Hydrology of an impounded lotic wetland—wetland sediment characteristics
Sediment organic matter content, bulk density, and hydraulic conductivity were examined in 56 sediment cores collected from a small lotic wetland in the Talladega Wetland Ecosystem (Hale County, Alabama, USA). All sediment characteristics varied spatially across the wetland. A distinctive demarcation in sediment characteristics occurred between the upper (0 to 30-cm) and lower (30 to 80-cm) depths. Sediments in the upper 30-cm contained a higher percentage of clay than deeper sediments and had high hydraulic conductivities (0.5 to 1100 cm d−1). Lower sediment depths contained greater percentages of silt and sand, but greater sediment compaction and lower organic matter concentrations resulted in low hydraulic conductivities (1 × 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 decreased significantly with depth (r2 = 0.51). In the lower sediments (30 to 80-cm depth), organic matter was lower and less variable (2 to 10% sediment dry weight). Sediment bulk density increased with increased sediment depth (r2 = 0.77) and was lower in vegetated areas (0.2 to 1.0 g cm−3) compared to the inflow and outflow stream sediments (0.6 to 1.4 g cm−3).
Key Wordshydrology hydraulic conductivity sediment organic matter wetland
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