Abstract In order to clarify the deposition amounts and processes of bioavailable nitrogen species including organic forms on forests, a simultaneous observation of rainfall, throughfall, stemflow, aerosols, and their precursor gases was conducted for a two-year period at a forested site on the northern foot of Mt. Fuji in Japan. About 80–90% of the rainfall waters reached the forest floor via the throughfall process and the remaining fraction can be considered to be intercepted by the forest canopy and not transported to the forest floor. Partitioning of the rainfall waters into stemflow waters was negligible. Deposition amounts of the total dissolved nitrogen by rainfall, throughfall, and stemflow were 2.204, 2.685, and 0.027 mgN m−2 day−1, respectively, on average. Contributions of the water-soluble organic nitrogen (WSON) to the dissolved nitrogen in the rainfall, throughfall, and stemflow deposition were about 51%, 58%, and 75%, respectively. The major fraction of the nitrogen species in the deposition was the organic forms. Among the inorganic nitrogen, the contribution of NH4+-N to the nitrogen deposition was significantly greater than that of NO3−-N in the rainfall deposition, whereas both were comparable in the throughfall deposition. The deposition amounts of NO3−-N and WSON by throughfall were greater than those by rainfall due to the influence of the dry deposition on the canopies and the leaching from trees, whereas the deposition amount of NH4+-N by throughfall was smaller than that by rainfall due to the uptake by trees. About 58% of the net nitrogen deposition on the forest floor, which is defined as the sum of the deposition amounts by the throughfall and stemflow, was explained by the WSON. In the remaining inorganic fraction, the contributions of NO3−-N and NH4+-N to the net nitrogen deposition were comparable, about 20% and 22%, respectively. The nitrogen deposition amount to the forest floor was estimated to be 2.711 mg m−2 day−1, which is equal to the value of the threshold for the condition of “nitrogen saturation” for the forest ecosystems. The modified canopy budget model can estimate that the contributions of the dry deposition to the sum of the dry and wet deposition were about 90%, 64%, 61%, and 22% for NO2−-N, NO3−-N, NH4+-N, and WSON, respectively. The canopy leaching was found only for the WSON, about 72%, 20%, and 8.5% of the net deposition of the WSON can be explained by the wet deposition, dry deposition, and canopy leaching, respectively. The remaining nitrogen compounds showed the canopy uptake. About 10%, 56% and 32% of NO2−-N, NO3−-N, and NH4+-N deposited on the canopy by the wet and dry processes would be transported to the forest floor and the remaining fractions (about 90%, 44%, and 68%, respectively) would be taken into the canopy. Comparisons of the dry deposition amount with the concentration in the surface atmosphere of the nitrogen compounds suggest that the modified canopy budget model can be considered to be better to estimate the amounts of the dry deposition and canopy exchange.

中文翻译：

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珠穆朗玛峰北麓红松林有机和无机氮沉积。日本富士

摘要 为了阐明包括有机形态在内的生物可利用氮物种在森林中的沉积量和沉积过程，在森林覆盖的林地进行了为期两年的降雨、穿透、茎流、气溶胶及其前体气体的同步观测。富士山北麓 日本富士。大约 80-90% 的降雨水通过直落过程到达森林地表，其余部分可以认为被森林冠层截留而没有输送到森林地表。将降雨水划分为茎流水是可以忽略不计的。降雨、贯流和茎流造成的总溶解氮沉积量平均分别为 2.204、2.685 和 0.027 mgN m-2 day-1。水溶性有机氮（WSON）对降雨、贯流和茎流沉积中溶解氮的贡献分别约为51%、58%和75%。沉积物中氮物质的主要部分是有机形式。在无机氮中，降雨沉降中NH4+-N对氮沉降的贡献显着大于NO3--N，而在直通沉降中两者相当。受树冠干沉降和树木淋失的影响，通过降雨对NO3--N和WSON的沉积量大于降雨，而通过降雨对NH4+-N的沉积量小于降雨。由于树木吸收的降雨。大约 58% 的森林地面净氮沉积，WSON 解释了它被定义为通过流量和茎流的沉积量的总和。在剩余的无机部分中，NO3--N 和 NH4+-N 对净氮沉积的贡献相当，分别约为 20% 和 22%。森林地面的氮沉降量估计为2.711 mg m-2 day-1，这等于森林生态系统“氮饱和”条件的阈值。修正的冠层预算模型可以估计干沉降对干湿沉降总和的贡献分别为 NO2--N、NO3--N、NH4+-的 90%、64%、61%和 22% N 和 WSON，分别。仅在 WSON 中发现了冠层浸出，大约 72%、20% 和 8.5% 的 WSON 净沉积可以解释为湿沉积、干沉积、和树冠浸出，分别。剩余的氮化合物显示了冠层吸收。大约 10%、56% 和 32% 的 NO2--N、NO3--N 和 NH4+-N 通过湿和干过程沉积在树冠上，将被输送到森林地面，其余部分（大约 90%、分别为 44% 和 68%）将被带入树冠。干沉降量与地表大气中氮化合物浓度的比较表明，修正的冠层收支模型可以更好地估计干沉降量和冠层交换量。通过干湿过程沉积在冠层上的 NH4+-N 和 NH4+-N 将被输送到林地，其余部分（分别约为 90%、44% 和 68%）将被带入冠层。干沉降量与地表大气中氮化合物浓度的比较表明，修正的冠层收支模型可以更好地估计干沉降量和冠层交换量。通过干湿过程沉积在冠层上的 NH4+-N 和 NH4+-N 将被输送到林地，其余部分（分别约为 90%、44% 和 68%）将被带入冠层。干沉降量与地表大气中氮化合物浓度的比较表明，修正的冠层收支模型可以更好地估计干沉降量和冠层交换量。