Trees (2004) 18: 677–685 DOI 10.1007/s00468-004-0350-y ORIGINAL ARTICLE Takeshi Izuta . Taeko Yamaoka . Tatsuro Nakaji . Tetsushi Yonekura . Masaaki Yokoyama . Ryo Funada . Takayoshi Koike . Tsumugu Totsuka Growth, net photosynthesis and leaf nutrient status of Fagus crenata seedlings grown in brown forest soil acidified with H 2 SO 4 or HNO 3 solution Received: 16 January 2004 / Accepted: 19 May 2004 / Published online: 31 July 2004 # Springer-Verlag 2004 Abstract To obtain basic information for evaluating critical loads of acid deposition for protecting Japanese beech forests, growth, net photosynthesis and leaf nutrient status of Fagus crenata seedlings grown for two growing seasons in brown forest soil acidified with H 2 SO 4 or HNO 3 solution were investigated. The whole-plant dry mass of the seedlings grown in the soil acidified by the addition of H 2 SO 4 or HNO 3 solution was significantly less than that of the seedlings grown in the control soil not supplemented with H + as H 2 SO 4 or HNO 3 solution. However, the degrees of reduction in the whole-plant dry mass and net photosynthetic rate of the seedlings grown in the soil acidified by the addition of H + as H 2 SO 4 solution at 100 mg l -1 on the basis of air-dried soil volume (S-100 treatment) were greater than those of the seedlings grown in the soil acidified by the addition of H + as HNO 3 solution at 100 mg l -1 (N-100 treatment). The concentra- tions of Al and Mn in the leaves of the seedlings grown in the S-100 treatment were significantly higher than those in the N-100 treatment. A positive correlation was obtained between the molar ratio of (Ca+Mg+K)/(Al+Mn) in the soil solution and the relative whole-plant dry mass of the seedlings grown in the acidified soils to that of the seedlings grown in the control soil. Based on the results, we concluded that the negative effects of soil acidification due to sulfate deposition are greater than those of soil acidification due to nitrate deposition on growth, net photosynthesis and leaf nutrient status of F. crenata, and that the molar ratio of (Ca+Mg+K)/(Al+Mn) in soil solution is a suitable soil parameter for evaluating critical loads of acid deposition in efforts to protect F. crenata forests in Japan. Keywords Fagus crenata . Soil acidification . Growth . Net photosynthesis . Leaf nutrient status Introduction Fagus crenata is the most widely distributed broad-leaved deciduous tree species in cool temperate forests in Japan. For example, virgin natural forests of F. crenata at the Shirakami Mountains, which are located in northeast Japan, were registered by UNESCO as a World Natural Heritage in December 1993. However, forest decline and dieback of F. crenata have recently been observed at several mountainous areas such as the Tanzawa Mountains in central Japan (Totsuka et al. 1997; Maruta et al. 1999). It has been suggested that acid deposition and gaseous air T. Izuta (*) . R. Funada Tokyo University of Agriculture and Technology, Institute of Symbiotic Science and Technology, Fuchu, Tokyo 183-8509, Japan e-mail: izuta@cc.tuat.ac.jp Tel.: +81-42-3675728 Fax: +81-42-3675728 T. Yamaoka Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan T. Nakaji Center for Global Environmental Research, National Institute for Environmental Studies, Tsukuba Ibaraki 305-8506, Japan T. Yonekura Center for Environmental Science in Saitama, Environmental Biology Group, Kitasaitama-gun, Saitama 347-0115, Japan M. Yokoyama Application Center, Horiba Ltd, Higashi-Kanda, Chiyoda, Tokyo 101-0031, Japan T. Koike FSC, Hokkaido University Forests, Sapporo 060-8589, Japan T. Totsuka Acid Deposition and Oxidant Research Center, Sowa, Niigata 950-2144, Japan