Plant–soil microbial diversity and structural attributes jointly dominate the multifunctionality of the temperate forest

Biodiversity is widely recognized as a crucial factor in driving ecosystem functioning. However, the processes that sustain forest ecosystem multifunctionality (EMF) through plant and soil microbial diversity are not yet fully understood. Here, we assessed eight ecosystem functions in a mixed temperate forest using averaging and weighted threshold methods to examine the associations between EMF and diversity across environmental gradients. The findings indicated that structural attributes serve as the optimal predictor of EMF. Both complementarity and selection effects had minor impacts on EMF, while the jack-of-all-trades effect drove the relationship between plant diversity and EMF. EMF was positively correlated with soil fungal diversity but negatively correlated with soil bacterial diversity. Soil microbial diversity influenced forest EMF by regulating the trade-offs between different functions. Additionally, we noted that forests situated on steep slopes may experience limitations in terms of multifunctionality, while nutrient-rich soils had a facilitative effect. This study underscores the significance of taking into account both aboveground and belowground diversity to improve forest functions. Within a certain range, more complex and diverse stand structures are effective strategies for sustainable forest management.