Low N2O and variable CH4 fluxes from tropical forest soils of the Congo Basin

Globally, tropical forests are assumed to be an important source of atmospheric nitrous oxide (N 2 O) and sink for methane (CH 4 ). Yet, although the Congo Basin comprises the second largest tropical forest and is considered the most pristine large basin left on Earth, in situ N 2 O and CH 4 flux measurements are scarce. Here, we provide multi-year data derived from on-ground soil flux ( n = 1558) and riverine dissolved gas concentration ( n = 332) measurements spanning montane, swamp, and lowland forests. Each forest type core monitoring site was sampled at least for one hydrological year between 2016 - 2020 at a frequency of 7-14 days. We estimate a terrestrial CH 4 uptake (in kg CH 4 -C ha −1 yr −1 ) for montane (−4.28) and lowland forests (−3.52) and a massive CH 4 release from swamp forests (non-inundated 2.68; inundated 341). All investigated forest types were a N 2 O source (except for inundated swamp forest) with 0.93, 1.56, 3.5, and −0.19 kg N 2 O-N ha −1 yr −1 for montane, lowland, non-inundated swamp, and inundated swamp forests, respectively. The Congo Basin is home to the second largest stretch of continuous tropical forest, but the magnitude of greenhouse fluxes are poorly understood. Here the authors analyze gas samples and find the region is not actually a hotspot of N2O emissions.