首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Forestry Forest Fire Why does the instructor say this:
Forestry Forest Fire Why does the instructor say this:
admin
2012-01-14
25
问题
Forestry Forest Fire
Why does the instructor say this:
We all know that change is a fact of life. For North American forests, change often comes in the form of fire. After thousands of years of living with fire, many plant and animal species have come to depend on its periodic presence. Without fire, ecosystems can stagnate and lose their diversity of life.
In the past, before we understood the role that fire plays in the natural life cycle of our forests, our goal was to prevent or contain all forest fires. For almost ninety years, our land management agencies tried to eliminate fires. In many cases, we protected the trees, but at the expense of the forest community. Now we know that fire is a natural agent that rejuvenates a forest. And we know that fire suppression can actually threaten the lives of healthy trees. So, today our policy is to allow natural fires to burn under close observation and to set "prescribed" fires under carefully controlled conditions.
Research shows that forests go through natural fire cycles. Periodic fires are necessary for several reasons. Fire removes nutrients from standing dead trees and returns them to the earth, where they become available to the root systems of new trees. Fire also opens the forest to sunlight. Openings in the tree cover benefit a variety of wildlife by stimulating the growth of lush green plants, which are eaten by several species of animals.
Fire is nature’s way of controlling insect infestations. By contrast, fire suppression preserves dead wood that harbors insect pests, like the larvae of the mountain pine beetle. These beetle larvae feed on the inner bark of some trees, which blocks the flow of nutrients and eventually kills the trees. When dead trees burn during periodic outbreaks of fire, the heat kills off great numbers of beetles and larvae, providing a natural method of pest control.
The exclusion of fire from the ecosystem is creating unhealthy, overcrowded forests that contain more fuel for larger, more severe fires. For example, when a huge fire threatened a grove of giant sequoias in California, observers noted that the flames were fed by dead wood and combustible debris that had accumulated on the forest floor over years of fire suppression.
A large-scale, intense forest fire causes more significant impacts to water, soil, and air resources than a managed prescribed fire. Prescribed fire, or controlled fire, has several purposes. Chiefly, it reduces the hazard of more serious wildfires by periodically burning accumulated weeds, brush, and other plants. If done carefully, prescribed burning also releases nutrients back into the soil and controls insect pests. In Florida, prescribed burns are carried out every three to five years in one of the national forests. These controlled burns keep the forest open and reduce the growth of problem species.
We recognize that fire is a natural and revitalizing process that enhances the diversity of the forest. However, we also know that fire has consequences. There may be smoky, hazy skies and patches of blackened forest for a long time after a fire. There’s also the risk of a fire becoming too large and threatening inhabited areas. But we have to accept these realities if our forests are to retain their ecological balance.
选项
A、To explain why good firefighters are needed
B、To tell about his own observation of a large fire
C、To find out if students have ever seen a fire
D、To give examples of the negative effects of fire
答案
D
解析
Why does the instructor say this:
"We recognize that fire is a natural and revitalizing process that enhances the diversity of the forest. However, we also know that fire has consequences. There may be smoky, hazy skies and patches of blackened forest for a long time after a fire. There’s also the risk of a fire becoming too large and threatening inhabited areas."
The instructor’s purpose is to give examples of the negative effects of fire. The instructor says ...fire has consequences (negative effects), and then he lists smoky, hazy skies and patches of blackened forest, and the risk of afire becoming too large as examples. (2.3)
转载请注明原文地址:https://kaotiyun.com/show/dUyO777K
0
托福(TOEFL)
相关试题推荐
ChooseTHREEletters,A-G.Writethecorrectlettersinbox13onyouranswersheet.WhichTHREEofthefollowingareadvantages
DothefollowingstatementsagreewiththeinformationgiveninReadingPassage3?Inboxes34-40onyouranswersheet,writeTR
DothefollowingstatementsagreewiththeinformationgiveninReadingPassage3?Inboxes34-40onyouranswersheet,writeTR
Youshouldspendabout20minutesonQuestions1-13whicharebasedonReadingPassage1below.AlfredNobelThemanbehindthe
TheHistoryoftheGuitarTheword’guitar’wasbroughtintoEnglishasanadaptationoftheSpanishword’guitarra,’whichwas,
HowdesertsareformedA.Adesertreferstoabarrensectionofland,mainlyinaridandsemi-aridareas,wherethereisal
AccordingtoMrSingh,onwhichthingdomanypeoplemakesuperficialobservations?HowmanychildrendoesMrSinghhave?
Whatwasthestudentsurprisedtodiscoverhehadalotof?Theprofessorpointsoutthattheuniversitylanguagecentre______
Whichattitudeisassociatedwiththefollowingpeopleduringtheconversation?ChooseSIXanswersfromtheboxandwritetheco
Whichattitudeisassociatedwiththefollowingpeopleduringtheconversation?ChooseSIXanswersfromtheboxandwritetheco
随机试题
国际电视的发展进程有什么特点?简述它的主要传送和接收方式。
骨与关节结核的病因,应除外下列哪项
患者,女,28岁。经来淋漓不净,经色鲜红,诊为崩漏,近日颜面长有痤疮,色红肿痛,舌红苔略黄,脉细数。治疗应首选
李某向自己妻子担任厂长的某集体企业大量采购不合格的原材料的行为构成()以下关于吴某行为的说法,正确的是()
预防机械伤害的对策包括实现机械本质安全和提高操作人员安全素质两方面。其中,选择实现机械本质安全措施的最佳顺序是()。
某生产性企业2004年1月申报2003年度企业所得税,申报全年主营业务收入6500000元,其他业务收入320000元,全年实现会计利润98000元,并缴纳企业所得税26460元,2004年4月,主管税务机关对该企业所得税进行检查,查出部分经济业务及账务处
下列各项中,注册会计师在记录已实施审计程序的性质、时间安排和范围时,应当记录的内容有()。
最长诉讼时效的起算点是()。
在报表中,若文本框控件的"控件来源"属性设置为:=[page]&"页/"&[pages]&"页",该报表共10页,则打印预览报表时第2页报表的页码输出为
Likeallanimalspecies,plantspeciesmustspreadtheiroffspringtosuitableareaswheretheycangrowandpassontheirparen
最新回复
(
0
)