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
7
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
LawrenceBragg,theCavendishProfessorofExperimentalPhysics,oncewrote:
GertrudeStein’slifedemonstratesher______,herrefusalevertogiveupwithou
Miningoperationsbytheirverynaturehavemajorimpacts,positiveandnega
[originaltext]Americanwomenareusedtobeingindependent.Theyareusedt
关于长期股权投资的处置,下列说法中正确的有()。A、处置采用成本法核算的长期股
股权投资基金管理人应具备至少2名( )。A.负责合规风控的高级管理人员 B.
GHb的测定可以反映测定前多长时间的平均血糖水平A.4~5周B.6~8周C.8~
下列哪一个药物具有吩噻嗪环结构()A.苯巴比妥 B.甲丙氨酯 C.安
以下关于资源税征收管理的描述,不正确的是( )。A.纳税人以自采原矿直接加工为非
(2011年真题)下列建筑装饰涂料中,常用于外墙的涂料是()。A.醋酸乙烯—丙烯
最新回复
(
0
)