Clarifying the response of soil microbial communities to vegetation restoration is essential to comprehend biogeochemical processes and ensure the long-term viability of forest development. To assess the variations in soil microbial communities throughout the growth of Pinus armandii plantations in the karst region, we utilized the “space instead of time” approach and selected four P. armandii stands with ages ranging from 10 to 47 years, along with a grassland control. The microbial community structure was determined by conducting Illumina sequencing of the 16 S rRNA gene and the ITS gene, respectively. The results demonstrated that afforestation with P. armandii significantly influenced soil microbial communities, as indicated by notable differences in bacterial and fungal composition and diversity between the plantations and the control. However, soil microbe diversity did not display significant variation across stand ages. Moreover, the bacterial community exhibited higher responsiveness to age gradients compared to the fungal community. Soil physicochemical factors play a critical role in elucidating microbial diversity and community composition variations during restoration processes. TN, AN, TP, AP, SOC, AK, and pH were the most significant influencing factors for the composition of bacterial community, while TC, SOC, pH, and TC_a were the most significant influencing factors for the composition of fungal community. Our findings indicate substantial changes in soil bacterial and fungal communities across successive stages of development. Additionally, the changes in dominant bacteria and fungi characteristics across the age gradient were primarily attributed to variations in the prevailing soil conditions and chemical factors.

Long-term studies have revealed that forest species composition was shifting under environment change and disturbance induced by loss of large trees. Yet, few studies explicitly analyzed their impacts on composition concurrently. To learn more about impacts of environment change and disturbance on driving forest community, we investigated shifts in functional composition over past 24 years in an old-growth subtropical forest in southern China. We analyzed nine traits that are mainly related to leaf nutrients, photosynthetic capacity, hydraulic conductivity, and drought tolerance of plants and examined hypotheses: (1) The functional composition change over time was directional instead of random fluctuation, (2) drought-tolerant species increased their abundance under soil dryness, (3) both environmental change and disturbance related to changes of functional composition significantly, and (4) initial trait values of quadrats strongly influenced their subsequent change rates in quadrat level (10 × 10 m). We found that species composition had shifted to favor species with high leaf nutrient content, high photosynthesis rate, high hydraulic conductivity, low water-use efficiency, and high drought tolerance traits, which was due to soil dryness and disturbance. These two factors explained 47–58% of quadrats’ trait value changes together. Considering rapidly increasing stem density, this pattern may indicate ecological processes of which disturbance provided numerous recruits of resource-acquisition strategy species and soil dryness conducted a selecting effect on shaping composition in the forest. Additionally, quadrats with initial trait values at the far end of change direction shifted faster in three traits, which also indicated that functional composition changes in quadrats were directional and homogenized. Our results implied that environment change and accompanied disturbance events possibly drove species composition change along a different trajectory in the subtropical forest that experienced high climatic variability.