Studied on the diffusion of acid fallout and the succession of urban forest in Kyoto City

本研究旨在厘清京都市降雨特征，厘清都市森林林分结构与动态。为了实现这一目标，我们收集了京都市内各处的降雨，并在关西地区的4个点使用了商业销售的酸雨收集器。我们调查了1980年以来建立的次生林的永久地块，这些次生林位于距离京都城区20公里的北部，在降雨开始时处处都是3级。随着时间的推移，pH逐渐升高，EC逐渐降低。高山深处pH值最高，EC值最低。工业区后面的森林pH值较低，EC值较高，但与京都市相比，pH值和EC值随时间的变化不大。京都市北部和东部pH值较高。虽然镇中心区域EC较高，但总体pH值不低，但在高速公路附近pH值最低，EC值最高。在pH值较低的地区，通过提高NO_3^-的速率可以使雨酸化，而在中心地区，通过提高NH_4^+的速率可以使雨中和。在该地区常见于木栗和蒙古栎混交林的下层树种减少，现在上层需光树种也逐渐减少。

The purpose of this study is to clear the characteristic of rainfall in Kyoto City and to clear the stand structure and the dynamics of urban forests. To achieve this object, we collected the rainfall here and there in Kyoto City, and besides at 4 points in Kansai District using commercially sold acid rain collector. And we investigated at the permanent plots of the secondary stand which were established from 1980 locating in the northern part about 20 km distant from the town area of Kyoto CitypH at the beginning of rain was 3 level everywhere. And pH was increasing and EC was decreasing gradually in the progress of time. pH was the highest and EC was the lowest in the depths of mountain. pH was lower and EC was higher in the forest behind a industrial area, and there pH and EC hardly changed in the progress of time as compared with Kyoto City.In Kyoto City pH was higher in northern and eastern parts. Though in center of the town area EC was higher, pH were not so low generally, but pH was the lowest and EC was the highest near the highway. And it was expected that the rain was acidified by increasing of the rate of NO_3^- in pH lower area, but it may well be neutralized by increasing of the rate of NH_4^+ in centerThe investigated forests were consisted of many types stands. In mixed stands of Castanea crenata and Quercus mongolica var. grosseserrata where we could see frequently in this area the species in the lower story decreased and now the species of the light demanding tree were decreasing in the upper story gradually, too.