Carbon dioxide and methane emissions from plants and peat soil in a Cyperus papyrus wetland in Uganda.

Tropical wetlands contribute significantly to global carbon dioxide (CO2) and methane (CH4) emissions; however, gaps exist in understanding emissions sources and drivers, especially in African peatlands. We captured plant-mediated and diffusive CH4 and CO2 emissions from monthly chamber sampling from both plants and soils in an intact Cyperus papyrus wetland in Eastern Uganda. This wetland was a strong source of atmospheric CH4 in the rainy season, with monthly plant-mediated CH4 fluxes averaging 3.6 ± 0.8 nmol CH4 stem-1 s-1 (± s.e. ), and monthly diffusive CH4 emissions averaging 918 ± 96 nmol CH4 m-2 s-1. Heterotrophic CO2 emissions sampled from trenched plots were highest during the dry season with a mean of 3410 ± 212 nmol CO2 m-2 s-1 over this period. Stem measurements varied seasonally in stem count and biomass, with higher C. papyrus biomass in the dry season, averaging 1888 ± 130 g dry biomass m-2. Linear models showed a significant effect of water levels on CH4 and CO2 emissions from soils and plants (p < 0.1 to p < 0.001). This study is the first to observe CH4 emissions directly from the C. papyrus plant and contributes to the limited datasets on carbon cycling in these systems. A French translation of this abstract is available in the supplementary material. This article is part of the discussion meeting issue 'African tropical peatlands: function, value and vulnerability'.