Hydrology of an impounded lotic wetland - Wetland sediment characteristics

Sediment organic matter content, bulk density, and hydraulic conductivity w ere examined in 56 sediment cores collected from a small lotic wetland in t he Talladega Wetland Ecosystem (Hale County, Alabama, USA). All sediment ch aracteristics varied spatially across the wetland. A distinctive demarcatio n in sediment characteristics occurred between the upper (0 to 30-cm) and l ower (30 to 80-cm) depths. Sediments in the upper 30-cm contained a higher percentage of clay than deeper sediments and had high hydraulic conductivit ies (0.5 to 1100 cm d(-1)). Lower sediment depths contained greater percent ages of silt and sand, but greater sediment compaction and lower organic ma tter concentrations resulted in low hydraulic conductivities (1 x 10(-3) to 55 cm d(-1)). Higher organic matter and lower bulk density occurred in the sediments of vegetated areas of the wetland compared to the areas near the inflow and outflow streams. Organic matter was higher and more variable (2 to 38% sediment dry weight) within the upper 30 cm of sediments and decrea sed significantly with depth (r(2) = 0.51). In the lower sediments (30 to 8 0-cm depth), organic matter was lower and less variable (2 to 10% sediment dry weight). Sediment bulk density increased with increased sediment depth (r(2) = 0.77) and was lower in vegetated areas (0.2 to 1.0 g cm(-3)) compar ed to the inflow and outflow stream sediments (0.6 to 1.4 g cm(-3)).