Litter Decomposition Rates in Six Mine Water Wetlands and Ponds in Oklahoma

Abstract

Six ecosystems were examined for litter decomposition rates: three volunteer wetlands in Tri-State Lead-Zinc Mining District and three ecologically engineered coal mine drainage passive treatment systems in Arkoma Basin of eastern Oklahoma. Litter bag decomposition experiments were completed using 5-g standing dead Typha spp., dried to constant weight, and homogenized in fiberglass screen bags. Replicates were placed in different hydrologic zones or treatment cells and bags were collected five times over 250 days. A single exponential decay model expressed decomposition rates and a least squares regression was fit to calculate decomposition rates. All volunteer wetlands showed similar decomposition rates despite differences in hydrology, though greater mass was lost in flooded hydrologic zones (59–66% flooded zones versus 69–71% saturated zones litter mass remaining). The passive treatment systems showed significant differences in rates between the different treatment cells and rates were greater in litter bags closer to system outflows (66–79% near inflow versus 17–60% near outflow litter mass remaining). System decay constants (k) from this study (k = 0.001–0.003) were within range for other Typha spp. systems (k = 0.001–0.024 day−1). This study of anthropogenically disturbed ecosystems showed that wetland hydrology influences litter decomposition rates and decomposition rates vary throughout passive treatment systems as water quality changes.