Leaf defense traits of birch, beech, and oak saplings grown under two types of soil in a free-air ozone exposure system

Abstract

ABSTRACT Since most leaf defense traits are derived from photosynthates, the increase of feeding damage in woody plants can be partially attributed to the recent increase in ground-surface O3 (elevated O3; eO3), which has suppressed the photosynthetic capacity of the plants. In different soil fertility conditions (fertile brown forest soil or infertile volcanic ash soil), we made research on leaf defense traits of the three species; birch (an early successional species), beech (a late successional species), and oak (an intermediate species). The results showed that except for lignin, the defensive capacity of birch leaves was reduced by eO3 as well as by a fertile soil condition. In beech as an O3-sensitive species, C/N was slightly higher in fertile soil; especially total phenolics and lignin concentrations, but increased with eO3. Therefore, carbon-nutrient balance hypothesis was not applicable in beech, which may be due to a different nutrient translocation system from birch and other trees. Oak, an O3-tolerant species, was less affected by eO3 and soil condition; C/N slightly tended to increase with eO3 due to a decrease in N. In addition, total phenolics of oak leaves tended to decrease by eO3 in infertile soil. From these results, O3 tolerance, which differs among tree species, can lead to new and altered plant-insect relationships through impact on defense functions, which can also lead to new relationships in biodiversity.