Factors Influencing the Change of Phyllosphere Microbial Community of Three Populus spp. in the Same Habitat

Plant leaves harbor a rich diversity of bacteria and fungi that, through their interactions with host plants, assume an influential role in plant physiological and metabolic processes. The unique phyllosphere environment of different plant species may shape and select distinct phyllosphere microbial communities. While most academic research has focused on the phyllosphere microorganisms within the same plant variety, there is relatively limited research on the phyllosphere microbial communities between different varieties. Populus L. is a typical tree species in temperate monsoon climates, widely distributed in northern China, and it constitutes a crucial component of China’s forestry resources. For the purpose of this study, we investigated the community structure and diversity of phyllosphere fungi and bacteria in different poplar varieties under identical growth conditions to elucidate the main factors contributing to differences in phyllosphere microbial communities among these varieties. Our findings revealed variations in nitrogen, phosphorus, starch, and soluble sugar contents among the three poplar species studied. Additionally, there were considerable disparities in both abundance and α diversity index of phyllosphere fungal and bacterial communities among these species. At the phylum level, Ascomycota and Basidiomycota have been identified as the dominant fungal communities; while Proteobacteria and Actinomycetes were dominant bacterial communities. The correlation analysis pointed out that chemical traits in the leaves, in particular the total phosphorus and the quantity of soluble sugar, had a significant correlation with the structure and diversity of the microbial community residing in the phyllosphere. Overall, our results demonstrate that even under identical site conditions, each poplar species harbors its own unique phyllosphere microbial community composition as well as distinct leaf characteristics—highlighting host plant diversity as a crucial factor driving differences in phyllosphere microbial composition.