Stabilization mechanisms of organic matter in four temperate soils: Development and application of a conceptual model |
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| Authors: | Margit von Lützow Ingrid Kögel‐Knabner Bernard Ludwig Egbert Matzner Heinz Flessa Klemens Ekschmitt Georg Guggenberger Bernd Marschner Karsten Kalbitz |
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| Institution: | 1. Technische Universit?t München, Lehrstuhl für Bodenkunde, WZW, Department für ?kologie, 85350 Freising‐Weihenstephan, Germany;2. Universit?t Kassel, Fachbereich Umweltchemie, Nordbahnhofstra?e 1a, 37213 Witzenhausen, Germany;3. Lehrstuhl für Boden?kologie, Universit?t Bayreuth, 95440 Bayreuth, Germany;4. Institut für Bodenkunde und Waldern?hrung, Georg‐August‐Universit?t G?ttingen, Büsgenweg 2, 37077 G?ttingen, Germany;5. IFZ – Tier?kologie, Justus‐Liebig‐Universit?t, Heinrich‐Buff‐Ring 26–32, 35392 Gie?en, Germany;6. Institut für Bodenkunde und Pflanzenern?hrung, Martin‐Luther‐Universit?t Halle‐Wittenberg, Weidenplan 14, 06108 Halle/Saale, Germany;7. Geographisches Institut, Ruhr‐Universit?t, 44780 Bochum, Germany |
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| Abstract: | Based on recent findings in the literature, we developed a process‐oriented conceptual model that integrates all three process groups of organic matter (OM) stabilization in soils namely (1) selective preservation of recalcitrant compounds, (2) spatial inaccessibility to decomposer organisms, and (3) interactions of OM with minerals and metal ions. The model concept relates the diverse stabilization mechanisms to active, intermediate, and passive pools. The formation of the passive pool is regarded as hierarchical structured co‐action of various processes that are active under specific pedogenetic conditions. To evaluate the model, we used data of pool sizes and turnover times of soil OM fractions from horizons of two acid forest and two agricultural soils. Selective preservation of recalcitrant compounds is relevant in the active pool and particularly in soil horizons with high C contents. Biogenic aggregation preserves OM in the intermediate pool and is limited to topsoil horizons. Spatial inaccessibility due to the occlusion of OM in clay microstructures and due to the formation of hydrophobic surfaces stabilizes OM in the passive pool. If present, charcoal contributes to the passive pool mainly in topsoil horizons. The importance of organo‐mineral interactions for OM stabilization in the passive pool is well‐known and increases with soil depth. Hydrophobicity is particularly relevant in acid soils and in soils with considerable inputs of charcoal. We conclude that the stabilization potentials of soils are site‐ and horizon‐specific. Furthermore, management affects key stabilization mechanisms. Tillage increases the importance of organo‐mineral interactions for OM stabilization, and in Ap horizons with high microbial activity and C turnover, organo‐mineral interactions can contribute to OM stabilization in the intermediate pool. The application of our model showed that we need a better understanding of processes causing spatial inaccessibility of OM to decomposers in the passive pool. |
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| Keywords: | recalcitrance spatial inaccessibility organo‐mineral interactions pool size 14C age density fractionation HF demineralization wet oxidation active pool intermediate pool passive pool |
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