| 9 | | Growth in carbon sinks in pristine tropical forests slowed down during recent decades in South America, but not in Africa. Potential drivers behind these continental differences include differences in climate, its change, vegetation properties and nutrient sources. The latter has been overlooked, despite growing evidence of the contrasting importance of atmospheric deposition as a nutrient source for forest ecosystems. Using a terrestrial biosphere model, we quantify the impact of changes in atmospheric nutrient deposition on ecosystem productivity and biomass carbon sink at a lowland forest site in Central Africa. We find that the increase in nutrient deposition since the 1980s has contributed to the carbon sink over the past four decades at an extent that is comparable to that from the combined effect of increasing atmospheric carbon dioxide and climate change. Further, we find that the modelled carbon sink responds asymmetrical to changes in phosphorus deposition, but less so to nitrogen deposition. The pronounced response of ecosystem productivity to changes in nutrient deposition illustrates a continental scale mechanism which controls nutrient constraints on carbon sinks in Central Africa. Monitoring of nutrient deposition is needed in this region of alteration of nutrient deposition due to human land use. |
