首页
登录
职称英语
In an intact plant community, undisturbed by human intervention, the compositi
In an intact plant community, undisturbed by human intervention, the compositi
游客
2023-12-16
43
管理
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. [br] 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://tihaiku.com/zcyy/3278164.html
相关试题推荐
HowmanyyearsdostudentshavetostudyatcommunitycollegeintheUnitedStat
HowmanyyearsdostudentshavetostudyatcommunitycollegeintheUnitedStat
TotheTunxisCommunityCollegeClassof2002,Ioffermycongratulations.
TotheTunxisCommunityCollegeClassof2002,Ioffermycongratulations.
Inanintactplantcommunity,undisturbedbyhumanintervention,thecompositi
SincejoiningtheEuropeanEconomicCommunityin______,Britainhasadoptedthe
Thecommunitycollegeisakindof______collegespopularin______tosatisfyth
CommunitycourtsandcommunityjusticeprevailedinEnglandatthetimeoft
CommunitycourtsandcommunityjusticeprevailedinEnglandatthetimeoft
Naturalhealersandevensegmentsoftheconventionalmedicalcommunityreco
随机试题
EffectiveAssignmentsUsingLibraryandInternetResourcesI.Se
Howmanyofyoudrinkcola?Nearlyeverybody.Didyouknowthatcolastarted
机体将热量传给与其直接接触的较冷物体,这种散热方式是( )。A.辐射散热 B
空调定流量水系统,下面的设置哪一条是正确的?()A.末端设备冷水管设置两通电
共用题干 Influenza(流感)Influenzahasbeenwi
护士为患急性乳腺炎的产妇讲解该病的主要病因是A.乳房过大 B.乳汁淤积 C.
《史记》体例有五:十二本纪,记帝王政迹,是编年的。十表,以分年略记世代为主。八书
北京国贸CBD商业园区,采用一路市政电源供电,柴油发电设备作为备用电源,商业园区
基础心理学是研究()。 (A)正常成人心理现象的心理学基础学科 (B
(2014年真题)关于施工企业法人与项目经理部法律关系的说法,正确的是( )。
最新回复
(
0
)