LB 38-318 - Mineral protection controls the stabilization of microbially-derived carbon and nitrogen in soil organic matter

Evidence is emerging that microbial production and residues (necromass) contribute greatly to stable soil organic matter (SOM), which calls for the necessity of separating the microbial necromass from other SOM pools in models. However, the understanding on how microbial necromass stabilizes in soil, especially the mineral protection mechanisms, is still lacking. In this study, we incubated 13C and 15N labelled microbial necromass in a serial of artificial soils varying in clay minerals ((kaolinite, illite, and montmorillonite) and metal oxides (goethite, gibbsite, and birnessite). We found the decomposition rate, adsorption, and desorption rates of necromass nitrogen were all higher than those of necromass carbon. The accumulation rates of necromass carbon and nitrogen in mineral-associated SOM was positively correlated with higher special areas of minerals. In conclusion, our results provide direct evidence for the effects of mineral protection on microbial necromass stabilization and a platform for simulating microbial necromass separately in SOM models.