Adesola Olaleye

By Olaleye Adesola Olutayo

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 (δ13C and δ15N) 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 δ13C 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 δ13C values and δ13N served as a robust indicator of wetland eutrophication. These results showed that soil indicators used as well as stable isotopes signatures used (i.e. δ13C and δ13N) may be used as monitoring tools for wetland management and restoration.

Part of the book: Wetlands Management

By Adesola Olaleye, Regina Mating, Tumelo Nkheloane, Tutu K. Samuel and Tolu Yetunde Akande

Monitoring is essential to evaluate the effects of wetland restoration projects. Assessments were carried-out after 6 years of restoration efforts on a wetland located in two agro-ecological zones (AEZ): the Mountains agro-ecological zone–Khalongla-lithunya (KHL) and the Foot Hills–Ha-Matela (HM). The former was under conservation and the latter non-conserved. Mini-pits were dug along transects for soil sampling. Runoff water was collected from installed piezometers into pre-rinsed plastic bottles with de-ionized water once a month for between 3 and 6 months. Soil and water samples were analyzed in the laboratory for Ca, Mg, K, Na, total nitrogen, and phosphorus, and soil samples were further analyzed for Cu, Fe, Zn, and Mn and vegetation isotopic N15. Water quality, soil organic matter (SOM), carbon pools, base cations, ratios (silt:clay & SOM:silt clay), texture, and N-15 isotopes were chosen as indicators. Results showed that base cations were significantly (p < 0.05) higher in the groundwater and soils of KHL wetlands compared with those from the HM. The soils of the KHL wetlands have higher (p < 0.05) clay, silt contents, SOM, and silt clay ratios compared with the HM. Furthermore, results of the N15 isotopes were between 2.52 and 2.93% (KHL) compared with 2.00 and 6.18% (HM). Similarly, the results of the δ13C showed significant negative values at KHL (28.13–28%) compared with HM (11.77–12.72%). The study concludes that after five years of rehabilitating the KHL wetlands, the soil indicators showed that restoration efforts are positive compared with the HM wetlands that are non-conserved.

Part of the book: Soil Science