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
The forest from which Man takes his timber is the tallest and most impressive plant community on Earth. In terms of Man’s brief
The forest from which Man takes his timber is the tallest and most impressive plant community on Earth. In terms of Man’s brief
admin
2010-01-26
41
问题
The forest from which Man takes his timber is the tallest and most impressive plant community on Earth. In terms of Man’s brief life it appears permanent and unchanging, save for the seasonal growth and fall of the leaves, but to forester it represents the climax of a long succession of events.
No wooded landscape we see today has been forest for all time. Plants have minimum requirements of temperature and moisture and, in ages past, virtually every part of Earth’s surface has at some time been either too dry or too cold for plants to survive. However, as soon as climatic conditions change in favour of plant life, a fascinating sequence of changes occurs, called a primary succession.
First to colonize the barren land are the lowly lichens, surviving on bare rock. Slowly, the acids preduced by these organisms crack the rock surface, plant debris accumulates, and mosses establish a shallow root-hold. Ferns may follow and, with short grasses and shrubs, gradually form a covering of plant life. Roots probe even deeper into the developing soil and eventually large shrubs give way to the first trees. These grow rapidly, cutting off sunlight from the smaller plants, and soon establish complete domination-closing their ranks and forming a climax community which may endure for thousands of years.
Yet even this community is not everlasting. Fire may destroy it outright and settlers may cut it down to gain land for pasture or cultivation. If the land is then abandoned, a secondary succession will take over, developing nmch faster on the more hospitable soil. Shrubs and trees are among the early invaders, their seeds carried by the wind, by birds and lodged in the coats of mammals.
For as long as it stands and thrives, the forest is a vast machine, storing energy and many elements essential for life.
Why is a "secondary succession" quicker?
选项
A、The ground is more suitable.
B、There is more space for new plants.
C、Birds and animals bring new seeds.
D、It is supported by the forest.
答案
A
解析
从第四段的中间,我们可以看出,根本的原因乃是土壤较为适宜。
转载请注明原文地址:https://kaotiyun.com/show/60dK777K
0
大学英语六级
相关试题推荐
Whatisthemainpurposeofthepassage?Inthesecondparagraph,theword"real"in"realgoods"couldbestbereplacedbywhi
Globalwarmingreferstotheaveragetemperatureoftheatmosphere,oceans,andlandmassesofEarth.Scientistsaregrowingcon
Globalwarmingreferstotheaveragetemperatureoftheatmosphere,oceans,andlandmassesofEarth.Todayatmosphericcarbond
Globalwarmingreferstotheaveragetemperatureoftheatmosphere,oceans,andlandmassesofEarth.Withoutgreenhouseeffect,
Whatissaidabouttheactualityofthepoliticalleadershipstructure?Inthelastparagraphofthepassage,the"communityre
Accordingtothepassage,fightingagainstgreenhouseeffectsuccessfullyrequires______.Whataretheresultsoftheglobalw
Atthe2004AthensOlympics,LiuXiangracedtovictoryinthe110-meterhurdles,clocking12.91secondsthat______theworld
Theoldestandsimplestmethod,then,ofdescribingdifferencesinpersonalitywasto(36)______peopleaccordingto(37)______
随机试题
在Excel2003中,对单元格$B$1的引用是混合引用。()
对肿瘤姑息性切除的描述,不正确的是
异烟肼与维生素B,合用,可减少氢氯噻嗪与氨苯蝶啶合用既可加强利尿,有可防止
管理的环境可分为()和具体环境两大类。
正确地选择施工方法是确定施工技术方案的关键,应从若干可行的施工方法中选择()的施工方法。
中国证监会收到上市公司报送的全部材料后,审核工作时间不超过()个工作日。
政府财政支出的选择目标是()。
下列不属于科学发展观实质的有()。
R国的工业界存在着一种看来矛盾的现象:一方面,根据该国的法律,工人终生不得被解雇,工资标准只能升不能降;但另一方面,这并没有阻止工厂主引进先进的生产设备,这些设备提高了劳动生产率,使得一部分工人事实上被变相闲置(例如让3个人干2人可以胜任的活)。
=________.
最新回复
(
0
)