But as Earth's climate has been warming, trees no longer have to just grow horizontally. Many can instead grow up toward the sky. This takes less energy. And with all that leftover energy, these trees have started producing more seeds. This happens especially in places where white spruce (白云杉) grows.
White spruce, which is a North American tree, is quite able to produce a lot of seeds, which can move long distances in the wind. When windblown seeds end up on the tundra beyond the tree line, they eventually can sprout(发芽) new trees. This explains how a forest can move. Of course, the process would work only if the tundra were warm enough. But in recent years, the whole planet has been warming.
New trees will provide shelters for some snow. Keeping the sun's rays from making the white surface disappear. Instead, the trees absorb the sun's heat. This warms the surrounding air. The extra warmth encourages even more trees to produce seeds. That further boosts a forest's ability to expand. In addition, more trees will trap more snow, preventing much of it from being blown away. Snow can trap heat in the soil below, which encourages trees to grow. The recent rise of temperatures has helped more trees grow past the tree line. People worry about impacts on the animals that depend on frozen conditions for food and shelter.
语篇解读:本文是一篇科研报告。主要研究了气温升高对北极圈植物的影响。
【2017版高考英语外研版一轮复习跟踪检测:选修8 Module1《Deep South》(含解析)】相关文章:
★ 2014高考英语(新人教版)一轮基础训练(14)A、B卷(附答案或解析)
★ 【浙江专用】2014届高考英语一轮复习课时作业(二十一)必修5Unit 1《Great scientists》
★ 【北师大版】2014届高考英语一轮复习指导课时作业:Unit 9 A卷 Word版含解析
★ (安徽专用)2014届高考英语一轮复习方案 作业手册(15)模块5 《Unit 15 Learning》(含解析) 北师大版必修1
★ 2017高考四川省广安市英语阅读理解一轮系列训练:29(含解析)
★ 2017高考四川省广安市英语阅读理解一轮系列训练:21(含解析)
★ (安徽专用)2014届高考英语一轮复习方案 作业手册(10)模块4 《Unit 10 Money》(含解析) 北师大版必修1
★ 2017届高考英语二轮复习大题冲关秘籍阅读理解七选五:考纲解读(含解析)
★ 2017届江苏省淮安市新马中学高考牛津译林版英语一轮复习活动单:模块7 unit 4《Public transport》
最新
2017-04-24
2017-04-24
2017-04-24
2017-04-24
2017-04-21
2017-04-21