Connectivity and Soil Carbon Stabilization.

Old organic matter may contain microbial polysaccharides and proteins, indicating that chemically labile organic matter can persist for long times in soils. This observation is often explained by matrix protection through sorptive interactions and reduced accessibility, but recent investigations suggest that significant quantities of organic material in soil may persist in spite of being chemically labile, unprotected, accessible and thus generally decomposable. This observation transforms microbial decomposition from a problem of ‘overcoming the intrinsic molecular defenses of a substrate’ to the fundamentally different problem of ‘optimizing the operating conditions of the soil bioreactor for a certain substrate’. In the former scenario, the material properties of the substrate ( i.e., its "recalcitrance") are considered to be the dominant obstacle to decomposition, in the latter, soil organic matter is seen as a reservoir of reduced carbon whose decomposition is inevitable but retarded by elements of connectivity: the site-specific logistical framework that determines the efficiency of the decomposer community.