Midterm impacts of fire severity on headwater stream ecosystems in the Klamath Mountains, California

Graduation Date

2015

Document Type

Thesis

Program

Other

Program

Thesis (M.S.)--Humboldt State University, Natural Resources: Environmental Studies, 2015

Committee Chair Name

Alison O’Dowd

Committee Chair Affiliation

HSU Faculty or Staff

Keywords

Headwater stream ecosystems, Wildfires, Humboldt State University -- Theses -- Natural Resources, Riparian areas

Abstract

Wildfire disturbances in riparian areas can impact stream chemistry, primary production, and trophic dynamics for years to decades after burning. Previous studies in headwater streams have focused on immediate and short term impacts, while effects during the midterm (1-10y) post-fire period are less understood. To evaluate responses of headwater stream communities 6-8 y post-fire, I compared water chemistry, benthic macroinvertebrate assemblages and periphyton biomass as chlorophyll a concentrations from 19 headwater streams categorized as unburned (n=5), low fire severity (n=5), moderate fire severity (n=4), or high fire severity (n=5). The hypothesized relationship between lower canopy densities and increased periphyton biomass was detected in moderate and high fire severity streams (p=0.008). Comparisons of feeding group ratios representing relative numerical abundances versus relative biomass of algal to detrital consumers indicated elevated biomass of algal consumers in high fire severity streams (p=0.05). Indirect ordination showed major overlap in community composition among severity categories, suggesting a general return to pre-disturbance stable states. These findings inform understanding of post-fire processes of Klamath Mountain aquatic ecosystems during a time when climatic and human-related changes have degraded aquatic habitats and increased the frequency and size of wildfires in the region.

https://scholarworks.calstate.edu/concern/theses/z316q3719

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