Changes of microbial residues after wetland cultivation and restoration

A potentially important factor for destabilization of soil organic C (SOC) in the conversion of ecosystems to arable land is the impact to microbial residues, which have been recently shown to be a significant source of SOC pool. Here, we present the results of a study investigating the changes of microbial residues along a chronosequence of cultivation (5, 15, and 25 years) and attempted restoration (6 and 12 years of agricultural abandonment) in a marsh wetland of China. The wetland cultivation depleted the fraction of SOC derived from microbes, in particular fungal residues. During agricultural abandonment and restoration, bacterial residues accumulated relatively more rapidly than fungal analogs, where fungal residues represented the major microbial SOC pool overall. These differential responses of microbial residues are illustrative of the susceptibility of this SOC pool and indicate their importance as a tool to track soil stability with land-use change. Our work points to the need for future research to focus more strongly on the nature and mechanisms of microbial residue-mediated C process during chronic land-use changes.