Kelebogile Cole

Title: The impact of hydro period and water chemistry on nutrient mineralization in a seasonal floodplain<br> of the Okavango Delta, Botswana.
Student: Kelebogile Cole
Country of origin: Botswana
University: University of Botswana
Degree:  MPhil (Natural Resources Management)
Supervisor: Prof. M. Bonyongo, Prof. W. Masamba
Year of registration: 2010

The Okavango Delta is a low nutrient pulsing wetland system with extended floodplain characterized by alternating periods of high and low floods. Despite the low nutrients, the Okavango Delta floodplain systems still remains highly productive even in years of high floods. In a similar trend observed in many tropical wetlands, nutrients in the Okavango Delta are carried into floodplain system by hydrologic inputs of precipitation, river flooding, and surface and groundwater inflows. Intrasystem nutrient cycling is generally, in turn, tied to pathways such as primary productivity and decomposition. When productivity and decomposition rates are high, as in flowing water or pulsing hydroperiod wetlands, nutrient cycling is rapid and the inverse is true. The hydroperiod of a wetland has significant effect on nutrient transformations, in the availability of nutrients to vegetation and on loss from wetland soils of nutrients that have gaseous forms. During low flood periods, there is an increase in ungulate populations in the seasonal floodplains which prove to have more palatable grasses for herbivores and this leads to increased nutrient depositions as the ungulates deposit dung in the floodplains. In most ecosystems external inputs of nutrients is very low and efficient recycling of nutrients maintains productivity of the system. Large herbivores can be an important component of biogeochemical; processes in ecosystems as they facilitate nutrient cycling by trampling and fragmenting plant tissue and by altering soil temperature and moisture conditions. This study investigates the influence of hydroperiod and water chemistry in nutrient mineralization using an experimental approach and field measurements. Although the dynamics of water chemistry of the Okavango Delta are well known, the soil nutrients dynamics are as influenced by variation in hydro periods and water chemistry are still largely not understood. The rate of nutrient mineralization in wetlands reflects a complex web of geologic, biotic and climatic factors. To date, the rate of decomposition of floodplain vegetation in the seasonal floodplain vegetation of the Okavango Delta is also largely not understood. This study investigates the influence water chemistry and varying hydro periods on the rate of decomposition of floodplain vegetation and large herbivore dung at both temporal and spatial scales. The results of this study are expected to contribute to the ongoing debate on nutrient dynamics of the Okavango Delta wetland systems.

Last Modified: Tue, 18 Aug 2015 13:08:10 SAST