Pine wilt disease (PWD) is a devastating forest disease that severely impacts pine trees, with widespread outbreaks leading to catastrophic damage in pine forests worldwide. Our study aims to investigate the dynamics of PWD infection on soil physicochemical properties and biological activities, as well as the interrelationships between them. Soil samples were collected from 0 to 10 cm and 10 to 20 cm depths in subtropical Pinus massoniana (Masson pine) forests with PWD infection years of 0 (non-infection), 6, 10, and 16 years. The physicochemical properties, microbial biomass, and enzymatic activities of these soil samples were measured. The results revealed that soil non-capillary porosity, clay, microbial biomass carbon and microbial biomass nitrogen decreased significantly in 6 years forests. Available potassium consistently decreased with longer invasion periods, while soil polyphenol oxidase, leucine amino peptidase, and available phosphorous peaked in 6 years forests and then declined over time. The soil physicochemical properties, biological activities all decreased as soil depth increased. Redundancy analysis and Mantel tests underscored the critical role of Total potassium, pH, Total phosphorous, and bulk density in shaping microbial activities. This study demonstrated that PWD infection significantly effect on soil physicochemical properties, microbial biomass, and enzymatic activities with the chronosequence progresses. These finding contribute to a deeper understanding of how invasive pathogens like PWD can reshape soil environments, with implications for forest conservation and restoration practices.

Vertical stratification of forest plays important roles in the local material balance and in maintaining forest health by distributing and redistributing precipitation materials through adsorption, fixation, and release. Differences in runoff nutrient concentrations among vertical layers are closely related to vertical stratification (factors such as the trunk, canopy, forest litter, and soil physical and chemical properties). Long-term forest observations revealed significant spatial differences in Pinus massoniana (Pinus massoniana Lamb.) forests in the Three Gorges Reservoir area. Pinus massoniana forests on downslopes were characterized by a dense canopy, green needles, and rich forest vegetation, while those on upslopes were characterized by low vegetation cover, dead trees, and decreases in the tree height, diameter at breast height, and volume per plant with increasing slope. By analyzing the soil at different sites, we found that the pH of the forest land soil differed significantly among different slope positions. Soil on upper slopes was significantly more acidic than soil on lower slopes, indicating that acidic substances were intercepted by filtration through the broad litter layer and the soil surface layer. This filtration process resulted in a normal rhizosphere environment suitable for the absorption of nutrients by vegetation on the lower slopes. In this way, downhill sites provided a good microenvironment for the growth of Pinus massoniana and other vegetation. Our results show that direct contact between needles and acid rain was not the main cause of root death. Instead, the redistribution of rainfall substances by forest spatial stratification caused changes in the soil microenvironment, which inhibited the absorption of nutrients by the roots of Pinus massoniana and the growth of understory plants in Pinus massoniana forests on upper slopes. These findings emphasize that increasing land cover with forests with vertical structural stratification plays an important role in woodland material redistribution and forest conservation.