Abstract: Soil pathogenic fungi play a critical role in forest succession and biodiversity maintenance. However, how litter decomposition regulates soil pathogenic fungal community structure, and subsequently influences seed germination and survival, remains poorly understood. In this study, we conducted a 360-day laboratory-based litterbag experiment using single-species and mixed-species litter collected from representative plant species across different successional stages in the subalpine forests of western Sichuan, China. The effects of litter decomposition on the community structure of soil total fungi and pathogenic fungi, as well as the mechanisms by which fungal community dynamics affect seed germination and survival, were systematically investigated. Results showed that remaining litter mass was significantly correlated with key physicochemical properties, including total carbon, nitrogen, phosphorus and lignin content. Litter decomposition significantly altered the community structures of both soil total fungi and pathogenic fungi, and further affected the germination and survival of plant seeds. Specifically, the decomposition of herb litter significantly altered the pathogenic fungal community structure, leading to a widespread inhibition of seed germination in plant species across all successional stages, whereas shrub and arbor litters influenced germination mainly during mid- to late-successional stages. These findings reveal an ecological pathway of ‘litter decomposition–pathogenic fungi–seed germination’, providing a novel perspective for understanding the mechanisms of plant community assembly during forest succession.

Key words: forest succession, western Sichuan subalpine, litter decomposition, plant pathogenic fungi, seed germination