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英语科普知识:世界上最大的生物之一

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世界上最大的生物之一,犹他的一种基因相同的树林,正在慢慢地被鹿吞噬。
 
潘朵拉震动的阿斯彭殖民地,也被称为“颤抖巨人”,可能存活数千年。但据《今日邮报》(PPLS)杂志(10月17日)发表的一篇新论文,约有80%是处于危险状态。
 
这个颤抖的巨人,重达1300万磅(590万公斤),占地106英亩(0.42平方公里)的犹他州鱼湖国家森林,由47000多根遗传上相同的茎组成,这些茎生长在一个地下亲本克隆上。
 
在这项新的研究中,一组研究人员测量了森林不同部分的健康状况,比如通过计算活树和死树的数量,计算新茎的数量,以及追踪掉进来咬一口的动物的粪便。他们发现,最能反映森林健康状况的指标——新芽能否存活——的最大障碍是骡鹿。
 
美国犹他州立大学西阿斯彭联盟的主任兼副教授保罗·罗杰斯告诉《生活科学》杂志说,老树干正在枯萎,这是很自然的。不正常的是,新的茎不发育,他说。在过去的几十年里,骡鹿和牛吃掉了从地下毛白杨中长出的所有新茎。在大多数地区,根本没有“中青年树木”。因此,用人类的术语来说,森林是“完全由非常年长的老年人组成”,Rogers说。
 
罗杰斯和他的团队还对比了72年间该地区的航空照片,发现白杨林正在变薄。回到1939,树冠都被触动了,但是从20世纪70年代开始,“你看到树之间有很多空隙,”他说。这意味着老树正在死亡,新的树木不会填补这些空白。
 
部分问题是,像骡鹿这样的游戏在这个地区不再有自然捕食者。在20世纪初,人类杀死了大多数自然捕食者,如狼和灰熊,罗杰斯说。现在,潘多岛的大部分场地都被留作娱乐用途,比如露营,在那里浏览器不受狩猎的侵害。鹿很早就知道了,他们发现这是一个安全的港湾。”
 
但实际上,“Pando因为人类的决定而失败了,”Rogers说。人类控制野生动物,特别是像鹿和麋鹿这样的野生动物。
 
颤抖的巨人的一部分正在茁壮成长。罗杰斯说,这个地区在2013年左右被围起来,在五年内,每英亩大约有12-15英尺(3.6-4.5米)高的成千上万根树干。这里,篱笆似乎在起作用。阿斯彭克隆所占据的面积的一半是被骡子鹿和牛轻易围住的。Rogers说,大约30%的区域用一个8英尺高(2.4米)的篱笆围住。但是,“围栏不起作用,所以它也处于贫困状态,”他说。不知怎的,这些动物仍在进食,这对我们来说有点神秘,”他说。他认为骡鹿(不是牛)正在跳跃。
 
Rogers说:“我们需要帮助控制动物——鹿和牛,让Pando休息一下,这样它就可以恢复。”他说,这可以通过剔除它们的数量,用适当的篱笆限制它们,或者像传统的捕食者那样让它们离开这个区域。
 
Rogers说:“我们不是在谈论这棵树,而是在谈论所有的植物和动物。”我们不能独立地管理野生动物和森林,我们必须协调一致地管理它们。
 
他说,保护Pando的方法可以推广到全世界的阿斯彭斯。

One of the largest organisms in the world, a Utah forest of genetically identical trees, is slowly being devoured by deer.
The Pando quaking aspen colony, also known as the "Trembling Giant," has likely survived for thousands of years. But about 80 percent of it is in a perilous state, according to a new paper published today (Oct. 17) in the journal PLOS One.
The trembling giant, weighing 13 million lbs. (5.9 million kilograms) and covering 106 acres (0.42 square kilometers) of Utah’s Fishlake National Forest, consists of over 47,000 genetically identical stems that grow from a single underground parent clone.
In this new study, a group of researchers measured the health of various parts of the forest, such as by counting the number of living versus dead trees, counting the number of new stems and tracking the feces of animals that dropped in for a bite. They found that the biggest obstacle to the strongest indicator of the forest’s health — whether new sprouts could survive — was mule deer.
It’s natural that the older stems are dying off, lead author Paul Rogers, the director of the Western Aspen Alliance and adjunct associate professor at Utah State University,told Live Science. What’s unnatural is that new stems aren’t growing, he said. For the past couple of decades, mule deer and cattle have been eating all the new stems that sprout from the underground mama aspen. In most areas, there’s no "young or middle-aged trees at all," he said. So the forest, to use human terms, is made up "entirely of very elderly senior citizens," Rogers said.
Rogers and his team also compared aerial photographs of the area that spanned 72 years and found that the aspen forest has been thinning. Back in 1939, the tree crowns all touched, but starting in the 1970s, "you see a lot of spaces between the trees," he said. This means that the old trees are dying and new ones aren’t coming in to fill in the gaps.
Part of the problem is that game such as mule deer do not have natural predators in the area anymore. In the early 1900s, humans killed off most natural predators, such as wolves and grizzly bears, Rogers said. Now, most of the grounds in Pando are set aside for recreational uses like camping, where the browsers are protected from hunting. "The deer know that very early on, and they find it a safe harbor."
But really, "Pando is failing because of human decisions," Rogers said. "Humans control wild animals, particularly wild-game species like deer and elk."
There is one part of the trembling giant that is thriving. This area was fenced in around 2013 and within five years, thousands of stems — some 12 to 15 feet (3.6 to 4.5 m) tall — have been growing per acre, Rogers said. Here, the fence seems to be working. Half of the area that the aspen clone takes up is unfenced and easily accessible by the mule deer and cattle. Around 30 percent of the area is fenced in with an 8-foot-tall (2.4 meters) fence, Rogers said. But "the fence is not doing its job, so it’s also in a poor state," he said. "Somehow, the animals are still getting in — it’s a bit of a mystery to us," he said. He thinks the mule deer (not the cattle) are jumping it.
"We need to help control the animals — both deer and cattle — and give Pando a break so that it can recover," Rogers said. This can be done by culling their numbers, restricting them with properly working fences or keeping them moving out of the area, as predators traditionally did, he said.
"We’re not talking about just the tree, but we’re talking about all the plants and animals dependent on it," Rogers said. "We can’t manage wildlife and forest independently, we have to manage them in concert and in coordination with each other."
And the approaches that work to protect Pando could be extended to aspens around the world, he said.
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