Using the natural 15N abundance to assess the main nitrogen inputs into the sand dune area of the North-Western Negev desert (ISRAEL)
Using the natural 15N abundance to assess the main nitrogen inputs into the sand dune area of the North-Western Negev desert (ISRAEL)
复制标题
利用自然 15N 丰度评估内盖夫沙漠西北部沙丘地区的主要氮输入（以色列）
DOI：
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发表时间：
2004
影响因子：
1.3
通讯作者：
T. Littmann
中科院分区：
文献类型：
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作者：
R. Russow;M. Veste;T. Littmann
天然15 N丰度的变化常被用来评价氮素的来源或氮素输入生态系统的途径。我们试图使用这种方法来评估的主要输入途径氮到沙丘地区的西北部内盖夫沙漠（以色列）。以下两条途径是氮素输入系统的主要来源：i.通过存在于生物结皮中的蓝细菌和固氮维管植物（例如灌木Retama raetam）对大气氮进行生物固定; ii.大气中氮的输入是通过降雨的湿沉降、含氮化合物的粉尘的干沉降和气态沉降。在1998年、1999年和2000年3月的三次实地调查中，从选定的环境隔室中取样，如生物结壳、结壳下的沙（深至90厘米）、固氮和非固氮植物、大气大量沉积物以及桑迪地区以北的可耕地土壤。δ 15 N值的变化范围为：草-2.5 ‰ ~+1.5‰;土壤氮含量为+0.5‰ ~+4.5‰，非固氮灌木+1‰ ~+7‰，生物结皮下砂层+4‰ ~+20‰（土层深度2-90 cm），北部耕地可达10‰。 因此，不同氮库的天然15 N丰度差异显着。因此，它应该是可行的，以评估不同的输入途径，从不同的15 N丰度的氮。如豆科灌木R.从15 N丰度测量reatam计算是46-86%的生物量N来自大气。生物结皮本身的15 N值一般为负值（−3‰至−0.5‰），这可以用生物固氮来解释。然而，地衣比例高的地区，无法固定大气氮，显示非常负的值，低至-10 ‰。大气氮沉降量为1.9- 3.8kgN/ha·a，15 N丰度在4.4‰ ~ 11.6‰之间，可能是由北方耕地降尘引起的。 因此，它也不能对测量的地衣的非常负的值负责。必须有来自负δ 15 N值的大气的额外N输入，例如气态N形式（NOx，NH3）。为了解释这些相互矛盾的发现，仍然需要关于氮的湿的、颗粒的和气态的大气沉积的详细信息。
The variation of the natural 15N abundance is often used to evaluate the origin of nitrogen or the pathways of N input into ecosystems. We tried to use this approach to assess the main input pathways of nitrogen into the sand dune area of the north-western Negev Desert (Israel). The following two pathways are the main sources for nitrogen input into the system: i. Biological fixation of atmospheric nitrogen by cyanobacteria present in biological crusts and by N2-fixing vascular plants (e.g. the shrub Retama raetam); ii. Atmospheric input of nitrogen by wet deposition with rainfall, dry deposition of dust containing N compounds, and gaseous deposition. Samples were taken from selected environmental compartments such as biological crusts, sand underneath these crusts (down to a depth of 90 cm), N2-fixing and non-N2-fixing plants, atmospheric bulk deposition as well as soil from arable land north of the sandy area in three field campaigns in March 1998, 1999 and 2000. The δ15N values measured were in the following ranges: grass −2.5‰ to +1.5‰; R. reatam: +0.5‰ to +4.5‰; non-N2-fixing shrubs +1‰ to +7‰; sand beneath the biological crusts +4‰ to +20‰ (soil depth 2–90 cm); and arable land to the north up to 10‰. Thus, the natural 15N abundance of the different N pools varies significantly. Accordingly, it should be feasible to assess different input pathways from the various 15N abundances of nitrogen. For example, the biological N fixation rates of the Fabaceae shrub R. reatam from the 15N abundances measured were calculated to be 46–86% of biomass N derived from the atmosphere. The biological crusts themselves generally show slight negative 15N values (−3‰ to −0.5‰), which can be explained by biological N fixation. However, areas with a high share of lichens, which are unable to fix atmospheric nitrogen, show very negative values down to −10‰. The atmospheric N bulk deposition, which amounts to 1.9–3.8 kg N/ha yr, has a 15N abundance between 4.4‰ and 11.6‰ and is likely to be caused by dust from the arable land to the north. Thus, it cannot be responsible for the very negative values of lichens measured either. There must be an additional N input from the atmosphere with negative δ15N values, e.g. gaseous N forms (NO x , NH3). To explain these conflicting findings, detailed information is still needed on the wet, particulate and gaseous atmospheric deposition of nitrogen.