Ecophysiological difference in co-existing beech and oak saplings grown in different soil types under a free-air ozone exposure system

Abstract

ABSTRACT To know effects of elevated ozone (eO3) response to beech (Fagus crenata) and oak (Quercus mongolica var. crispula) saplings, focusing on shoot elongation and leaf nutrient characteristics, beech and oak were grown in a free-air ozone-enrichment system (concentration: 35 ppb (aO3) vs. 75 ppb (eO3)) for two years under different soils (volcanic ash soil vs. brown forest soil). This treatment resulted in lower O3 tolerance in beech than in oak. The ratio of 2nd shoot flush showed a characteristic response to eO3 fumigation in beech and oak. For beech, the ratio was less than 0.5, while for oak, it ranged between 0.4 and 0.6. There was no difference in the photosynthetic rate of oak, although the photosynthetic rate of beech was slightly lower under elevated O3. Principal component analysis provided a good summary of the traits of beech and oak in response to O3 enrichment and soil combination, with O3-enriched beech characterized by higher Ca and lower N, P, K and A max in the 1st component and lower Mg and Mn in the 2nd component. O3 -treated oak in O3-enriched brown forest soils was characterized by high N, P, K and A max, while the influence of the 2nd component was small. Increased soil acidification will increase soil Mn and Al concentrations and may reduce the photosynthetic activity of beech saplings in eO3.