Glob. Change Biol. http://doi.org/cg5q (2017)

Net primary productivity (NPP) of tropical forests is a key source of uncertainty in the global carbon cycle. African tropical forests in particular constitute Earth’s second largest tropical forest block but have received far less research attention than South American and Southeast Asian forests.

Sam Moore from the University of Oxford and colleagues begin to redress this balance by providing a comprehensive analysis of NPP and carbon allocation to wood, canopy and root growth at contrasting lowland West African forest sites — evergreen (EF), semi-deciduous (SDF), dry forests (DF) and woody savannah (WS) — spanning a rainfall gradient.

They find that above and belowground carbon stocks follow the climate gradient more closely than NPP. Total NPP is highest in SDF, followed by EF then DF and WS sites, with each forest type having distinct carbon allocation patterns. Woody growth rate is found to be a poor proxy for overall forest productivity — canopy and root growth rates perform better. Residence time is the primary driver of observed patterns of wood, leaf and root biomass across the rainfall gradient. These findings point to the importance of directly measuring the main components of above and belowground NPP, requiring the establishment of permanent monitoring plots across the tropics.