青海省湟水流域红桦林的分布规律

Distribution Law of Betula albo-sinensis Qinghai Huangshui River Valley

通过二类资源调查数据总结了青海湟水流域的红桦林的分布及生境、组成与结构、林型、生长规律及更新与演替。调查结果表明:红桦林分布地区气候干湿季分明,分布区海拔2300～2900m;林分结构和组成不稳定且复杂;林型同龄单层纯林居多,主要有为苔草红桦林和灌木红桦林2种,相林不整齐,生长缓慢,树干分叉多枝,干形弯曲,尖削度较大,立木多呈团状分布。林分分层明显,可分为乔木层、下木层、草被层、苔藓层等四个层次;20龄后开始结实,40年后进入盛期,非常有利于天然更新。现有红桦林绝大部分是云杉林被破坏后而形成的次生林,红桦幼树随着年龄的增大,需光量也随之增加,常因不能忍受林内较弱的光照而逐渐衰弱和死亡,属云杉林演替过程中的一个过渡阶段。

Through Two types of resources survey data the paper summarize distribution and habitat, the composition and structure of forest types, growth regulation, and update and succession of Betula albo-sinensis Huangshui valley Qinghai. The survey results show that：distribution of regional climate wet and dry season clearly, the distribution of district elevation 2300-2900 ; stand structure and composition of the instability and complexity; forest types have monolayer pure forest, and shrub birch, forest irregular, slow growth, trunk forked branch, trunk-shaped bend, taper, stump mostly slug distribution. The obvious stand stratification, can be divid- ed into four levels of the tree layer,the understory layer,grass layer, moss layer; strong after 20 age ,40 years after the peak, is very conducive to natural regeneration. Existing birch, most of the spruce forest is destroyed after the formation of secondary forest, with age increases, the required amount of light also increases, often because they can not put up with weak light in the forest and gradually weakened and death, is a transitional stage in the spruce forest succession process.