Tropical forests cover large areas of equatorial Africa and play a substantial role in the global carbon cycle. However, there has been a lack of biometric measurements to understand the forests' gross and net primary productivity (GPP, NPP) and their allocation. Here we present a detailed field assessment of the carbon budget of multiple forest sites in Africa, by monitoring 14 one-hectare plots along an aridity gradient in Ghana, West Africa. When compared with an equivalent aridity gradient in Amazonia, the studied West African forests generally had higher productivity and lower carbon use efficiency (CUE). The West African aridity gradient consistently shows the highest NPP, CUE, GPP, and autotrophic respiration at a medium-aridity site, Bobiri. Notably, NPP and GPP of the site are the highest yet reported anywhere for intact forests. Widely used data products substantially underestimate productivity when compared to biometric measurements in Amazonia and Africa. Our analysis suggests that the high productivity of the African forests is linked to their large GPP allocation to canopy and semi-deciduous characteristics.

AMAP CIRAD CNRS INRA IRD Université de Montpellier Montpellier France

Centro Euro Mediterraneo sui Cambiamenti Climatici Leece Italy

Department of Earth System Science Ministry of Education Key Laboratory for Earth System Modeling Institute for Global Change Studies Tsinghua University Beijing China

Department of Forest Ecology Faculty of Forestry and Wood Sciences Czech University of Life Sciences Praha Czech Republic

Department of Natural Resources Management CSIR College of Science and Technology Kumasi Ghana

Environmental Change Institute School of Geography and the Environment University of Oxford Oxford United Kingdom

Forestry Division Food and Agriculture Organization of the United Nations Panama City Panama

Forestry Research Institute of Ghana Council for Scientific and Industrial Research Kumasi Ghana

Georgina Mace Centre for the Living Planet Department of Life Sciences Imperial College London Silwood Park Campus Buckhurst Road Ascot United Kingdom

Groningen Institute for Evolutionary Life Sciences University of Groningen P O Box 11103 9700 CC Groningen The Netherlands

Leverhulme Centre for Nature Recovery University of Oxford Oxford United Kingdom

School of Biological Sciences University of Adelaide Adelaide South Australia Australia

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