Effects of Buffelgrass Removal and Nitrogen Addition on Soil Microbial Communities During an Extreme Drought in the Sonoran Desert

Abstract

Understanding the aboveground-belowground links between buffelgrass (Cenchrus ciliaris) invasion and soil microbial communities will be critical for developing a comprehensive understanding of arid ecosystems and for deploying successful control strategies. Buffelgrass, an invasive grass in the arid areas of the US, has drastically modified natural ecosystems. Buffelgrass control efforts have been generally unsuccessful, partly due to the insufficient understanding of how this species might alter belowground conditions in a way that promotes its own spread. In a randomized-block field experiment located at Tumamoc Hill, Arizona, we investigated the effects of buffelgrass removal via hand pulling and nitrogen addition (and their interaction) on soil microbial communities during an extreme drought. We found that these treatments did not significantly impact bacterial and archaeal community diversity and composition, while plant removal weakly 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 may favor fungal endophyte death around and inside of leftover intact roots of buffelgrass, which may result in an increment of chitinolytic bacteria thriving on the degradation of fungal cell walls. Overall, my results suggest that buffelgrass removal can alter soil fungal communities and the proportion of certain microbial functional groups, and low levels of nitrogen addition during an extreme drought may not influence the effects of buffelgrass on soil microbial communities.