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UBC Theses and Dissertations

Biotic response to riparian disturbance in head-water streams in British Columbia Goodwin, Adam


Five forest disturbance regimes (wildfire, mountain pine beetle (MPB), commercial harvest, and two sets of references) were investigated to determine transitive effects on aquatic ecosystems in fifteen headwater streams in the southern interior of British Columbia. The particular focus for this study was aquatic macro-invertebrates and their trophic resources (forest litter, periphyton, and particulate organic matter). At each site, sampling occurred three times over the summer and fall of 2009, across a one-hundred meter reach. Disturbances resulted in clear alterations of canopy coverage and litter loading. The two canopy consuming disturbances (fire and harvesting) showed marked decreases in their proportional canopy coverage. Litter loading in MPB was significantly greater, while fire streams’ litter loading was directly related to canopy coverage, and significantly less than reference sites. Periphyton mean growth was unrelated to disturbance; however inter-stream variance was reduced in the burned systems and increased in the MPB systems. Macro-invertebrate measurements were not different across disturbances, however, abundances and biomass did exhibit different temporal interactions with the Montane Spruce disturbances. Abundances of invertebrate functional feeding groups were unrelated to their food resource, and did not differ across disturbance type. Invertebrate diversity measurements were also similar across disturbance regime. While aquatic ecosystems were generally robust in response to riparian disturbance events in this study, we were able to uncover slight differences across disturbance regimes. The temporal and spatial findings in this paper are of particular importance as they illustrate differences between MPB and salvage logging effects.

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