Abstract: Five sample plots subjected to invasion by Eupatorium adenophorum in Yunnan Province and Sichuan Province were studied with the quadrat sampling method,investigating species composition and population of indigenous herbage and shrubbery,and analyzing their richness index,diversity index and evenness index.Results show that a total of 87 indigenous species were collected and among them,32 species were common indigenous plants,falling into 31 genus,and 19 families.Invasion of Eupatorium adenophorum caused significant(P<0.05 or P<0.01) decline of richness index in all the habitats involved,and of Simpson index and Shannon-Wiener index in all the plots,except for Plot d.No obvious regularity was observed with the impact on Pielou evenness index.Seasonal change in vegetation community differed between habitats.Communities dominated with annual herbs showed a more significant declining trend than those with perennial herbs and shrubs did in Simpson index,Shannon-Wiener index and Pielou index.

Key words: alien invasive plant, Eupatorium adenophorum, richness index, Simpson index, Shannon-Wiener index, Pielou index