Decomposition and nutrient dynamics of plant litter in Nyando floodplain wetland, Kenya
Decomposition plays an important function in wetlands as it regulates wetland biogeochemistry and by extension determine carbon reservoir in wetlands. As a result, it forms the base for wetland ecosystem food web through nutrient cycling, transport and storage but also form a habitat to numerous life forms. More studies have been done on the decomposition of macrophytes especially under ex situ experiments. However, little is understood on the decay rate of macrophytes in a papyrus-dominated wetland influenced by seasonal changes in water depth and livelihood exploitation activities. The main objective of this study was to examine plant decomposition and nutrient dynamics in a natural papyrus-dominated floodplain wetland in Nyando, Kenya. In this study, which covered a period of 112 days (between August and December 2010), in-situ litterbag technique was applied to quantify variation that exists in decomposition rate among the plant species and between transects. Over a period of 56 days, weight loss of plant materials ranged from 11 % to 24 %, 51 % to 77 % and 39 % to 61 % for Ipomoea aquatica, papyrus umbel and papyrus culm, respectively. Papyrus umbel in Singida transect displayed the lowest decay rate (k = 0.002 d-1) while I. aquatica showed the highest decay rate in Ogenya (k = 0.012 d-1). Nitrogen and phosphorus content varied over the collection dates. Nutrient content of remaining plant litter showed an accumulation effect for carbon in papyrus parts than in Vossia cuspidata and I. aquatica. Changes in surface water depth and dissolved oxygen (DO) had a significant effect on the decomposition rate. Understanding decomposition rates of different plants within the wetland is important as the process influences nutrient cycling, affecting both primary production and general wetland ecosystem health.
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