title: Radiocarbon constraints imply reduced carbon uptake by soils during the 21st century.
abstract: Soil is the largest terrestrial carbon reservoir and may influence the sign and magnitude of carbon cycle-climate feedbacks. Many Earth system models (ESMs) estimate a significant soil carbon sink by 2100, yet the underlying carbon dynamics determining this response have not been systematically tested against observations. We used14C data from 157 globally distributed soil profiles sampled to 1-meter depth to show that ESMs underestimated the mean age of soil carbon by a factor of more than six (430 ± 50 years versus 3100 ± 1800 years). Consequently, ESMs overestimated the carbon sequestration potential of soils by a factor of nearly two (40 ± 27%). These inconsistencies suggest that ESMs must better represent carbon stabilization processes and the turnover time of slow and passive reservoirs when simulating future atmospheric carbon dioxide dynamics.
authors.affiliation: Department of Earth System Science, University of California, Irvine, CA, USA. yujie.he@uci.edu.
authors.forename: Yujie
authors.initials: Y
authors.lastname: He
authors.affiliation: Department of Biogeochemical Processes, Max-Planck-Institute for Biogeochemistry, Jena, Germany.
authors.forename: Susan E
authors.initials: SE
authors.lastname: Trumbore
authors.affiliation: Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
authors.forename: Margaret S
authors.initials: MS
authors.lastname: Torn
authors.affiliation: U.S. Geological Survey, Menlo Park, CA, USA. Stanford University, Stanford, CA, USA.
authors.forename: Jennifer W
authors.initials: JW
authors.lastname: Harden
authors.affiliation: Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
authors.forename: Lydia J S
authors.initials: LJ
authors.lastname: Vaughn
authors.affiliation: Department of Earth System Science, University of California, Irvine, CA, USA. Department of Ecology and Evolutionary Biology, University of California Irvine, Irvine, CA, USA.
authors.forename: Steven D
authors.initials: SD
authors.lastname: Allison
authors.affiliation: Department of Earth System Science, University of California, Irvine, CA, USA.
authors.forename: James T
authors.initials: JT
authors.lastname: Randerson