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Science:澳大利亚发现“仙女圈”

摘要 : 仙女圈已经让生态学家困惑几十年了。

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仙女圈已经让生态学家困惑几十年了。点缀南部非洲干燥草原的那些一片片圆形的裸土有几个奇异的特征。从天空看,它们覆盖着大地,呈现出类似蜂巢的正六边形图案。圆圈的中心没有植物,而边缘往往围了一圈超高杂草形成的矮墙,最终给人一个印象这是小仙女们建造的一个聚会地点。是圆圈中心的土壤里积累了毒素?还是穴居昆虫在地下的植物根部肆虐的杰作?究其根源,这当然不会是一个超自然现象,但目前所提出的、对这一现象的解释的数量看起来几乎和研究它的科学家的数量一样多。去年,一项研究对过去十年来纳米比亚的卫星图像进行了分析,结果显示仙女圈的出现和消失同降雨量相关。雨水充足的年份过后,圆圈的规模和数量会缩减,再在旱季之后升高,直到大旱之年,它们开始再次消失。但是,如果非洲南部的仙女圈是源于这样一种普遍的机制,而不是具体和当地相关,那么难道不该在地球上其它地方看见类似的现象吗?而事实正是如此。今天出版的《美国国家科学院院刊》中,科学家报告说在澳大利亚西部内陆地区也存在仙女圈。尽管这些仙女圈包含完全不同种类的植物和动物,在这片荒凉的澳洲风景(上图)中发现的这个盲区有着同样的六角形布局。基于已知的降水和草生物质之间的反馈所建立的生态系统计算机模型生成了和仙女圈非常相同的图案,这表明非洲和澳大利亚的这些图案有着相同的形成机制。

原文链接:

‘Fairy circles’ spotted in Australia

原文摘要:

Fairy circles have stumped ecologists for decades. The circular patches of denuded soil that dot the dry grasslands of southern Africa have several curious features. As seen from the sky, they cover the landscape in a regular hexagonal pattern similar to a beehive. The center of the circle is devoid of plants, wheras the edges are often fringed with a low wall of extra-high grasses that complete the impression of a gathering place built by wee fairies. Has a toxin accumulated in the soil at the center? Is it the work of burrowing insects wreaking havoc on the roots beneath? The cause is certainly not supernatural, but there are seemingly nearly as many proposed explanations as there are scientists who study the phenomenon. Last year, a study of a decade's worth of satellite imagery of Namibia showed that fairy circles wax and wane in relation to rainfall. After wet years, the circles shrink in both size and number, then grow after dry ones—until it becomes too dry and they start to disappear again. But if the fairy circles of southern Africa are due to such a universal mechanism, rather than something local and specific, then shouldn't they appear elsewher on Earth? Indeed they do. Today in the Proceedings of the National Academy of Sciences, scientists report that fairy circles exist in the outback of western Australia. In spite of having completely different species of plants and animals, the dead spots found in this desolate Australian landscape (above) have the very same hexagonal distribution. A computer model of the ecosystem based on what is known about the feedbacks between precipitation and grass biomass generated the very same patterns of fairy circles, suggesting that the pattern-forming mechanism is the same in both Africa and Australia.

来源: Science 浏览次数:0

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