浙江中部夏熟作物田主要杂草生态相似性的数量分析

应用七级目测法对浙江中部地区27个夏熟作物田样点的杂草进行了优势等级调查，将所得数据转换成重要值，以杂草在27个样点中的重要值为运算指标，应用主成分分析法和图论聚类中的最小生成树法，对24种杂草的生态学相似性进行了比较，指出了长期使用单一的除草剂导致农田杂草种群迅速更迭的原因：杂草对除草剂的敏感性差异及不同杂草间的生态学特性的差异。

Quantiative Analyses on Main Weed Species Ecological Similarity in Summer Ripe Fields of Middle Zhejiang Province

In the summer ripe fields of middle Zhejiang Province, 27 random sampling fields of 27 sites on different ecological conditions were surveyed in detail with seven scales by visualization of weed dominance to summer ripe to obtain the weed important value. The principal components analysis (PCA) and the method of minimal spanning tree(MST) were used to reveal the ecological similarity of 24 main weeds in summer ripe fields. The fast shift of weed populations under succesive application of a certain herbicide in a long peroid of time results from two factors:the different sensitivity of various weeds to the herbicides applied and the different ecological demands of weeds in crop fields, which makes it important to study the difference between various weeds in crop fields.