To assess ozone sensitivity of subtropical broadleaved tree species and explore possible underlying mechanisms, six evergreen and two deciduous native species were exposed to either charcoal-filtered air or elevated O₃ (E-O₃, ∼150ppb) for one growing season. Initial visible symptoms in deciduous species appeared much earlier than those in evergreen species. The species which first showed visible symptoms also had the largest reductions in biomass. E-O₃ induced significant decreases in photosynthesis rate, chlorophyll content and antioxidant capacity but a significant increase in malondialdehyde content in two deciduous species and two evergreen species (Cinnamomum camphora and Cyclobalanopsis glauca). Except C. glauca, however, E-O₃ had no significant effects on stomatal conductance (gₛ), total phenols and ascorbate contents. Difference in O₃ sensitivity among all species was strongly attributed to specific leaf mass rather than gₛ. It suggests that some subtropical tree species will be threatened by rising O₃ concentrations in the near future.

Foliar δ³⁴S values of three soil-growing plant species (Platanus Orientalis L., Osmanthus fragrans L. and Cinnamomum camphora) have been analyzed to indicate atmospheric sulfur. The foliar δ³⁴S values of the three plant species averaged −3.11±1.94‰, similar to those of both soil sulfur (−3.73±1.04‰) and rainwater sulfate (−3.07±2.74‰). This may indicate that little isotopic fractionation had taken place in the process of sulfur uptake by root or leaves. The δ³⁴S values changed little in the transition from mature leaves to old/senescing leaves for both the plane tree and the osmanthus tree, suggestive of little isotope effect during sulfur redistribution in plant tissues. Significantly linear correlation between δ³⁴S values of leaves and rainwater sulfate for the plane and osmanthus trees allowed the tracing of temporal variations of atmospheric sulfur by means of foliar sulfur isotope, while foliage δ³⁴S values of the camphor is not an effective indicator of atmospheric sulfur.