Effects of Elevated Ozone Concentrations on Root Characteristics and Soil Properties of Elaeocarpus sylvestris and Michelia chapensis.

The increasing concentration of surface ozone (O) was observed during recent decades in the world, which affects tree roots and forest soils. Meanwhile, the impact of ozone on tree roots is greatly affected by soil condition. However, there is a lack of knowledge about the possible effects of ozone on tree roots and soil processes. In this study, The influences of surface ozone (O) stress on the root biomass, morphology, nutrients, soil properties, and soil enzyme activity of Elaeocarpus sylvestris and Michelia chapensis seedlings were examined at four O concentrations (charcoal-filtered air, 1 × O air, 2 × O air, and 4 × O air). Elevated O concentrations were found to significantly increase the root C content, N content, C/P ratio, and N/P ratio, and significantly decrease the root biomass, number of root tips, and root C/N ratio of both species. The soil organic matter content, pH, total N content, and urease and catalase activities of both species tended to increase. The limitation in root growth and responses in the root structure of E. sylvestris induced by elevated O concentrations led to increased bulk density and decreased soil porosity and void ratio. These profound effects of O concentrations on the roots and soil characteristics of these two species underscore the importance of research in O science.