问题 问答题 简答题

简述林地土壤管理措施。

答案

参考答案:

(1)松土除草

松土:切断毛细管联系,减少水分物理蒸发;改善土壤的保水性、透水性和通气性;促进土壤微生物的活动,加速有机质的分解。在干旱地区,可蓄水,防止蒸发,在湿润地区,提高地温,改善通气状况。在盐碱地,减少春秋季返盐碱时盐分在地表的积累,除掉树周围的盐碱结皮。

除草:排除灌木、杂草等对水、肥、光、热的竞争,及杂草根系对幼树根系生长的妨碍,保持土壤水分。持续年限应根据树种、立地、造林密度和经营强度确定。第一年2-3次,第二年2次,第三年1次。时间根据杂草灌木的形态特征和生活习性,造林树种的生长规律、水分养分动态规律而定。方式和方法:全面、带状;手工、机械、化学方法。深度:5~20cm。

(2)中耕(深翻耕)

(3)施肥

施肥是造林时和林分生长过程中,改善人工林营养状况和增加土壤肥力的措施。发达国家广泛使用,国内尚未全面开展。主要是N、P、K、微量元素肥料配合使用,以发挥各养分之间的相互促进作用。需考虑的因素包括树种特性、土壤贫瘠程度、林龄。有效的施肥时间为林木生长旺盛期,即春季和初夏,此时有利于根系吸收。应用在经济林、速生丰产林。方法包括基肥、追肥、叶面。

(4)灌溉

有条件的地方可以进行,灌水流量根据土壤渗透性能、灌沟长度、灌溉定额及灌溉时间而定。灌水量随树种、林龄、季节和土壤条件而定。以土壤含水量保持在相当于田间持水量的60~70%时生长最佳。干旱区要力争多灌;半干旱半湿润区2~3次∕年。灌溉时间与林木的生长发育节奏相协调,即在树木发芽前后或速生期之前。

灌溉方法:

漫灌、畦灌、沟灌、滴灌、喷灌等。

选择题
单项选择题

Who won the World Cup 1994 football game What happened at the United Nations How did the critics like the new play (1) an event takes place, newspapers are on the streets (2) the details. Wherever anything happens in the world, reporters are on the spot to (3) the news.

Newspapers have one basic (4) , to get the news as quickly as possible from its source, from those who make it to those who want to (5) it.

Radio, telegraph, television, and (6) inventions brought competition for newspaper. So did the development of magazines and other means of communication. (7) , this competition merely spurred the newspapers on. They quickly made use of the newer and faster means of communication to improve the (8) and thus the efficiency of their own operations. Today more newspapers are (9) and read than ever before. Competition also led newspapers to branch out into many other fields. Besides keeping readers (10) of the latest news, today’s newspapers (11) and influence readers about politics and other important and serious matters. Newspapers influence readers’ economic choices (12) advertising. Most newspapers depend on advertising for very (13) .

Newspapers are sold at a price that (14) even a small fraction of the cost of production. The main (15) of income for most newspapers is commercial advertising. The (16) in selling advertising depends on a newspaper’s value to advertisers. This (17) in terms of circulation. How many people read the newspaper

Circulation depends (18) on the work of the circulation department and on the services or entertainment (19) in a newspaper’s pages. But for the most part, circulation depends on a newspaper’s value to readers as a source of information (20) the community, city, county, state, nation, and world—and even outer space.

15()

A.source

B.origin

C.course

D.finance