『新东方在线托福阅读』为托福考生准备了ETS托福TPO/Official 39 Passage 3阅读练习：In paragraph 3, what is the author’s purpose in describing the natural cycle of fires in ponderosa pine forests?真题题目及答案解析，TPO/Official 39 Passage 3阅读原文范文音频翻译

托福TPO/Official 39 Passage 3阅读原文In paragraph 3, what is the author’s purpose in describing the natural cycle of fires in ponderosa pine forests?题目答案及解析-新东方托福官方网校手机版

最近，在美国西部的某些森林类型中，森林火灾的强度和程度有所增加。

Forest fires have recently increased in intensity and extent in some forest types throughout the western United States.

最近发生的大火部分是由于气候变化（近来炎热干燥的夏季趋势）造成的，部分是由于人类活动造成的，原因很复杂，大约30年前，林务员逐渐认识到这一点，但其相对重要性仍存在争议。

This recent increase in fires has resulted partly from climate change (the recent trend toward hot, dry summers) and partly from human activities, for complicated reasons that foresters came increasingly to understand about 30 years ago but whose relative importance is still debated.

一个因素是伐木的直接影响，它通常使森林变成类似大堆的引火柴的东西（用于燃烧的木材）：在砍伐的森林中，地面可能仍然覆盖着树枝和树梢，而当有价值的树干被运走时，它们就会被留下来。茂密的新植被如雨后春笋般涌现，进一步增加了森林的燃料负荷；砍伐和运走的树木当然是最大，最耐火的个体，留下的树木较小且易燃。

One factor is the direct effect of logging, which often turns a forest into something approximating a huge pile of kindling (wood for burning): the ground in a logged forest may remain covered with branches and treetops, left behind when the valuable trunks are carted away; a dense growth of new vegetation springs up, further increasing the forest’s fuel loads; and the trees logged and removed are of course the biggest and most fire-resistant individuals, leaving behind smaller and more flammable trees.

另一个因素是，美国林务局在20世纪的前十年采取了灭火政策（试图扑灭森林大火），原因很明显，它不希望有价值的木材化为灰烬或让人们的家和生命受到威胁。

Another factor is that the United States Forest Service in the first decade of the 1900s adopted the policy of fire suppression (attempting to put out forest fires) for the obvious reason that it did not want valuable timber to go up in smoke, or people’s homes and lives to be threatened.

林务局宣布的目标是“在首次报告后的第二天早上10点之前扑灭每场森林大火。”

The Forest Service’s announced goal became “Put out every forest fire by 10:00 A.M.on the morning after the day when it is first reported.”

1945年后，由于改进了消防技术，消防员更加容易达成这项目标。

Firefighters became much more successful at achieving that goal after 1945, thanks to improved firefighting technology.

几十年来，每年烧毁的土地数量减少了百分之八十。

For a few decades the amount of land burnt annually decreased by 80 percent.

这种乐观的状况在20世纪80年代开始发生变化，这是由于大森林火灾的发生率不断增加，除非降雨和低风相结合，否则基本上无法扑灭大火。

That happy situation began to change in the 1980s, due to the increasing frequency of large forest fires that were essentially impossible to extinguish unless rain and low winds combined to help.

人们开始意识到，美国联邦政府的灭火政策正在助长这些大火，而雷击引发的自然火以前曾在维护森林结构方面发挥了重要作用。

People began to realize that the United States federal government’s fire-suppression policy was contributing to those big fires and that natural fires caused by lightning had previously played an important role in maintaining forest structure.

火灾的自然作用随海拔，树木种类和森林类型的不同而不同。

The natural role of fire varies with altitude, tree species, and forest type.

