首页
登录
职称英语
The cause of the decline of North Africa is popularly attributed to climatic
The cause of the decline of North Africa is popularly attributed to climatic
游客
2024-02-23
56
管理
问题
The cause of the decline of North Africa is popularly attributed to climatic changes, the theory being that the area became hotter and drier and the people were forced to abandon a thriving civilization. However, some geologists, after carefully weighing the evidence, have challenged the conclusion that the climate has changed in any important way since Roman tithes. Although climatological factors may also have contributed, it was man who destroyed the balance of nature responsible for maintaining soil fertility and moisture.
Why is it that under certain circumstances, the plant cover is unable to regenerate itself, thus setting the stage for serious erosion(腐蚀)? To answer this question, let us take an extreme example, the destruction of tropical rain forests. In general, the equatorial(赤道附近的)soil is poor: forests can exist in these regions only because they are part of a balanced cycle. All that the forest produces is returned to the forest. The organic matter that falls from the trees constitutes the humus(腐殖土)that the forest requires. When people cut down all the trees to make room for crops, the soil is laid bare and, deprived of shade, heats up. An increase in soil temperature increases the rate of decomposition(分解)of organic matter. Organic nitrogen(氮)is converted into soluble ammonia(氨)and nitrates(硝酸盐), which the rains quickly leach(沥滤,溶滤)away. It has been calculated that a rise in temperature from 77 to 78.8 may increase the loss of nitrogen by fifteen to twenty pounds per acre per year. With the fertility of soil destroyed, an irreversible change from forest to desert can be initiated. [br] Increase in the temperature of tropical soil ______.
选项
A、might cause the overflow of flood
B、may lead to the loss of organic nitrogen in it
C、will produce a great deal of organic nitrogen
D、is harmless to the growth of rain forests
答案
B
解析
这三句话表明温度升高会导致大量有机氮的流失。选项B符合原文意思。
转载请注明原文地址:https://tihaiku.com/zcyy/3474736.html
相关试题推荐
Theminister___________(拒绝回答关于)therumorsofhisresignation.declinedtocom
Thedeclineinmoralstandards--whichhaslongconcernedsocialanalysts--ha
Thedeclineinmoralstandards--whichhaslongconcernedsocialanalysts--ha
Thedeclineinmoralstandards--whichhaslongconcernedsocialanalysts--ha
Thedeclineinmoralstandards--whichhaslongconcernedsocialanalysts--ha
Thedeclineinmoralstandards--whichhaslongconcernedsocialanalysts--ha
Thedeclineinmoralstandards--whichhaslongconcernedsocialanalysts--ha
Someobservershaveattributedthedramaticgrowthintemporaryemploymentt
Someobservershaveattributedthedramaticgrowthintemporaryemploymentt
[originaltext]CamerooninWestAfricaisanationof24separatelanguages
随机试题
Thestudentsarevery______toMissLewisforherkindnessandhardwork.A、grace
【B1】[br]【B2】[originaltext]Ifyouweresupposedtobeatmyhouseat6:00p.m
Searchingforloveisnolongerjustafavoritesubjectforsongs.Ithasal
当地基中塑性展开区最大深度等于1/3或1/4基础宽度,此时对应的荷载称为()
高应变试验时,传感器与桩顶间的距离不宜小于1倍的桩径或桩长()。
2010~2015年间,中国国际出口带宽增速高于30%的年份有多少个?A.
(2019年真题)下列有关子公司和分公司的说法,正确的是()。 Ⅰ.分公司的重
2020年全国农民工总量28560万人,比上年减少517万人。其中,外出农民工1
下列单位或者个人中,一般不是物业管理招标主体的是()。A.物业建设单位
通过图5-2-1-5,关于城市最佳规模与均衡规模之间的关系叙述,正确的是( )
最新回复
(
0
)