title: Lateral transport of soil carbon and land-atmosphere CO2 flux induced by water erosion in China.
abstract: Soil erosion by water impacts soil organic carbon stocks and alters CO2 fluxes exchanged with the atmosphere. The role of erosion as a net sink or source of atmospheric CO2 remains highly debated, and little information is available at scales larger than small catchments or regions. This study attempts to quantify the lateral transport of soil carbon and consequent land-atmosphere CO2 fluxes at the scale of China, where severe erosion has occurred for several decades. Based on the distribution of soil erosion rates derived from detailed national surveys and soil carbon inventories, here we show that water erosion in China displaced 180 ± 80 Mt C⋅y(-1) of soil organic carbon during the last two decades, and this resulted a net land sink for atmospheric CO2 of 45 ± 25 Mt C⋅y(-1), equivalent to 8-37% of the terrestrial carbon sink previously assessed in China. Interestingly, the "hotspots," largely distributed in mountainous regions in the most intensive sink areas (>40 g C⋅m(-2)⋅y(-1)), occupy only 1.5% of the total area suffering water erosion, but contribute 19.3% to the national erosion-induced CO2 sink. The erosion-induced CO2 sink underwent a remarkable reduction of about 16% from the middle 1990s to the early 2010s, due to diminishing erosion after the implementation of large-scale soil conservation programs. These findings demonstrate the necessity of including erosion-induced CO2 in the terrestrial budget, hence reducing the level of uncertainty.
authors.affiliation: The Key Laboratory of Water and Sediment Sciences, Ministry of Education, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, People's Republic of China; School of Water Resources and Hydropower Engineering, Wuhan University, Wuhan 430072, People's Republic of China;
authors.forename: Yao
authors.initials: Y
authors.lastname: Yue
authors.affiliation: The Key Laboratory of Water and Sediment Sciences, Ministry of Education, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, People's Republic of China; nijinren@iee.pku.edu.cn.
authors.forename: Jinren
authors.initials: J
authors.lastname: Ni
authors.affiliation: Laboratoire des Sciences du Climat et de l'Environnement, Institut Pierre Simon Laplace, Commissariat à l'Énergie Atomique et aux Ènergies Alternatives, CNRS, Université de Versailles Saint-Quentin-en-Yvelines, 91191 Gif-sur-Yvette, France;
authors.forename: Philippe
authors.initials: P
authors.lastname: Ciais
authors.affiliation: Department of Ecology, Peking University, Beijing 100871, People's Republic of China; Key Laboratory of Alpine Ecology and Biodiversity, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, People's Republic of China; CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, People's Republic of China;
authors.forename: Shilong
authors.initials: S
authors.lastname: Piao
authors.affiliation: Key Laboratory of Alpine Ecology and Biodiversity, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, People's Republic of China; CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, People's Republic of China;
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
authors.affiliation: Department of Ecology, Peking University, Beijing 100871, People's Republic of China;
authors.forename: Mengtian
authors.initials: M
authors.lastname: Huang
authors.affiliation: School of Engineering, The University of Edinburgh, Edinburgh EH9 3JL, United Kingdom;
authors.forename: Alistair G L
authors.initials: AG
authors.lastname: Borthwick
authors.affiliation: The Key Laboratory of Water and Sediment Sciences, Ministry of Education, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, People's Republic of China;
authors.forename: Tianhong
authors.initials: T
authors.lastname: Li
authors.affiliation: The Key Laboratory of Water and Sediment Sciences, Ministry of Education, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, People's Republic of China;
authors.forename: Yichu
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Land & Water, Commonwealth Scientific and Industrial Research Organisation, Canberra, ACT 2601, Australia;
authors.forename: Adrian
authors.initials: A
authors.lastname: Chappell
authors.affiliation: Earth and Life Institute, Georges Lemaître Centre for Earth and Climate Research, Université Catholique de Louvain, B-1348 Louvain, Belgium.
authors.forename: Kristof
authors.initials: K
authors.lastname: Van Oost
keywords: land−atmosphere CO2 flux; national scale; soil carbon displacement; water erosion