Nitrogen wet deposition stoichiometry: the role of organic nitrogen, seasonality, and snow
Nitrogen wet deposition stoichiometry: the role of organic nitrogen, seasonality, and snow
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DOI：
10.1007/s10533-022-00966-0
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发表时间：
2022-08
期刊：
影响因子：
4
通讯作者：
D. Murray;Michelle D. Shattuck;W. McDowell;A. Wymore
中科院分区：
文献类型：
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作者：
D. Murray;Michelle D. Shattuck;W. McDowell;A. Wymore
溶解无机氮（N）的湿沉降在全国范围内正在下降，伴随着氮的化学计量从主要氧化形式向还原形式的转变。化学计量的趋势，包括N湿沉降的有机部分尚未进行评估，在人为的压力和全球变化，包括季节性变化。在这里，我们使用17年的每周，全年湿沉降数据从温带流域在新罕布什尔州（美国），以评估长期和季节性的趋势NO3-，NH 4+，和溶解有机氮（DON），并量化的N化学计量依赖于降水类型（雨或雪）。DON的浓度、负荷和相对丰度正在增加，这是美国以前从未报道过的模式。该地点的总溶解氮沉积量正在下降，但NH 4+日益耗尽，这与全国趋势相反。无机氮的化学计量对降水类型非常敏感，雪中含有的NO3−明显多于雨，雨中相对富集NH 4+。气候变化对季节性的影响，如暖冬，可能会导致更大比例的降水进入生物圈的雨水，是相对丰富的还原氮，在区域尺度上的流域生态地球化学循环的重大影响。本研究表明，在当代氮沉降输入的变化，包括化学计量学的趋势，并探讨了有机氮和季节性的作用，调节内部和内部的变化，氮沉降化学计量学。
Wet deposition of dissolved inorganic nitrogen (N) is declining nationally, accompanied by a shift in stoichiometry from predominantly oxidized to reduced forms of N. Stoichiometric trends that include the organic fraction of N wet deposition have yet to be assessed in light of anthropogenic pressures and global change, including shifting seasonality. Here we use 17 years of weekly, year-round wet deposition data from a temperate watershed in New Hampshire (USA) to assess long-term and seasonal trends in NO3−, NH4+, and dissolved organic nitrogen (DON), and quantify the dependence of N stoichiometry on precipitation type (rain or snow). Concentration, load, and relative abundance of DON are increasing, a pattern previously unreported in the U.S. Deposition of total dissolved nitrogen at this site is declining, but is increasingly depleted in NH4+, contrary to national trends. The stoichiometry of inorganic N is highly sensitive to precipitation type with snow containing significantly more NO3−than rain, which was relatively enriched in NH4+. The effects of climate change on seasonality such as warmer winters could result in a greater proportion of precipitation entering the biosphere as rain that is relatively enriched in reduced N, with significant implications for watershed biogeochemical cycles at the regional scale. This study demonstrates variability in contemporary N deposition inputs including trends in stoichiometry and explores the role of organic N and seasonality in regulating inter- and intra- variability in N deposition stoichiometry.