青海高寒黄土区典型水源涵养林健康评价

青海高寒黄土区水源涵养林的健康状况直接影响到该地区退耕还林（草）工程生态效益的发挥。以青海省大通回族土族自治县塔尔沟林场的青海云杉Picea crassifolia林，华北落叶松Larix principis-rupprechtii林，白桦Betula platyphylla林，青海云杉-华北落叶松混交林以及青海云杉-白桦混交林等5种典型水源涵养林为研究对象，采用森林健康相关理论和专家咨询法，构建森林健康评价指标体系，利用熵权法确定评价指标权重，最后根据综合指数法进行水源涵养林健康指数计算并分析比较。结果表明:青海云杉-白桦混交林为优质林，白桦林为健康林，青海云杉林和青海云杉-落叶松混交林为亚健康林，华北落叶松林为不健康林。健康评价指标体系中，森林火险等级、叶面积指数和病虫害程度等3项指标的权重较大，依次为0.242 3，0.128 8和0.122 2，是影响森林健康的重要因子。总体上看，混交林健康程度优于纯林，阔叶林健康程度优于针叶林，青海云杉-白桦混交林是相对较好的水源涵养林树种配置模式。

Health evaluation of typical water conservation forests in the alpine loess area of Qinghai

The ecological effect of the Grain for Green Project in the alpine loess area of Qinghai, affected the health status of water conservation forests. However, there is a lack of scientific evaluation method in this area present. This study was aimed to identify the key environmental factors affected the forest and find suitable vegetation types by making health evaluation on water conservation forests. Five typical water conservation forests, including Picea crassifolia, Larix principis-rupprechtii, Betula platyphylla, Picea crassifolia-Larix principis-rupprechtii, and Picea crassifolia-Betula platyphylla, in the Taergou Forest Farm of Datong County were taken as research objects. Three standard samples (20 m×20 m) were selected in every stand for plant (trees, shrubs and herbs) investigation and soil properties measurement. The theory of forest health, combined with expert consultation were used along with the entropy weight method to construct the forest health evaluation index system. The health status of these five forests were evaluated and analyzed by the integrated health index. Results showed that P. crassifolia-B. platyphylla was a high quality forest, B. platyphylla was a healthy forest, P. crassifolia and P. crassifolia-L. principis-rupprechtii were fairly healthy forests, and L. principis-rupprechtii was an unhealthy forest. In the health evaluation index system, the three most important indexes, or critical factors affecting forest health, and their weights, were forest fire risk rating (0.242 3), leaf area index (0.128 8), and degree of pests and disease (0.122 2). Generally, the health of a mixed forest was better than a pure forest, a broadleaf forest was better than a coniferous forest, and the P. crassifolia-B. platyphylla forest was a relatively good tree species allocation model for a water conservation forest.