Production of Reactive Oxygen Species and Its Role in Mediating the Abiotic Transformation of Organic Carbon in Sandy Soil under Vegetation Restoration

The significant impact of vegetation restoration on the turnover of organic carbon (OC) is mainly attributed to biological processes. However, the contribution of abiotic processes associated with reactive oxygen species (ROS) during vegetation restoration has remained largely overlooked. Therefore, we systematically explored ROS distribution and production mechanisms in sandy soil and their corresponding effects on OC oxidation through field monitoring and incubation experiments. The cumulative concentrations of hydroxyl radicals ( • OH) produced within 24 h varied in different soils undergoing vegetation restoration, ranging from 2.36 to 22.05 μmol kg ‒1 , which were derived from the Fenton-like reaction of hydrogen peroxide (H 2 O 2 ) and biotic-induced Fe(II). In addition, during the oxidation of reductive SOC, H 2 O 2 can be formed and react with Fe(II) to generate • OH. Further, • OH significantly induced the abiotic transformation of OC, accounting for 15.93%‒25.80% of carbon dioxide (CO 2 ) efflux. Specifically, 1 mol • OH can induce the production of 0.01–0.02 mol CO 2 for particulate organic carbon (POC) and 0.03‒0.23 mol CO 2 for mineral-associated organic carbon (MOC), as demonstrated by chemical quenching and sterilisation experiments. This indicated that MOC was more sensitive to • OH attacks. Collectively, our findings provide insights into the accumulation of ROS in sandy soils during vegetation restoration, with • OH playing a key role in SOC oxidation, as well as the patterns of SOC turnover and its response to changes in the soil environment. Graphical Abstract