The global significance of omitting soil erosion from soil organic carbon cycling schemes

Journal name:
Nature Climate Change
Volume:
6,
Pages:
187–191
Year published:
DOI:
doi:10.1038/nclimate2829
Received
Accepted
Published online

Soil organic carbon (SOC) cycling schemes used in land surface models (LSMs) typically account only for the effects of net primary production and heterotrophic respiration1. To demonstrate the significance of omitting soil redistribution in SOC accounting, sequestration and emissions, we modified the SOC cycling scheme RothC (ref. 2) to include soil erosion. Net SOC fluxes with and without soil erosion for Australian long-term trial sites were established and estimates made across Australia and other global regions based on a validated relation with catchment-scale soil erosion. Assuming that soil erosion is omitted from previous estimates of net C flux, we found that SOC erosion is incorrectly attributed to respiration. On this basis, the Australian National Greenhouse Gas inventory overestimated the net C flux from cropland by up to 40% and the potential (100 year) C sink is overestimated by up to 17%. We estimated global terrestrial SOC erosion to be 0.3–1.0PgCyr−1 indicating an uncertainty of −18 to −27% globally and +35 to −82% regionally relative to the long-term (2000–2010) terrestrial C flux of several LSMs. Including soil erosion in LSMs should reduce uncertainty in SOC flux estimates3, 4 with implications for CO2 emissions, mitigation and adaptation strategies and interpretations of trends and variability in global ecosystems5.

At a glance

Figures

  1. Temporal variation in measured (symbols) and modelled (lines) soil organic carbon for the Waite rotation trial plots.
    Figure 1: Temporal variation in measured (symbols) and modelled (lines) soil organic carbon for the Waite rotation trial plots.

    ae, RothCE model predictions used established decomposition rates for Australia (RPM = 0.15yr−1) without soil erosion (black line), with soil erosion estimated using the Australian empirical model (blue line) and the mass-balance model (green line) and optimized erosion estimates using the RothC model (red line). TOC, total organic carbon; HUM, humic pool; POC, particulate organic carbon; IOM, inert organic matter; RPM, resistant plant material. The rotation acronym (as defined in Table 1) is indicated in the top left corner of each plot.

  2. Relation between soil erosion and the difference in net C flux.
    Figure 2: Relation between soil erosion and the difference in net C flux.

    The model RothC was calibrated with and without soil erosion using Australian experimental (plot scale) trial data (blue diamonds). Validation data (not used to produce the model; red squares) at the catchment scale was provided from global data22. Both axes are in log scale.

References

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Author information

Affiliations

  1. CSIRO, Land and Water, GPO Box 1666, Canberra, Australian Capital Territory 2601, Australia

    • Adrian Chappell
  2. CSIRO, Agriculture, Urrbrae, South Australia 5064, Australia

    • Jeffrey Baldock &
    • Jonathan Sanderman
  3. Woods Hole Research Center, 149 Woods Hole Road, Falmouth, Massachusetts 02540, USA

    • Jonathan Sanderman

Contributions

A.C. conceived of the project in consultation with J.B. and J.S. J.S. organized the soil samples and measurement of 137Cs and A.C. calculated the estimates of soil redistribution. A.C. wrote the code in Matlab to analyse the data, performed the analyses and interpreted the results in consultation with J.B. and J.S. A.C. led the manuscript writing with contributions from J.B. and J.S.

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The authors declare no competing financial interests.

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