VOA标准英语2011--ontrolled Time Machine Tests Prairie Fut

Climate-Controlled Time Machine Tests Prairie Future

Researchers from the University of Oregon have set up a kind of time machine to test how a warmer climate might affect grasslands¹ and prairies around the world.
Today, grasslands cover between 25 and 40 percent of the earth's land surface. The researchers want to see what happens to biodiversity as the climate warms.
Will invasive species start to dominate the landscape Will different native plants move in What about the native species trying to survive now?
Ecologist Scott Bridgham helped design the experiment, which uses watering hoses and circles of electric heat lamps. He's one of the leaders of the University of Oregon team trying to mimic² what climatologists predict for this region 50 to 80 years from now.
The chest-high outdoor heat lamps aim to keep the plants in the experiment at a constant three degrees Celsius³ hotter than they would be otherwise. Sprinklers add further realism to the model.
The researchers have set up their windows-on-the-future at three widely-spaced nature preserves in western Oregon and Washington state. At each location, the team has staked out experimental plots in a prairie. Some circles get extra heat and rain on top of what nature currently provides and others are left alone to serve as controls.
More wildflowers bloom in a heated (left) vs. untreated control plot (right).
"Climate change may be good for some of these species," says Bridgham. "It may be bad for some of these species. And so we're trying to sort that out."
Bart Johnson, the co-principal investigator⁴, says all the team members periodically get on their hands and knees to count and measure. "It's very difficult to predict. I think there's no better way to do it than an empirical study like this where we are putting additional heat out here and seeing what the effects are."
At the northernmost of the three sites is a prairie being restored by the private environmental group called The Nature Conservancy. White oxeye daisies catch the eye alongside colorful ground-hugging natives such as blue lupines, purple owl's clover, green bracken fern and a yellow flower called Oregon sunshine. The researchers collect data here.
Some of the plots with heat lamps have more flowers.
"It's kind of cold," says Johnson. "The plants under the heater lamps are not unhappy at all about having a little extra heat right now."
However, other plants flourish in the cold.
"When we go all the way down to southern Oregon, what we have seen there is that there are a small number of the introduced species which are quite invasive that do really well on the plots because now they have cold winters down there, but they have enough warmth and enough moisture in the heated plots to grow very rapidly," says Johnson. "They are emerging before the native species are and tending to smother⁵ out the other plants."
Johnson says having a string of experimental plots stretching 600 kilometers from south to north could also allow the researchers to predict shifts in the ranges of native and exotic plants. Bridgham says the team hopes to extrapolate their results to other regions of the world.
The University of Oregon team received $1.8 million from the U.S. Department of Energy to study climate impacts on dwindling⁶ prairies for three growing seasons. They're about halfway⁷ to the finish line.

1 grasslands   

n.草原，牧场( grassland的名词复数 )

参考例句：

• Songs were heard ringing loud and clear over the grasslands. 草原上扬起清亮激越的歌声。 来自《现代汉英综合大词典》
• Grasslands have been broken and planted to wheat. 草原已经开垦出来，种上了小麦。 来自《简明英汉词典》

2 mimic   

v.模仿，戏弄；n.模仿他人言行的人

参考例句：

• A parrot can mimic a person's voice.鹦鹉能学人的声音。
• He used to mimic speech peculiarities of another.他过去总是模仿别人讲话的特点。

3 Celsius   

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。

4 investigator   

n.研究者，调查者，审查者

参考例句：

• He was a special investigator for the FBI.他是联邦调查局的特别调查员。
• The investigator was able to deduce the crime and find the criminal.调查者能够推出犯罪过程并锁定罪犯。

5 smother   

vt./vi.使窒息；抑制；闷死；n.浓烟；窒息

参考例句：

• They tried to smother the flames with a damp blanket.他们试图用一条湿毯子去灭火。
• We tried to smother our laughter.我们强忍住笑。

6 dwindling   

adj.逐渐减少的v.逐渐变少或变小( dwindle的现在分词 )

参考例句：

• The number of wild animals on the earth is dwindling. 地球上野生动物的数量正日渐减少。 来自《简明英汉词典》
• He is struggling to come to terms with his dwindling authority. 他正努力适应自己权力被削弱这一局面。 来自辞典例句

7 halfway   

adj.中途的，不彻底的，部分的；adv.半路地，在中途，在半途

参考例句：

• We had got only halfway when it began to get dark.走到半路，天就黑了。
• In study the worst danger is give up halfway.在学习上，最忌讳的是有始无终。