Abstract:

Root-associated microbes play an essentialrole in mediating plant growth, health, and habitat adaptability. However, it is unknown which microbial taxa help develop host fitness and how habitats shape root-associated microbial assembly patterns. As an endemic species of subalpine forests in western Sichuan, China, Minjiang fir (Abies fargesii var. faxoniana) is dominant on cold-shaded northwestern slopes while absent on warm sunlit southwestern slopes. In this study, fungal and bacterial communities were investigated in three spatial compartments (endosphere, rhizosphere, and bulk soil) associated with Minjiang fir saplings on a cold-shaded northwestern slope and a warm sunlit southwestern slope. Habitats differentiated the microbial communities regardless of the spatial compartment and microbial taxa. Slope aspect variations caused shifts in root-associated (rhizosphere and endosphere) microbial compositions. Compared with the southwestern slope, the cold-shaded northwestern slope harbored a higher abundance of the growth-promoting bacteria Burkholderia and ectomycorrhizal fungi Cortinarius and Piloderma. The slope aspect had stronger effects on fungal diversity than bacterial diversity, with higher fungal endemism and lower bacterial endemism. Slope aspect variations were the dominant drivers of root-associated microbial communities, with lower contribution by soil properties and higher contribution by plant traits on the northwestern slope. Findings from this study could improve the understanding of plant habitat adaptability from the perspective of microbial community assembly. It is suggested that forest management should consider root-associated microbiomes for enhancing species fitness and habitat adaptability.

Key words: Species fitness, Root-associated microbes, Microbial assembly patterns, Habitat conditions