Abstract: Two native forage species (Sorghum bicolor × Sorghum sudanense and Astragalus adsurgens) were chosen to replace and control the exotic invasive plant Flaveria bidentis, and a field experiment was conducted to examine the effect of the replacement control with the two forage species on the growth and physiological characteristics of F. bidentis. The replacement control suppressed the growth and reproduction of F. bidentis effectively. Compared with that of monoculture F. bidentis, the total biomass of F. bidentis mixed cultured with A. adsurgens and S. bicolor × S. sudanense was decreased by 90.2% and 94.2%, respectively. Except for leaf biomass ratio, all the other biomass indices of F. bidentis in the replacement treatments decreased by more than 90%. The flower mass ratio of F. bidentis decreased significantly in A. adsurgens replacement treatment but increased in S. bicolor × S. sudanense replacement treatment. In the two replacement treatments, the net photosynthetic (P_n), stomatal conductance (G_s), transpiration rate (T_r), water use efficiency (WUE), and chlorophyll content of F. bidentis all had a significant decrease, and the P_n of F. bidentis in S. icolor × S. sudanense treatment was only 2.15 μmol CO₂·m^-2·s^-1. The results revealed that under the replacement control with the forage species, insufficient light supply limited the carbon assimilation of F. bidentis. Plasticity analysis showed that F. bidentis had higher phenotypic plasticity, and the phenotypic index of flower mass ratio reached up to 0.91, indicating the high invasive potential of the invasive plant. It was suggested that field replacement control could realize a win-win situation of economic value and ecological benefits.

Key words: calcium cyanamide, continuous cropping obstacles, soil microbial biomass carbon, soil microbial biomass nitrogen, soil enzyme activity.