中文摘要：

田间条件下建立了入侵植物黄顶菊（Flaveria bidentis）和伴生草本植物马唐（Digitaria sanguinalis）、益母草（Leonurus japonicus）单独种植（以下简称单种）和混合种植（以下简称混种,比例1∶1）小区,设置施氮肥和不施氮肥处理,研究两者对黄顶菊入侵土壤微生物的影响。结果表明：黄顶菊单种小区,土壤增施氮肥黄顶菊的生物量显著升高,且促进了真菌的生长,抑制放线菌、有机磷细菌和钾细菌的生长。黄顶菊与马唐竞争生长,施肥显著抑制了放线菌、有机磷细菌和钾细菌的生长,黄顶菊的竞争攻击力系数（aggressivity,以下简称AG）小于0,在竞争中黄顶菊不占优势;不施肥时细菌、放线菌、有机磷细菌的数量与黄顶菊生物量显著正相关（P〈0.05）,且AG〉0,在竞争中黄顶菊占优势。黄顶菊与益母草竞争生长,施肥与否仅有机磷细菌数量显著高于裸土,且微生物数量与黄顶菊生物量都无显著相关性（P〉0.05）,黄顶菊的AG都小于0,在竞争中不占优势。由此,黄顶菊与马唐或益母草竞争生长,增施氮肥改变了土壤微生物数量,降低了黄顶菊的种间竞争能力,不利于实现黄顶菊的入侵。

英文摘要：

The effect of nitrogen fertilizer on the microbes in rhizosphere soils of Flaveria bidentis in competitive growth with two native species, Digitaria sanguinalis （L.） Scop. and Leonurus japonicus Houtt., planted singly or mixed with F. bidentis （1： 1）, respectively, was studied in the field. The results showed that nitrogen addition increased the biomass of F. bidentis and promoted the growth of fungi in the monoculture of F. bidentis, but de- creased actinomycetes, phosphorus bacteria and potassium bacteria. When F. bidentis competed with D. sangui- halls, nitrogen addition was significantly inhibited the growth of actinomycetes, phosphorus bacteria and potassium bacteria. The aggressivity of the invasive species was less than 0, so the competition was disadvantageous for F. bidentis. A positive significant correlation existed between the counts of bacteria, actinomycetes, phosphorus bacteria and the biomass of F. bidentis treated with non-fertilizer control. The aggressivity of the invasive species was more than 0, and F. bidentis was dominant in the competition. When F. bidentis competed with L. japoni- cus, the microbes were less than in bare soils except for phosphorus bacteria, and no matter fertilizer added or not, there was no significant correlation between soil microbial quantity and the biomass of F. bidentis. The aggressivity of the invasive species was less than 0, indicating that the competition was advantageous to F. bidentis. To sum up, nitrogen addition changed the quantity of soil microorganisms and decreased the competitive ability of the invasion species.