Wildfire reshapes the composition and symbiotic networks of soil microbial communities in alpine marshy meadows

• Bacterial and fungal α-diversity responded differently to wildfire. • Fire improved the stability and robustness of bacterial co-occurrence network. • Fire made the fungal co-occurrence network less robust but more resilient. • Soil pH and the C:N ratio drove post-fire bacterial community composition. • Keystone taxa critically influenced microbial stability in the burnt soil. The accelerating pace of global climate warming and the increasing frequency of extreme weather events have markedly heightened the risk of wildfires worldwide. This study investigates the impacts of wildfire on soil physicochemical properties and microbial communities in an alpine marshy meadow, with an emphasis on identifying the primary drivers of fire-induced changes. Results showed that wildfire did not significantly alter the dominant bacterial and fungal taxa at the phylum level; however, it induced pronounced shifts in community structure (β-diversity), exerting a stronger influence on bacterial than on fungal assemblages. Notably, bacterial α-diversity increased following fire, facilitating the colonization of favorable niches by beneficial taxa and resulting in a bacterial interaction network of greater complexity, stability, and robustness ( p < 0.05), albeit with reduced resilience. In contrast, wildfire significantly decreased the robustness of the fungal network ( p < 0.05) while enhancing its resilience. Mantel test indicated that the bacterial community was shaped primarily by soil pH and the C:N ratio, whereas the fungal community was mainly correlated with available phosphorus (AP) content. Keystone taxa were identified as critical regulators of microbial community stability. Overall, this study elucidates the structural and functional responses of soil microbial communities to wildfire, yielding valuable theoretical insights for promoting post-fire ecosystem restoration.