Impacts of the invasive annual herb Ambrosia artemisiifolia L. on soil microbial carbon source utilization and enzymatic activities

There is currently much interest in the interactions between exotic plants and soil organisms. Exotic invasive species can have profound effects on the microbial community of the soil and positive feedback of soil biota to invasive plants may facilitate their successful invasion. To better understand the impacts of Ambrosia artemisiifolia L. invasion on microbial carbon source utilization and related microbiological parameters, soils were sampled from two invaded sites, i.e., historically-invaded (HINVA), recently-invaded (LINVA) sites and two non-invaded sites, i.e., grassland (NINVA) and native-plant (NATIV) sites in late April. Soil biochemical properties, enzyme activities, and microbial biomass were determined. Meanwhile, carbon source utilization intensity was examined based on the Biolog community-level physiological profile (CLPP) method. The two invaded sites had significantly higher total phosphorus, available nitrogen and phosphorus than non-invaded sites. Microbial biomass nitrogen and phosphorus, and invertase and catalase activities were also significantly higher in soils from invaded sites. The soil microbial community from the HINVA site most profoundly improved soil fertility. Microbial utilization of carbohydrate groups significantly increased in the invaded sites relative to non-invaded sites, especially the utilization of carbohydrates and amines/amides. Soil from the HINVA site had higher efficiency in carbon source utilization, especially for carbohydrates and amino acids. Principal components analysis (PCA) of carbon substrate utilization data revealed distinct differentiation in soil microbial community functions among the four studied sites. Redundancy analysis (RDA) indicated that better soil biochemical conditions, especially the microbial quotient (Cmic/Corg) and available nitrogen values were associated with higher soil carbon utilization in A. artemisiifolia invaded sites. The improvement of soil fertility as well as microbial community function in invaded soils may be beneficial to A. artemisiifolia and contribute to its establishment in new habitats.