PNNL

Abstract

Aims Grasslands dominated by non-native (exotic) species have replaced purely native-dominated areas in many parts of the world forming ‘novel’ ecosystems. It is still poorly understood how soil microbial communities and their functions are affected between these native- and exotic-dominated sites. Methods We sampled 64 experimental grassland plots in central Texas with plant species mixtures of either all native or all exotic species; half with summer irrigation. We tested how native vs. exotic plant species mixtures and summer irrigation affected bacterial and fungal community composition and structure, microbial phylotype co-occurrence, and rates of mineralization across sampling years. Results Plant origin significantly affected fungal community composition and structure, but not diversity, throughout the length of the study, while changes in bacterial communities were limited to certain years. Nitrogen and phosphorus mineralization rates were higher under native plant mixtures, and correlated with changes in particular fungal species. Microbial communities were more structured in exotic than native grassland plots, especially for the fungal community. Conclusions The results indicate that conversion of native to exotic grasslands will more strongly impact fungal than bacterial communities structure. Furthermore, these impacts can alter ecosystem functioning belowground via changes in nitrogen and phosphorus cycling.