotinous species throughout three summers near Burney, California. Additionally, I identified the capacity for seed survival relative to heat exposure with seven heat treatments at: no heat (control, ~20℃), 100℃, 150℃, 200℃, 300℃, 400℃, 600℃, followed by viability testing. The accumulated heat sum was significantly associated with seed maturity, indicating over 50% maturity from late July to August (1358 ℃ to 1889 ℃ ). Higher heat exposure was negatively associated with seed survival, although seed survival occurred with temperatures as high as 340°C for 150 seconds. My findings identify conditions suitable for the occurrence of facultative serotiny following stand-replacing fires for four non-serotinous conifers in northern California. The temporal window that permits facultative serotiny for these species can be incorporated into post-fire regeneration modeling and aid in future non-serotinous conifer forest management in fire-prone ecosystems.
Citation Style
APA
Recommended Citation
Lopez, Madeleine A., "Investigating seed maturation and mortality: a mechanism for post-fire regeneration in non-serotinous conifers" (2022). Cal Poly Humboldt theses and projects. 536.
https://digitalcommons.humboldt.edu/etd/536