Piedmont Stream Litter Inputs and Fluxes: Correlation with Riparian Conditions and Urbanization

Leaf litter inputs, processing, and retention in aquatic ecosystems are controlled by biological, physical, and chemical factors that can be related to both local reach conditions and large scale watershed features. It is well known that leaf litter is an essential driver of river ecosystem structure, but the complexity of input, transport, and utilization processes has obscured the effects of land management on litter availability. In this study, we evaluated how urbanization affects litter stocks by comparing autumn and spring standing crops in urban and forested streams in the Piedmont of Georgia. We also measured vertical leaf litter inputs across a gradient of canopy coverage and compared the shredder fraction of the macroinvertebrate assemblages between urban and forested streams. Our results indicate that in Georgia Piedmont streams shading appears to be influenced by condition of the riparian zone at the reach scale, while leaf litter seems to be controlled by catchment conditions and factors indirectly tied to land use, such as velocity and timing of inputs. Overall, sites with less urbanization have greater litter inputs during December, however higher rates of retention occur in more urbanized areas, where channels receive continuous inputs from lawns and storm drains. Macroinvertebrate taxa and intolerant species were negatively affected by watershed landuse, although shredder abundance was not.