Changes in global nitrogen cycling during the Holocene epoch
Changes in global nitrogen cycling during the Holocene epoch
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DOI：
10.1038/nature11916
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发表时间：
2013-03-21
期刊：
影响因子：
64.8
通讯作者：
Jeffers, Elizabeth S.
中科院分区：
文献类型：
--
作者：
McLauchlan, Kendra K.;Williams, Joseph J.;Jeffers, Elizabeth S.
人类活动使地球上活性氮的供应量在工业化前增加了一倍，而且未来的增长速度预计还会加快(1)。然而，人们对生物圈缓冲增加的氮流入的能力知之甚少。更新世末期冰川消退后全球生态系统的过去变化为更好地了解陆地生物圈中的氮循环如何响应碳循环的变化提供了机会。我们分析了六大洲 86 个湖泊沉积物中已发表的稳定氮同位素值 (Delta N-15) 记录。在这里，我们发现沉积三角洲 N-15 的值从 15,000 年前下降到 7,056 +/- 597 年前，这是大气二氧化碳浓度和陆地碳积累增加的时期(2)。将氮同位素记录与陆地上的碳积累和大气中的一氧化二氮进行比较表明，在距今约 11,000 年的更新世-全新世过渡期间，陆地生态系统中氮的可用性已经下降了数千年。相比之下，尽管人为来源的温度变化和氮流入存在潜在影响，但我们在过去 500 年中没有观察到全球沉积三角洲 N-15 值的一致变化。我们认为，缺乏单一反应可能表明，现代大气二氧化碳和生物圈净碳封存的增加有可能抵消一些生态系统中最近增加的活性氮供应。
Human activities have doubled the pre-industrial supply of reactive nitrogen on Earth, and future rates of increase are expected to accelerate(1). Yet little is known about the capacity of the biosphere to buffer increased nitrogen influx. Past changes in global ecosystems following deglaciation at the end of the Pleistocene epoch provide an opportunity to understand better how nitrogen cycling in the terrestrial biosphere responded to changes in carbon cycling. We analysed published records of stable nitrogen isotopic values (delta N-15) in sediments from 86 lakes on six continents. Here we show that the value of sedimentary delta N-15 declined from 15,000 years before present to 7,056 +/- 597 years before present, a period of increasing atmospheric carbon dioxide concentrations and terrestrial carbon accumulation(2). Comparison of the nitrogen isotope record with concomitant carbon accumulation on land and nitrous oxide in the atmosphere suggests millennia of declining nitrogen availability in terrestrial ecosystems during the Pleistocene-Holocene transition around 11,000 years before present. In contrast, we do not observe a consistent change in global sedimentary delta N-15 values during the past 500 years, despite the potential effects of changing temperature and nitrogen influx from anthropogenic sources. We propose that the lack of a single response may indicate that modern increases in atmospheric carbon dioxide and net carbon sequestration in the biosphere have the potential to offset recent increased supplies of reactive nitrogen in some ecosystems.