National Geographic News：气候变暖导致树木北移

hanouyan

图说：
Sugar maples stand interlaced with mist in West Virginia's Monongahela National Forest. The tree is among 40 major species over 30 Eastern U.S. states that are moving north at an unexpected rate, likely due to global warming, a February 2009 study says.

Photograph by James P. Blair/NGS
Bruce Dorminey
for National Geographic News
February 9, 2009

(糖枫树交错地立于西维吉尼亚的Monongahela 国家森林的薄雾中。2009年2月的一项研究显示，在超过30个美国东部州的约40种主要的树种，正以意想不到的速度向北迁移，很有可能是由全球气候变暖造成的。

国家地理杂志James P. Blair拍摄
2009年2月9日)

Other than the Ents of Lord of the Rings fame, trees generally aren't known for their mobility. So news that some tree species may be headed north at an average clip of 62 miles (100 kilometers) a century may come as a surprise.

At that rate, stands of yellow birch in the U.S., for example, may move well north of the Canadian border by the early 2100s.

That's the finding of a new study led by the U.S. Forest Service, which concludes that a few dozen tree species in the eastern U.S. are moving north at an unexpected rate, likely due to global warming.

In a paper appearing this month in the journal Forest Ecology and Management, the study authors documented the northward march of 40 major tree species over 30 eastern states based on the distribution of seedlings versus mature trees.

Previous studies of plant migrations had been done using only computer simulations, or they focused on how some species are climbing up hills and mountains, said co-author Chris Oswalt, of the Forest Service's Southern Research Station in Knoxville, Tennessee.

By contrast, the new study looked at movement based on latitude, using a sampling of the forest service's most recent ground-based data.

The finding confirms a link between global warming and forest migration, said lead study author Chris Woodall, of the Forest Service's Northern Research Station in St. Paul, Minnesota.

"This is no longer conjecture," he said.

Trees on the Move

Woodall and colleagues studied data from 15 northern species, 15 southern species, and 10 species found in both regions. They compared the latitudes of seedlings—trees less than 20 years old, on average—with those of their older counterparts.

Eleven of the 15 northern species appear to have shifted more than 12 miles (20 kilometers), on average, from their historic ranges.

Among the species headed north are the northern white cedar, American basswood, sugar maple, black ash, bigtooth aspen, and yellow birch.

The basswood and maple appear to have moved the most, perhaps as much as 30 miles (50 kilometers).

"This is the first serious attempt at documenting a forest shift for a wide array of species across a broad geographical setting," said Mark Schwartz, a plant-conservation biologist at the University of California, Davis, who was not involved in the study.

"I find it very significant that a cohesive climate change signal emerges from the data."

"Baseball Bat" Trees

Northern trees don't do well in very warm conditions, so the hope is that the climate won't change faster than the species can move.

Some tree species, however, are at the mercy of intervening wildlife when it comes to where and when their seeds take root.

Unless a cedar's pinecone is snatched up by a waiting blue jay, for example, the seed likely won't fall far from the tree.

Meanwhile, cottonwoods, poplars, ashes, and maples have seeds that are light enough to be dispersed by the wind over several miles.

Such highly mobile seeds might allow some species to migrate at rates that even exceed the Forest Service estimate—creating the potential for economic busts—said Dan Botkin, an ecologist at the University of California, Santa Barbara, who was also not a part of the research.

"Northern Pennsylvania and southern New York State are where the best white ash for baseball bats are grown," Botkin noted, "so few [people in those states] would be happy if the trees head north."
译文:
除了《指环王》电影中的树人族外，树通常被人们认为是无法移动的。因此，一些树种可能正以平均每一个世纪100公里的速度向北部迁移也许是一个令人意想不到的新闻。

照这种速度迁移，举例来说，现在还长在美国的黄桦树可能到22世纪初就会移动到加拿大边境还要往北的地方了。

这项发现出自美国林务局领导的一个新的研究项目，得出的结论是美国东部几十种树种都正以出乎意料的速度向北迁移，很有可能是全球气候变暖造成的。

在这个月的《森林生态和管理》杂志的一篇论文中，研究者们记录了跨越美国东部30个州的40种主要树的种类，基于幼苗与成熟树木的比例，在向北部行进。

以前关于植物迁移的研究仅仅使用电脑模拟完成，或者只是侧重于一些物种如何爬上山坡或山脉，合著者——位于田纳西州诺克斯维尔德的林务局南部研究站的Chris Oswalt说道。

相对而言，这项新研究通过使用林务局最新地面统计资料的抽样，研究基于纬度上的移动。

这项研究的主要作者，位于明尼苏达州圣保罗的林务局北部研究站的Chris Woodall表示，这个发现证实了全球变暖和森林迁移之间的联系。

“这不再仅仅是个猜想了。”他说。

移动中的树

Woodall和同事研究了15种北部物种，15种南部物种，和10种两个区域都有的物种的资料。他们用这些物种的幼苗（年龄小于20）和他们年长的同类物种的纬度平均值作比较。

15种北部物种中的11种表现出已经从它们的历史范围平均向北移动了超过20公里。

向被迁移的物种包括北部白雪松，美国椴木，糖枫树，黑梣树，大齿白杨和黄桦。

椴木和枫树是其中移动最多的，达到50公里。

“这是第一个试图正式记录拥有许多不同树木物种、跨越一个很广阔的地理范围的森林的迁移。” 没有参与到这项研究的、来自加利佛尼亚大学戴维斯分校的植物保护生物学家Mark Schwartz说。

“我认为大气变化信号从这些资料中很显著的显现出来。”

“棒球蝙蝠”树

北部的树木在温暖的情况下生长不好，因此希望大气变暖的速度不要超过物种移动的速度。

然而一些树种对于给它们传播种子的野生动物在何处与何时播种它们的种子束手无策。

举例来说，雪松的松果如果不是被等待的蓝樫鸟叼走的话，它的种子是不会掉到离树很远的地方的。

同时，棉花，杨树，梣树以及枫树的种子都轻得足以被风吹到几里地之外。

如此容易移动的种子可能会允许一些物种以高出林务局估计的速度迁移——造成潜在的经济崩溃——同样未参与这个研究项目的、来自加利福尼亚大学圣巴巴拉分校的生态学家Dan Botkin说。

“北宾夕法尼亚州和南纽约州有着供棒球蝙蝠生长的最好的白梣树，”Botkin表示：“因此（在这些州的人们）是不会对树木北移感到高兴的。”

xizizi

气候环境大变 地球要面目全非了

19751218

今天去了趟水泥厂,让人触目惊心啊,那个污染啊,国家还要加大力度关小水泥厂啊

温恒乐

人类发展的步伐要适当缓一缓！

sih

发展的代价太大了..........