长期稻鸭共作对稻田杂草群落组成及物种多样性的影响

INFLUENCE OF LONG-TERM RICE-DUCK FARMING SYSTEMS ON THE COMPOSITION AND DIVERSITY OF WEED COMMUNITIES IN PADDY FIELDS

2000～2003年连续4年研究了稻鸭共作条件下田间杂草群落的特征及其动态变化规律。结果表明，在长期稻鸭共作条件下，田间杂草密度逐年降低，下降趋势符合阻滞模型Y=k＋a·e^bx，模型参数b反映了杂草种群的下降速率。在稻田6种主要杂草中，水虱草（Fimbristylis miliaceae）、陌上菜（Lindernia procumbens）、丁香蓼（Ludwigia prostrata）种群数量降低较快，鸭舌草（Monochoria vaginalis）、异型莎草（Cyperus difformis）次之，稗（Echinochloa crusgalli）最慢。稻鸭共作使稻田杂草群落的物种多样性持续降低，群落均匀度提高，群落相似性与稻鸭共作前相比逐年降低。说明稻鸭共作改变了田间杂草的群落结构，有利于限制杂草的发生危害。随着稻鸭共作的连年进行，对田间杂草的控制效果逐渐上升，4年后达99％以上。稻鸭共作是稻田替代化学除草的一种非常有效的生物、生态控草措施，具有显著的经济和生态效益。

Weed infestation is a major threat to rice production, and herbicides have been used extensively to control weeds in paddy fields. However, increasing environmental pressures against herbicide use have led farmers to consider alternative approaches to weed control and more emphases have been placed on the development of ecologically sound weed management strategies. Ducks can be used to control weeds, and rice-duck farming systems, which integrate raising ducks into rice cultivation methods, provide an innovative approach to weed management. Field studies were conducted during 2000 - 2003 in Danyang, Jiangsu Province, to evaluate the long-term influence of rice-duck fanning systems on the structure and dynamics of weed communities in paddy fields, including effects on the population density, species richness, species diversity, community evenness and similarity of weed communities across years. The results showed that under long-term rice-duck farming systems, the density of paddy weeds decreased annually and the trend was best fit by the model, y = k ＋ a· e^bx, where the parameter b indicated the rate of decrease of different weed populations. Of the six main weed species in paddy fields, the population density of Fimbristylis miliaceae, Lindernia procumbens, and Ladwigia prostrata decreased rapidly, followed by slower decreases in Monochoria vaginalis, Cyperus difformis, and Echinochloa crusgalli. Rice-duck fanning decreased the species richness and species diversity in paddy fields, and increased the evenness of weed communities. Compared to weed communities before the introduction of ducks, Sorensen＇ s similarity indices of weed communities in paddy fields decreased every year, revealing that the structure of weed community was changed substantially. Rice-duck fanning provided a more diversified environment for weed growth and seed storage, which greatly limited weed infestation in paddy fields. Consecutive surveys showed that rice-duck farming was an effective control of paddy weeds with more than a 99% overall reduction by the end of the fourth year. Rice-duck farming is an effective and ecologicallybased weed management strategy that has significant economic and ecological benefits.