它们占据着森林上线至永久雪线之间的高山带和广阔的高原面，从高原东南部至西北部有水平方向的地域分异。
These plant communities occupy the alpine belts between the upper line of forest and the permanent snow-line , and they distributively have horizontal regional differentiation from the southeast to the northwest of the Plateau .
永久雪线