Tropospheric ozone (O₃) is considered one of the most critical air pollutants in many parts of the world due to its detrimental effects on plants growth. However, the stoichiometric response of tree species to elevated ozone (O₃) is poorly documented. In order to understand the effects of elevated ozone on the stoichiometry and nutrient pools of Phoebe bournei (Hemsl.) Yang (P. bournei)and Phoebe zhennan S. Lee et F. N. Wei (P. zhennan), the present study examined the carbon (C), nitrogen (N), and phosphorous (P) concentrations, stoichiometric ratios, and stocks in foliar, stem, and root for P. bournei and P. zhennan with three ozone fumigation treatments (Ambient air, 100 ppb and 150 ppb). The results suggest that elevated ozone significantly increased the N concentrations in individual tissues for both of P. bournei and P. zhennan. On the contrary, elevated ozone decreased the C:N ratios in individual tissues for both of P. bournei and P. zhennan because the C concentration remained stable under the ozone stress. The P concentration, and C:P and N:P ratios in individual tissues for both P. bournei and P. zhennan did not exhibit consistent variation tendency with elevated ozone. Elevated ozone sharply reduced the total C, N, and P stocks and altered the pattern of C, N, and P allocation for both P. bournei and P. zhennan. The present study suggests that tropospheric ozone enrichment should be considered an important environmental factor on stoichiometry of tree species.

Although the underlying mechanisms remain unknown, soils from different forest types exhibit distinct acidification-buffering capacities. We investigated soil properties and bacterial communities across five plantation types and different soil horizons in a severely acid-polluted site in Southwest China and evaluated the potential mechanisms driving differences in community structure. Soils collected from pure stands of Pinus massoniana Lamb.or Schima superba Gardn. et Champ. or mixed stands of these species showed the lowest soil pH and greater abundances of acid-producing and acidophilic taxa (Halanaerobiales and Rhodospirillales). Soils from pure stands of Cinnamomum camphora (Linn) Presl, or a mixture of C. camphora and P. massoniana, yielded the greatest concentrations of exchangeable calcium (Ca) and magnesium (Mg) and greater soil pH. Increased relative abundances of beneficial taxa may have contributed to soil aggregate formation (e.g., Bradyrhizobium canariense and Terracidiphilus sp.) and heightened environmental stress resistance (e.g., Gaiellales). Fewer acid-producing and acidophilic taxa found in soils associated with C. camphora suggest that planting C. camphora may help soils recover from acidification, while planting S. superba may not be as beneficial. Our findings illustrate how differences in soil microbial communities may impact soil-acidification-buffering capacity across different forest types, which have important implications for understanding environmental functions within the context of microbial diversity.

There are very few studies about the effects of relatively higher CO₂ concentration (e.g., 1000 μmol·mol⁻¹) or plus N fertilization on woody plants. In this study, Schima superba seedings were exposed to ambient or eCO₂ (550, 750, and 1000 μmol·mol⁻¹) and N fertilization (0 and 10 g·m⁻²·yr⁻¹, hereafter: low N, high N, respectively) for one growth season to explore the potential responses in a subtropical site with low soil N availability. N fertilization strongly increased leaf mass-based N by 118.38%, 116.68%, 106.78%, and 138.95%, respectively, in different CO₂ treatments and decreased starch, with a half reduction in leaf C:N ratio. Leaf N was significantly decreased by eCO₂ in both low N and high N treatments, and N fertilization stimulated the decrease of leaf N and mitigated the increase of leaf C:N by eCO₂. In low N treatments, photosynthetic rate (Pn) was maximized at 733 μmol·mol⁻¹ CO₂ in August and September, while, in high N treatments, Pn was continuously increased with elevation of CO₂. N fertilization significantly increased plant biomass especially at highly elevated CO₂, although no response of biomass to eCO₂ alone. These findings indicated that N fertilization would modify the response of S. superba to eCO₂.

The resources (light, nitrogen and water) utilization efficiency of plant is a key indicator reflecting the adaptive ability of plant to environment. CO2 enrichment would increase photosynthesis substrate supply and nutrient absorption in plants，and may also change the utilization efficiencies of light (LUE), nitrogen (NUE) and water (WUE) and their trade-offs relationship. However, the knowledge regarding how the LUE, NUE and WUE of woody plant change in the context of CO2 enrichment is still weak. In order to understand the impacts of CO2 enrichment on the LUE, NUE and WUE of Schima superba and their trade-offs, one-year-old container seedlings of S. superba were grown with ambient air (AA treatment), 550 ppm of CO2 concentration (E1-CO2 treatment), 750 ppm of CO2 concentration ( E2-CO2 treatment) and 1000ppm of CO2 concentration (E3-CO2 treatment) using open top chambers. In the growing season, we regularly examined the net photosynthetic rate, stomatal conductance, transpiration rate, nitrogen concentration and photosynthetic pigment concentration of S. superba leaves. In addition, the different organ biomass, leaf area, soil nitrate and ammonium nitrogen concentrations were also simultaneously examined. The results demonstrate that three CO2 enrichment treatments significantly increased the LUE and NUE of S. superba leaves at the end of June, while the leaf nitrogen concentration and soil nitrate nitrogen significantly decreased under both the E2-CO2 and E3-CO2 treatments compared with those under the AA treatment. In contrast, only the E1-CO2 treatment significantly increased the LUE and NUE of S. superba leaves at the end of August. The NUE of S. superba leaves under both the E2-CO2 and E3-CO2 treatments were significantly higher than that under the AA treatment at the end of October. With regard to the WUE of S. superba leaves, there were no significant differences between the four treatments. At the end of October, the total biomass of S. superba under the E1-CO2 treatment was significantly higher than that under both the AA and E3-CO2 treatments, while the total biomass of S. superba under the AA treatment was not significantly different from that under both the E2-CO2 and E3-CO2treatments. During the experiment, the LUE, NUE, stomatal conductance, and transpiration rate of S. superba leaves were significantly and positively related to each other. The LUE also had a significantly positive correlation with specific leaf weight. Furthermore, the NUE was significantly and positively correlated with the total biomass and the ratio of underground and aboveground biomass. Meanwhile, the NUE was significantly and negatively correlated with the chlorophyll a concentration, chlorophyll b concentration, carotenoid concentration, leaf nitrogen concentration, soil ammonia nitrogen and nitrate nitrogen concentration. The WUE was significantly and negatively related to the stomatal conductance, transpiration rate and total biomass. CO2 enrichment may enhance both the LUE and NUE of S. superba seedlings, whereas the impacts of CO2 enrichment on the LUE and NUE of S. superba seedlings varied with time. S. superba seedlings would appear photosynthesis acclimation with the persistently high CO2 enrichment.