Abstract: Aims Biodiversity plays an important role in regulating ecosystem functioning. Fire is an important disturbance factor in forest ecosystems, and both above- and below-ground biodiversity in forests can be significantly altered by fire. However, our understanding of how biodiversity affects relevant ecosystem functions such as forest biomass accumulation and nutrient availability (i.e., ecosystem multifunctionality, EMF) following prescribed burning is still poorly understood. Methods In this study, we selected Pinus koraiensis plantations in Hongqi Forestry Farm, Hegang City, Heilongjiang Province, where prescribed burning was conducted in 2018, and used structural equation modeling to assess the relationships between understory plant diversity (species diversity, functional diversity, traitefficiency, and traitquantity) and soil microbial diversity (fungi and bacteria) and EMF following prescribed burning when the forest environment stabilized four years after the prescribed burning. Important findings We found that the prescribed burning increased understory plant diversity and EMF. In aboveground plant diversity, both traitquantity (i.e., total leaf nitrogen per unit area) and functional diversity (i.e., FDis based on leaf dry matter content) were significantly positively correlated with EMF, while the effect of belowground microbial diversity on EMF was not significant. The prescribed burning explained the highest variation in EMF (33.7%), followed by traitquantity (27.5%) and functional diversity (13.9%). The results suggest that in P. koraiensis plantations, enhancing nutrient accumulation and trait diversity in the understory vegetation within the community is an effective strategy to improve EMF after prescribed burning. Meanwhile, in forest management in the context of global change, prescribed burning is not only an effective way to reduce forest fire risks, but will also play a positive role in maintaining the biodiversity of understory vegetation and EMF.

Key words: Understory plant diversity, Soil microbial diversity, Selection effect, Niche complementing effect, Trait quantity