中文摘要：

为探寻入侵植物与本地植物竞争是否存在一定的规律性,研究了黄顶菊、三叶鬼针草、豚草3种菊科植物与本地不同植物（狗尾草、藜、草木樨）竞争,对土壤酶活性和土壤养分的影响.结果显示：1）3种入侵植物对可利用氮的利用能力显著高于本地植物,且三叶鬼针草、豚草单种对氮素的利用能力要强于黄顶菊;3种入侵植物所需速效钾的含量较低;2）入侵植物对土壤生态的影响还与入侵域本地植物种类密切相关：3种入侵植物与狗尾草竞争过程中脲酶活性显著升高,入侵植物利用铵态氮的能力要强于硝态氮,3种入侵植物与藜竞争,入侵植物利用硝态氮的能力要强于铵态氮,有机碳含量呈上升趋势.3种入侵植物与草木樨竞争,速效钾含量显著升高.黄顶菊、三叶鬼针草、豚草入侵可以改变土壤养分和土壤酶活性,创造对自身生长有利的土壤环境,并借此增强其竞争能力.

英文摘要：

The effects of the invasion of three exotic asteraceae species （Flaveria bidentis, Bidens pi- losa, Ambrosia artemisiifolia ） on soil nutrient contents and enzyme activities in their competition with different native plant species （Setaria viridis, Chenopodium album, Melilotus suaveolens） were deter- mined to explore the regularity of the competition between invasive and native plants. The result showed that the available nitrogen absorption ability of the invasive plants was significantly higher than that of n- ative plants. The available nitrogen utilization ability of B. pilosa and A. artemisiiJ＇olia was .stronger than that of F. bidentis respectively. The concentrations of available potassium of the three inva- sive plants were significantly lower than those of the native plants. The impacts of invasive plant on soil e- cosystem were related with the kinds of native plant species. The activities of urease were increased signifi- cantly in the process of competition between three kinds of invasive plants and Setaria viridis. The utiliza- tion ability of NH4--N was higher than NO3- N for the invasive plants. The utilization ability of NO3- N was higher than NH4-N for the invasive plants when they competed with C. album and the trend of or- ganic carbon content increased. When the invasive plants competed with M. suaveolens the concentration of available potassium of the invasive plants was significantly increased. To sum up, the invasion of F. bi-dentis, B. pilosa, and A. artemisiifolia changed the soil nutrients and enzymes, created the soil environ- ment that benefited its own growth and then increased its competitive ability.