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Fire history and serotiny in the Rocky Mountains of Colorado

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dc.contributor.authorAoki, Carissa F., author
dc.contributor.authorRomme, W. H. (William H.), advisor
dc.contributor.authorBrown, Peter M., advisor
dc.contributor.authorLaituri, Melinda, committee member
dc.contributor.authorCafaro, Philip, 1962-, committee member
dc.coverage.spatialSan Juan Mountains (Colo. and N.M.)
dc.coverage.spatialRocky Mountain National Park (Colo.)
dc.coverage.spatialColorado
dc.date.accessioned2007-01-03T04:53:38Z
dc.date.available2007-01-03T04:53:38Z
dc.date.issued2010
dc.descriptionDepartment Head: Michael J. Manfredo.
dc.description.abstractFire is a natural part of forested ecosystems in Colorado, playing an essential role in regenerating and maintaining forests. I studied two aspects of fire: historical fire regime in mixed-conifer forests, and serotiny in lodgepole pine. I. During the 1990s and early 2000s, fire management in the western United States was often based on lessons learned from fire regime studies in ponderosa pine ecosystems in the Southwestern states. As managers sought to apply these policies to an ever-broader range of forest types, it became clear that different forest types were characterized by different fire regimes and thus required further research as well as new management strategies. Mixed-conifer forests have been particularly hard to quantify in terms of their historical fire regimes. My study aimed to understand the historical range of variability (HRV) in a mesic mixed-conifer forest in southwestern Colorado. Banded Peak Ranch, located in the San Juan Mountains of Colorado, provided a unique setting in which to study the historical fire regime of this forest type in the southern Rocky Mountains. I used a combination of stand age structure, species composition, and fire scar data, collected at two different spatial scales on 40 plots, in both logged and unlogged stands. At both scales, I found a combination of mixed- and high-severity fire regimes. The spatial distribution of fire severity appears to have been patchy, with mixed- and high-severity stands lying in close proximity to one another. Species composition and age structure varied widely among both the high- and mixed- severity stands, suggesting that a variety of future disturbance regime trajectories might be expected. II. Regeneration in Rocky Mountain lodgepole pine (Pinus contorta var. latifolia) is characterized by two methods of reproduction: serotinous cones, which open and release their seeds only under heat from fire; and non-serotinous cones, which open and release their seeds with cone maturity. Stands with a high proportion of serotinous cones can thus regenerate strongly following stand-replacing fire. I used data from across Rocky Mountain National Park (ROMO) to quantify the distribution of serotiny on the landscape and to try to understand the key abiotic variables controlling serotiny. I found that serotiny varied from 0-97% per stand, with an average across the landscape of 58%. Because my data did not correlate strongly with any single variable, I used regression tree analysis to explore the combined effects of abiotic variables on serotiny. Elevation, aspect, and topographic convergence index (a measure of local moisture) were the key variables in the resulting regression tree, and higher serotiny was correlated with the range of each variable that is more conducive to fire—lower, more west-facing, drier. Previous research has shown that serotiny is affected by stand-replacing fire, but not by low-severity fire. In an environment such as the lodgepole pine forests of ROMO, where stand-replacing fire is the predominant fire regime, serotiny is highly related to the environmental variables that generally contribute to fire occurrence. III. Serotinous cones remain on living trees for many years, holding within them the canopy seed bank for regeneration after fire. After large-scale mortality caused by mountain pine beetle (Dendroctonus ponderosae), however, the seeds in serotinous cones may remain on the dead trees for a number of years. I tested seeds from living and beetle-killed serotinous stands to determine whether they remain viable after tree death, and whether germination rates were affected by cone age. There was no significant difference between germination success rates from the living stand vs. the dead stand. While there was a significant relationship between cone age and germination success, cones that were 21-25 yrs still had >30% germination rates. I conclude that post-beetle regeneration likely will not be limited by viable seed availability in stands with serotinous cone-bearing trees.
dc.format.mediummasters theses
dc.identifier2010_Spring_Aoki_Carissa.pdf
dc.identifierETDF2010100002FRWS
dc.identifier.urihttp://hdl.handle.net/10217/38990
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado State University. Libraries
dc.relation.ispartof2000-2019
dc.rightsCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.
dc.titleFire history and serotiny in the Rocky Mountains of Colorado
dc.typeText
dcterms.rights.dplaThis Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).
thesis.degree.disciplineForest, Rangeland, and Watershed Stewardship
thesis.degree.grantorColorado State University
thesis.degree.levelMasters
thesis.degree.nameMaster of Science (M.S.)

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