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VOA慢速英语2009-SCIENCE IN THE NEWS - Tree Deaths in Western US

时间:2009-03-13 06:08:11

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(单词翻译)

VOICE ONE:

This is SCIENCE IN THE NEWS in VOA Special English. I'm Bob Doughty1.

VOICE TWO:

And I'm Faith Lapidus. This week, we will tell about one explanation for many trees dying in the western United States. We will tell about a project to make electronic maps of soil in Africa. And, we tell how one kind of caterpillar2 can trick another insect.

(MUSIC)

VOICE ONE:
 
Idaho's Clearwater National Forest in the northwestern U.S.

Scientists have found that trees are dying at an increasing rate in the western United States. The scientists say they believe the tree deaths were partly a result of warmer and drier weather conditions linked to climate change.

A team of eleven researchers reported their findings last month in Science magazine. The researchers work for the United States Geological Survey, the Forest Service and several universities.

They studied trees in seventy-six long-term forests in six American states and the Canadian province of British Columbia. The thirty-year study is said to be the largest ever investigation3 of North America's old growth forests.

VOICE TWO:

The researchers say they were concerned by the findings. The trees they observed were dying two times as fast as trees were thirty years ago. Additionally, the increased death rate was higher than the rate of new tree growth.

The findings are similar to those of other recent observations and studies, including one involving bark beetles4. That study blamed the insect for the destruction of more than one million hectares of pine forest.

VOICE ONE:

The new study found increasing death rates of several kinds of forests, like pine, fir and hemlock5. The higher rates were observed among trees of different ages and sizes.

The elevation6 of the forests was not considered important. Trees high in the mountains were dying at about the same rate as those closer to sea level.

The researchers investigated other possible causes of the tree deaths like insects, fires and air pollution. They also look at issues like operations to clear forests, and increasing competition among trees. Yet the researchers say none of these are as likely to blame for the tree deaths as climate change.

VOICE TWO:

Nathan Stephenson was a lead writer of the report. He says temperatures have increased in the areas where forests are found. Since the nineteen seventies, temperatures have increased almost half a degree Celsius7 in each ten-year period.

Mister Stephenson says summers are becoming longer and hotter in the western United States. This makes trees weaker and decreases their ability to survive insect attacks and forest fires.

The researchers say the long-term effects of the increased death rates are hard to predict. However, they say, there could be fewer forests in the future.

VOICE ONE:

Forests are important to the environment because they take in carbon dioxide and release another gas -- oxygen. This process removes carbon from the atmosphere. However, carbon is released when trees die or burn. If trees take in less carbon dioxide, scientists say, it could increase the effects of climate change.

Some researchers say new measures may be needed to keep the forests alive. Mister Stephenson says one of the best answers is to reduce the amount of pollution that people produce.

(MUSIC)

VOICE TWO:
 
Women farming in the Central African Republic

Poor soil keeps many farmers in Africa from growing good crops. Low soil fertility has slowed agricultural production in parts of the continent for years. The United Nations says that one-third of the people south of the Sahara Desert suffer from hunger.

But a newly announced project promises help for the situation. A not-for-profit agency is working toward developing soil maps and making them available on the Internet. The agency is called the International Center for Tropical Agriculture. It plans to describe the soil in forty-two nations in sub-Saharan Africa.

VOICE ONE:

When the project is completed, farmers will be able to get information that will help them decide what to plant and how to care for their land. In the past, it often has been hard to get complete information about soil conditions. Maps for the purpose exist. But they are in paper form and often not widely available.

The Tropical Soil Biology and Fertility Institute in Kenya will supervise the project. Institute director Nteranya Sanginga says supervision8, or management, of soil in sub-Saharan Africa must improve. He said the improvements are needed if the area is to reduce poverty and feed growing populations. He said the improvements also are needed to fight the effects of climate change.

VOICE TWO:

Researchers from the African Soil Information Service will study earth samples and rate them. The researchers will also use satellite technology to create images showing the nutrients9 and wetness of the samples. The images also will show the amount of organic material in the soil.

The researchers also will study chemical and physical qualities of the soil with a method called infrared10 spectroscopy. The method can quickly judge the soil's ability to hold water and take-in nutrients. Project information manager Peter Okoth says a majority of farmers may have the information on-line in three years.

The Bill and Melinda Gates Foundation and the Alliance for a Green Revolution in Africa have given eighteen million dollars to collect the information. The money will be provided over four years. Project partners include the Earth Institute at Columbia University in the United States

(MUSIC)

VOICE ONE:

Have you ever wondered what it would be like to be treated like an important leader? A European butterfly species has found a way to make that wish come true.

Insect experts say ants communicate mainly through touch and chemical signaling. But scientists now believe that the leader of an ant community, the queen ant, makes sounds that set her apart from other ants. Because of the sounds, worker ants feed and protect the queen ant.

VOICE TWO:

The scientists say they found that one kind of caterpillar has ways to reproduce a sound that the worker ants think is their queen. The caterpillars11 grow to become Maculinea rebeli, also known as the Rebel's Large Blue butterfly.

The caterpillars also release chemicals that trick the ants into bringing them to their communities, or colonies. Once inside, the caterpillars make the sounds of the queen ant. The ants feed and care for them during a period when they are inactive. After eleven to twelve months, the caterpillars form pupae and become butterflies.

VOICE ONE:

New electronic technology made it possible for the scientists to record the queen and worker ant sounds. The sound the caterpillar makes was also recorded. When played back to the worker ants, they reacted the same way to the caterpillar sounds as they did to the queen ant sounds. They gathered around a device making the sounds and did not move for hours.

The queen ant and the caterpillar sound very different to the human ear. However, scientists say similarities in what they called resonant12 frequency were found through sound tests.

