Mechanism of the declining process of forest caused by the deposition of acid fog on forest canopies and the regeneration of the forest.

在小山山的山坡上，经常形成雾，并且由于NOx形成的硝酸，雾水的pH值较低。LWC低时雾组分浓度高，每年约有20%的雾期出现雾水pH值低于3.5的酸雾事件。结果表明，雾对穿透雨的贡献随高度的增加而增加，雾的沉降主要取决于雾的形成频率和雾滴的沉降速率，而雾滴的沉降速率取决于风速。通过雾滴沉积的氢离子与叶片细胞中的金属离子进行交换，穿透雨中的金属离子，钙，镁和钾离子的浓度对于淋溶是大的。为明确酸雾对杉木和山毛榉幼苗的影响，采用移动的雾室，用硝酸、硫酸铵、氯化钠按2：1：1的摩尔比配制成pH为3和pH为5的模拟酸雾（SAF）处理杉木和山毛榉幼苗。在pH3条件下，SAF处理的幼苗在株高、茎粗、叶片数和干物质生产方面的生长都有所降低。此外，在生长期暴露于pH 3的SAF可诱导叶片提前脱落，脱落率比对照高出近2倍。室内模拟酸雾处理的试验结果也表明，金属离子的淋溶量较大，且淋溶量随模拟酸雾溶液pH值的降低而增加。无论是野外观察还是室内试验都表明，酸沉降对树木的影响很大。

In the mountain slope of Mt.Oyama, fog is frequently formed and pH of fogwater is low for nitric acid formed from NOx. The concentration of fog components becomes high when LWC is low, and acid fog events with fog water pH lower than 3.5 occurs for about 20% of fog duration there every year. It has been observed that the throughfall amount increased with the altitude for the contribution of fog, and the fog deposition may be dominated by the fog formation frequency and the deposition rate of fog droplets depending on the wind velocity. Deposited hydrogen ion via fog droplets is exchanged with metal ions in the cells in the leaves, and the concentrations of metal ions, calcium, magnesium, and potassium ions, in the throughfall is large for the leaching. In order to clarify the influence of acid fog on fir and beech, their seedlings were treated with simulated acid fog (SAF) at pH 3 and pH 5 prepared with a mixed solution of nitric acid, ammonium sulfate, sodium chloride with a molar ratio of 2:1:1 in a mobile fog chamber. The growth of the seedlings treated with the SAF at pH 3 had been reduced in plant height, stem diameter, the number of leaves, and dry matter production. Furthermore, the exposure to the SAF at pH 3 during growth phase induced early falling of leaves, and the falling rate were nearly 2 times greater than that at control. The laboratory experiment of the application of the simulated acid fog on their leaves also showed a large leaching of metal ions, and the leaching amount increased with the decreasing pH of the simulated fog solution. Not only the field observation but also laboratory experiments show the large effect of acid depositions on the trees.