Tree Demography Exhibits a Strong Association With Soil Fungal Pathogens and Stability of Soil Fungal Community in a Subtropical Forest

Question: While interactions between trees and soils have been widely studied in micro- and mesocosm experiments, the associations between tree demography and soil fungi in natural forests remain poorly understood due to the complexity of forest ecosystems. This study aimed to investigate the potential relationship between tree demography and soil fungi, as well as the stability of soil fungal community within a subtropical forest. Location: A 20-ha subtropical forest dynamic plot at Tiantong National Station for Forest Ecosystem Research, East China. Methods: A total of 1287 soil samples were collected for the purpose of conducting DNA analysis of soil fungi and assessing soil physicochemical properties. Tree demographic rates were calculated from two forest censuses conducted over a 10-year interval (2010–2020), including recruitment rate [based on newly recorded individuals with diameter at breast height (DBH) ≥ 1 cm], mortality rate, juvenile (DBH < 10 cm) and adult (DBH ≥ 10 cm) abundance growth rates. We analyzed the effects of both biotic (e.g., soil pathogenic and mycorrhizal fungi) and abiotic factors (e.g., soil physicochemical properties and topographic features) on tree demography. Results: During the period from 2010 to 2020, the recruitment rate was found to exceed the mortality rate, while the juvenile growth rate was higher than the adult growth rate. Community composition of soil fungal pathogens, but not mycorrhizal fungi, exhibited significant associations with tree demography. These pathogens were negatively correlated with recruitment and juvenile growth rates, while positively correlated with mortality and adult growth rates. In contrast, fungal community stability was positively associated with recruitment and juvenile growth rates but negatively associated with the mortality rate. Furthermore, abiotic factors, including soil physicochemical and topographic variables, were identified as important predictors for tree demography rates. Conclusion: Our results showed that both soil pathogenic fungi and the stability of fungal community can serve as effective bioindicators of forest regeneration potential, with greater fungal community stability promoting tree recruitment and juvenile growth rates. These findings underscore the essential role of soil fungi in shaping forest dynamics and emphasize their relevance for biodiversity conservation and forest management, particularly in the context of ongoing climate change.