托福TPO1閱讀真題原文及答案翻譯part3
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托福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.
托福TPO1閱讀真題題目Part3
1. The word "dramatic" in the passage is closest in meaning to
○gradual
○complex
○visible
○striking
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?
○B(yǎng)oth are treeless zones.
○B(yǎng)oth mark forest boundaries.
○B(yǎng)oth are surrounded by desert areas.
○B(yǎng)oth suffer from a lack of moisture.
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?
○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: 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
○require
○resist
○achieve
○endure
6. The word "they" in the passage refers to
○valleys
○trees
○heights
○ridges
7. The word "prone" in the passage is closest in meaning to
○adapted
○likely
○difficult
○resistant
8. According to paragraph 3, which of the following is true of trees in the middle and upper latitudes?
○Tree growth is negatively affected by the snow cover in valleys
○Tree growth is greater in valleys than on ridges.
○Tree growth on ridges is not affected by high-velocity winds.
○Tree growth lasts longer in those latitudes than it does in the tropics.
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.
○B(yǎng)ecause of their deformed shapes at high altitudes, trees are not likely to be seriously harmed by the strong winds typical of those altitudes.
○As altitude increases, the velocity of winds increase, leading to a serious decrease in the number of trees found at high altitudes.
○The deformed shapes of trees at high altitudes show that wind velocity, which increase with altitude, can cause serious hardship for trees.
○Increased wind velocity at high altitudes deforms the shapes of trees, and this may cause serious stress for trees.
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?
○To argue that none of several environment factors that are believed to contribute to that phenomenon do in fact play a role in causing it.
○To argue in support of one particular explanation of that phenomenon against several competing explanations
○To explain why the primary environmental factor responsible for that phenomenon has not yet been identified
○To present several environmental factors that may contribute to a satisfactory explanation of that phenomenon
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
○predictable
○widespread
○successful
○developed
12. According to paragraph 6, all of the following statements are true of plants in the alpine zone EXCEPT:
○B(yǎng)ecause they are low, they are less exposed to strong winds.
○B(yǎng)ecause they are low, the winter snow cover gives them more protection from the extreme cold.
○In the equatorial mountains, they tend to be lower than in mountains elsewhere.
○Their low growth form keeps them closer to the ground, where there is more heat than further up.
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
○B(yǎng)irch is one of the few species of tree that can survive in the extreme environments of the upper timberline.
○There is no agreement among scientists as to exactly why plant growth is sharply different above and below the upper timberline.
○The temperature at the upper timberline is probably more important in preventing tree growth than factors such as the amount of snowfall or the force of winds.
○The geographical location of an upper timberline has an impact on both the types of trees found there and their physical characteristics.
○High levels of ultraviolet light most likely play a greater role in determining tree growth at the upper timberline than do grazing animals such as the ibex.
○Despite being adjacent to the timberline, the alpine tundra is an area where certain kinds of low trees can endure high winds and very low temperatures
托福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…
托福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?jīng)]有樹的苔原是一種非常戲劇化的轉(zhuǎn)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(qū)域被稱為上行樹帶界線或林木線。在許多干旱的地區(qū)存在著下行樹帶界線，在這里由于缺乏水分森林變成干草原，甚至在最下端會出現(xiàn)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(qū)的海平面到干燥的亞熱帶地區(qū)的海拔4 500米處以及潮濕的熱帶地區(qū)海拔3 500米至4 500米處都有上行樹帶界線。樹帶界線內(nèi)通常是常綠樹，它們和處于上行樹帶界線處極端惡劣環(huán)境中生長的落葉樹木相比，具有一定的優(yōu)勢。然而，在部分地區(qū)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(qū)，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(qū)的樹木，這些地區(qū)的樹木往往會在山脊上長得更高，而在熱帶地區(qū)的樹木則在山谷里長得更高;因為中高緯度地區(qū)樹帶界線受積雪覆蓋時間和深度的影響很大。由于山谷中積雪覆蓋較厚且持續(xù)時間很長，樹木即便是生長在大風(fēng)和貧瘠的土地里，也往往會在山脊上長得更高。在熱帶地區(qū)山谷里更有利于生長，因為山谷不易干涸、很少結(jié)霜，并且有更深的土壤。
目前還沒有一個普遍認(rèn)同的解釋來說明為什么會在樹帶界線上出現(xiàn)樹木停止生長這種戲劇化的現(xiàn)象。多種環(huán)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(jié)的時間，樹苗無法生長;另外，風(fēng)速會隨著海拔的升高而增加，增加樹木承受的壓力，很明顯，正是這種風(fēng)速帶來的壓力導(dǎo)致樹木在高緯度地區(qū)發(fā)生變形。一些科學(xué)家提出，隨著海拔的上升而不斷增強(qiáng)的紫外線、野生山羊等動物的放養(yǎng)，都是導(dǎo)致樹帶界線形成的因素?；蛟S最重要的環(huán)境因素是溫度，因為如果生長季節(jié)太短并且氣溫太低，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為高山苔原的地帶。由于緊挨著樹帶界線，苔原上都是矮灌木、草本植物和牧草。隨著海拔的增加，物種的數(shù)量和多樣性會逐漸減少，直到出現(xiàn)大量空地伴著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(huán)境中生存，世界上海拔最高的植物是出現(xiàn)在喜馬拉雅山上6 100百米的馬卡魯峰。在這個高度上，被陽光溫暖過的巖石可以將小雪堆融化。
高山植物最突出的特點是其低矮的生長形態(tài)。這種特點使他們能夠避開大風(fēng)最強(qiáng)勢的勢頭，并且有助于他們利用緊鄰地面相對較高的溫度。在這樣一個低溫限制生命的地區(qū)，地表提供的額外溫度是至關(guān)重要的。低矮的生長形態(tài)也可以幫助植物充分利用冬季積雪所提供的保溫環(huán)境。在赤道區(qū)的山脈上低矮的生長形態(tài)并不常見。
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托福TPO1閱讀真題原文及答案翻譯part3
