Wenting Fenga Alain F. Plantea 
Anthony K. Aufdenkampeb Johan Sixc. Soil organic matter stability in organo-mineral complexes as a function of increasing C loading. Soil Biology and Biochemistry Volume 69 February 2014 Pages 398–405
Abstract
Soil carbon (C) saturation behavior predicts that soil C storage efficiency observed under field conditions decreases as a soil approaches C saturation. This may be due to a decline in soil organic matter (SOM) stability as the result of changes in the type strength or turnover time of organo-mineral interactions with increasing organic C input. The goal of this study was to test whether the stability of organic matter bound to soil minerals decreases as organo-mineral complexes approach C saturation with increasing C loading. A series of batch sorption experiments with natural dissolved organic matter (DOM) and soil mineral components was conducted to obtain organo-mineral complexes with a range of organic C loadings. The relative stability of C in these organo-mineral complexes was subsequently assessed using evolved CO2 gas analysis during thermal analyses and laboratory incubations. Results indicated that differences in dissolved organic C before and after sorption overestimated the amount of sorbed C when compared to differences in solid-phase C concentrations. Values of C-N δ13C and δ15N of the organo-mineral complexes were significantly smaller or more negative than initial soil samples or the stock DOM solution consistent with the concept of molecular fractionation by sorption to minerals and suggesting that the composition of the organic matter in the organo-mineral complexe
