Available at: https://digitalcommons.calpoly.edu/theses/2724
Date of Award
12-2023
Degree Name
MS in Environmental Sciences and Management
Department/Program
Natural Resources Management
College
College of Agriculture, Food, and Environmental Sciences
Advisor
Chris Surfleet
Advisor Department
Natural Resources Management
Advisor College
College of Agriculture, Food, and Environmental Sciences
Abstract
This post-fire study was conducted to characterize and observe fire induced changes in physical habitat parameters, water-quality conditions and macroinvertebrate assemblages in the Little Creek watershed, a tributary to Scotts Creek located in Cal Poly’s Swanton Pacific Ranch in Davenport, California. Pre-fire data was collected by a Cal Poly student, John Hardy, for his 2017 thesis. Post-burn bioassessment surveys for this study were repeated at four of the same study sites used by Hardy to provide comparisons to the California Stream Condition Index via a modified version of the State of California’s Surface Water Ambient Monitoring Program protocol. Macroinvertebrates were taxonomically identified to the family level. Commonly used bioassessment indices were utilized in conjunction with Stepwise regression and Analysis of Variance on both pre- and post-fire datasets to illustrate how physical habitat and water quality parameters changed after the fire and to determine the significance of collected environmental variables (stream shading, cross sectional area, and median particle size) as predictors of macroinvertebrate community structure. Despite most of Little Creek having moderate and high burn severities, it was found that physical habitat, water quality and benthic macroinvertebrate populations were not greatly disturbed by the 2020 CZU lighting complex fire. Proportions of highly disturbance/pollution sensitive taxa and increased following the wildfire and there was a dramatic shift from collector-gatherer to predator organisms. Comparison of pre- and post-fire data in this study showed fire having a minimal effect on the studied watershed. Difference in study goals and associated protocols used in the pre- and post-fire studies and the low water year following the wildfire, complicates statistical comparisons and poses threat to the validity of results. However, there is opportunity for further investigation about the ability of an ecosystem to successfully recover from natural disasters and disturbances, specifically when there is little human impact (or influence) on the ecosystem.