Basing on both a site gradient as well as a gradient in management intensities the influence of these factors on different SOM pools was investigated: (A) a very easily decomposable C pool, (B) a C pool which is related to clay fraction and representing a relatively inert pool, (C) a C pool which is not, or only loosely connected to the mineral soil part representing the intermediates between the extreme C pools (A) and (B). The decomposable C pool was measured by the parameter of hot water extractable carbon (HW-C). The clay related and not clay related SOM pools were isolated by a combined fractionation according to both particle sizes (clay fraction < 1 μm and 1 – 2 μm) and specific densities (light fraction < 1.8 g/cm³ and 1.8 – 2.0 g/cm³). Fertilization increases easily decomposable SOM pools reflected in C content of a hot water extractable SOM fraction and in mass of specific light SOM fractions but to a certain extent the C pool associated with clay minerals as well. At comparable management (fertilization) levels transformation conditions at a site (temperature and precipitation) have an influence on the accumulation of the decomposable SOM pool (effective biological transformation time – WMZ)