Soil rather than root traits drives variation in the rhizosphere microbial community of Pinus taiwanensis in a subtropical mountain ecosystem

Rhizosphere microbes enhance plant resilience to adverse conditions, which is critical for plant growth and survival. The processes determining the composition of plant rhizosphere communities remain unclear, especially under natural conditions in forest ecosystems. Variations in elevation and season exert considerable influence on both plant traits and soil properties, both of which could be expected to significantly impact rhizosphere microbial community composition. Despite this, limited studies have simultaneously considered root traits and soil properties when estimating the relative importance of elevational and seasonal variation in predicting the distribution of rhizosphere microbial communities. We sampled rhizosphere microbial communities in Pinus taiwanensis forests across three elevations and two times of year in sub-tropical eastern China. We tested the roles of bulk soil physico-chemical properties (pH, temperature, total carbon, nitrogen and phosphorus concentration) and fine root functional traits (root diameter, specific root length, specific root area) in structuring the rhizosphere microbial community. The composition of rhizosphere microbial communities varied significantly across both elevations and seasons but the Shannon and Simpson diversity indices of microbial communities exhibited a more pronounced variation across elevations than across different seasons. Rhizosphere bacterial and fungal communities were influenced by both bulk soil physico-chemical properties and fine root functional traits, with the former having a greater influence. Bulk soil N:P was the most important driver of both the rhizosphere fungal and bacterial communities. Overall, soil properties rather than root traits appear to drive the spatial and temporal variation of the rhizosphere microbial community of P. taiwanensis in this subtropical mountain ecosystem.