Combined Effects of Ozone and Other Environmental Factors on Japanese Trees

Abstract

Plant responses to ozone (O3) are highly dependent on other environmental factors. Elevated atmospheric CO2 concentrations may reduce stomatal O3 uptake in some tree species in certain environmental conditions. In addition, changes in the carbon availability and allocation pattern within a plant body under elevated CO2 may confer compensative capacity against O3 stress. The influence of the soil nitrogen load on growth and photosynthetic response to O3 is highly species-specific. The soil nitrogen load enhanced the negative impact of O3 on Fagus crenata, whereas lower O3-induced growth reduction of Larix kaempferi was observed under a higher nitrogen load. It is predicted that soil-water stress would induce lower stomatal O3 uptake due to stomatal closure, and therefore the negative impacts of O3 on trees would decrease under water-stress conditions. In fact, some antagonistic effects of O3 and soil water stress were observed in F. crenata, although these effects may depend on the severity of the water stress. The number of studies on the combined effects of O3 and other environmental factors on Japanese forest tree species is limited and further research is crucial to accumulate the required datasets.