Publication Date:
2014-12-26
Description:
Publication date: 1 February 2015 Source: Earth and Planetary Science Letters, Volume 411 Author(s): Y. Li , T.A. Quine , H.Q. Yu , G. Govers , J. Six , D.Z. Gong , Z. Wang , Y.Z. Zhang , K. Van Oost Humans are now the most important geomorphic agent on the planet and accelerated erosion in agricultural landscapes results in high magnitude lateral organic carbon (OC) fluxes and significant perturbation of the land–ocean carbon flux. Nevertheless, the net effect of these lateral carbon fluxes on the C cycle is poorly constrained and there is no consensus as to whether they drive a net source or net sink of atmospheric CO 2 . Here, we test the hypothesis that, under sustained erosional forcing, soil carbon stocks on hillslopes reach a new equilibrium state in which all carbon exported with erosion is replaced; and, therefore, erosion results in a net sink for atmospheric CO 2 at the scale of eroding hillslopes. The evidence from our study site, in the Loess Plateau of China, is consistent with this hypothesis. Despite net export of OC equivalent to ca. 10% NPP, we found that all of the eroded OC was replaced and, therefore, that the sink strength was equal to the C export rate. This sets the upper limit of the erosion-induced sink term at the scale of whole watershed. The fate of the exported carbon in reservoirs, floodplains, riverbeds and the ocean ultimately controls the watershed-scale sink strength. Nevertheless, the full replacement observed here suggests that erosion does not induce a C source, irrespective of the fate of the exported carbon, at least for high-input agricultural systems. Finally, we propose that assessment of the C cycle perturbation associated with erosion-induced lateral C fluxes must be made an integral part of accounting mechanisms for climate change mitigation strategies that are based on land use change and C sequestration in terrestrial environments.
Print ISSN:
0012-821X
Electronic ISSN:
1385-013X
Topics:
Geosciences
,
Physics
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