Response of soil bacterial communities to secondary compounds released from Eupatorium adenophorum

Abstract

Exotic plant species can benefit from altering soil microbial communities; however, the knowledge of the mechanisms through which this occurs is limited. The exotic species, Eupatorium adenophorum is a perennial plant that is aggressively invading southern China. Its invasiveness is attributed partially to its ability to release secondary chemicals that affect native plant species. Nevertheless, their effect on soil bacterial communities has rarely been explored. Here, we used natural fresh leaf and root leachate of E. adenophorum, and two pure, phytotoxic chemicals amorpha-4,7(11)-dien-8-one, and 6-hydroxy-5-isopropyl-3,8-dimethyl-4a,5,6,7,8,8a-hexahydraphthalen-2(1H)-one to evaluate: (a) short-term (3 days) effects of secondary chemicals on soil bacterial communities in mixed forests and (b) long-term (6 months) effects of leaf leachate on soil bacterial communities in three habitats. Additionally, the composition and diversity of soil bacterial communities were explored with high throughput sequencing using IlluminaMiSeq. In the short-term experiments, all treatments affected soil bacterial communities, but leaf leachate most significantly reduced soil bacterial richness and diversity. In the long-term experiments, leaf leachate altered bacterial communities in all soil samples, and reduced bacterial richness and diversity in soils from the forest and wasteland, but increased bacterial richness and diversity in soils from roadside. Redundancy analysis indicated that changes in bacterial communities were associated with soil organic carbon, nitrogen content, and pH. These results indicate that the water-dissoluble secondary chemicals of E. adenophorum, especially from its leaves, have an impact on soil bacterial communities, though the degree of the impact depends on soil ecotype.