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
In an intact plant community, undisturbed by human intervention, the composition of a community is mainly a function of the clim
In an intact plant community, undisturbed by human intervention, the composition of a community is mainly a function of the clim
admin
2011-02-11
78
问题
In an intact plant community, undisturbed by human intervention, the composition of a community is mainly a function of the climate and the type of soil. Today, such original communities are very rare—they are practically limited to national parks and reservations.
Civilization has progressively transformed the conditions determining the composition of plant communities. For several thousand years vast areas of arable land have been hoed, ploughed, harrowed and grassland has been cut or grazed. During the last decades the use of chemical substances, such as fertilizers and most recently of weed killers (herbicides) has greatly influenced the composition of weed communities in farm land.
All selective herbicides have specific ranges of activity. They control the most important weeds but not all the plants of a community. The latter profit from the new free space and from the fertilizer as much as the crop does; hence they often spread rapidly and become weeds unless another herbicide for their eradication is found.
The soil contains enormous quantities of seeds of numerous specie—up to half a million per square meters according to scientific literature—that retain their ability to germinate for decades. Thus it may occur that weeds that were hardly noticed before emerge in masses after the elimination of their competitors. Hence, the knowledge of the composition of weed communities before selective weed killers are applied is not only of scientific interest since the plant species present in the soil in the form of seeds must be considered as potential weeds. For efficient control the identification of weeds at the seedling stage, i.e. at a time when they can still be controlled, is particularly necessary; for the choice of the appropriate herbicide depends on the composition of the weed community.
The composition of a plant community______.
选项
A、depends on climate and soil type in a virgin environment undamaged by human beings
B、was greatly affected by human beings before they started using chemical substances on the soil
C、was radically transformed by uncivilized human beings
D、refers to plants, trees, climate, type of soil and the ecological environment
答案
A
解析
本题为细节判断题。原文的第一段的第一句话就告诉了我们:植物种群,尤其是未被人类破坏的植物种群,它的构成主要取决于气候和土壤的类型。A与原文描述的内容相符。B,C,D的描述与原文不相符合。
转载请注明原文地址:https://kaotiyun.com/show/MleO777K
0
专业英语八级
相关试题推荐
A、youngageB、hisattitudeonIraqwarC、lackofexperienceininternationalaffairsD、majordisagreementwithKerryC
TheAmericanTaxSystemGovernmentsraiserevenuesthroughtaxation,Ataxisa【1】______paymenttogovernment.IntheUnit
TheAmericanTaxSystemGovernmentsraiserevenuesthroughtaxation,Ataxisa【1】______paymenttogovernment.IntheUnit
Byascribingculturaltransmissiontolanguage,wemeanthat______.
1Duringtheadolescence,thedevelopmentofpoliticalideologybecomesapparentintheindividual;ideologyhereisdefined
1"Internationalcommunication"iscommunicationbetweenmembersofdifferentcultures.Thisdefinitionissimple.Butthep
NewYorkwasoncethemurdercapitaloftheworld.Thankstothezero-tolerancepolicingpolicyintroducedbyGiuliani,themean
从前有个愚人,有一天想上市去买双新鞋。他便先用尺子把脚量了量。拿了根稻秆,记下尺码。可是因为急于赶路,把稻秆忘在家里了。他来到市上,找到了卖鞋的摊子,摸了摸口袋,记尺码的稻秆不见了,就对卖鞋的说:“尺码忘在家里了,不晓得大小,让我回家拿尺码去!”说罢,拔腿
B英国文学之作家概况。DanielDefoe是英国现实主义小说家,被誉为“英国及欧洲小说之父”,其代表作为RobinsonCrusoe(《鲁滨逊漂流记》)。
AdviceforFamiliesfromtheScottishCouncilforResearchinEducation."Ifyouareworrieddiscussthiswithateacher."
随机试题
本题的功能是将文件java2.java复制为文件java2.java.bak。importjava.io.*;publicclassjava2{publicstaticvoidmain(Stringsarg[]){try{File
根据《图书质量管理规定》,图书的设计质量主要涉及()等。
使个人改变以前的知识结构、价值标准和行为模式,建立起新的、符合社会要求和新的形势需要的知识结构、价值标准和行为模式的过程,被称为【】
男,20岁,神志不清2小时入院,既往患1型糖尿病5年,长期皮下注射胰岛素,近3天因腹泻而停用。体检:血压70/50mmHg,皮肤中度失水征,呼吸深大。有烂苹果味,心率130次/分。需立即采取的治疗措施是
患者男,68岁。因间歇、无痛性肉眼血尿诊断为膀胱癌入院。诊断膀胱癌最可靠的方法是()。
工程建设项目投资按()分类,可分为工业、农业、城市基础设施工程建设项目等。
室内给水管与排水管平行埋设时管外壁的最小允许距离为( )。
下列各项中,不会导致留存收益总额发生增减变动的有()。(2013年)
2017年3月,某企业对已使用过3年的不动产(作为生产车间使用)进行改建,该不动产原值500万元,改建增加原值300万元,改建中发生进项税20万元(均取得增值税专用发票),改建工程当月完工,则以下说法正确的是()。
下面关于集线器特点的描述中,错误的是______。
最新回复
(
0
)