Quantitative analysis of weed communities in wheat fields in Jiangsu.
Outputs of the principal component analysis (PCA) of weed communities in wheat fields in Jiangsu, China, were ecologically interpreted after the comprehensive infestation indices of all weed populations from 150 sampling sites were assessed by visual scoring of the level of weed infestation of wheat in a 7-point scale. The main factors determining the weed communities and infestations in wheat fields in Jiangsu were the geographic climate and soil properties. PCA showed the 150 sampling sites could be divided into 5 groups, i.e. wheat rotated with rice south of the Changjiang river (group A), wheat rotated with dry crops in the Ning-Zhen-Yang hill region (group B), wheat rotated with dry crops in the coastal region (group C), wheat rotated with dry crops in the Xu-Huai region (group D) and wheat rotated with rice in the riverside regions of Changjiang and north of Jiangsu (group E). The dominant weeds in each group were determined using the comprehensive infestation index values and frequency and a weed management strategy was suggested based on the weed distribution pattern in each group.