2019 Volume 75 Issue 1 Pages 39-46
Ozone (O3) is an air pollutant that negatively affect carbon budget in woody plants. In the present study, we aimed to clarify the effects of ozone on soil respiration rate of Siebold’s beech seedlings (Fagus crenata) grown under different soil-nutrient conditions. Seedlings were grown under three levels of O3 fumigation (charcoal-filtered air or O3 at 1.0 or 1.5 times ambient concentration) in combination with three levels of nutrient supplies (non-, low- or high-fertilised) for two growing seasons. We determined soil respiration rate in July, August, September, and October of the second growing season. The seedlings were harvested to determine the dry mass in October. Significant effect of O3 on soil respiration rate was not observed in all measurements. There was a significant interaction between O3 and nutrient supply for whole-root dry mass. The dry mass in non-fertilised and low-fertilised treatments was reduced by O3, whereas O3 did not affect dry mass in the high-fertilised treatment. On the other hand, neither significant effects of O3, nor a significant interaction between O3 and nutrient supply for the biomass allocations were observed. Coefficient of positive correlation in the relation of soil respiration rate with dry mass of fine-root across the all treatments was higher than that in the relation of soil respiration rate with coarse-root and whole-root dry mass. These results indicate that no significant effect of O3 on soil respiration was mainly attributable to no response of fine root dry mass to elevated O3. Soil nutrient supply decreased soil respiration rate in August. Our results emphasize the importance of fine root in the response of soil respiration to elevated O3. To clarify the response of soil respiration to elevated O3, future researches on the effect of O3 on fine root dynamics including turnover and indirect effect on soil microbial respiration are needed.
