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

• Structural attributes are the optimal predictors of ecosystem multifunctionality. • High plant diversity is critical for multifunctionality at low thresholds. • Increased soil fungal diversity promotes multifunctionality, bacteria show opposite trend. • Nutrient-rich soils have an enabling effect on forest multifunctionality. • Topography induces tradeoffs limiting synchronization optimizing diverse functions. 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. [ABSTRACT FROM AUTHOR]