Fungal community diversity dominates soil multifunctionality in freeze-thaw events

Global climate change has altered soil freeze-thaw (FT) patterns but less is known about the responses of soil microbial diversity, soil multifunctionality, and their relationship to FT events. Daxing'an Mountains in China, located in high-latitude permafrost ecosystems, are one of the most sensitive areas to climate change and FT patterns. Here, simulated FT conditions were used to determine the impact of FT events on soil microbial diversity and multifunctionality as well as to elucidate the relationships between bacterial and fungal diversity and multifunctionality. Community composition, α-diversity index, and co-occurrence network complexity of fungi significantly changed during FT events, whereas the same parameters did not exhibit significant alterations for bacteria. Soil fungal communities were more sensitive to FT events than soil bacterial communities. FT events significantly affected soil multifunctionality. A random forest analysis showed that the fungal diversity index was the main predictor of soil multifunctionality. Moreover, changes in soil abiotic factors also affected the relationship between soil microbial diversity and multifunctionality. Soil multifunctionality was also constrained by fungal community network complexity. Structural equation model showed that the FT amplitude and FT cycles exerted different impact paths on soil multifunctionality. The effect of FT cycles on soil multifunctionality (0.289) was greater than that of FT amplitude (0.080). As global climate change is expected to accelerate in the future, extension of the FT period in high-altitude and high-latitude regions may have a severe impact on soil function compared to extreme low temperatures caused by the presence of thin snow cover.