Abstract:In order to reveal the invasion mechanism of Mikania micrantha affecting soil nutrient circulation through allelopathy, the effects of two allelopathic substances from M. micrantha (i.e. chlorogenic acid and β-caryophyllene) on soil nitrogen and related functional bacteria of nitrogen cycle were studied using exogenous addition culture experiments. The results showed that both chlorogenic acid and β-caryophyllene significantly reduced the content of soil ammonium nitrogen, and chlorogenic acid increased significantly the content of soil nitrate nitrogen, while β-caryophyllene had no significant effect. The main reason was that both chlorogenic acid and β-caryophyllene significantly inhibited the reproduction of azotobacter and ammonifying bacteria, and chlorogenic acid significantly promoted the growth of ammonia-oxidizing bacteria and nitrifying bacteria, while β-caryophyllene only promoted the reproduction of ammonia-oxidizing bacteria, and had no effect on nitrifying bacteria. So, it was concluded that M. micrantha invasion could affect the growth of functional bacteria associated with nitrogen cycle through the allelochemicals, thus altered the soil nitrogen cycle.