·天新网首页·加入收藏·设为首页·网站导航
数码笔记本手机摄像机相机MP3MP4GPS
硬件台式机网络服务器主板CPU硬盘显卡
办公投影打印传真
家电电视影院空调
游戏网游单机动漫
汽车新车购车试驾
下载驱动源码
学院开发设计
考试公务员高考考研
业界互联网通信探索
您现在的位置:天新网 > 考试 > 托福(TOEFL) > 托福心得
2010年新托福考试阅读材料:树的年轮 你知道吗
http://www.21tx.com 2010年08月17日

  What Do They Do?

  1、Read the patterns of wide and narrow rings in wood from different trees. They match patterns from different trees to identify the year that a tree produced a particular ring. This process of matching across specimens is "cross-dating."

  2、Estimate archaeological ages. Andrew Ellicott Douglas was the first dendrochronologist. He BECame famous for his studies of Pueblo ruins, which he analyzed by cross-dating, the tool that he developed as his "key to prehistoric chronology."

  3、Predict future drought, flood, and other conditions. A. E. Douglas proposed that tree rings would be allow us to measure past climate and, potentially, to predict drought and flood over a period of years, which would provide economic advantage.

  What Causes Variations in Tree Rings?

  When conditions encourage growth, a tree adds extra tissue and produces a thick ring. In a discouraging year, growth is slowed and the tree produces a thin ring. Much of the variation in tree rings is due to variations year-to-year in:

  1、Higher springtime temperature. If spring starts early, the growing season is likely to be longer than usual, causing a tree to have a wider ring.

  2、Lower springtime temperature. A late spring is likely to shorten the growing season, causing a tree to have a narrower tree ring.

  3、Abundant rainfall increases growth, producing a wider ring.

  4、Drought decreases growth, producing a narrower ring.

  5、Species of tree do differ in their response to weather changes. One might respond strongly to changes in overall rainfall, another might be more sensitive to the amount of rain during the late summer, and another to a temperature change that alters the length of the growing season.

  6、Crowding from neighboring trees. This causes a series of narrow rings. Crowding is suspected when the series of narrow rings is more than three, because droughts are usually only one to three years.

  7、If the rings are narrow on one side of a tree with wide rings on the other, the tree was crowded on the side of the tree where the rings are narrow.

  8、A series of many narrow rings followed immediately by wide rings probably means that an encroaching neighbor died, releasing the crowded tree into a growth spurt.

  9、Fire scars suggest past forest fires. The number of annual rings between fire scars shows the period between fires.

  10、Scars due to insect plagues indicate insect infestations.

上一篇: 托福写作:政府应该集中保护环境还是发展经济
下一篇: 2010年托福阅读:会吃虫子的植物-猪笼草

Copyright © 2000-2011 21tx.com, All Rights Reserved.
晨新科技 版权所有 Created by TXSite.net