问题 问答题

简述森林群落对水分的影响。

答案

参考答案:(1)群落能截留降水,保蓄水分,因而能创造群落内部特殊的空气和土壤湿度条件。
(2)使降落在群落中的水分进行再分配,一部分被林冠阻留,直接蒸发返回大气,降水的大部分到达地表,这到达地表的水分,大部分渗入土壤,被土壤保持或渗入地下形成潜流,只有一部分成为地表径流,土壤水分被植物吸收,经蒸腾和蒸发而保留在群落内。
(3)由于群落能阻挡降水,增加土壤水分的入渗,大大减少地表径流,减少了对表土的冲刷。
(4)群落中植物根系交织成网,对土壤有固结作用,可提高群落内土壤抗冲刷的能力。利用群落保持水土,涵养水源,调节小气候。

阅读理解

阅读理解。

    Newspapers are very important in our everyday life. Many people begin their day by reading the paper.

  In this way they learn what is going on in the world. But sometimes they don't have the time to read the

 newspaper carefully and must be pleased with a quick look at the front page. Sometimes they may be in

 such a hurry that they have time only to look at the headlines quickly.

    There are newspapers to please every reader. In big cities there are many kinds with several different

 editions (版本) every day. In small towns there are fewer newspapers and perhaps only one edition each

  day. Some papers in small towns have several editions, especially (尤其)  on Sundays. Besides (除……

 以外)  the front page with the most important news, there is the sports page, the amusement (娱乐)  

 page, the business page and so on.

 1. If people don't have enough time to read all the pages of a newspaper carefully, _____.

    A. they sometimes read the front page

    B. they sometimes read the headlines

    C. they don't read it at all

    D. Both A and B

2. The word headlines may mean _____.   

     A. important editions

     B. words in large letters above stories in a newspaper

     C. interesting stories

     D. some sports and amusement pages

3. By reading the newspaper, people can know _____.    

    A. what is happening in the world

    B. how many editions there are each day

    C. the headlines are not so important

    D. the sports page isn't as clear as the others      

4. Some newspapers in small towns have _____ on Sundays than usual.

    A. more editions

    B. more pictures

    C. fewer editions

    D. fewer pictures

5. If' you want to watch a football match,  you'd better read _____ in the newspaper.

    A. the business page

    B. the front page

    C. the sports page

    D. the amusement page

问答题