托福阅读真题+题目+答案：Grassland Environment

托福阅读真题+题目+答案：Grassland Environment

As opposed to forests, grasslands receive markedly less precipitation. ■ This is one of the reasons why trees, which usually require a significant amount of moisture, are spaced relatively sparsely in grasslands. ■ Due to the facts that most grasslands are situated in the center of continental landmasses, and that costal mountain ranges can block west-to-east winds as is the case with the Great Plains in North America, air masses from the north and south are highly influential on grasslands. ■ The Great Plains receive cold Arctic air in winter and hot tropical air in summer. ■ A typical grassland climate includes hot summers with long periods of desiccation and cold winters with erratic snow cover. Consequently, plants in these grassland areas experience low soil moisture and, additionally, are exposed to fixll sun, strong dry winds, and extreme summer heat and winter cold. Grassland plants must adapt to these conditions.

To support research on various types of ecosystems, during the 1970s, The National Science Foundation started what is known as the Long-Term Ecological Research (LTER) program. With the LTER program, scientists working at far-away sites can share data and collaborate to identify and understand large scale ecological patterns. At one LTER site in the Flint Hills of Northeastern Kansas, scientists made an important discovery about the influence of precipitation on plant productivity, the fuel on which ecosystems run. It was found that grasslands respond more strongly to pulses in rainfall than any other ecosystem. Dramatic bursts of plant growth and significant increases in primary productivity result from intermittent rainfall in grasslands. This pattern indicates that grasslands have a high underlying growth potential that surfaces when enough water is suddenly available. Because of these findings, LTER scientists have proposed that grassland annual primary productivity can be a useful indicator of global climate change. Similar to the canaries that miners used to carry into mines to warn of poisonous gases, grasslands may be able to serve as a warning of climate change and how it is affecting plants and humans. 

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托福阅读真题题目：

1. According to paragraph 1, grassland regions have extreme summer heat and winter cold as a result of those areas being

(A) affected primarily by air masses that move from east to west

(B) surrounded by mountains on all sides

(C) in the middle area from both the tropics and the Arctic

(D) isolated from west-to-east air movements

2. The word collaborate in the passage is closest in meaning to

(A) work together

(B) make an attempt ,

(C) compare outcomes

(D) acquire evidence

3. Why does the author use the phrase the fuel on which ecosystems run?

(A) To explain why grasslands are a difficult ecological pattern to study

(B) To illustrate what discovery scientists made at the LTER site in the Flint Hills of northeastern Kansas

(C) To point out that research run by the LTER program can lead to practical results

(D) To emphasize the fundamental importance of precipitation on ecosystems

4. The word intermittent in the passage is closest in meaning to

(A) strong

(B) regular

(C) occasional

(D) unusual

5. According to paragraph 2, what indicates the strong growth potential underlying in grasslands?

(A) The frequency with which they occur geographically

(B) The average rate in which they reproduce

(C) The way they respond to rainfall

(D) The speed with which they respond to global climate changes

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