Continental-scale measurement of the soil organic carbon pool with climatic, edaphic, and biotic controls

Authors

  • Jonathan G. Wynn,

    1. Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia
    2. Now at School of Geography and Geosciences, University of St. Andrews, St. Andrews, UK.
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  • Michael I. Bird,

    1. Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia
    2. Now at School of Geography and Geosciences, University of St. Andrews, St. Andrews, UK.
    3. Also at Research School of Biological Sciences, Australian National University, Canberra, ACT, Australia.
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  • Lins Vellen,

    1. Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia
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  • Emilie Grand-Clement,

    1. Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia
    2. Now at Department of Soil Science, University of Reading, Reading, UK.
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  • John Carter,

    1. Queensland Department of Natural Resources and Mines, Indooroopilly, Queensland, Australia
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  • Sandra L. Berry

    1. School of Resources, Environment and Society, Australian National University, Canberra, ACT, Australia
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Abstract

[1] We present data on soil organic carbon (SOC) inventory for 7050 soil cores collected from a wide range of environmental conditions throughout Australia. The data set is stratified over the spatial distribution of trees and grass to account for variability of SOC inventory with vegetation distribution. We model controls on SOC inventory using an index of water availability and mean annual temperature to represent the climatic control on the rate of C input into the SOC pool and decomposition of SOC, in addition to the fraction of soil particles <63 μm in diameter as a measure of textural control on SOC stabilization. SOC inventories in the top 30 cm of soil increase from 35 mg/cm2 in the driest regions to a modeled plateau with respect to a threshold of water availability at 335 mg/cm2, excluding variables controlling SOC decomposition. Above this threshold, decomposition factors begin to control SOC inventory, which we attribute to energetic control on microbial decomposition rates, and relatively weak stabilization of SOC in association with fine particles. When combined, these relationships provide an overall prediction of SOC inventory that accounts for 89–90% of the variance observed in the measured data set. Deviations from this relationship are most likely due to additional factors that also control decomposition rate such as hydrochemical and soil drainage conditions not accounted for by soil texture. Outliers within this data set are explained with respect to these conditions.

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