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在一张表示植被类型的世界地图上,某些森林类型似乎形成环绕北半球的明显圈环,大致按着现在的气候排列。1.冻原“在北极圈附近地区,当然没有任何植被。但是,从常年冰冻地区逐渐往南是一个在夏季几星期内地下土层解冻达几英寸的地带。这个
On a map of the world that represents the type of vegetation, some of the forest types seem to form distinct rings around the Northern Hemisphere, roughly aligned with the current climate. 1. The tundra "There is certainly no vegetation in the area around the Arctic Circle, but progressively south of the year-round frozen area is a zone that is thawed a few inches below the ground in the summer weeks.