Relative Magnitude and Controls of in Situ N2 and N2O Fluxes due to Denitrification in Natural and Seminatural Terrestrial Ecosystems Using (15)N Tracers.
Relative Magnitude and Controls of in Situ N2 and N2O Fluxes due to Denitrification in Natural and Seminatural Terrestrial Ecosystems Using (15)N Tracers.
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DOI：
10.1021/acs.est.5b03513
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发表时间：
2015-11
影响因子：
11.4
通讯作者：
F. Sgouridis;S. Ullah
中科院分区：
文献类型：
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作者：
F. Sgouridis;S. Ullah
反硝化是氮 (N) 循环中最不确定的组成部分，阻碍了我们评估其对反应性氮 (Nr) 去除的贡献的能力。这种不确定性源于测量原位土壤氮产量的困难以及过程本身的高时空变异性。 2013 年 4 月至 2014 年 10 月期间，每月对英国两个流域的自然（有机和森林）和半自然生态系统（半改良和改良草原）进行原位反硝化测量。采用(15)N-气体通量法，添加少量(15)NO3(-)示踪剂，N2和N2O的最小可检测通量分别为4 μg N m(-2) h(-1)和0.2 ng N m(-2) h(-1)。有机土壤和森林（分别为8和10 kg N ha(-1) y(-1)）的反硝化率低于半改良和改良草地土壤（分别为13和25 kg N ha(-1) y(-1)）。 N2O/N2 + N2O 的比率较低，范围为 <1% 至 7%。反硝化作用的变化是由不同地点的土壤呼吸、硝酸盐、C:N 比、容重、湿度和 pH 值的差异驱动的。总体而言，反硝化对自然生态系统中氮去除的贡献约为年大气氮沉降的 50%，使得这些生态系统容易受到长期氮饱和的影响。
Denitrification is the most uncertain component of the nitrogen (N) cycle, hampering our ability to assess its contribution to reactive N (Nr) removal. This uncertainty emanates from the difficulty in measuring in situ soil N2 production and from the high spatiotemporal variability of the process itself. In situ denitrification was measured monthly between April 2013 and October 2014 in natural (organic and forest) and seminatural ecosystems (semi-improved and improved grasslands) in two UK catchments. Using the (15)N-gas flux method with low additions of (15)NO3(-) tracer, a minimum detectable flux rate of 4 μg N m(-2) h(-1) and 0.2 ng N m(-2) h(-1) for N2 and N2O, respectively, was achieved. Denitrification rates were lower in organic and forest (8 and 10 kg N ha(-1) y(-1), respectively) than in semi-improved and improved grassland soils (13 and 25 kg N ha(-1) y(-1), respectively). The ratio of N2O/N2 + N2O was low and ranged from <1% to 7% across the sites. Variation in denitrification was driven by differences in soil respiration, nitrate, C:N ratio, bulk density, moisture, and pH across the sites. Overall, the contribution of denitrification to Nr removal in natural ecosystems was ~50% of the annual atmospheric Nr deposition, making these ecosystems vulnerable to chronic N saturation.