Loss of plant species after chronic low-level nitrogen deposition to prairie grasslands
Loss of plant species after chronic low-level nitrogen deposition to prairie grasslands
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DOI：
10.1038/nature06503
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发表时间：
2008-02-07
期刊：
影响因子：
64.8
通讯作者：
Tilman, David
中科院分区：
文献类型：
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作者：
Clark, Christopher M.;Tilman, David
在许多发达国家，由于化石燃料的燃烧和农业施肥，生物活性氮（N）在大气中的沉积速率是工业化前的2 - 7倍（1，2）。预计在未来50年内，亚洲和南美洲的工业化国家也将出现类似的增长（2）。虽然高氮添加率对环境的影响已经得到了很好的研究（3-8），但对于地球仪中大部分地区所特有的较低的慢性速率，情况并非如此。在这里，我们提出了第一个多年代际实验的结果，以检查长期的，实验性的氮添加低至10公斤氮公顷（-1）年（-1）以上的环境大气氮沉降（6公斤氮公顷（-1）年（-1）在我们的网站）的影响。这一总输入率与许多工业化国家的陆地氮沉降相当（2）。我们发现，相对于接受环境氮沉降的对照组，这种慢性低水平氮添加率使植物物种数量减少了17%。此外，在较低的添加率下，每单位添加氮，物种数量减少得更多，这表明慢性但低水平的氮沉积可能对多样性的影响比之前认为的更大。第二个实验表明，停止氮添加后十年，相对植物物种数，虽然不是物种丰度，已经恢复，表明氮添加的一些影响是可逆的。
Rates of atmospheric deposition of biologically active nitrogen ( N) are two to seven times the pre- industrial rates in many developed nations because of combustion of fossil fuels and agricultural fertilization(1,2). They are expected to increase similarly over the next 50 years in industrializing nations of Asia and South America(2). Although the environmental impacts of high rates of nitrogen addition have been well studied(3-8), this is not so for the lower, chronic rates that characterize much of the globe. Here we present results of the first multi- decadal experiment to examine the impacts of chronic, experimental nitrogen addition as low as 10 kg N ha(-1) yr(-1) above ambient atmospheric nitrogen deposition ( 6 kg N ha(-1) yr(-1) at our site). This total input rate is comparable to terrestrial nitrogen deposition in many industrialized nations(2). We found that this chronic low- level nitrogen addition rate reduced plant species numbers by 17% relative to controls receiving ambient N deposition. Moreover, species numbers were reduced more per unit of added nitrogen at lower addition rates, suggesting that chronic but low- level nitrogen deposition may have a greater impact on diversity than previously thought. A second experiment showed that a decade after cessation of nitrogen addition, relative plant species number, although not species abundances, had recovered, demonstrating that some effects of nitrogen addition are reversible.