Abstract: Based on intensive field investigation, this paper compared the growth characteristics and relative competitive ability between invasive Plantago virginica and native P. asiatica. The results showed that P. asiaticahad higher vegetative growth effort, whereas P. virginica showed higher sexual reproductive ability. P. virginica was found remarkably in advantageous position in terms of mean spike length and spike number per plant than P. asiatica. However, the leaf area of P. virginica was smaller than that of P. asiatica. It was indicated that P. virginica invested most on reproduction, whereas P. asiatica invested on vegetative growth. Both intraspecific and interspecific competitions between P. virginica and P. asiatica negatively affected various growth parameters such as spike number per plant, mean spike length, individual’s above-ground biomass and its total biomass. The interspecific relative competitive ability measured as relative neighbor effect index (RNE) of P. asiatica was significantly higher than that of P. virginica. The results conclusively showed thatP. asiatica would not be replaced by P. virginica in nature.

Key words: Tree roots, Senescence, Environmental factors