Towards a nitrogen budget for different forests types of the central Congo Basin

Marijn BAUTERS1,2, Hans VERBEECK2, Landry CIZUNGU3 and Pascal BOECKX1

1 Isotope Bioscience Laboratory – ISOFYS, Ghent University, Coupure Links 653, 9000 Gent, Belgium

2 CAVElab, Computational and Applied Vegetation Ecology, Department of Applied Ecology and Environmental Biology, Ghent University, Coupure Links 653, 9000 Gent, Belgium

3 Faculty of Agronomy, Université Catholique de Bukavu, Avenue de la mission, BP 285, Bukavu, DR Congo.

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Recent data analyses and modelling activities have shown that the CO2 uptake by terrestrial ecosystems strongly depends on site fertility, i.e. nutrient availability. Accurate projections of future net forest growth and terrestrial CO2 uptake thus necessitate an improved understanding on nutrient cycles and how these are coupled to the carbon cycle. This holds especially for tropical forests, since they represent about 40–50% of the total carbon that is stored in terrestrial vegetation. Central African forests are very poorly characterized and their role in global change interactions shows distinct knowledge gaps. Research in the Congo Basin region should combine assessments of both carbon stocks and the underlying nutrient cycles, which directly impact the forest productivity. We set up a monitoring network for carbon stocks and nitrogen fluxes in different forest types in the Congo Basin, which is now operative. Preliminary data show an atmospheric N deposition of 20-30 kg N ha-1 yr-1 with N mainly derived from fires and different N dynamics in mixed vs. mono-dominant forests, whereby the N economy of ectomycorrhizal fungi is likely the driving force for establishment mono-dominant forest ecosystems and nitrate leaching.