Differential Responses of Tree Phyllosphere and Rhizosphere Microbiomes to Mycorrhizal Types and Planting Patterns in a Young Subtropical Forest Plantation.

Arbuscular mycorrhizal (AM) and ectomycorrhizal (EM) tree species are ubiquitous in subtropical forests and have distinctive root colonisation characteristics and leaf traits, resulting in differences in nutrient acquisition strategies and ecological functions. Here, we investigated the responses of bacteria, fungi and protists inhabiting tree phyllosphere and rhizosphere to tree mycorrhizal types (AM vs. EM) and planting patterns (single or double tree species planting with the same or different mycorrhizal type) in two seasons. Both leaf- and root-associated fungal richness and community composition were strongly structured by tree mycorrhizal type, whereas the bacterial community was primarily influenced by leaf habit. Protistan communities, however, exhibited weak host specificity and were dominated by stochastic processes, with seasonal variation acting as the main influencing factor. Overall, the phyllosphere microbiomes were jointly shaped by leaf traits and seasonal effects, but rhizosphere fungal communities were directly and indirectly regulated by tree mycorrhizal type via root nutrient and colonisation statuses. Altogether, tree phyllosphere and rhizosphere microbiomes differ from the interaction of mycorrhizal symbiosis, planting pattern and seasonality, with distinct ecological processes manipulating across bacteria, fungi and protists. This study highlights the necessity of integrating tree mycorrhizal types and above- and belowground habitats perspectives to better understand forest microbiomes.