Even if trees cannot walk,they are still on the move.
In
parts
of
the
Arctic,entire
forests
are
moving northward . Across the Arctic,temperatures are rising faster
than anywhere else in the world.As that happens,the tree line that marks where forests stop and the treeless tundra (冻原) starts has been shifting northward.Trees growing along the tree line must protect themselves from the cold wind.To do this(水平的) branches low to the ground.The energy it takes for trees to grow this way means they don't have enough energy to make seeds.ppens especially in places where white spruce (白云杉) grows.-blown seeds end up on the tundra beyond the tree linehey eventually can sprout (发芽) new trees.This explains how a forest can move.Of courseping 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.
【【南方新课堂】2017高考英语二轮复习专题训练:组合练 1阅读理解+“七选五”(含解析)】相关文章:
★ 【三维设计】2017版(江苏专用)二轮复习练习:必修1 Unit 3《Looking good feeling good》课时跟踪检测A卷(含解析)
★ 【优化方案】2017届高考英语二轮复习全国卷Ⅱ题型重组训练:第9组(含解析)
★ 【北师大版】2014届高考英语一轮复习指导课时作业:Unit 8 B卷 Word版含解析
★ 湖南省岳阳市2014高考英语一轮单项选择训练题(8)及答案
★ 2017高考四川省广安市英语阅读理解一轮系列训练:6(含解析)
★ 2017届高考英语二轮复习大题冲关秘籍语法填空:体验真题(含解析)
★ 2017高考四川省广安市英语阅读理解一轮系列训练:12(含解析)
★ 湖南省汝城二中2014届高考英语一轮复习阅读训练 (8)
★ 湖南省汝城二中2014届高考英语一轮复习阅读训练 (42)
最新
2017-04-24
2017-04-24
2017-04-24
2017-04-24
2017-04-21
2017-04-21