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
64
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
WhoisTom?[br][originaltext]F:What’syourbrother’sname,Mike?M:Hisname
Whenthefirstgummedpostagestampwasintroduced,somepeoplecalled______a"l
PASSAGETWO[br]Whydoestheauthorchoosetobe"abuy-and-holdinvestor"?Beca
下面属于双音节的单纯词略写法的是()。A.苹果——苹 B.帮助——帮 C.
A.阿胶B.三七C.砂仁D.珍珠母E.葶苈子采用后下方法的药物为()。
海螵蛸的别名是A.穿山甲B.安息香C.乌贼骨D.大腹子E.元寸
影响铅酸蓄电池容量的因素:放电率、、终止电压、极板几何尺寸、电解液浓度等。
使用访谈调查法容易产生偏差。
A.症状轻,非典型病例多 B.排病原体时间长,易转为慢性 C.果酱样大便
甲公司于2013年11月1日向乙公司销售一批产品,货款为8000元,增值税税率为
最新回复
(
0
)