Seasonal variation modifies the response patterns of abundant and rare fungal groups in a permafrost ecosystem

Soil freeze-thaw is a common phenomenon at high latitude permafrost regions, and it can alter soil physical properties and microbial diversity. However, how the abundant and rare fungal groups respond to environmental temperature changes (i.e., seasonal variations), particularly freeze-thaw events, are still not well understood. In this study, we investigated the dynamics of soil properties, fungal community diversity, structure, and co-occurrence network in a typical seasonally frozen ecosystem, we sampled three times during the non-freeze-thaw period, freeze-thaw period, and freezing period, respectively. Our findings revealed that significant variations in the fungal community diversity were detected at different sampling stages. Notably, abundant and rare fungal taxa exhibited the differential response patterns. Compared to the non-freeze-thaw period, freeze-thaw cycling reduced the alpha diversity of the abundant fungal taxa, but increased the alpha diversity of rare fungal taxa. We also found that changes in community composition of rare taxa were more senstive to environmental temperature changes than abundant taxa, and they contributed more to the stability of co-occurrence network. Soil moisture content, organic carbon, total nitrogen, and total phosphorus were the primary factors affecting fungal community structure. Although soil pH had no significant impact on fungal community structure, it exhibited significant correlations with the rare taxa of p_Chytridiomycota and p_Mucoromycota. Overall, the study results provide useful information on the prediction of soil microorganisms in response to environmental temperature changes in seasonally permafrost regions under the background of global warming.