问题描述：
The walk can be done over four days,or three if you opt to exit at Rainbow Reach.The trail takes in the lake,rivers,gorges,
glacier-carved valleys and beech forest.On the first day you reach the tree line,giving panoramic views.
这是一段关于户外徒步的句子,请问tree line是啥意思?
glacier-carved valleys and beech forest.On the first day you reach the tree line,giving panoramic views.
这是一段关于户外徒步的句子,请问tree line是啥意思?
问题解答：
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