The Effects of Hydromulch and Fire Intensity on Post-Fire Chaparral: A Griffith Park Case Study
Students: Stephanie Debats, Deidre Pilotte, and Rashmi Sahai
Question: Does hydromulch as a post-fire erosion mitigation treatment affect vegetation recovery in a chaparral ecosystem?
Location: Griffith Park, Los Angeles, California.
Methods: Vegetation sample transect plots were marked at two separate locations within the park, one to which hydromulch was applied, and one to which it was not. At the two locations, we selected one transect plot each of high and low burn severity, and species and number of individuals were sampled. The heights and widths of several indicator species were also sampled. Paired t-tests were used to test our hypothesis.
Results: Species diversity was found to statistically insignificant when comparing hydromulched to non-hydromulched areas. Plant density was found to be statistically significant with greater plant density found in non-hydromulched area. Plant growth, in terms of height and width, was found to have no conclusive trends or differences between hydromulched and non-hydromulched areas.
Conclusions: While species diversity was not statistically significant, the p-value was very close to being significant, signifying that a larger sample might have yielded a statistically significant result. The species diversity seemed to converge over time, as the number of herbaceous annuals reduced in the low fire intensity/non-hydromulched transect. The statistically significant higher plant density in non-hydromulched area signifies that hydromulch acts as a physical barrier, impeding vegetation recovery. Therefore, policymakers should be aware that hydromulch will reduce initial plant density. The plant growth data was inconclusive, because a random sampling of individuals does not account for individual growing conditions and varying germination times.