Isotopic Signatures (?13C and ?15N) and Characteristics of Two Wetland Soils in Lesotho, Southern Africa

There is sparse data on comparative analysis of soil indicators and isotopic signatures to monitor the health of wetland ecosystems in Lesotho. This study used (i) soil indicators (i.e. soil organic carbon (SOC), soil organic carbon density, and silt:clay ratio) and (ii) isotopic signatures (?13C and ?15N) to monitor environmental change aquatic ecosystems of Lesotho. Transects of 2000 m were chosen in two agro-ecological zones (AEZ) (Lowlands and Mountains) of Lesotho and sub-divided into upper (US), middle (MS) and toe slopes (TS). Soil samplings were made horizon-wise (1.20 m deep) in triplicates, labeled and shipped to the laboratory in plastic bags. Aquatic vegetation samples were randomly collected along these transects for stable isotopes. All samples analyzed using standard procedures. Results showed that wetlands located in the Lowlands (Ha-Matela) AEZ were much more degraded and heavily impacted. This indicated by low silt/clay ratios, low SOC contents and SOC density and less negative ?13C compared to that of Mountains AEZ (Butha Buthe). Thus, these indicators can be used to predict degradation of wetlands. However, the severity of degradation, can be easily predicted the ?13C values and ?13N served as a robust indicator of wetland eutrophication. These results showed that soil indicators used as well as stable isotopes signatures used (i.e. ?13C and ?13N) may be used as monitoring tools for wetland management and restoration.