This manuscript consists of 21-typed pages including figure legends, 1 table and 3 figures. Takahashi et al. 2 To show what climatic conditions affect the growth of tree species in the upper and lower distribution limits of an altitudinal ecotone, tree-ring width chronologies were developed for Abies veitchii, Betula ermanii and Betula platyphylla var. japonica in their altitudinal ecotone (about 1600 m above sea level) on Mt. Norikura, central Japan.This altitude was the lower distribution limit for A. veitchii and B. ermanii in the subalpine zone, and was the upper distribution limit for B. platyphylla var. japonica in the montane zone on Mt. Norikura. The tree-ring widths of the two Betula species and A. veitchii were positively correlated with the August precipitation of the current year and that of the previous year, respectively. Precipitation in the hottest month of August was less compared with other months during summer. The tree-ring width of B. platyphylla var. japonica showed no correlation with temperatures of any month in its upper distribution limit. In contrast, the tree-ring widths of B. ermanii and A. veitchii were negatively correlated with the August temperatures of the current year and of the previous year, respectively, in the lower distribution limit of these species. Therefore, the two Betula species and A. veitchii responded to climatic conditions of the current year and those of the previous year, respectively. This study also suggests that water deficit in August reduces the growth of the three species in this altitudinal ecotone, irrespective of the upper or lower distribution limit, and that a high August temperature is more detrimental to the growth of A. veitchii and B. ermanii in their lower distribution limit. Thus, the examined three species with different altitudinal distributions differently responded to climatic conditions in this altitudinal ecotone on Mt. Norikura.