Size fractions of organic matter pools influence their stability: Application of the Rock-Eval® analysis to beech forest soils

Soil organic matter (SOM) is a complex heterogeneous mixture formed through decomposition and organo-mineral interactions, characterization of its composition biogeochemical stability challenging. From this perspective, Rock-Eval® rapid efficient thermal analytical method that combines the quantitative qualitative information SOM, including several parameters related to stability. This approach has already been used monitor changes in (OM) properties at landscape, cropland, soil profile scales. study was aimed assess SOM pools by characterizing grain size fractions from forest litters topsoils using analysis. Litter (organic) topsoil samples were collected beech Normandy (France), whose management last 200 years documented. Fractionation wet sieving separate large debris (> 2 000 μm) coarse (200–2 fine particulate OM (POM) (50–200 as well μm), medium (< 50 samples. able provide sensitive enough fine-scale processes. In layers, explained progressive labile compounds plant finest particles. Meanwhile, presented different characteristics. The showed higher C contents, albeit with composition, stability, greater degree than forming layer. These results are consistent those previous studies microbial activity more effective fraction. low highest degree, which can be stronger interactions mineral matrix. Therefore, it suggested dynamics interpreted light plant-microbe-soil continuum. Finally, three distinct thermostable highlighted heterogeneity SOM: free (large particles), weakly protected (bio)aggregates (coarse fraction topsoil), stabilized topsoil, resulted within complexes. empirically illustrate conceptual models emphasizing roles drivers played gradual protection most thermally constituents.