Rhizospheric Bacillus-Facilitated Effects on the Growth and Competitive Ability of the Invasive Plant Ageratina adenophora

Abstract

The rhizospheric microbial community affects the population establishment of invasive plants in introduced areas, among which <i>Bacillus</i> has numerous functions in promoting plant growth. This study isolated and enriched the <i>Bacillus</i> community in the rhizospheric soil of the invasive plant <i>Ageratina adenophora</i> and the native accompanying plant <i>Rabdosia amethystoides</i>. The effects of these rhizospheric <i>Bacillus</i> communities on the growth and competition of <i>A. adenophora</i> and <i>R. amethystoides</i> were evaluated in pot experiments. The results showed that the number and diversity of <i>Bacillus</i> in the rhizospheric soil of <i>A. adenophora</i> were higher than those of <i>R. amethystoides</i> (<i>A. adenophora</i>: 122 strains in soil, 16 <i>Bacillus</i> taxa; <i>R. amethystoides</i>: 88 strains in soil, 9 <i>Bacillus</i> taxa). After <i>Bacillus</i> inoculation of <i>A. adenophora</i> in a pot experiment, <i>Bacillus idriensis</i>, <i>Bacillus toyonensis</i> and <i>Bacillus cereus</i> were accumulated in the rhizospheric of <i>A. adenophora</i>, which significantly increased the nitrate nitrogen (NO₃ ^--N) content in the soil and the total carbon and nitrogen concentrations in <i>A. adenophora</i> in the mixed treatment. The selective accumulation of <i>Bacillus</i> enhanced the competitive advantage of <i>A. adenophora</i> over the native accompanying plant; the corrected index of relative competition intensity of <i>A</i>. <i>adenophora</i>-inoculated <i>Bacillus</i> reached double that of the uninoculated treatment, and the growth of native plants was greatly suppressed under mixed planting. Our study confirmed that invasion of <i>A. adenophora</i> can lead to the accumulation of specific <i>Bacillus</i> taxa in the rhizospheric soil, which in turn can increase the competitive advantage of <i>A. adenophora</i>.