Browsing by Author "Mutuo, Paul"

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    Greenhouse gas fluxes in different vegetation types along an African tropical wetland
    (Environmental and Sustainability Indicators, 2026-09-01) Byekwaso, Flavia; Kansiime, Frank; Kaggwa, Rose; Aine, Amon; Ongua, Fanuel; Mutuo, Paul; Weigelhofer, Gabriele; Langergraberi, Guenter; Hein, Thomas
    This study quantified how vegetation type and seasonality influence soil–atmosphere exchanges of CO2, CH4, and N2O across Lubigi Wetland, an urban tropical wetland in Uganda receiving wastewater effluent and stormwater from Kampala. Four sites were examined: an upstream Vossia cuspidata zone near inflows, an upstream non-vegetated mudflat, a midstream Phragmites mauritianus stand, and a downstream Cyperus papyrus section. Monthly static chamber measurements were conducted over 12 months, spanning wet and dry seasons, to assess spatial and temporal flux patterns, calculate site-specific global warming potentials (GWPs), and relate emissions to hydrology and soil characteristics. CO2 and N2O fluxes peaked during the dry season, especially in the upstream Vossia zone. CH4 emissions were also highest in the dry season, with Phragmites areas producing the strongest fluxes and mudflats the lowest. Hydrology was the main controlling factor: water levels below 50 cm promoted CO2 and N2O hotspots, while levels above 50 cm favored CH4 emissions. Across the wetland, CH4 contributed the largest share of annual GWP (about 55.6%), followed by CO2 (39.8%). The highest GWP occurred in the Phragmites zone due to sustained CH4 emissions, while mudflats had the lowest. Carbon and nitrogen cycles were tightly linked, with negative CO2–CH4 and positive CO2–N2O relationships. CH4 emissions were positively associated with microbial biomass carbon and negatively with bulk density. Vegetated soils contained higher organic carbon and nitrogen than mudflats. Management should prioritize CH4 mitigation, improve wastewater treatment, and apply seasonally adaptive water-level management to reduce overall GWP while maintaining ecosystem functions. Graphical abstract Spatial and temporal variations of greenhouse gases from upstream reaches with Vossia grass showed the highest N2O and CO2 emissions, followed by non-vegetated mudflat areas during the dry season. In the midstream reaches, at Phragmites reed, showed the highest CH4 emissions in the dry season, and in the downstream reaches, Papyrus sedge showed the second highest CH4 emissions during the wet season in Lubigi wetland. The sizes of the arrows indicate increasing GHG emissions with seasons in the vegetated and non-vegetated zones of a tropical freshwater wetland.