Responses of Soil Microbial Community Size, Respiration Rate and Functional Diversity to Invasive Plant Species Richness

Co-invasion of exotic plant species is common in the field, but works to date have focused on the study of single or two exotic species. Few studies tested effects of plant species richness over two invasive species on plant, soil and microbial properties. In the study, three-invasive species vegetation produced greater plant biomass than the native, single- and two- invasive species vegetations. The soil covered by three-invasive species vegetation harbored higher soil organic carbon, NH4+-N and pH, but less NO3- -N than the soils covered by other vegetations. The three-invasive species vegetation enhanced bacterial utilizations of carbohydrate and miscellaneous compounds to 2.2 and 2.5 times greater, and also fungal utilizations of amino acid and miscellaneous compounds to 1.3 and 2.5 times greater than the native soil. Principal components analysis identified a significant difference of fungal carbon utilization patterns between the native and three-invasive species soils, which was mainly mediated by SOC and total nitrogen contents as confirmed by redundancy analysis and linear fitting. Overall, the roles the invasive plant richness played in mediating plant biomass, soil and microbial biomass and carbon utilization properties are mostly positive and non-additive, thus facilitating the further co-invasion of exotic plant species