Vegetation restoration changes topsoil biophysical regulations of carbon fluxes in an eroding soil landscape

The dynamics of biophysical regulations of carbon fluxes can have a major effect on an ecosystems' carbon budget. Only a handful of comprehensive assessments of such dynamics exist. To better understand the carbon cycle, we measured all major carbon flux by biophysical regulations including rainfall, runoff, infiltration, and sediment yield at eight runoff plots in an eroding soil landscape on the Chinese Loess Plateau, a typical vegetation restoration area for the region. Results show that topsoil carbon flux by infiltration into deep soil layers was the largest efflux from topsoil in plots with vegetation, followed by runoff and sediment carbon effluxes. On the contrary, the carbon flux by sediment was the largest efflux from topsoil in plot without vegetation, followed by infiltration and runoff carbon effluxes. Total topsoil carbon flux by biophysical regulations to the deep layer is about 71 +/- 10% of the typical carbon sequestration rate in the region. Topsoil carbon sequestration capacity might be underestimated by up to 43 +/- 3% if the infiltrated carbon was not factored into estimates. The results of this study improve understanding of soil carbon dynamics and expand the dynamic carbon replacement hypothesis; photosynthesis replaces not only lateral carbon lost by erosion but also vertical carbon lost by infiltration.