VOICE TWO:

An international team of researchers carried out the study. The researchers come from Britain's Centre for Ecology and Hydrology, the University of Oxford13 and Italy's University of Turin. The findings were reported last month in Science magazine.

Jeremy Thomas is a professor at the University of Oxford. He found that ants will rescue a caterpillar they believe to be the queen when their ant colony is threatened.

His research showed the worker ants would do this before protecting their young. The ants have even been observed using ant larvae14 to feed a caterpillar when food supplies are low.

VOICE ONE:

Francesca Barbero from the University of Turin was the lead writer of the report. She says the findings show that sounds are more important in the communication between ants than scientists had thought.

The Rebel's Large Blue butterfly has become endangered because of changes to its environment. Currently, it is only found in grassy15 areas within the mountains of Europe.

The scientists believe their findings will help in designing new methods to protect the endangered insects. Scientists are also interested in discovering whether other species have developed ways to use a similar kind of trickery to survive.

(MUSIC)

VOICE TWO:

This SCIENCE IN THE NEWS program was written by Jerilyn Watson and Brianna Blake, who was also our producer. I'm Faith Lapidus.

VOICE ONE:

And I'm Bob Doughty. Read and listen to our programs at voaspecialenglish.com. Join us again next week for more news about science in Special English on the Voice of America.


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点击收听单词发音收听单词发音  

1 doughty Jk5zg     
adj.勇猛的,坚强的
参考例句:
  • Most of successful men have the characteristics of contumacy and doughty.绝大多数成功人士都有共同的特质:脾气倔强,性格刚强。
  • The doughty old man battled his illness with fierce determination.坚强的老人用巨大毅力与疾病作斗争。
2 caterpillar ir5zf     
n.毛虫,蝴蝶的幼虫
参考例句:
  • A butterfly is produced by metamorphosis from a caterpillar.蝴蝶是由毛虫脱胎变成的。
  • A caterpillar must pass through the cocoon stage to become a butterfly.毛毛虫必须经过茧的阶段才能变成蝴蝶。
3 investigation MRKzq     
n.调查,调查研究
参考例句:
  • In an investigation,a new fact became known, which told against him.在调查中新发现了一件对他不利的事实。
  • He drew the conclusion by building on his own investigation.他根据自己的调查研究作出结论。
4 beetles e572d93f9d42d4fe5aa8171c39c86a16     
n.甲虫( beetle的名词复数 )
参考例句:
  • Beetles bury pellets of dung and lay their eggs within them. 甲壳虫把粪粒埋起来,然后在里面产卵。 来自《简明英汉词典》
  • This kind of beetles have hard shell. 这类甲虫有坚硬的外壳。 来自《现代汉英综合大词典》
5 hemlock n51y6     
n.毒胡萝卜,铁杉
参考例句:
  • He was condemned to drink a cup of hemlock.判处他喝一杯毒汁。
  • Here is a beech by the side of a hemlock,with three pines at hand.这儿有株山毛榉和一株铁杉长在一起,旁边还有三株松树。
6 elevation bqsxH     
n.高度;海拔;高地;上升;提高
参考例句:
  • The house is at an elevation of 2,000 metres.那幢房子位于海拔两千米的高处。
  • His elevation to the position of General Manager was announced yesterday.昨天宣布他晋升总经理职位。
7 Celsius AXRzl     
adj.摄氏温度计的,摄氏的
参考例句:
  • The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
  • The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。
8 supervision hr6wv     
n.监督,管理
参考例句:
  • The work was done under my supervision.这项工作是在我的监督之下完成的。
  • The old man's will was executed under the personal supervision of the lawyer.老人的遗嘱是在律师的亲自监督下执行的。
9 nutrients 6a1e1ed248a3ac49744c39cc962fb607     
n.(食品或化学品)营养物,营养品( nutrient的名词复数 )
参考例句:
  • a lack of essential nutrients 基本营养的缺乏
  • Nutrients are absorbed into the bloodstream. 营养素被吸收进血液。 来自《简明英汉词典》
10 infrared dx0yp     
adj./n.红外线(的)
参考例句:
  • Infrared is widely used in industry and medical science.红外线广泛应用于工业和医学科学。
  • Infrared radiation has wavelengths longer than those of visible light.红外辐射的波长比可见光的波长长。
11 caterpillars 7673bc2d84c4c7cba4a0eaec866310f4     
n.毛虫( caterpillar的名词复数 );履带
参考例句:
  • Caterpillars eat the young leaves of this plant. 毛毛虫吃这种植物的嫩叶。
  • Caterpillars change into butterflies or moths. 毛虫能变成蝴蝶或蛾子。 来自辞典例句
12 resonant TBCzC     
adj.(声音)洪亮的,共鸣的
参考例句:
  • She has a resonant voice.她的嗓子真亮。
  • He responded with a resonant laugh.他报以洪亮的笑声。
13 Oxford Wmmz0a     
n.牛津(英国城市)
参考例句:
  • At present he has become a Professor of Chemistry at Oxford.他现在已是牛津大学的化学教授了。
  • This is where the road to Oxford joins the road to London.这是去牛津的路与去伦敦的路的汇合处。
14 larvae w2CxP     
n.幼虫
参考例句:
  • Larvae are parasitic on sheep.幼虫寄生在绵羊的身上。
  • The larvae prey upon small aphids.这种幼虫以小蚜虫为食。
15 grassy DfBxH     
adj.盖满草的;长满草的
参考例句:
  • They sat and had their lunch on a grassy hillside.他们坐在长满草的山坡上吃午饭。
  • Cattle move freely across the grassy plain.牛群自由自在地走过草原。

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