Abstract: Investigations on weed community characteristics and weed infestation in paddy fields under longterm laboursaving cultivation was conducted in 138 randomly sampled fields of 14 sites in Yangzhou, Taizhou and Nantong Prefectures in the middle of Jiangsu Province, China by the sevenscale visualization. The data were analyzed by principal component analysis combined with comprehensive evaluation. Thirtysix weed species, belonging to 33 genus of 18 families, were found. The families including the most weed species were Gramineae, Cyperaceae, Compositae, Scrophulariaceae, Alismataceae and Lythraceae. Four weed species Echinochloa crusgalli,Ammannia baccifera,Eclipta prostrata and Leptochloa chinensis showed high dominance and frequency in the three surveyed prefectures, with frequencies of or near 100%. However, there were regional differences in weed infestation level. Yangzhou was the worsthit area, followed by Taizhou and Nantong. Different cultivation techniques corresponded to different dominant weeds, such as Monochoria vaginalis and A. baccifera in the mechanizedtransplanting mode; A. baccifera, Digitaria sanguinalis, M. vaginalis and L. chinensis in the wheatrice interplanting mode; E. crusgalli, M. vaginalis and Ammannia baccifera in the parachute transplanting mode; E.crusgalli, A. baccifera and M. vaginalis in the flooded direct seeding mode; E. crusgalli, A. baccifera and L. chinensis in the dry direct seeding mode. Compared with the conventional manual transplanting mode, the weed communities in paddy fields under the laboursaving cultivations not only had higher species richness, but also had higher dominance. The order of the weed infestation level, from low to high, were conventional manual transplanting＜mechanizedtransplanting＜parachute transplanting＜flooded direct seeding＜dry direct seeding＜wheatrice interplanting.

Key words: weed community, paddy field, laboursaving cultivation, principal component analysis

摘要： 利用“七级目测法”结合定量分析和综合评价对江苏中部的扬州、泰州和南通3个地区6种不同栽培模式稻田的杂草群落进行了调查研究，以期揭示经多年轻型栽培的稻田杂草群落结构及杂草危害特点。在轻型栽培稻田中共发现杂草36种，隶属于18个科33个属。其中，杂草种类较多的科依次为禾本科、莎草科、菊科、玄参科、泽泻科、千屈菜科等。在3个地区皆表现出较高的优势度和发生频率的杂草有4种：稗、水苋菜、鳢肠和千金子，其发生频率都达到或接近100%。然而，地区间草害水平存在差异，扬州地区的杂草危害最重，泰州地区次之，南通地区相对最轻。不同的稻作模式皆对应着不同的优势杂草。机插秧模式中优势度值与发生频率皆较高的杂草为鸭舌草、水苋菜；麦套稻模式中，主要的优势杂草包括水苋菜、马唐、鸭舌草、半边莲等；抛秧稻田中为稗、鸭舌草、水苋菜等；水直播稻作模式下是稗、水苋菜、鸭舌草等；旱直播模式中为稗、水苋菜、千金子等。与传统的手工插秧相比，轻型栽培稻作模式下的杂草群落中，不仅物种丰富度高，而且优势度也高。6种稻作模式杂草危害程度由低到高的顺序为：传统手工插秧＜机插秧＜抛秧＜水直播＜旱直播＜麦套稻。

关键词: 杂草群落, 稻田, 轻型栽培, 主成分分析