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前言桦树是我国北方天然次生林区的主要树种之一,在青海,它的面积占次生林总面积的41％,蓄积占29.8％。从祁连山地的北麓到青南高原的峡谷,都可见到桦树的踪迹,它垂直分布在海拔1800—3800米之间。桦树喜光,耐寒,也能在较干旱和浅薄的土层上生长,生态环境非常广阔。它繁殖力强,天然下种和萌芽更新都有很好的效果。早期生长较快,在一般情况下它常成为云杉林的先锋树种和过渡树种。在祁连山东段它和云杉、
Foreword Birch is one of the main tree species in the natural secondary forest area of northern China. In Qinghai, its area takes up 41% of the total area of secondary forest and its volume accounts for 29.8%. From the northern foot of the Qilian Mountains to the canyons of the Qingnan Plateau, you can see the traces of birch trees, which are vertically distributed at an altitude of 1800-3800 meters. Birch hi light, cold, but also in the more dry and shallow soil growth, the ecological environment is very broad. It is fertile, natural and sprout regeneration has a good effect. Early rapid growth, under normal circumstances it often become a pioneer spruce tree species and transitional tree species. In the eastern Qilian Mountains it and spruce,