Effect of Riparian Forest Cover on Cellulose Decomposition in Agricultural Streams

Abstract

Agricultural practices often result in human impacts to aquatic ecosystems. The presence of riparian forests has been shown to mitigate some of these impacts, however, there is limited knowledge of how riparian forests can mitigate human impacts on microbial community function. This study investigates effects of riparian forest cover on in-stream cellulose decomposition. The study used the cotton strip assay to compare two sets of streams in summer, fall, and winter seasons to assess the association between riparian forest cover and cellulose decomposition in summer in agricultural catchments. Results from summer and autumn show there is greater cellulose decomposition in streams with riparian forest cover than streams without riparian forest cover. Cellulose decomposition also increased linearly with riparian forest in the summer. Decomposition in the assessed streams was also compared to cellulose decomposition in reference streams within the same region. Significant differences were observed between reference and non-forested streams, but not reference and forested streams, in the summer. These differences were not explained by typical environmental parameters (e.g., temperature, nutrients). These results suggest that riparian forest cover influences the decomposition by protecting organic matter processing in streams, though the specific threats against which riparian forests provide protection remain unclear. In future studies, considering agricultural contaminants (e.g., pesticides, pharmaceuticals) and investigating the differences in microbial community composition between groups may help close this knowledge gap.