Establishing slash pine plantations is the primary method for restoring sandification land in the Houtian area of South China.
However, the microbial variation pattern with increasing stand age remains unclear. In this study, we investigated microbial
community structure and function in bare sandy land and four stand age gradients, exploring ecological processes that
determine their assembly. We did not observe a significant increase in the absolute abundance of bacteria or fungi with stand
age. Bacterial communities were dominated by Chloroflexi, Actinobacteria, Proteobacteria, and Acidobacteria; the relative
abundance of Chloroflexi significantly declined while Proteobacteria and Acidobacteria significantly increased with stand
age. Fungal communities showed succession at the genus level, with Pisolithus most abundant in soils of younger stands
(1- and 6-year-old). Turnover of fungal communities was primarily driven by stochastic processes; both deterministic and
stochastic processes influenced the assembly of bacterial communities, with the relative importance of stochastic processes
gradually increasing with stand age. Bacterial and fungal communities showed the strongest correlation with the diameter
at breast height, followed by soil available phosphorus and water content. Notably, there was a significant increase in the
relative abundance of functional groups involved in nitrogen fixation and uptake as stand age increased. Overall, this study
highlights the important effects of slash pine stand age on microbial communities in sandy lands and suggests attention to
the nitrogen and phosphorus requirements of slash pine plantations in the later stages of sandy management.