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首页> 外文期刊>Ecosystems >Chronic Atmospheric NO 3 ? Deposition Does Not Induce NO 3 ? Use by Acer saccharum Marsh.
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Chronic Atmospheric NO 3 ? Deposition Does Not Induce NO 3 ? Use by Acer saccharum Marsh.

机译：慢性大气NO 3 ？沉积不会导致NO 3 ？被Acer saccharum Marsh使用。

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摘要

The ability of an ecosystem to retain anthropogenic nitrogen (N) deposition is dependent upon plant and soil sinks for N, the strengths of which may be altered by chronic atmospheric N deposition. Sugar maple (Acer saccharum Marsh.), the dominant overstory tree in northern hardwood forests of the Lake States region, has a limited capacity to take up and assimilate NO 3 ? . However, it is uncertain whether long-term exposure to NO 3 ? deposition might induce NO 3 ? uptake by this ecologically important overstory tree. Here, we investigate whether 10 years of experimental NO 3 ? deposition (30 kg N ha?1 y?1) could induce NO 3 ? uptake and assimilation in overstory sugar maple (approximately 90 years old), which would enable this species to function as a direct sink for atmospheric NO 3 ? deposition. Kinetic parameters for NH 4 + and NO 3 ? uptake in fine roots, as well as leaf and root NO 3 ? reductase activity, were measured under conditions of ambient and experimental NO 3 ? deposition in four sugar maple-dominated stands spanning the geographic distribution of northern hardwood forests in the Upper Lake States. Chronic NO 3 ? deposition did not alter the V max or K m for NO 3 ? and NH 4 + uptake nor did it influence NO 3 ? reductase activity in leaves and fine roots. Moreover, the mean V max for NH 4 + uptake (5.15 μmol 15N g?1 h?1) was eight times greater than the V max for NO 3 ? uptake (0.63 μmol 15N g?1 h?1), indicating a much greater physiological capacity for NH 4 + uptake in this species. Additionally, NO 3 ? reductase activity was lower than most values for woody plants previously reported in the literature, further indicating a low physiological potential for NO 3 ? assimilation in sugar maple. Our results demonstrate that chronic NO 3 ? deposition has not induced the physiological capacity for NO 3 ? uptake and assimilation by sugar maple, making this dominant species an unlikely direct sink for anthropogenic NO 3 ? deposition.
机译：生态系统保留人为氮（N）沉积的能力取决于植物和土壤汇入的氮，其强度可能因长期的大气氮沉积而改变。枫糖树（Acer saccharum Marsh。）是湖州地区北部硬木森林中占主导地位的树种，吸收和吸收NO 3的能力有限。？。然而，尚不清楚长期暴露于NO 3 ？沉积物是否会诱导该生态上重要的树种吸收NO 3 ？。在这里，我们调查10年的实验NO 3 吗？ 沉积（30千克N ha？1 y？1 ）可能会导致故事情节的枫糖（大约90岁）吸收NO 3 ？并被同化。 ，这将使该物种能够充当大气NO 3 ？沉积的直接汇。细根吸收NH 4 + 和NO 3 ？的动力学参数，以及叶和根NO 3 ？还原酶的活性在大气和实验性NO 3沉积条件下，在四个糖枫为主的林分中，该林分分布在上湖州北部硬木森林的地理分布中。 NO 3 ？的慢性沉积不会改变NO 3 ？和NH 4 +的V max 或K m 的吸收也不影响叶片和细根中NO 3 ？的还原酶活性。此外，NH 4吸收的平均V max + （5.15μmol15 N g？1 h？1 ）是八倍。大于NO 3吸收的V max （0.63μmol15 N g？1 h？1 ），表明该物种具有更高的吸收NH 4 + 的生理能力。此外，NO 3 α还原酶的活性低于文献中先前报道的大多数木本植物的值，这进一步表明糖中NO 3 α同化的生理潜力较低。枫。我们的结果表明，长期的NO 3 ？沉积没有诱导糖枫吸收和吸收NO 3 ？的生理能力，因此该优势种不太可能直接下沉。为人为的NO 3 ？沉积。

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