美国国家公共电台 NPR Getting Fire From A Tree Without Burning The Wood

 

MICHEL MARTIN, HOST:

At the Oak Ridge¹ National Laboratory in Tennessee, scientists have been investigating something very strange - a flammable gas leaking from the inside of a tree. NPR science correspondent Joe Palca recently went to Oak Ridge to learn more.

JOE PALCA, BYLINE²: There's a 40 or 50-foot-tall cottonwood tree growing right behind one of the research buildings on the national lab campus. Cottonwoods are tall, straight trees with leaves the shape of spades. Chris Schadt is an environmental microbiologist. He offered to try to demonstrate the phenomenon. He starts assembling a tool he's brought out to the tree.

So hang on. Tell me what you just put together there.

CHRIS SCHADT: So I put together what we call an increment³ borer. It's got a hollow tube and a handle. It's a T-formation. And you can just pick a spot in the tree.

PALCA: Schadt picks a spot about chest-high.

SCHADT: So once we get to what would be approximately the center, you take the extractor...

PALCA: The extractor is basically a long, thin spatula⁴ that slides inside the borer.

SCHADT: Insert it in here, give a couple of turns backwards⁵, you can pull out a core of a tree.

PALCA: In this case, we're not interested in the core. We're interested in what might be coming out of the hollow tube that's now stuck into the tree.

SCHADT: Some of the trees produce methane⁶ in the tree.

PALCA: Methane is the gas in natural gas.

SCHADT: And you could actually light the methane on fire coming out of it. This one does not appear to have any trapped methane.

PALCA: But many do. So what's going on here? Why is methane coming out of a tree? Well, the answer lies with a property of cottonwoods.

SCHADT: The wood in this particular species sort of naturally has this condition called wetwood where it's saturated⁷ within the trunk of the tree.

PALCA: And this wetwood makes for a welcoming home for all sorts of microorganisms.

MELISSA CREGGER: You can't actually see a lot of the organisms because we can't grow a lot of these organisms, so we're able to identify them using their gene⁸ sequences.

PALCA: Melissa Cregger is an ecologist at Oak Ridge. She says some of those organisms called archaea turned out to be known methane producers. So it's not the trees themselves producing the methane. It's the microbes living in the tree. Cregger says scientists have known for a while that these organisms existed in forests but not in the trees themselves.

CREGGER: We had historically worked below ground looking at soil communities, root communities.

PALCA: Cregger says because methane is a potent⁹ greenhouse gas, it's important to see how much the trees are actually producing. And that raises a surprising notion - yes, trees take carbon dioxide out of the atmosphere, a good thing. But they also add methane, a potentially bad thing. But University of Delaware ecologist Rodrigo Vargas says trees are most likely doing more good than harm.

RODRIGO VARGAS: It's not like now trees are the bad actors, and now they're emitting methane, and now we're seeing a big source of that. It's not like that.

PALCA: Vargas says that's because the amount of methane coming from the trees is small compared with other sources. Vargas is interested in getting a better understanding of the gases trees produce. He's developing an automated¹⁰ system because doing the measurements manually would be a giant pain.

VARGAS: Because then you would need to be there in the tree and measuring (laughter) every half an hour forever, right? And if it rains, you have to be there. If it's - you actually have to be there. No, if you're uncomfortable, hungry, you have to be there.

PALCA: Once his automated system is up and running, he's hoping to be able to see if the amount of methane increases from time to time, for example after a big storm or when the temperature suddenly changes.

VARGAS: We have the opportunity to see these patterns that no one has seen before.

PALCA: Perhaps this is one of those cases where it's more important to see the trees than the whole forest.

Joe Palca, NPR News.

1 ridge   

n.山脊；鼻梁；分水岭

参考例句：

• We clambered up the hillside to the ridge above.我们沿着山坡费力地爬上了山脊。
• The infantry were advancing to attack the ridge.步兵部队正在向前挺进攻打山脊。

2 byline   

n.署名；v.署名

参考例句：

• His byline was absent as well.他的署名也不见了。
• We wish to thank the author of this article which carries no byline.我们要感谢这篇文章的那位没有署名的作者。

3 increment   

n.增值，增价；提薪，增加工资

参考例句：

• Each increment of knowledge tells us more of our world.知识的点滴增长都会增进我们对世界的认知。
• She receives a salary increment each year.她每年得到加薪。

4 spatula   

n.抹刀

参考例句：

• He scraped the mixture out of the bowl with a plastic spatula.他用塑料铲把盆里的混合料刮了出来。
• She levelled the surface of the cake mixtured with a metal spatula.她用金属铲抹平了蛋糕配料。

5 backwards   

adv.往回地，向原处，倒，相反，前后倒置地

参考例句：

• He turned on the light and began to pace backwards and forwards.他打开电灯并开始走来走去。
• All the girls fell over backwards to get the party ready.姑娘们迫不及待地为聚会做准备。

6 methane   

n.甲烷，沼气

参考例句：

• The blast was caused by pockets of methane gas that ignited.爆炸是由数袋甲烷气体着火引起的。
• Methane may have extraterrestrial significance.甲烷具有星际意义。

7 saturated   

a.饱和的，充满的

参考例句：

• The continuous rain had saturated the soil. 连绵不断的雨把土地淋了个透。
• a saturated solution of sodium chloride 氯化钠饱和溶液

8 gene   

n.遗传因子，基因

参考例句：

• A single gene may have many effects.单一基因可能具有很多种效应。
• The targeting of gene therapy has been paid close attention.其中基因治疗的靶向性是值得密切关注的问题之一。

9 potent   

adj.强有力的，有权势的；有效力的

参考例句：

• The medicine had a potent effect on your disease.这药物对你的病疗效很大。
• We must account of his potent influence.我们必须考虑他的强有力的影响。

10 automated   

a.自动化的

参考例句：

• The entire manufacturing process has been automated. 整个生产过程已自动化。
• Automated Highway System (AHS) is recently regarded as one subsystem of Intelligent Transport System (ITS). 近年来自动公路系统(Automated Highway System,AHS)，作为智能运输系统的子系统之一越来越受到重视。