The aim of this paper is to determine the biological dynamism of the organic C forms bonded to soil particles mobilized by water erosion in Andosols of the Canary Islands, to evaluate their susceptibility towards mineralization processes and the role of sediments as sources or sinks of atmospheric CO(2) in these soils. The study was carried out in Tenerife (Canary Islands) on three 200 m(2) experimental plots of the RESEL Programme on silic Andosols under forest, 3 years after being subjected to clear-cutting. Eroded sediments were collected for analysis from five significant winter rainfall episodes. For each event, samples of surface (0-5 cm) soil in situ were also collected. CO(2)-C was measured by incubation in all the samples, as well as microbial biomass-linked C. The results obtained show an enrichment in the eroded sediments of microbial biomass (7.5+/-1.6 g kg(-1) vs. 3.8+/-1.5 g kg(-1)) and of potentially mineralizable C (1419 mg CO(2)-C kg(-1) vs. 386 mg CO(2)-C kg(-1)). In addition, there was twice as much mineralization of C compounds in eroded sediments as in the soil surface horizon.