Impacts of the C4 sedge Cyperus papyrus L. on carbon and water fluxes in an African wetland

Fluxes of CO2 and H2O vapour were measured by eddy covariance from a stand of the C-4 emergent sedge Cyperus papyrus ( papyrus), which formed a fringing swamp on the north- west shore of Lake Naivasha, Kenya. The fluxes of CO2 and H2O vapour between the papyrus swamp and the atmosphere were large but variable, depending on the hydrology of the wetland system and the condition of the vegetation. These measurements, combined with simulation modelling of annual fluxes of CO2, show that papyrus swamps have the potential to sequester large amounts of the carbon (similar to 1.6 kg C m(-2) y(-1)) when detritus accumulates under water in anaerobic conditions, but they are a net source of carbon release to the atmosphere (similar to 1.0 kg C m(-2) y(-1)) when water levels fall to expose detritus and rhizomes to aerobic conditions. Evapotranspiration from papyrus swamps ( E) was frequently lower than evaporation from open water surfaces ( E-o) and plant factors have a strong influence on the flux of water to the atmosphere. For the period of measurement E/E-o was 0.36.