以蒙大拿州的低海拔美国黄松林为例，历史记录，加上一年生的年轮计数和树桩上的火伤痕迹表明，美国黄松林在自然条件下大约每十年经历一次雷电火灾（即在1910年左右灭火政策发布，并在1945年后取得成效之前。）

To take Montana’s low-altitude ponderosa pine forest as an example, historical records, plus counts of annual tree rings and datable fire scars on tree stumps, demonstrated that a ponderosa pine forest experiences a lightning-lit fire about once a decade under natural conditions (i.e., before fire suppression began around 1910 and became effective after 1945).

成熟的黄松树树皮厚两英寸，相对耐火，而烧掉的是森林的下层植被，它们是上次火灾之后生长出来的对火敏感的花旗松幼苗。

The mature ponderosa trees have bark two inches thick and are relatively resistant to fire, which instead burns out the understory—the lower layer—of fire-sensitive Douglas fir seedlings that have grown up since the previous fire.

但是，在下一次火灾发生之前，这些幼苗只生长了十年，它们的高度仍然太低，火无法从它们扩散到美国黄松树的树冠中。

But after only a decade’s growth until the next fire, those young seedling plants are still too low for fire to spread from them into the crowns of the ponderosa pine trees.

因此，火势仍局限在地面和下层植被。

Hence the fire remains confined to the ground and understory.

结果，许多天然的美国黄松林都具有公园般的外观，燃料负荷低，大树隔开，并且下层植被相对清晰。

As a result, many natural ponderosa pine forests have a parklike appearance, with low fuel loads, big trees spaced apart, and a relatively clear understory.

但是，伐木工人集中精力清除那些大的，古老的，有价值的，耐火的美国黄松，而数十年的灭火却使下层植被充满了花旗松树苗，而这些树苗在成年后又变得很有价值。

However, loggers concentrated on removing those big, old, valuable, fire-resistant ponderosa pines, while fire suppression for decades let the understory fill up with Douglas fir saplings that would in turn become valuable when full-grown.

树木的密度从每英亩30棵增加到200棵，森林的燃料负荷增加了6倍，政府一再未能拨出钱来稀疏树苗。

Tree densities increased from 30 to 200 trees per acre, the forest’s fuel load increased by a factor of 6, and the government repeatedly failed to appropriate money to thin out the saplings.

当树苗丛生的森林最终起火时，无论是由于闪电，人为疏忽，还是（经常令人遗憾地）故意纵火，茂密，高大的树苗（幼树）都可能成为梯子，使火势跃入树木的树冠。

When a fire finally does start in a sapling-choked forest, whether due to lightning or human carelessness or (regrettably often) intentional arson, the dense, tall saplings (young trees) may become a ladder that allows the fire to jump into the crowns of the trees.

结果就是，有时这种情况会造成不可阻挡的地狱之火。

The outcome is sometimes an unstoppable inferno.

如今，林务员发现西方森林管理中最大的问题是如何应对上半个世纪有效灭火期间增加的燃料负荷。

Foresters now identify the biggest problem in managing Western forests as what to do with those increased fuel loads that built up during the previous half century of effective fire suppression.

在潮湿的美国东部，枯树的腐烂速度比干燥的西部要快，在干燥的西部，枯树像巨大的火柴棍一样存留。

In the wetter eastern United States, dead trees rot away more quickly than in the drier West, where more dead trees persist like giant matchsticks.

在理想的情况下，林业局应该管理和恢复森林，稀疏它们，并通过砍伐或控制小火来移走茂密的林下植被。

In an ideal world, the Forest Service would manage and restore the forests, thin them out, and remove the dense understory by cutting or by controlled small fires.

但没有任何政治家或选民愿意花费这样做所需的成本。

But no politician or voter wants to spend what it would cost to do that.

The word “approximating” in the passage is closest in meaning to

All of the following are mentioned in paragraph 1 as consequences of logging that can promote forest fires EXCEPT:

What can be inferred from paragraph 2 about forest-fire suppression before 1900?

Why does the author include the quotation “Put out every forest fire by 10:00 A.M. on the morning after the day when it is first reported”?

