Abstract : Organic matter stabilization in soil is generally recognized to occur by physical protection or by
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Abstract : Organic matter stabilization in soil is generally recognized to occur by physical protection or by chemical and biochemical stabilization. Chemical stabilization occurs as a result of chemical or physico-chemical binding to soil mineral surfaces. The term biochemical stabilization refers to the biotic or abiotic production of organic substances which are resistant to decomposition by microorganisms and which induce, through condensation and complex formation the stabilization of otherwise easily decomposable substrates. Under natural conditions, humic substances normally accumulate in soil under cool temperate climates. Mineralization of humic substances is very slow, because they are not composed of a regular sequence of repeating subunits. However, there is evidence that they are metabolised by the biomass and can be degraded co-metabolically by a variety of soil microrganisms. However, humic substances represent without any doubt, the largest and most persistent pool of biochemically stabilized soil organic C. Biochemical stabilization has received comparatively less attention, probably because there have been relatively few attempts to correlate analytical fractions and laboratory incubations with conceptual model C pools.
In this work, labile, non humified organic matter (NH) and four fractions of humic substances (HS), obtained by sequential extraction of soil organic matter (SOM), corresponding to biochemically stabilised (free fulvic acid, FA, and humic acids, HA) and chemically plus biochemically stabilised (bound FA and HA), were extracted from soils of different organic C inputs and characterized by 13C NMR and isotope analysis. Our aim was to better understand the dynamics of C sequestration/decomposition and the role of the soil microbial biomass in these processes.
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