VOA英语2010年-Mummified Forest Reveals Clues About Climate

A discovery of a mummified forest that's between two and 10 million years old is giving scientists a new window on climate change.

Joel Barker, a research scientist at the Byrd Polar Research Center at the Ohio State University, discovered the mummified forest in 2009. He says a forest ranger¹ on a remote Island in the Canadian Arctic pointed² out a stick in the mud in an otherwise barren landscape.

"And sure enough there was all this wood debris³ at the bottom of this valley," Barker says.

The Ellesmere Island site is one of about a dozen in the Canadian Arctic where warming temperatures and reduced snowfall have caused the glacial ice sheets to retreat and expose land where ancient forests once stood. Barker says what makes this particular forest site unique is that it was so far north.

"To find the source of where this stuff was coming from was pretty exciting. And then to sort of dig in the soil and find leaves, much like the leaves that you'd find in the Spring sort of emerging from a melting snow pack. They look sort of weathered, but you can pick them up and they are still leaves you are holding in your hands from a couple of million years ago."

Barker says these mummified trees - unlike petrified⁴ or fossilized wood - didn't decompose⁵ or turn to stone. He suspects they were buried suddenly by a massive landslide⁶ and entombed in the dry, airless soil. "So, you take away water. You take away oxygen. Things get preserved," he says.

The ancient forest debris looks much as nature left it. The birch, pine and spruce logs, branches and leaves from long ago are remarkably⁷ well-preserved, and it's easy to see that they don't match the hardy⁸ scrub growing in the Arctic today. The mummified woods more closely resemble the trees found in forests now hundreds of kilometers south.

Ocean sediment⁹ cores and the absence of the previously¹⁰ common Metasequoia redwood known to have lived in the region 10 million years ago date the newly-found arctic forest to between two and 10 million years. Barker says the low species diversity is a sign of an ecosystem¹¹ on the edge of extinction¹².

 
Joel Barker
The ancient forest was discovered in a valley that today is largely barren landscape.
"This forest existed at a time when the Arctic was cooling and climate was deteriorating¹³ very quickly. And so I think this allows us, by looking at the mummified remains¹⁴, to see how the ecosystem responded to the cooling, how rapidly the cooling occurred and to maybe identify any thresholds that were reached. And once we identify those thresholds, we can start making predictions about how quickly the ecosystem will respond to future warming."

The growth rings on some trees put their age at about 75 years old when they were suddenly buried. Barker notes that the branches appear spindly, with very narrow rings, suggesting the trees were suffering a great deal of stress when they were alive. The polar scientist plans to do further analysis with chemical and DNA¹⁵ testing. His preliminary findings were presented this week at the American Geophysical Union meeting in San Francisco.

1 ranger   

n.国家公园管理员，护林员；骑兵巡逻队员

参考例句：

• He was the head ranger of the national park.他曾是国家公园的首席看守员。
• He loved working as a ranger.他喜欢做护林人。

2 pointed   

adj.尖的，直截了当的

参考例句：

• He gave me a very sharp pointed pencil.他给我一支削得非常尖的铅笔。
• She wished to show Mrs.John Dashwood by this pointed invitation to her brother.她想通过对达茨伍德夫人提出直截了当的邀请向她的哥哥表示出来。

3 debris   

n.瓦砾堆，废墟，碎片

参考例句：

• After the bombing there was a lot of debris everywhere.轰炸之后到处瓦砾成堆。
• Bacteria sticks to food debris in the teeth,causing decay.细菌附着在牙缝中的食物残渣上，导致蛀牙。

4 petrified   

adj.惊呆的；目瞪口呆的v.使吓呆，使惊呆；变僵硬；使石化(petrify的过去式和过去分词)

参考例句：

• I'm petrified of snakes. 我特别怕蛇。
• The poor child was petrified with fear. 这可怜的孩子被吓呆了。 来自《简明英汉词典》

5 decompose   

vi.分解；vt.（使）腐败，（使）腐烂

参考例句：

• The eggs began to decompose after a day in the sun.鸡蛋在太阳下放了一天后开始变坏。
• Most animals decompose very quickly after death.大多数动物死后很快腐烂。

6 landslide   

n.(竞选中)压倒多数的选票；一面倒的胜利

参考例句：

• Our candidate is predicated to win by a landslide.我们的候选人被预言将以绝对优势取胜。
• An electoral landslide put the Labour Party into power in 1945.1945年工党以压倒多数的胜利当选执政。

7 remarkably   

ad.不同寻常地，相当地

参考例句：

• I thought she was remarkably restrained in the circumstances. 我认为她在那种情况下非常克制。
• He made a remarkably swift recovery. 他康复得相当快。

8 hardy   

adj.勇敢的，果断的，吃苦的；耐寒的

参考例句：

• The kind of plant is a hardy annual.这种植物是耐寒的一年生植物。
• He is a hardy person.他是一个能吃苦耐劳的人。

9 sediment   

n.沉淀，沉渣，沉积(物)

参考例句：

• The sediment settled and the water was clear.杂质沉淀后，水变清了。
• Sediment begins to choke the channel's opening.沉积物开始淤塞河道口。

10 previously   

adv.以前，先前（地）

参考例句：

• The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
• Let me digress for a moment and explain what had happened previously.让我岔开一会儿，解释原先发生了什么。

11 ecosystem   

n.生态系统

参考例句：

• This destroyed the ecosystem of the island.这样破坏了岛上的生态系统。
• We all have an interest in maintaining the integrity of the ecosystem.维持生态系统的完整是我们共同的利益。

12 extinction   

n.熄灭，消亡，消灭，灭绝，绝种

参考例句：

• The plant is now in danger of extinction.这种植物现在有绝种的危险。
• The island's way of life is doomed to extinction.这个岛上的生活方式注定要消失。

13 deteriorating   

恶化，变坏( deteriorate的现在分词 )

参考例句：

• The weather conditions are deteriorating. 天气变得越来越糟。
• I was well aware of the bad morale and the deteriorating factories. 我很清楚，大家情绪低落，各个工厂越搞越坏。

14 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

15 DNA   

(缩)deoxyribonucleic acid 脱氧核糖核酸

参考例句：

• DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。
• Gene mutations are alterations in the DNA code.基因突变是指DNA密码的改变。