Mesquite-associated soil and phyllosphere microbial communities differ across land use types in drylands

Plant-associated microbiomes play prominent roles in maintaining plant health and productivity. Here, we characterized the soil and phyllosphere microbiomes associated with mesquite trees in grazing and urban areas compared to natural areas in the arid Southwestern USA. Our results showed that grazing areas were associated with higher phyllosphere fungal richness, while urban areas had higher phyllosphere richness for both fungi and bacteria/archaea, and additionally, urban soils had lower fungal richness. Specifically, grazing areas were characterized by larger proportions of nitrogen-fixing bacteria in the soil and fungal plant pathogens in the phyllosphere, while urban areas presented higher proportions of fungal plant pathogens in both the soil and phyllosphere as well as nitrifying and denitrifying bacteria in the phyllosphere, but a lower proportion of cellulolytic bacteria in the soil. Furthermore, in urban areas more phyllosphere microorganisms were sourced from the soil. Collectively, these results suggest that plant-associated microbiomes change significantly across land use types, and these patterns are different between above- and below-ground parts of plants, and between bacteria/archaea and fungi. These changes in plant-associated microbiomes across land use types might have important implications for nutrient cycling, plant health, and ecosystem restoration.