Chronic elevated nitrogen deposition has increased nitrogen availability in many forest ecosystems globally, and this phenomenon has been suggested to increase soil nitrification. Although it is believed that increased nitrogen availability would also increase nitrous oxide (N 2 O) emissions from forest ecosystems, its impact on N 2 O flux is poorly known. In this study, 3-years monitoring of N 2 O emissions was performed in a forested watershed receiving elevated nitrogen deposition and located in the suburbs of Tokyo, Japan. In addition, a comparative field survey was carried out in nine temperate forest sites with varying nitrogen availabilities. In the intensively studied forest site showing typical nitrogen saturation, the average annual N 2 O emissions from the whole watershed were estimated to be 0.88 kg N ha −1 year −1 , comparable to the highest observed levels for temperate forests except for some very high emission sites in Europe. Although no correlation was found for humid spots with WFPS > 60%, a clear positive correlation was noted between N 2 O flux and net nitrification rate in situ for plots with water-filled pore space (WFPS) < 60%. The N 2 O flux varied across nine forest sites almost in proportional to the stream water NO 3 − concentration in the watershed that ranged from 0.14 to 1.64 mg N/L. We conclude that N 2 O emissions are related to nitrification in moist temperate forest, which may be associated with the magnitude of nitrogen saturation.

中文翻译：

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潮湿温带森林中一氧化二氮排放与硝化作用成正比

在全球许多森林生态系统中，慢性氮沉积增加了氮的可用性，这种现象被认为会增加土壤硝化作用。尽管人们认为增加氮的可用性也会增加森林生态系统的一氧化二氮 (N 2 O) 排放，但其对 N 2 O 通量的影响却鲜为人知。在这项研究中，对位于日本东京郊区的氮沉降增加的森林流域进行了为期 3 年的 N 2 O 排放监测。此外，在九个具有不同氮可用性的温带森林地点进行了比较实地调查。在显示出典型氮饱和度的深入研究的林地中，整个流域的年平均 N 2 O 排放量估计为 0.88 kg N ha -1 年 -1 ，除了欧洲的一些非常高的排放地点外，与温带森林的最高观察水平相当。尽管 WFPS > 60% 的湿点没有发现相关性，但在充满水的孔隙空间 (WFPS) < 60% 的地块中，N 2 O 通量与原位净硝化速率之间存在明显的正相关关系。N 2 O 通量在九个森林地点的变化几乎与流域中的河流水NO 3 - 浓度成比例，范围从0.14 到1.64 mg N/L。我们得出结论，N 2 O 排放与潮湿温带森林中的硝化作用有关，这可能与氮饱和度的大小有关。对于充满水的孔隙空间 (WFPS) < 60% 的地块，发现 N 2 O 通量与原位净硝化率之间存在明显的正相关。N 2 O 通量在九个森林地点的变化几乎与流域中的河流水NO 3 - 浓度成比例，范围从0.14 到1.64 mg N/L。我们得出结论，N 2 O 排放与潮湿温带森林中的硝化作用有关，这可能与氮饱和度的大小有关。对于充满水的孔隙空间 (WFPS) < 60% 的地块，发现 N 2 O 通量与原位净硝化率之间存在明显的正相关。N 2 O 通量在九个森林地点的变化几乎与流域中的河流水NO 3 - 浓度成比例，范围从0.14 到1.64 mg N/L。我们得出结论，N 2 O 排放与潮湿温带森林中的硝化作用有关，这可能与氮饱和度的大小有关。