CR 17:183-193 (2001)  -  doi:10.3354/cr017183

ABSTRACT: Global climate change has been modifying ecosystem carbon cycling, which has produced feedbacks on climate by affecting the concentration of atmospheric CO₂. The importance of biospheric CO₂ uptake or release to climate change has generated great interest in quantifying the dynamic responses of terrestrial ecosystem carbon cycling to climate change. However, less attention has been given to Africa, although it accounts for about one-fifth of the global net primary production and is one of the regions that have the greatest climate change. Here we use a biogeochemical model to simulate the dynamic variations in the carbon fluxes and stocks of African ecosystems caused by changes in climate and atmospheric CO₂ from 1901 and 1995. We estimate that climate change reduces plant production and soil carbon stocks and causes net CO₂ release, but the fertilization effect of increasing atmospheric CO₂ on photosynthesis reverses the reduction and leads to carbon accumulation in vegetation. Therefore, the combined effect of climate change and increasing atmospheric CO₂ causes net CO₂ uptake, particularly in central Africa. The mean rate of the carbon sequestration in the period 1981-1995 is calculated to be 0.34 Gt C yr^-1. Nevertheless, Africa is not necessarily a significant carbon sink, because a large part of the carbon sequestration is offset by the carbon release arising from land use changes.

KEY WORDS: Carbon cycle · Climate change · Africa Ecosystem modeling