Reactive oxygen species in paddy rice systems: Links with environmental parameters and soil microbial communities

Reactive oxygen species (ROS) play crucial yet poorly understood roles in biogeochemical processes within paddy rice systems. A microcosm experiment was conducted to determine the factors that affect the formation of ROS (particularly hydrogen peroxide and hydroxyl radical) in the overlying water and soil-water interface and establish the relationships between the ROS and the soil microbial communities. The results showed that the production of ROS was a result of interaction between biotic and abiotic processes. Rainfall and solar radiation were the most important factors that control the concentration of ROS in the overlying water, while pH, Eh, DOC and Fe (II) played more important roles in regulating ROS production at the soil-water interface. In a cycle of pre-rainfall/rainfall/post-rainfall, the generation rate of ROS was highest during the rainfall phase, followed by the post-rainfall phase, and was lowest during the pre-rainfall phase. Furthermore, microbial analysis showed H₂O₂ positively correlated with Methylomirabilota and Obertrumia but negatively with Desulfobacca; ^·OH was positively linked to Ohtaekwangia and negatively to Nitzschia, with bacteria responding more strongly than eukaryotes. These findings elucidate the coupled abiotic-biotic mechanisms and multi-interface processes driving ROS dynamics, crucial for understanding biogeochemical cycling in agricultural watersheds.