Tuesday, 25 January 2011
Washington State Convention Center
Generally, there is sparse information on the impact of anthropogenic pressures on the wetlands of Lesotho. Thus, the objective of this study was to assess the impacts of anthropogenic activities on the physicochemical characteristics of Ts'akholo wetland and to compare Ts'akholo wetland's physicochemical and morphological characteristics with other land uses surrounding the wetland such as pasture/grazing land and the cropped land. The three demarcated land use types (LUTs) were demarcated: wetland, grazing/pastureland and cropped land. The analyzed physicochemical properties include the pH, organic carbon, available phosphorus (avP), total Nitrogen (TN), CEC, K, particle size analysis, hydraulic conductivity, bulk density, silt: clay ratio and SOM/(silt + clay) ratio (SSCR). The determined morphological characteristics used were the soil colour, structure, texture, consistency, roots, mottles, and the presence of stones and quartz abundance. An eighty three year (1923-2006) rainfall distribution was used to assess the contribution of rainfall to the condition of Ts'akholo wetland. Results showed that there is high spatial variation between the three LUTs in terms of the morphological and physicochemical properties. Organic carbon (OC) contents were found to be of the order pasture/grazing>wetland>cropped lands. When compared with undisturbed wetlands (OC=12%), the OC were low. Generally, the TN, avP, exchangeable K and CEC were very low when compared with undisturbed wetlands in the area. The pH reaction in the wetland was alkaline (pH> 8.5) and dominated by high exchangeable Na, while that in the cropped and grazed lands were almost neutral. Results further showed that the SSCR were low suggesting high impact of anthropogenic pressure on the three LUTs. Rainfall amount has declined successively over the years. Most of the indicator weed species typifying wetlands have been replaced by invasive grass species. It can be concluded that largely, there has been a very high anthropogenic impact on these wetland when compared to an undisturbed wetland occurring in the area.
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