Soil erosion, particularly that caused by agriculture, is closely linked to the global carbon (C) cycle. There is a wide range of contrasting global estimates of soil-atmosphere C exchange partly due to limited understanding of how geomorphology, topography, and land management practices affect erosion and transport of soil organic C (SOC). Here we present a physically-based approach that stresses the fine dynamics and spatial heterogeneity of SOC erosion and atmospheric C sequestration. The methodology was implemented in tRIBS-ECO (Triangulated Irregular Network-based Real-time Integrated Basin Simulator-Erosion and Carbon Oxidation), a spatially-explicit model of SOC dynamics built within an existing coupled physically-based hydro-geomorphic model. We study a region recovering from some of the most serious agricultural erosion in North America. We utilize measurements of biogeochemical characteristics at multiple depths. We found that topographically induced variations of C erosion and replacement can be markedly higher than the variability among reported point estimates globally. We estimated that the net atmospheric C exchange ranges from a maximum source to a sink of 14.5 g m-2 yr-1 and 18.2 g m-2 yr-1, respectively. Applying results globally yields a maximum source and sink of 0.73 Pg yr-1 and 0.91 Pg yr-1, respectively. We conclude that the small scale complexity of C erosion and burial driven by topography exerts a strong control on the landscape's capacity to serve as a C sink or a source. We suggest that the significant spatial variability of C fluxes should be explicitly accounted for in regional and global C budgets.
Dialynas, Y. G., Bastola, S., Bras, R. L., Billings, S. A., Richter, D. deB., and Markewitz, D. (2015): Topographic variability in the influence of soil erosion on the carbon cycle. Calhoun CZO 2015 Summer Science Meeting.
This Paper/Book acknowledges NSF CZO grant support.