In paragraph 3, what is the author’s purpose in describing the natural cycle of fires in ponderosa pine forests?

According to paragraph 4, why is the human preservation of Douglas fir sapling trees a threat to the ponderosa pine forest?

The word “regrettably” in the passage is closest in meaning to

According to paragraph 5, people in the United States would probably not support the described forest-management and restoration techniques because they

Look at the four squares  that indicate where the following sentence could be added to the passage. Such a reduction seemed to demonstrate that the program of fire suppression was having its desired effect.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.

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.

Forest Fire Suppression Forest fires have recently increased in intensity and extent in some forest types throughout the western United States. This recent increase in fires has resulted partly from climate change (the recent trend toward hot, dry summers) and partly from human activities, for complicated reasons that foresters came increasingly to understand about 30 years ago but whose relative importance is still debated. One factor is the direct effect of logging, which often turns a forest into something approximating a huge pile of kindling (wood for burning): the ground in a logged forest may remain covered with branches and treetops, left behind when the valuable trunks are carted away; a dense growth of new vegetation springs up, further increasing the forest’s fuel loads; and the trees logged and removed are of course the biggest and most fire-resistant individuals, leaving behind smaller and more flammable trees. Another factor is that the United States Forest Service in the first decade of the 1900s adopted the policy of fire suppression (attempting to put out forest fires) for the obvious reason that it did not want valuable timber to go up in smoke, or people’s homes and lives to be threatened. The Forest Service’s announced goal became “Put out every forest fire by 10:00 A.M. on the morning after the day when it is first reported.”  Firefighters became much more successful at achieving that goal after 1945, thanks to improved firefighting technology.  For a few decades the amount of land burnt annually decreased by 80 percent.  That happy situation began to change in the 1980s, due to the increasing frequency of large forest fires that were essentially impossible to extinguish unless rain and low winds combined to help.  People began to realize that the United States federal government’s fire-suppression policy was contributing to those big fires and that natural fires caused by lightning had previously played an important role in maintaining forest structure. The natural role of fire varies with altitude, tree species, and forest type. To take Montana’s low-altitude ponderosa pine forest as an example, historical records, plus counts of annual tree rings and datable fire scars on tree stumps, demonstrated that a ponderosa pine forest experiences a lightning-lit fire about once a decade under natural conditions (i.e., before fire suppression began around 1910 and became effective after 1945). The mature ponderosa trees have bark two inches thick and are relatively resistant to fire, which instead burns out the understory—the lower layer—of fire-sensitive Douglas fir seedlings that have grown up since the previous fire. But after only a decade’s growth until the next fire, those young seedling plants are still too low for fire to spread from them into the crowns of the ponderosa pine trees. Hence the fire remains confined to the ground and understory. As a result, many natural ponderosa pine forests have a parklike appearance, with low fuel loads, big trees spaced apart, and a relatively clear understory. However, loggers concentrated on removing those big, old, valuable, fire-resistant ponderosa pines, while fire suppression for decades let the understory fill up with Douglas fir saplings that would in turn become valuable when full-grown. Tree densities increased from 30 to 200 trees per acre, the forest’s fuel load increased by a factor of 6, and the government repeatedly failed to appropriate money to thin out the saplings. When a fire finally does start in a sapling-choked forest, whether due to lightning or human carelessness or (regrettably often) intentional arson, the dense, tall saplings (young trees) may become a ladder that allows the fire to jump into the crowns of the trees. The outcome is sometimes an unstoppable inferno. Foresters now identify the biggest problem in managing Western forests as what to do with those increased fuel loads that built up during the previous half century of effective fire suppression. In the wetter eastern United States, dead trees rot away more quickly than in the drier West, where more dead trees persist like giant matchsticks. In an ideal world, the Forest Service would manage and restore the forests, thin them out, and remove the dense understory by cutting or by controlled small fires. But no politician or voter wants to spend what it would cost to do that.