Assessing the impacts of human-induced degradation on stream ecosystem function

Riparian vegetation provides many ecosystem services to streams, especially as a source of organic matter critical for many aquatic organisms. Kimball Creek (De Beque, CO) is a heavily degraded stream in which loss of riparian vegetation and altered hydrologic regimes may have caused a decrease in litter resources and increased light penetration, inducing a shift from an allochthonous based system to an autochthonous one. In two stream reaches, “reference” and “degraded”, tiles were submerged in riffle habitat to estimate algal growth. While benthic algae biomass was not significantly different between reaches, chlorophyll a was highest in the reference reach after four weeks submergence. In addition, a leaf pack experiment was conducted using box-elder and willow to estimate litter decomposition over time. As expected, box-elder decayed significantly faster than willow in both reaches. Interestingly, box-elder decayed faster in the degraded reach, while willow decayed at the same rate in both the reference and degraded reaches. Future research is needed to further investigate the effects of riparian loss on stream food web and bottom-up pathways in this and other degraded streams