Journal Article

Simulating Erosion‐Induced Soil and Carbon Delivery From Uplands to Rivers in a Global Land Surface Model

Regnier, Pierre, Yuan, Wenping, Zhang, Haicheng, Guenet, Bertrand, Ciais, Philippe, Camino‐Serrano, Marta, Naipal, Victoria, Van Oost, Kristof, Lauerwald, Ronny

2020

Overview

Global water erosion strongly affects the terrestrial carbon balance. However, this process is currently ignored by most global land surface models (LSMs) that are used to project the responses of terrestrial carbon storage to climate and land use changes. One of the main obstacles to implement erosion processes in LSMs is the high spatial resolution needed to accurately represent the effect of topography on soil erosion and sediment delivery to rivers. In this study, we present an upscaling scheme for including erosion‐induced lateral soil organic carbon (SOC) movements into the ORCHIDEE LSM. This upscaling scheme integrates information from high‐resolution (3″) topographic and soil erodibility data into a LSM forcing file at 0.5° spatial resolution. Evaluation of our model for the Rhine catchment indicates that it reproduces well the observed spatial and temporal (both seasonal and interannual) variations in river runoff and the sediment delivery from uplands to the river network. Although the average annual lateral SOC flux from uplands to the Rhine River network only amounts to 0.5% of the annual net primary production and 0.01% of the total SOC stock in the whole catchment, SOC loss caused by soil erosion over a long period (e.g., thousands of years) has the potential to cause a 12% reduction in the simulated equilibrium SOC stocks. Overall, this study presents a promising approach for including the erosion‐induced lateral carbon flux from the land to aquatic systems into LSMs and highlights the important role of erosion processes in the terrestrial carbon balance. Plain Language Summary Global land surface models (LSMs) are the main tools used to simulate the terrestrial carbon (C) cycle and to predict its response to climate and land cover changes. Currently, the processes of vertical C fluxes between soils, plants, and the atmosphere (e.g., photosynthesis, plant growth, and litter and soil organic matter decomposition) has been well represented in many LSMs; however, the lateral soil C delivery through the river network caused by water erosion is still missing in most LSMs. This study introduces a LSM approach which is suitable to simulate the large‐scale soil C delivery from upland soils to inland waters at high temporal resolution (daily) and accounting for the small‐scale (~90 m) spatial variability in topography and soil properties. Evaluation of our model in the Rhine catchment demonstrates a good performance with regard to reproducing the spatial and temporal (daily, seasonal, and interannual) variability of soil C delivery rate from uplands to river networks at large spatial scale and for exploring the impacts of changes in vegetation cover (land use change) and climate (e.g., changes in rainfall amounts and regimes) on the regional soil C balance. Key Points We presented an upscaling scheme for including erosion‐induced lateral soil and carbon transfers into a global land surface model Our model is a useful tool to estimate the impacts of climate and land cover changes on erosion‐induced soil carbon loss at large scale Model application for the Rhine basin demonstrates that erosion‐induced soil carbon losses substantially reduce soil carbon stocks

• Publisher: John Wiley & Sons, Inc,American Geophysical Union,John Wiley and Sons Inc,American Geophysical Union (AGU)
• Subject: Annual / Aquatic environment / Bias / Biogeochemical Cycles, Processes, and Modeling / Biogeochemical Kinetics and Reaction Modeling / Biogeochemistry / Biogeosciences / Carbon / Carbon capture and storage / carbon cycle / Carbon Cycling / Carbon sequestration / Climate and land use / Climate change / Cryosphere / Earth Sciences / Earth System Modeling / Ecosystems / Environmental Sciences / Erosion processes / Fluvial sediments / Geodesy and Gravity / Global Change / Global Change from Geodesy / Interannual variations / land surface model / Land surface models / Land use / lateral carbon transport / Natural Hazards / Oceanography: Biological and Chemical / Organic carbon / Paleoceanography / Physical Modeling / Primary production / Resolution / River discharge / River flow / River networks / River runoff / Rivers / Runoff / Sciences of the Universe / Sediment / Sediment transport / Soil erodibility / Soil erosion / Stocks / Topographic effects / Topography / upscaling / Vegetation / Watersheds