Clay-Size Organo-Mineral Complexes in Temperate Soils: Relative Contributions of Sorptive and Physical Protection
C. Chenu, I. Virto, A. Plante, F. Elsass, 2009. "Clay-Size Organo-Mineral Complexes in Temperate Soils: Relative Contributions of Sorptive and Physical Protection", Carbon Stabilization by Clays in the Environment: Process and Characterization Methods, David A. Laird, Javiera Cervini Silva, Yona Chen, Claire Chenu, Françoise Elsass, Javier M. Gonzalez, Michael H.B. Hayes, David A. Laird, Alain Plante, Andre J. Simpson, Guixue Song, Jorge Tarcjotzly, Michael L. Thompson, I. Virto, Robert L. Wershaw
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Soils contain the largest C pool at the surface of the continents with more than 1500 Gt C (IPCC 2001). Managing soil C has been proposed as a way to reduce the increase of CO2 concentration in the atmosphere. However, choosing the best management option requires an appropriate knowledge of the mechanisms responsible for organic matter stabilization in soils in the long term.
Several processes can explain the stabilization of organic matter in soils (Figure 1), including (i) the selective preservation of recalcitrant molecules, (ii) chemical stabilization, which involves all intermolecular interactions between organic substances and inorganic ones leading to a decrease in availability of the organic matter, i.e. surface adsorption and precipitation and (iii) physical stabilization that is related to the decrease in the accessibility of organic substrates to micro-organisms due to occlusion in small pores (Sollins et al., 1996; Baldock and Skjemstad, 2000).
One of the major controls of soil C stocks is soil texture. Indeed, clayey soils are generally richer in C than coarser-textured soils, and several authors have established correlations between soil texture and C contents. For example, Hassink et al. (1997), Feller and Beare (1997) and later (Six et al., 2002) showed that the amount of C stored in the silt + clay fraction of soil (i.e. < 20μm particle size or < 50μm particle size) increased with the abundance of this fraction. Keil et al. (1994) and Mayer (1994)