Coupling soil bacterial and fungal community traits to multifunctionality in grassland ecosystem

Understanding how bacterial and fungal community traits affect ecosystem functions, and thus provide ecosystem services, is becoming increasingly necessary. However, the relationship between microbial community traits and ecosystem multifunctionality, as well as the mechanisms underlying diversity and multifunctionality, remains a topic of concern. Here, we explored the bacterial and fungal communities and linked them with ecosystem multifunctionality (including enzymatic activity and nutrient pool) in continuous grassland ecosystems (desert, typical and meadow). We found a significant and positive correlation between abundance, diversity, network properties of bacteria and fungi and ecosystem multifunctionality. Bacterial and fungal diversities were the most important factor determining the multifunctionality in grassland ecosystems, whereas their abundance becomes more crucial than diversity in desert grasslands, where the abundances were as low as 1.11 × 10 ⁷ and 3.67 × 10 ⁶ copies g ⁻¹ soil for bacteria and fungi, respectively. The relative contributions of bacteria and fungi on multifunctionality changed along with grassland types, with the relative contributions of fungi increasing from desert (49.5 %) to typical (50 %), and to the meadow grasslands (67.8 %). Moreover, bacterial and fungal assembly processes were mainly determined by stochastic processes, especially in meadow grasslands, and the microbial assembly processes were significantly positively correlated with diversity-multifunctionality relationship (the correlation coefficients between α diversity and multifunctionality relationships). Taken together, our results reveal the importance of bacterial and fungal abundance and diversity in maintaining soil multifunctionality, and provide strong support for the relationship between assembly process and diversity-multifunctionality in grassland ecosystems.