Abstract: The multiple De Wit replacement method were used to investigate the competitive effect of the invasive plant Phytolacca Americana and forage grass Medicago sativa ‘Ghillie’,Dolichos lablab ‘Rongai’ and Sorghum dochna ‘Hunnigreen’. The results showed that the plant height and biomass of P. Americana mixed with other forage grass species were significantly lower than that of single-planted P. Americana. Plant height and biomass of P. Americana mixed with D. lablab significantly than that of single-planted. Under high density,when compared with single-planted P. Americana,the plant height and biomass were decreased by 53.52%~81.95% and 90.22%~98.67% respectively. In the competitive relationship between P. Americana and D. lablab,the relative yield (RY) of P. Americana was significantly lower than 1.0 under each replacement combination. However,the RY of D. lablab was higher than 1.0 under medium and high densities. The aggressivity of D. lablab against P. Americana was significantly higher than 0,suggesting that the competitive capability of D. lablab was higher than that of P. Americana under P. Americana and D. lablab mixed planting. D. lablab had a great potential to suppress P. Americana,which prohibited the growth of P. Americana under mixed planting.

Key words: Phytolacca Americana, Pasture species, Replacement control, Plant competition

摘要： 以美洲商陆（Phytolacca americana）和紫花苜蓿‘吉利’（Medicago sativa ‘Ghillie’）、拉巴豆‘润高’（Dolichos lablab ‘Rongai’）、甜高粱‘大力士’（Sorghum dochna ‘Hunnigreen’）为试验材料，采用复合De Wit取代试验方法，探讨入侵植物与牧草间的竞争效应。结果表明：美洲商陆与3种牧草低密度混种下，其株高与生物量均显著低于单种的美洲商陆；在高密度混种下，美洲商陆与拉巴豆混种时的差异最显著，其株高比单种降低53.52%~81.95%，生物量比单种降低90.22%~98.67%；在美洲商陆与拉巴豆两者的竞争关系中，美洲商陆相对产量（relative yield，RY）值均极显著小于1.0，拉巴豆RY值在中、高密度下均大于1.0，且拉巴豆对美洲商陆的攻击力系数（aggressivity，A）显著大于0，表明两者混种时，拉巴豆的攻击力大于美洲商陆，混种阻碍了美洲商陆的生长，拉巴豆对美洲商陆具有较强的控制潜力。

关键词: 美洲商陆, 牧草, 替代控制, 植物竞争