The role of fungal keystone taxa in soil multifunctionality across subtropical forests

Abstract

Soil multifunctionality plays a crucial role in ecosystems, not only supporting nutrient cycling and plant productivity but also preserving biodiversity, thus ensuring the health and stability of the ecosystem. Forest soils harbor highly diverse microbial communities which fundamentally regulate the global elemental cycle and ecosystem multifunctionality. Keystone taxa act as “goalkeeper” in microbial community, which deeply portray community composition and functions. However, the mechanisms through which keystone taxa of soil microbes influence the dynamics of soil multifunctionality remain insufficiently elucidated within forest ecosystems. Our study analyzed the soil microbial community structures, soil properties and multifunctionalities of three typic forest stands in subtropic areas in south China, and identified the keystone taxa of bacteria and fungi by constructing co-occurrence networks, respectively. Further, partial least squares path modeling (PLS-PM) was conducted to explore the impact of different microbial taxa on soil multifunctionality. Our findings revealed considerable changes in soil multifunctionality across various forest types, with broad-leaved forest being the highest, then the mixed forest, and then followed by the coniferous forest. Compared with bacterial communities, soil fungal microbial networks in forest ecosystems had higher network nodes and higher module aggregation. Comparative analyses revealed that fungi exhibited greater type heterogeneity relative to bacteria inter-forest, with fungal keystone taxa demonstrating a pronounced influence on the multifaceted functional capacities of soil ecosystems. PLS-PM analysis further confirmed that soil properties (SOC, TN, and MBC) and fungal keystone taxa diversity (r = 0.319, p < 0.05) exert significant direct effects on soil multifunctionality. Furthermore, the total effects analysis highlighted fungal keystone taxa diversity and soil properties were critical determinants of soil multifunctionality. Additionally, this study emphasizes the significance of keystone fungal species in controlling soil multifunctionality in forest ecosystems. Promoting the diversity and abundance of fungal keystone taxa is essential for maintaining and enhancing soil multifunctionality, thereby supporting forest ecosystem health and productivity.