託福TPO1閱讀真題原文及答案翻譯part3

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       託福TPO1閱讀真題原文Part3

Timberline Vegetation on Mountains

The transition from forest to treeless tundra on a mountain slope is often a dramatic one. Within a vertical distance of just a few tens of meters, trees disappear as a life-form 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.

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 3,500-4,500 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.

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 high-velocity 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.

There is still no universally agreed-on explanation for why there should be such a dramatic cessation of tree growth at the upper timberline. Various environmental factors may play a role. Too much snow, for example, can smother trees, and avalanches and snow creep can damage or destroy them. Late-lying snow reduces the effective growing season to the point where seedlings cannot establish themselves. Wind velocity also increases with altitude and may cause serious stress for trees, as is made evident by the deformed shapes at high altitudes. Some scientists have proposed that the presence of increasing levels of ultraviolet light with elevation may play a role, while browsing and grazing animals like the ibex may be another contributing factor. Probably the most important environmental factor is temperature, for if the growing season is too short and temperatures are too low, tree shoots and buds cannot mature sufficiently to survive the winter months.

Above the tree line there is a zone that is generally called alpine tundra. Immediately adjacent to the timberline, the tundra consists of a fairly complete cover of low-lying shrubs, herbs, and grasses, while higher up the number and diversity of species decrease until there is much bare ground with occasional mosses and lichens and some prostrate cushion plants. Some plants can even survive in favorable microhabitats above the snow line. The highest plants in the world occur at around 6,100 meters on Makalu in the Himalayas. At this great height, rocks, warmed by the sun, melt small snowdrifts.

The most striking characteristic of the plants of the alpine zone is their low growth form. This enables them to avoid the worst rigors of high winds and permits them to make use of the higher temperatures immediately adjacent to the ground surface. In an area where low temperatures are limiting to life, the importance of the additional heat near the surface is crucial. The low growth form can also permit the plants to take advantage of the insulation provided by a winter snow cover. In the equatorial mountains the low growth form is less prevalent.

Paragraph 1: The transition from forest to treeless tundra on a mountain slope is often adramatic one. Within a vertical distance of just a few tens of meters, trees disappear as a life-form 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.

託福TPO1閱讀真題題目Part3

1. The word "dramatic" in the passage is closest in meaning to

2. Where is the lower timberline mentioned in paragraph 1 likely to be found?

3. Which of the following can be inferred from paragraph 1 about both the upper and lower timberlines?

Paragraph 2: 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 3,500-4,500 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?

Paragraph 3: 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 high-velocity 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.

5. The word "attain" in the passage is closest in meaning to

6. The word "they" in the passage refers to

7. The word "prone" in the passage is closest in meaning to

8. According to paragraph 3, which of the following is true of trees in the middle and upper latitudes?

Paragraph 4：There is still no universally agreed-on explanation for why there should be such a dramatic cessation of tree growth at the upper timberline. Various environmental factors may play a role. Too much snow, for example, can smother trees, and avalanches and snow creep can damage or destroy them. Late-lying snow reduces the effective growing season to the point where seedlings cannot establish themselves. Wind velocity also increases with altitude and may cause serious stress for trees, as is made evident by the deformed shapes at high altitudes. Some scientists have proposed that the presence of increasing levels of ultraviolet light with elevation may play a role, while browsing and grazing animals like the ibex may be another contributing factor. Probably the most important environmental factor is temperature, for if the growing season is too short and temperatures are too low, tree shoots and buds cannot mature sufficiently to survive the winter months.

9. Which of the sentences below best express the essential information in the highlighted sentence in the passage? In correct choices change the meaning in important ways or leave out essential information.

10. In paragraph 4, what is the author's main purpose in the discussion of the dramatic cessation of tree growth at the upper timberline?

Paragraph 6: The most striking characteristic of the plants of the alpine zone is their low growth form. This enables them to avoid the worst rigors of high winds and permits them to make use of the higher temperatures immediately adjacent to the ground surface. In an area where low temperatures are limiting to life, the importance of the additional heat near the surface is crucial. The low growth form can also permit the plants to take advantage of the insulation provided by a winter snow cover. In the equatorial mountains the low growth form is lessprevalent.

