The composition of the functional pools of labile organic matter in the zonal range of automorphic soils of the central Russian Plain

The granule-densimetric fractionation method was used to identify the characteristic features of the composition of different functional pools of labile organic matter (OM) from the automorphic soils of a zonal range from the center of the Russian Plain. Labile OM included free organic matter (FM) represented by a light fraction (LFR) of a density lower than 1.8 g/cm3 and a size larger than 53 μm, and aggregated discrete organic matter (LFAGR1) represented by an organic matter LF of a density lower than 1.8 g/cm3 and a size smaller than 53 μm and a phytolith LF (LFAGR2) (density 1.8–2.0 g/cm3). The composition of the fractions isolated was studied using electron microscopy, microanalysis, and chemical analysis.