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Anders Ahlström

Anders Ahlström

Senior lecturer

Anders Ahlström

Toward more realistic projections of soil carbon dynamics by Earth system models

Author

  • Yiqi Luo
  • Anders Ahlström
  • Steven D. Allison
  • Niels H. Batjes
  • Victor Brovkin
  • Nuno Carvalhais
  • Adrian Chappell
  • Philippe Ciais
  • Eric A. Davidson
  • Adien Finzi
  • Katerina Georgiou
  • Bertrand Guenet
  • Oleksandra Hararuk
  • Jennifer W. Harden
  • Yujie He
  • Francesca Hopkins
  • Lifen Jiang
  • Charlie Koven
  • Robert B. Jackson
  • Chris D. Jones
  • Mark J. Lara
  • Junyi Liang
  • A. David McGuire
  • William Parton
  • Changhui Peng
  • James T. Randerson
  • Alejandro Salazar
  • Carlos A. Sierra
  • Matthew J. Smith
  • Hanqin Tian
  • Katherine E.O. Todd-Brown
  • Margaret Torn
  • Kees Jan Van Groenigen
  • Ying Ping Wang
  • Tristram O. West
  • Yaxing Wei
  • William R. Wieder
  • Jianyang Xia
  • Xia Xu
  • Xiaofeng Xu
  • Tao Zhou
Show all

Summary, in English

Soil carbon (C) is a critical component of Earth system models (ESMs), and its diverse representations are a major source of the large spread across models in the terrestrial C sink from the third to fifth assessment reports of the Intergovernmental Panel on Climate Change (IPCC). Improving soil C projections is of a high priority for Earth system modeling in the future IPCC and other assessments. To achieve this goal, we suggest that (1) model structures should reflect real-world processes, (2) parameters should be calibrated to match model outputs with observations, and (3) external forcing variables should accurately prescribe the environmental conditions that soils experience. First, most soil C cycle models simulate C input from litter production and C release through decomposition. The latter process has traditionally been represented by first-order decay functions, regulated primarily by temperature, moisture, litter quality, and soil texture. While this formulation well captures macroscopic soil organic C (SOC) dynamics, better understanding is needed of their underlying mechanisms as related to microbial processes, depth-dependent environmental controls, and other processes that strongly affect soil C dynamics. Second, incomplete use of observations in model parameterization is a major cause of bias in soil C projections from ESMs. Optimal parameter calibration with both pool- and flux-based data sets through data assimilation is among the highest priorities for near-term research to reduce biases among ESMs. Third, external variables are represented inconsistently among ESMs, leading to differences in modeled soil C dynamics. We recommend the implementation of traceability analyses to identify how external variables and model parameterizations influence SOC dynamics in different ESMs. Overall, projections of the terrestrial C sink can be substantially improved when reliable data sets are available to select the most representative model structure, constrain parameters, and prescribe forcing fields.

Department/s

  • Dept of Physical Geography and Ecosystem Science
  • MERGE: ModElling the Regional and Global Earth system
  • BECC: Biodiversity and Ecosystem services in a Changing Climate

Publishing year

2016-01-01

Language

English

Pages

40-56

Publication/Series

Global Biogeochemical Cycles

Volume

30

Issue

1

Document type

Journal article

Publisher

American Geophysical Union (AGU)

Keywords

  • CMIP5
  • Earth system models
  • realistic projections
  • recommendations
  • soil carbon dynamics

Status

Published

ISBN/ISSN/Other

  • ISSN: 0886-6236