Methods for studying soil organic matter: Nature, dynamics, spatial accessibility, and Interactions with minerals
Résumé
Soil organic matter (SOM) is extremely complex because of the variety of its inputs (e.g., plant tissues, microorganisms, animals) and their different stages of decomposition. This chapter presents fractionation methods that intend, either chemically, thermally, or physically, to separate meaningful subsets of SOM. Whole SOM or SOM fractions are characterized with wet chemical methods to identify their biochemical components or with spectroscopic methods that do not require prior extraction of SOM. Visualization methods allow for location of SOM within soil structure and to decipher its interaction with soil minerals, even at nm scales. The dynamics of SOM can be determined by combining incubation and long-term experiments, 13C or 15N natural abundance or labeling, or 14C dating or labeling. An integrated understanding of the dynamics and functions of SOM in different pedological, land use, and climate contexts is best attained by combining fractionation methods with characterization of the composition and turnover rate of fractions, down to the molecular scale.