合成酸性雨処理が樹木の成育に及ぼす影響

抄録

Effects of simulated rain solutions of pH 1.6, 2.6, 3.6, 4.6, and deionized water (SO_4^<2->:NO_3^-=1: 1) on growth, dry weight increment, and ethylene production in seedlings of woody species were investigated. Application of the pH 1.6 solution to the shoot system of plants with a hand spray twice a week for 2 months significantly decreased the dry weight of needles of Larix leptolepis and leaves of Ulmus Davidiana seedlings. In Pinus densiflora seedlings dry weight of old needles was markedly reduced by the treatment with the pH 1.6 solution, whereas no effect was found in current needles. There was no noticeable symptom in seedlings of P. Thunbergii sprayed with the pH 1.6 solution. Treatment with other solutions had no significant effects on dry weight increament of all of these species. Application of the pH 1.6 solution to the soil surface for 3 months significantly decreased the biomass of potted Cryptomeria japonica and Chamaecyparis obtusa seedlings. Dry weight reduction was more drastic in seedlings planted in sand or decomposed granite than in andisol. Application of the pH 1.6 solution through the basal end of cuttings of L. leptolepis, C. japonica, and C. obtusa strongly enhanced ethylene production by needles.