Effects of atmospheric nitrogen deposition on nutrient balances in forest ecosystems

青森市七野河地区氮沉降超过10 kg N ha^<-1> yr^<-1>。然而，没有出现氮饱和的症状。本研究旨在探讨大气沉降对杉木林分氮动态和其他元素收支的影响。夏季东南或南风吹时，开放性降水引起的铵态降水输入量增加。夏季林冠对氮的吸收量增加。这表明日本雪松林缺乏氮，因此大气氮沉降可能会促进森林生长。氮素转化产生的酸性影响土壤剖面总产酸量。产生的酸度被阳离子交换和/或风化所消耗。凋落物层钙离子供给量超过10 cm深度的淋失量。杉木针叶中含有大量的钙，有助于钙离子的供给和积累。因此，该杉木林土壤酸化程度较低。此外，凋落物分解速率较低时，碱阳离子在凋落物层中积累较多。在高分解速率下，碱性阳离子在土壤剖面中积累。凋落物层不仅影响碱性阳离子的积累，而且影响渗透水量。凋落物层的物理性质对估算森林生态系统的养分收支具有重要意义。

Nitrogen deposition exceeded 10 kg N ha^<-1> yr^<-1> at Shichinohe in Aomori. Nevertheless, there were no symptoms of nitrogen saturation. The aim of this study was to examine the effects of atmospheric deposition on nitrogen dynamics and budget of other elements in Japanese cedar (Cryptomeria japonica) stands.Ammonium input owing to open bulk precipitation increased in summer when wind blew from southeast or south. Uptake of nitrogen in the canopy increased in summer. This suggests that Japanese cedar stands are deficient in nitrogen and atmospheric nitrogen deposition is therefore likely to increase forest growth.Production of acidity due to nitrogen transformation affected on the total acid production in soil profile. Produced acidity was consumed by cation exchange and/or weathering. Calcium ion supply from litter layer exceeded leaching from the depth of 10 cm. Japanese cedar needle contained large amounts of calcium contributed to supply and accumulation of calcium ion. Therefore, it was concluded that serious soil acidification scarely arise in this Japanese cedar stands. In addition, base cations were accumulated in litter layers when litter decomposition rate was low. Incase of high decomposition rate, base cations were accumulated in soil profile. Litter layer affected not only on base cation accumulation, but also on percolated water amounts. Physical properties of litter layer are important to estimate nutrient budget in forest ecosystems.