酸性沉降物包括干沉降物和湿沉降物，日本把ｐＨ值低于５．６的降水称为酸性降水。近年来，日本降雨的ｐＨ值为３．８０～５．５０。酸性沉降对森林生态系统的物质循环会产生一定的影响。人工模拟酸雨实验结果表明，ｐＨ值低于４时可减少杉木苗细根伸长和个体生长，而日本酸雨ｐＨ值多为４以上，可见酸雨直接造成杉木苗枯萎的可能性并不大，但酸雾的危害不可忽视；酸性沉降物与臭氧的协同作用越来越引起人们的关注。酸性沉降不仅对林木生长产生直接影响，而且通过土壤还对林木产生间接影响。对土壤酸化作为森林衰退可能原因之一也开展了深入研究，但目前有关森林衰退原因仍未得出一个肯定的结论 Acidic sediments include dry sediments and wet sediments. Japan calls precipitation with pH below 5.6 for acid precipitation. In recent years, Japan’s rainfall of pH 3.80 ~ 5.50. Acid deposition has a certain impact on the material circulation of forest ecosystems. The results of artificial simulated acid rain experiment showed that when the pH value was lower than 4, the fine root elongation and individual growth of Chinese fir seedling could be reduced. However, the pH value of Japanese acid rain was more than 4, which indicated that the acid rain might not directly cause the seedling wilt. The harm of acid mist can not be ignored; the synergistic effect of acid deposition and ozone has drawn more and more attention. Acidic sedimentation not only has a direct impact on the growth of trees, but also affects the trees indirectly through soils. In-depth studies have also been conducted on soil acidification as one of the possible causes of forest decline, but at present there is still no conclusive conclusion as to the causes of forest decline