The effect of soil redistribution on soil organic carbon: an experimental study

[摘要] Soil erosion, transport and deposition by water drastically affect thedistribution of soil organic carbon (SOC) within a landscape. Furthermore,soil redistribution is assumed to have a large impact on the exchange ofcarbon (C) between the pedosphere and the atmosphere. There is, however,significant scientific disagreement concerning the relative importance of thekey-mechanisms at play. One of the major uncertainties concerns the fractionof SOC that is mineralized when soil is eroded by water, from the moment whendetachment takes place until the moment when the SOC becomes protected byburial. In this study, the changes in C-exchange between soil and atmosphereas affected by soil redistribution processes were experimentally quantified.During a laboratory experiment, three types of erosional events weresimulated, each of which was designed to produce a different amount of erodedsoil material with a different degree of aggregation. During a 98-day period,CO₂-efflux was measured in-situ and under field conditions onundisturbed soils with a layer of deposited soil material. Depending on theinitial conditions of the soil and the intensity of the erosion process, asignificant fraction of eroded SOC was mineralized after deposition. However,results also suggest that deposition produces a dense stratified layer ofsediment that caps the soil surface, leading to a decrease in SOCdecomposition in deeper soil layers. As a result, the net effect of erosionon SOC can be smaller, depending on the functioning of the whole soil system.In this study, soil redistribution processes contributed an additionalemission of 2 to 12% of total C contained in eroded sediment.

[学科分类] 地球化学与岩石