Measurement of foliar H₂O₂ concentration can be an indicator of riparian vegetation management

Riparian vegetation is frequently exposed to abiotic stress, which generates reactive oxygen species (ROS) caused by strong differences in a river's hydrological conditions. Among different ROS, hydrogen peroxide (H₂O₂) is relatively steady and can be measured appropriately. Thus, the quantification of plant H₂O₂ can be used as a stress indicator for riparian vegetation management. The current study examines the spatial distribution of plants by riparian vegetation communities across the elevation gradient of riparian zones through quantification of environmental stress using foliar H₂O₂ concentration. The trees Salix spp., Robinia pseudoacacia, Ailanthus altissima with Juglans mandshurica, and the herbs Phragmites australis, Phragmites japonica, and Miscanthus sacchariflorus were selected for this study. Leaf tissues were collected to analyze H₂O₂ concentration, meanwhile riparian soil was sampled to measure total nitrogen (TN), total phosphorus (TP), and moisture content. The H₂O₂ concentration of tree species increased with higher soil moisture content, which was negatively correlated for Salix and herb spp., in which H₂O₂ concentration always decreased with high soil moisture. In this study, we found a unique significant interaction between soil moisture content and H₂O₂ concentration, both positively or negatively correlated relationships, when compared with other parameters, such as TN or TP concentrations or TN: TP in riparian soil. The species-specific distribution zones can be explained by the H₂O₂ concentration in the plant for gravelly and sandy channels on a theoretical range of soil moisture. Each species' H₂O₂ concentration was estimated through derived equations and is directly related to an elevation above the channel. The comparison with the observed distribution of plant elevations in the field indicated that all species showed a spatial distribution that acts as species-specific elevations where H₂O₂ concentrations stayed below 40 μmol/gFW. Hence, the present study suggests that foliar H₂O₂ concentration can be a useful benchmark for the distribution potentiality of riparian vegetation.