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Unformatted text preview: 在在在在在在 www.liuwenyong.com 在在在在在在在在在在在在在在在,在在在在在在在在在在 Paragraph 1 在 The transition from forest to treelesstundra on a mountain slope is often a dramatic one. Within a vertical distance of just a few tens of meters, trees disappear as a lifeform and are replaced by low shrubs, herbs, and grasses. This rapid zone of transition is called the upper timberline or tree line. In many semiarid areas there is also a lower timberline where the forest passes into steppe or desert at its lower edge, usually because of a lack of moisture. 1. The word “dramatic” in the passage is closest in meaning to ○Gradual
2. Where is the lower timberline mentioned in paragraph 1 likely to be found? ○In an area that has little water ○In an area that has little sunlight
○Above a transition area
○On a mountain that has on upper timberline.
3. Which of the following can be inferred from paragraph 1 about both the upper and lower timberlines? ○Both are treeless zones ○Both mark forest boundaries.
○Both are surrounded by desert areas.
○Both suffer from a lack of moisture.
Paragraph 2在The upper timberline, like the snow line, is highest in the tropics and lowest in the Polar Regions. It ranges from sea level in the Polar Regions to 4,500 meters in the dry subtropics and 3,5004,500 meters in the moist tropics. Timberline trees are normally evergreens, suggesting that these have some advantage over deciduous trees (those that lose their leaves) in the extreme environments of the upper timberline. There are some areas, however, where broadleaf deciduous trees form the timberline. Species of birch, for example, may occur at the timberline in parts of the Himalayas.
4. Paragraph 2 supports which of the following statements about deciduous trees? ○They cannot grow in cold climates.
○They do not exist at the upper timberline.
○They are less likely than evergreens to survive at the upper timberline.
○They do not require as much moisture as evergreens do.
Paragraph 3 在 At the upper timberline the trees begin to become twisted and deformed. This is particularly true for trees in the middle and upper latitudes, which tend to attain greater heights on ridges, whereas in the tropics the trees reach their greater heights in the valleys. This is because middle and upper latitude timberlines are strongly influenced by the duration and depth of the snow cover. As the snow is deeper and lasts longer in the valleys, trees tend to attain greater heights on the ridges, even though they are more exposed to highvelocity winds and poor, thin soils there. In the tropics, the valleys appear to be more favorable because they are less prone to dry out, they have less frost, and they have deeper soils.
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5. The word attain in the passage is clo...
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This note was uploaded on 09/17/2013 for the course LANGUAGE 13DL208 taught by Professor Wang during the Fall '13 term at East China Normal University.
- Fall '13