Nutrient supply to soil offsets the ozone-induced growth reduction in Fagus crenata seedlings

Abstract

Ozone-induced reduction in the whole-plant dry mass of high-fertilised Fagus crenata seedlings was offset by the increase in leaf area, although the exposure to ozone decreased net photosynthetic rate. To clarify the effects of ozone (O3) on the growth of Fagus crenata seedlings under different soil nutrient conditions, seedlings were grown for two growing seasons under nine treatments comprised of a combination of three levels of gas treatments (charcoal-filtered air or O3 at 1.0 or 1.5 times ambient concentration), with three levels of soil nutrient treatments (non-fertilised or a supply of relatively low or high concentrations of compound fertiliser). Significant interactive effects of O3 and nutrient supply to soil on net photosynthetic rate, area of first-flush leaves, and the whole-plant dry mass were detected during the second growing season. The O3-induced reduction in dry mass was observed in the non- and low-fertilised seedlings, but not in the high-fertilised seedlings. However, the extent of O3-induced reduction in net photosynthetic rate was higher in the low- and high-fertilised seedlings than in the non-fertilised seedlings. Although the O3-induced reduction in the leaf area was detected in the non- and low-fertilised seedlings, leaf area of the high-fertilised seedlings tended to be increased by the exposure to O3. Therefore, O3-induced reduction in the whole-plant dry mass of the high-fertilised seedlings is considered to be offset by the O3-induced increase in the area of first-flush leaves during the second growing season. To accurately assess the effects of O3 on dry matter production of F. crenata, the modification of the sensitivity to O3 due to soil nutrient conditions must be taken into consideration.