Effect of Riparian Impervious Cover on Leaf Litter Decomposition Rates and Lotic Benthic Macroinvertebrate Diversity

Riparian impervious cover has been implicated in reducing benthic biodiversity. We examined the impact of impervious cover on the decomposition and colonization of leafpacks in 6 sites located on three streams. The six sites ranged in impervious cover, in the drainage basin from 98% upstream at Meeting of the Waters Creek to 25% upstream on Bolin Creek. 5g leafpacks of dogwood leaves (Cornus florida), were placed at each site on October 15, 2004 and 5 replicates per site were collected on Oct. 25, Nov. 8 and Nov. 22. Decomposition rates were highest (AFDM remaining lowest) where forested cover was greatest, and lowest where impervious cover was greatest. The diversity of the initial macroinvertebrate colonization was highest with least impervious cover, and was dominated by chironomids where impervious cover was greatest. The negative impact of increasing impervious cover on stream community diversity is supported by this study. The ecosystem level process of leaf litter decomposition is also negatively affected.