Abstract: Difference in responses to the competitions between rice and barnyardgrass with different seedling emergence time under FACE(Free-air CO2 enrichment)was studied by the field experiments.Under the FACE conditions,the tiller number,biomass and yield of rice increased,while those of the weed decreased.The ratios of aboveground biomass,tiller number and yields of rice and barnyardgrass in transplanting paddy field were increased significantly.The competitiveness of rice was enhanced relatively,while that of weed was weakened.The changing trends of the competitive relation were similar to the foregoing statement between rice and barnyardgrass in nursery beds at the vegetative growth stage,while the alteration was not significant at the reproductive stage.The yield and the biomass of rice competing with barnyardgrass generated from nursery beds increased 22.7% and 8.2% in the end,while those of barnyardgrass increased 9.5% and 11.9%,respectively.The ratios of aboveground biomass,tiller number and yield did not increase significantly.It was suggested that the responses to competition between rice and barnyardgrass under FACE were influenced by barnyardgrass emergence time.

Key words: air carbon dioxide enrichment, rice, barnyardgrass, competition

摘要： 通过田间试验，研究了FACE（开放式空气CO2浓度升高）条件下，移栽稻田水稻（Oryza sativa）与不同发生时期稗草（Echinochloa crusgalli）生长和竞争的响应差异。结果显示，FACE条件下水稻与稗草比例为1∶1时，水稻分蘖、生物量和产量均增加，而稗草则减少。水稻与移栽稻田本田萌生稗草的生物量比率增加181.7%、产量比率增加259.7%、茎蘖比率增加24.2%、有效分蘖比率增加186.3%，水稻竞争优势增加,而移栽稻田本田萌生稗草竞争能力下降。水稻与秧田萌生稗草的竞争关系变化趋势在营养生长期与上述情况相同，但进入生殖生长后水稻竞争优势不再显著，FACE条件下与秧田萌生稗草竞争的水稻最终生物量和产量分别增加22.7%和8.2%，但秧田萌生稗草的最终生物量和产量也增加了11.9%和9.5%。水稻与秧田萌生稗草的生物量比率、茎蘖比率和产量比率增加均不显著。 可见，田间大气CO2浓度升高条件下水稻与稗草的竞争关系发生的变化与稗草发生时期有重要关系。

关键词: 大气二氧化碳浓度升高, 水稻, 稗草, 竞争