Land use change from agriculture to forest is supposed as one possibility to increase the amount of Soil Organic (SOM) matter in soils and to decrease the atmospheric content of the greenhouse gas CO2. This kind of SOM sequestration will only be sustainable by increasing the amounts of stabilized SOM. Pedogenetic parameters like soil acidity and soil mineralogical properties are emphasized to be strongly related to SOM stabilization. Therefore it can be assumed that the extent of SOM sequestration due to afforestation is affected by the status of pedogenesis, but the quantification of these relationships is still insufficient. The aim of the study is to investigate in which extent pH, contents of amorphous metal oxides and clay minerals determine the differences in amount, content and composition of stable SOM parts of topsoils of different pedogenesis and land use. For this we investigate ten sites (land use pairs) throughout Germany, which differ in soil forming factors and genetic conditions, respectively, and which are characterized by the following conditions: i) direct neighbourhood of the studied plots under arable land and forest (land use pairs), ii) land use continuity at single plots for more than 50 years, iii) comparable pedogenetic conditions in the land use pairs. Stable SOM parts from top soils will be isolated using a sequential extraction procedure, dated by 14C, chemically characterized by using FTIR- spectroscopy and calculated as amounts per m2. If a relationship between SOM stabilization and pedogenetic parameters (pH, amorphous metal oxides, clay minerals) exists, the sustainability of afforestation to mitigate the greenhouse effect can be better assessed due to soil type stratification.