Soil organic carbon and nitrogen stocks along a seasonal wetland (dambo) transect in central Zimbabwe

Abstract

Ecosystems of central and southern Africa are occupied by some of the largest seasonal wetlands commonly called dambos. Dambos are likely to store huge stocks of soil organic carbon (SOC) because of their saturated conditions. However, most available literature report average SOC concentrations while ignoring pedological and hydrological variations. The objectives of the study were to quantify effects of catena position and hydrology on SOC and nitrogen stocks along a dambo transect in Chiota, Zimbabwe. Soil organic carbon stocks varied significantly with catena and were 7.3, 9.5, 30.4, 12.9 and 7.2 Mg ha⁻¹ for upland, margin, middle slope (midslope), lower slope and bottom, respectively, for the 0–40 cm depth. Corresponding nitrogen stocks were 0.6, 0.8, 2.1, 1.1 and 0.7 Mg ha⁻¹ for upland, margin, midslope, lower slope and bottom, respectively. The dry-season water table was 8, 1.5, 1.0, 1.3 and 1.5 m, whereas the wet-season water table was 6, 0.5, 0, 0 and 0.9 m below the surface for the upland, margin, midslope, lower slope and bottom, respectively. Biomass stand was highest in the midslope and least in the bottom. It was concluded that SOC and nitrogen stocks varied significantly with catena and this was attributed to differences in wetness.

Keywords: carbon stocks, dambo catena, nitrogen stocks, seasonal wetland