[Changes in the structure and function of soil prokaryotic communities in subalpine Picea asperata plantations]

The structural and functional characteristics of soil prokaryotic community are important for maintaining ecosystem functions. In this study, we examined the diversity and compositions, the key drivers, as well as functional characteristics of prokaryotic communities in the rhizosphere and non-rhizosphere soils of Picea asperata with different stand ages using high-throughput sequencing technique and bioinformatics methods. The results showed that β-diversity of soil prokaryotic communities in both rhizosphere and non-rhizosphere showed significant differences among different stand ages, but no significant difference between rhizosphere and non-rhizosphere in the same stand age. In terms of community composition at the phylum level, the relative abundances of Proteobacteria and Rokubacteria showed an increasing trend with the increases of stand age, while the relative abundance of Actinobacteria showed a decreasing trend, but no significant difference was observed between 75 year-old planted forests (PF75) and natural forests (NF). The relative abundances of Firmicutes and Thaumarchaeota in the soil of the 25 year-old planted forests (PF25) were significantly higher than in other planted forests and NF. At the genus level, the relative abundances of RB41, Terrimonas and Acidibacter showed an increasing trend with the increases of stand age, and RB41 and Terrimonas in rhizosphere soil of PF75 were significantly higher than those in NF. Soil properties and vegetation characteristics jointly influenced the structure of soil prokaryotic communities, with herb layer coverage, soil pH, total phosphorus, and total nitrogen as major drivers. The functional characteristics of soil prokaryotic communities were significantly different among different stand ages. The relative abundances of functions involved in carbon and nitrogen cycle, e.g., cellulolysis and nitrification, decreased with the increases of stand age, whereas that of sulfate respiration involved in the sulfur cycle increased. We proposed that the structure and functional characteristics of soil prokaryotic communities could serve as important indicators of the development stages of P. asperata forests. In the later stages of plantation forest development, soil nutrient availability could be improved by mediating phosphorus-dissolving and nitrogen-enhancing microorganisms to maintain the stability of the plantation ecosystem.