Study on weathering that alleviate soil acidification due to atmospheric nitrogen deposition

大气氮沉降导致土壤酸化，但土壤具有各种酸缓冲反应。我们的目的是研究的贡献，风化和供应的盐基阳离子，由于凋落物分解的基础上的氮动态变化，酸的生产，和缓冲反应，由于收割下的日本雪松（柳杉）林下植被。林下植被收割后对氮素和水分的吸收减少。土壤温度的升高（收割区比未收割区高2℃左右）影响了土壤有机氮的矿化和随后的硝化作用。这也是氮淋失增加的原因。此外，土壤温度的升高增加了0层（枯落物层）溶解性有机碳的供应，也影响了土壤的矿化和硝化活性，氮素淋溶的增加使氮素转化产生的产酸量增加。这种酸的产生具有最高的相关系数之间的硅动员和其解释因素。锶同位素比值（~ 1 <87>Sr /~ 1 <86>Sr）与二氧化硅浓度呈负相关。由于矿物具有较低的^<87>Sr/^<86>Sr，与降雨和植物或土壤相比，风化应有助于酸缓冲反应。并对提取物进行了<87>Sr/Sr<86>比值分析，以测定O层中全钙和交换性钙的含量。从Oi层（未分解的凋落物）到Oe层（腐殖化的凋落物），这一比例逐渐增加。说明凋落物中交换性钙的增加与凋落物重量的减少不仅是由非交换性钙转化而来的，也是由降雨中钙的转化所致。由于0层钙的供应缓解了土壤酸化，我们应该尝试研究风化与钙供应的关系。

Atmospheric nitrogen deposition causes soil acidification but soils have various acid buffer reactions. We aimed to examine contribution of weathering and supplies of base cations owing to litter decomposition based on changes in nitrogen dynamics, acid production, and buffering reaction due to reaping understory vegetation under Japanese cedar (Cryptomeria japonica). Reaping understory vegetation decreased in uptake of nitrogen and water. Increase in soil temperature owing to reaping (about 2℃ higher in reaping area than in un-reaping area) affected on activities of mineralization of organic nitrogen and subsequent nitrification. This was also a cause of increases in nitrogen leaching. In addition, increase in supplies of dissolved organic carbon from 0 horizon(Litter layer)due to increase in soil temperature also affected on activities of mineralization and nitrification.Increases in nitrogen leaching made increase in acid production due to nitrogen transformation. This acid production had the highest correlation coefficient between silica mobilization and its explanatory factors. Strontium isotope ratio (^<87>Sr /^<86>Sr) was negatively proportional to silica concentration. Since minerals have lower^<87>Sr/^<86> Sr, compared rainfall and plants or soils, weathering should contribute to acid buffering reaction. We also analyzed^<87>Sr/^<86>Sr of extracts, which analysis for total and exchangeable calcium (Ca) contents in O horizon. The ratio increased from Oi horizon (not decomposed litters) to Oe horizon (humified litters). It suggested that increase in exchangeable Ca in litter accompanied with decrease in litter weight would be ascribed to not only transformation from non-exchangeable form but to Ca in rainfall. Since supplies of calcium from 0 horizon alleviate soil acidification, we should try to examine relationship between weathering and supplies of Ca.