Tree species identity and leaf ageing alter the composition of phyllosphere communities through changes in leaf traits

Phyllosphere microorganisms are essential for plant growth and health, notably through their action on nitrogen fixation and pathogens control. However, whether and how the composition of phyllosphere communities vary with plant traits and leaf age remain still unclear. We used high-throughput sequencing to explore the phyllosphere microbial diversity and composition communities in needles of different ages (i.e., originating from different cohorts) for three evergreen coniferous species (Pinus koraiensis, Picea asperata and Abies fabri). We then assessed the relationships between the composition of phyllosphere microorganisms and needle traits. The results showed that needle age explained relatively well the phyllosphere microbiome α diversity, whereas tree species identity explained the phyllosphere microorganisms β diversity. The changes in the composition of phyllosphere microbial communities between newly-formed and perennial needles were greatest in Pinus koraiensis. Overall, Cyanobacteria and Gammaproteobacteria were dominant in newly-formed needles. Plant traits such as leaf dry matter content (LDMC), leaf mass per area (LMA) and total phosphorus content (TP) were the main predictors of phyllosphere community. Our results provide new insights into the mechanisms of community assembly among different evergreen tree species and provide a better understanding of the interactions between plant traits and phyllosphere microorganisms during needle ageing.