Reviewing the carbon cycle dynamics and carbon sequestration potential of Cyperus papyrus L. wetlands in tropical Africa

Abstract

Tropical papyrus wetlands have the ability to assimilate and sequester significant amounts of carbon. However, the spatial extent, productivity and carbon sink strength associated with papyrus wetlands remains poorly characterised. The objective of this study was to collate information from peer-reviewed publications and relevant government and NGO reports to better understand carbon dynamics within papyrus dominated wetlands, and to assess the processes that regulate the magnitude of the carbon sink. Papyrus wetlands were shown to exhibit high rates of photosynthetic carbon dioxide (CO2) assimilation of up to 40 μmol CO2 m−2 s−1 where the incident photosynthetic photon flux density was ≥1,000 μmol m−2 s−1, high rates of net primary production ranging between 14 and 52 g DM m−2 d−1 and represent a significant carbon sink where up to 88 t C ha−1 is stored in the aboveground and belowground components of the papyrus vegetation. Under flooded conditions significant detrital and peat deposits accumulate in excess of 1 m in depth, representing an additional carbon store in the order of 640 t C ha−1. This study also highlighted the lack of empirical data on emissions of other radiatively important trace gases such as methane and nitrous oxide and also the vulnerability of these carbon sinks to both future changes in climate, in particular periods of hydrological drawdown, and anthropogenic land use change where the papyrus vegetation is removed in favour of subsistence agricultural cropping systems.