Effects of buffelgrass removal and nitrogen addition on soil microbial communities during an extreme drought in the Sonoran Desert

Buffelgrass (Cenchrus ciliaris), an invasive perennial grass in arid regions of the United States, has drastically modified natural ecosystems. Understanding the aboveground-belowground links between buffelgrass invasion and soil microbial communities will be critical for developing a comprehensive understanding of arid ecosystems and for deploying successful control strategies. In a randomized block-field experiment located in Tucson, AZ, U.S.A., we investigated the effects of buffelgrass removal via hand pulling and nitrogen addition (and their interaction) on soil microbial communities during an extreme drought (summer 2020). We found that experimental treatments did not significantly impact bacterial and archaeal community diversity and composition, while plant removal affected fungal community diversity and composition. In addition, the removal treatment increased the proportion of putative chitinolytic bacteria (genus Lysobacter) and decreased the proportion of putative fungal endophytes (genus Darksidea). Buffelgrass manual removal appeared to favor fungal endophyte death around and inside of leftover intact roots, which may result in an increase of chitinolytic bacteria thriving on the degradation of fungal cell walls. Overall, our results suggest that hand removal-which is a common type of buffelgrass control-can alter soil fungal communities and the proportion of certain microbial functional groups. As these changes could subsequently affect native plants, more research is needed to develop a comprehensive understanding of the effect of buffelgrass control efforts on target plants as well as surrounding ecosystem dynamics.