Abstract: Eupatorium adenophorum is one of the most noxious invasive weeds in China. To explore the effects of this weed invasion on soil fertility, the activities of six enzymes and 12 physical and chemical factors were compared among the soil within 0~30 cm depth under a more than 10 years old invaded grassland by E. adenophorum, a secondary grassland (abandoned maize field in November of 2001), a primary grassland of Themeda yunnanensis and a two years old artificial grassland of Setaria sphacelata. The results showed that each variable measured in this study changed significantly among communities and soil layers according to a two-way ANOVA. The activities of polyphenol oxidase, alkaline phosphatase and urase, the contents of organic matter, total N, total P, total Ca, hydrolytic N, active P, active K, and pH value decreased with the increase of soil depth. In general, the activities of alkaline phosphatase and urase, the contents of organic matter, total N, total P, total Ca, hydrolytic N, active P, and pH value were higher in the soil under E. adenophorum community compared to the soils under other communities. Total soil K content was lower in the soil under E. adenophorum than in the soils of other communities, while the active K content was similar among the four communities. These results indicate that E. adenophorum invasion for more than 10 years can increase soil fertility, create favorable soil conditions for itself.

Key words: Eupatorium adenophorum Sprengel, soil enzyme activities, soil physical and chemical factors, soil fertility, biological invasion