Changes in soil microbial community and enzyme activity along an exotic plant Eupatorium adenophorum invasion in a Chinese secondary forest

The exotic plant, Eupatorium adenophorum, has invaded rapidly across southwest China, damaging native ecosystems and causing great economic losses. Soil microbes, as an important component of belowground community, can drive nutrient cycling and regulate plant competition in terrestrial ecosystems. Therefore, knowledge of the soil microbial community and function will enhance our understanding of the mechanism of exotic plant invasive process in natural ecosystems. In this study, we examined the soil microbial community, soil enzyme activity, soil property and plant community along an invasive gradient of E. adenophorum in a southwest Chinese secondary forest. The soil analysis demonstrated that heavy invasion significantly increased the total P and NO ₃ ^? -N contents, whereas it significantly decreased the total N and soil organic matter contents. The available P content was significantly decreased by moderate invasion. The E. adenophorum invasion significantly decreased the biomass of total soil microbes, as well as Gram-negative bacteria, actinomycetes, arbuscular mycorrhizal (AM) fungi and non-AM fungi. However, E. adenophorum invasion significantly increased the activities of soil urease, acid phosphatase, polyphenol oxidase and peroxidase. Non-metric multidimensional scaling showed that soil microbial composition and soil enzyme composition were significantly different in the three E. adenophorum invaded sites. Partial Mantel tests indicated that plant composition was the most important factor for structuring soil microbial and enzyme compositions. The results suggest that changes in soil microbial community structure and enzyme activity may play an important role in the process of E. adenophorum invasion in a Chinese secondary forest ecosystem.