11. The word "prevalent" in the passage is closest in meaning to

12. According to paragraph 6, all of the following statements are true of plants in the alpine zone EXCEPT:

Paragraph 5: Above the tree line there is a zone that is generally called alpine tundra. █Immediately adjacent to the timberline, the tundra consists of a fairly complete cover of low-lying shrubs, herbs, and grasses, while higher up the number and diversity of species decrease until there is much bare ground with occasional mosses and lichens and some prostrate cushion plants. █Some plants can even survive in favorable microhabitats above the snow line. The highest plants in the world occur at around 6,100 meters on Makalu in the Himalayas. █At this great height, rocks, warmed by the sun, melt small snowdrifts. █

13. Look at the four squares [█] that indicate where the following sentence could be added to the passage.

This explains how, for example, alpine cushion plants have been found growing at an altitude of 6,180 meters.

Where would the sentence best fit?

14. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

At the timberline, whether upper or lower, there is a profound change in the growth of trees and other plants.

Answer choices

託福TPO1閱讀真題答案Part3

答案：

1. ○4

2. ○1

3. ○2

4. ○3

5. ○3

6. ○2

7. ○2

8. ○1

9. ○3

10. ○4

11. ○2

12. ○3

13. ○4

14. There is no agreement among…

Despite being adjacent …

The geographical location of…

　託福TPO1閱讀真題Part3原文翻譯

山上樹帶界線的植被

通常從山坡上的森林到沒有樹的苔原是一種非常戲劇化的轉變。在一個垂直距離只有幾十米的地方，樹木這種生命形式就消失了，取而代之的是低矮的灌木、草本植物和牧草。這種快速過渡的區域被稱爲上行樹帶界線或林木線。在許多幹旱的地區存在着下行樹帶界線，在這裏由於缺乏水分森林變成乾草原，甚至在最下端會出現沙漠。

上行樹帶界線，和雪線一樣，在熱帶最高，在極地最低。從極地地區的海平面到乾燥的亞熱帶地區的海拔4 500米處以及潮溼的熱帶地區海拔3 500米至4 500米處都有上行樹帶界線。樹帶界線內通常是常綠樹，它們和處於上行樹帶界線處極端惡劣環境中生長的落葉樹木相比，具有一定的優勢。然而，在部分地區也有由落葉闊葉林組成的樹帶界線。例如，在喜馬拉雅的部分地區，樺樹就在樹帶界線上。

上行樹帶界線的樹木開始扭曲和變形，尤其在中高緯度地區的樹木，這些地區的樹木往往會在山脊上長得更高，而在熱帶地區的樹木則在山谷里長得更高;因爲中高緯度地區樹帶界線受積雪覆蓋時間和深度的影響很大。由於山谷中積雪覆蓋較厚且持續時間很長，樹木即便是生長在大風和貧瘠的土地裏，也往往會在山脊上長得更高。在熱帶地區山谷裏更有利於生長，因爲山谷不易乾涸、很少結霜，並且有更深的土壤。

目前還沒有一個普遍認同的解釋來說明爲什麼會在樹帶界線上出現樹木停止生長這種戲劇化的現象。多種環境因素都起到作用，例如，積雪過多會讓樹木透不過氣，雪崩和雪移能摧毀樹木;長時間積雪縮短了有效生長季節的時間，樹苗無法生長;另外，風速會隨着海拔的升高而增加，增加樹木承受的壓力，很明顯，正是這種風速帶來的壓力導致樹木在高緯度地區發生變形。一些科學家提出，隨着海拔的上升而不斷增強的紫外線、野生山羊等動物的放養，都是導致樹帶界線形成的因素。或許最重要的環境因素是溫度，因爲如果生長季節太短並且氣溫太低，樹芽和樹苗都無法充分地成長而存活過冬季。

在林木線之上有一個稱爲高山苔原的地帶。由於緊挨着樹帶界線，苔原上都是矮灌木、草本植物和牧草。隨着海拔的增加，物種的數量和多樣性會逐漸減少，直到出現大量空地伴着零星的苔蘚和地衣這樣的伏地墊狀植物。有些植物甚至可以在雪線以上有利的微環境中生存，世界上海拔最高的植物是出現在喜馬拉雅山上6 100百米的馬卡魯峯。在這個高度上，被陽光溫暖過的岩石可以將小雪堆融化。