While most landscape restoration projects focus their efforts on the aboveground biota, much of what occurs belowground is overlooked. Our research seeks to understand how the soil microbiota responds to different restoration treatments because of the strong interdependency between the soil microbial composition and plant diversity. Our research site is dominated by an invasive shrub, buckthorn (Rhamnus cathartica) that elevates soil N. We hypothesized that incorporating C-rich substrates would interrupt this pattern by reducing soil N levels and enhancing the microbial community. We evaluated soil microbial community responses to four restoration treatments that had been applied the previous year: (1) control plot with the original buckthorn thicket; (2) commercially available mulch tilled into the soil followed by native seed application (3) buckthorn mulch tilled into the soil followed by native seed application; and (4) 'business as usual', i.e, cutting buckthorn, applying herbicide to stumps, and native seed application (no tilling). We also analyzed soils from the Shaw prairie, a remnant native tallgrass prairie with high plant biodiversity. In each sample, we analyzed the soil microbial biomass, fungal to bacterial ratio, nitrate and ammonia concentrations, and used Inter-Simple Sequence Repeat (ISSR) markers to obtain a microbial community profile. Results/Conclusions

Our results indicated that, even in the first year of restoration, microbial communities responded positively to the two mulch treatments. Among the four restoration treatments, plots tilled with buckthorn mulch showed the greatest similarity in soil fungal to bacterial ratio, microbial biomass C: N, soil N levels, and microbial community profiles to the Shaw Prairie. The incorporation of commercial mulch also produced similar results. In the control plots (buckthorn thicket), however, the microbial biomass C: N and fungal to bacterial ratio were low, and the microbial community profile showed little resemblance to the reference site, Shaw prairie. As a result, differences in microbial processes, especially decomposition and the availability of nutrients to decomposers, may help explain the dominance of invasive plants in this system. The 'business as usual' treatment was intermediate between the mulch treatments and control. These results support the importance of soil microbial communities in invasive plant dynamics, and suggest that the incorporation of woody mulch provides an environment that immediately supports the recovery of the soil microbial biota during restoration.