Soil carbon stock and river carbon fluxes in humid tropical environments: The Nyong River basin (South Cameroon)

This study is focused on the transfers of carbon under its different forms in the tropical humid environment, from analyses realized on soils and waters in nested silicated catchments of the South Cameroon forested area (Nyong river basin). The carbon stock reaches 59000 t.kmm2.yr in the soi1 caver (mean thickness = 30 m), presenting a notable enrichment in the 2 Upper meters of the profiles. The dissolved organic carbon fluxes (0.3 t.kms2.yr-), SO that the atmospheric/soil CO, uptake by weathering are weak, in relation with a low weathering rate (3 mm/1000yr). The dissolved organic carbon appears very abundant in the coloured drainage waters (fluxes between 5 and 8 t.kms2.yr- after the stations), from the same magnitude than the total dissolved minera1 species; it plays a leading role in the dissolution and the transport of trace elements, SO that in the compensation of the anionic deficit observed in these waters. The particulate organic carbon (fluxes between 0.6-l .4 t.kmm2.yr-) represents about 20% of the total suspended solids. From the total carbon outputs determined here, the turn over of this element in the soils cari be estimated to 9000 yr; however, this value considerably decreases considering that only the carbon contained in the Upper part of the soi1 caver is easily mobilizable and reactive.