Fungal community assembly and limiting factors of logs in the initial decomposition phase in temperate forests

Abstract Background In forest ecosystems, the decomposition of deadwood, primarily driven by fungal communities, constitutes a fundamental ecological process. The initial phase of deadwood decomposition is particularly critical, marked by significant shifts in fungal community composition. However, the assembly mechanisms, key drivers shaping wood-inhabiting fungal communities and whether fallen logs degradation has home-field advantage or not during this phase remain inadequately understood. Methods This study focused on this crucial yet understudied initial decay phase by establishing a chronosequence of decomposition initiation and quantifying differential decay rates between Korean pine ( Pinus koraiensis ) and white birch ( Betula platyphylla ) under “home” versus “away” field conditions. Results Notably, Korean pine logs exhibited slower decomposition rate compared to white birch, accompanied by divergent successional trajectories in their respective fungal communities. No significant home-field advantage was observed in either fungal community composition or structural assembly during log decomposition. Correlation analyses identified nitrogen content within the logs as a key limiting factor regulating fungal communities in both tree species, with distinct adaptation thresholds and ranges identified among taxa. Fungal community assembly was governed by a combination of stochastic processes, dispersal limitation, and homogenizing selection, reflecting a complex, multidimensional mechanism. Conclusions By elucidating fungal-mediated decomposition dynamics, this study provides critical insights into the degradation mechanisms of forest deadwood and its ecological functions in biogeochemical cycling, while offering a novel perspective for interpreting forest ecosystem succession.