Management-Induced Changes in Organic Carbon Pools of Temperate Soils: C-14 and C-13 Evidence
Abstract
Interpretation of soil organic carbon (SOC) dynamics has been difficult because SOC is a mixture of materials with vast different turnover times. This heterogeneous nature of SOC necessitates the differentiation of component pools in order to describe the turnover kinetics. Currently no satisfactory method is available to separate those SOC pools physically. Recent advances in bulk SOC methods using natural C-14 and C-13 signatures, however, have gained insights into the turnover of SOC in temperate soils. This paper presents the findings of SOC turnover dynamics in North America croplands by interpreting data from published literature using the bulk carbon paired-plot approach. The analysis indicates that management-induced changes in SOC are mainly in the active pools that have turnover time ranging from15-93 y. The ages of the refractory pools are in the range of 899-5138 y. Management may change the sizes of active pools drastically but not their turnover times. The results suggest a bimodal distribution of SOC in temperate surface soils which can be approximated by two distinct SOC groups: active SOC pools turnover in decades or less and refractory pools turnover in hundreds of years or more. Temperate soils can be sources or sinks of atmospheric CO2 depending on management which affects the sizes of active SOC. Active SOC will reach a new equilibrium in 30-200 y depending on the nature of soils and climates. The mechanism that preserves the refractory SOC is not clear at this point, however, certain aggregates formed by clay and organic matter may hold the key to the protection of refractory SOC.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.B51C..06H
- Keywords:
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- 0315 Biosphere/atmosphere interactions;
- 0330 Geochemical cycles