Considering the influence of sequestration duration and carbon saturation on estimates of soil carbon capacity |
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| Authors: | Tristram O West Johan Six |
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| Institution: | (1) Environmental Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831–6335, USA;(2) Department of Plant Sciences, University of California, Davis, CA, USA |
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| Abstract: | Rates of soil C sequestration have previously been estimated for a number of different land management activities, and these
estimates continue to improve as more data become available. The time over which active sequestration occurs may be referred
to as the sequestration duration. Integrating soil C sequestration rates with durations provides estimates of potential change
in soil C capacity and more accurate estimates of the potential to sequester C. In agronomic systems, changing from conventional
plow tillage to no-till can increase soil C by an estimated 16±3%, whereas increasing rotation intensity can increase soil
C by an estimated 6±3%. The increase in soil C following a change in rotation intensity, however, may occur over a slightly
longer period (26 yr) than that for tillage cessation (21 yr). Sequestration strategies for grasslands have, on average, longer
sequestration durations (33 yr) than for croplands. Estimates for sequestration rates and durations are mean values and can
differ greatly between individual sites and management practices. As the annual sequestration rate declines over the sequestration
duration period, soil C approaches a new steady state. Sequestration duration is synonymous with the time to which soil C
steady state is reached. However, soils could potentially sequester additional C following additional changes in management
until the maximum soil C capacity, or soil C saturation, is achieved. Carbon saturation of the soil mineral fraction is not
well understood, nor is it readily evident. We provide evidence of soil C saturation and we discuss how the steady state C
level and the level of soil C saturation together influence the rate and duration of C sequestration associated with changes
in land management. |
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