Spatiotemporal variability of CO 2 , N 2 O and CH 4 fluxes from a semi-deciduous tropical forest soil in the Congo Basin

Résumé

Tropical forests play an important role in the greenhouse gas exchange between the biosphere and atmosphere. Despite having the second largest tropical forest globally, the Congo Basin is generally understudied and ground-based greenhouse gas flux data are lacking. In this study, high-frequency measurements spanning 16 months from automated and manual fast-box soil chambers are combined to characterize spatiotemporal variability in soil greenhouse gas fluxes from a lowland tropical forest in Yangambi in the Congo Basin. Based on subdaily continuous measurements for CO 2 , a total emission of 15.3 ± 4.4 MgCha-1yr-1 was calculated, with the highest fluxes at the start of the wetter periods and a decline in emissions during drier periods. For CH 4 , the total uptake was −3.9 ± 5.2 kgCha-1yr-1. Over the whole period the soil acted as a sink. However, sporadic emission events were also observed. For N 2 O an emission of 3.6 ± 4.1 kgNha-1yr-1 was calculated, which is higher than most previously reported tropical forest estimates. N 2 O emissions decreased substantially during drier periods and emission pulses were detected after rain events. High spatial and temporal variability was observed for both CH 4 and N 2 O, although less so for CO 2 . Higher spatial variability was assessed through the manual measurements compared to the automated measurements. Overall, the tropical forest soil acted as a major source of CO 2 and N 2 O and a minor sink of CH 4 .

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