Plant Community Responses to Large-scale wildfires at four wildlife areas in southern California

Type: report

Article abstract: In 2003 and 2007, southern California experienced several large fires which burned thousands of hectares of wildlife habitats and conserved lands. In order to investigate the effects of the fires on plant communities, we compared the results from vegetation sampling conducted prior to the fires to results from four consecutive years of post-fire sampling among 38 burned and 17 unburned plots. The sampling plots were spread over four vegetation types (chaparral, coastal sage scrub, woodland/riparian, and grassland) and four open space areas within San Diego County. Our survey results indicated that burned plots of chaparral and coastal sage scrub lost shrub and tree canopy cover after the fires and displayed shifts in overall community structure. Post-fire community structure within burned chaparral and coastal sage scrub plots was more similar to that found in grasslands. We did not find differences in species richness or community composition in grasslands or woodland/riparian vegetation where shrub and tree cover did not significantly change after the fires. Across all plots both before and after the fires, non-native grass was the most abundant “species”, followed by chamise (Adenostoma fasciculatum) which was consistently the second most abundant species. We saw increases in the cover rates for several species, including peak rush-rose (Helianthemum scoparium) and Ceanothus spp., in burned chaparral and coastal sage scrub plots. California sagebrush (Artemisia californica) and California buckwheat (Eriogonum fasciculatum) appear to have declined drastically in our coastal sage scrub samples with little to no signs of recovering. Chamise, Tecate cypress (Cupressus forbesii), and pines (Pinus spp.) also declined, but it apprears that there has been some progress in the post-fire recovery of these species. We discuss these individual species results as they relate to specific life history traits, such as susceptibility to initial mortality and post-fire changes in habitat suitability. We foresee that a continued unnatural fire regime for southern California will result in a simplification of the southern California vegetation communities, especially in the shrublands.

Number of pages: 94

Authors: Rochester, Carlton; Mitrovich, Milan; Clark, Denise; Mendelsohn, Mark; Stokes, Drew; Fisher, Robert N.;

Year: 2010

Publisher: U.S. Geological Survey

Prepared for: San Diego Association of Governments;

Prepared by: U.S. Geological Survey, Western Ecological Research Center;

Threats: Altered fire regime


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File owner: San Diego Management and Monitoring Program
8-Post-fire Vegetation.pdf