Leaf stoichiometry of deciduous tree species in different soils exposed to free-air O3 enrichment over two growing seasons

The effects of elevated O3 in different soil conditions on foliar elements stoichiometry were investigated in 3 native tree species with a free-air enrichment system in northern Japan over two growing seasons. Essential elements (Mg, K, Ca, Mn, Fe, Ni, P, N) and two non-essential elements (Cr, Al) were analyzed in leaf samples obtained from 6 different treatments of O3 and soils at 5 collection times from 2014 to 2015. In this study, relationships among the foliar elements within each species were investigated and negative correlations between foliar N and the metal elements were observed in birch (Betula platyphylla var. japonica). From the differences of foliar contents as well as their retranslocation rate, beech (Fagus crenata) with determinate shoot growth pattern were rather more sensitive to O3 stress on foliar contents, meanwhile oak (Quercus mongolica var. crispula) was possibly susceptible to O3 on dynamics of immobile elements. Soil nutrients have distinct impacts on retranslocation rate of K, Fe, and P. Principal component analysis revealed that Mn and K can become indices in assessing the O3 and soil effects in both short and long term monitoring of the growth of these tree species. Our findings are essential in further comprehension to nutrient conservation mechanism in the nutrient dynamics of cool-temperate forests.