Priority Effect of Endophyte Community in Newly Fallen Leaves of Quercus acutissima Carruth. on Litter Decomposition and Saprotrophic Microbial Community

This study examines the role of endophytic microbial colonization on the decomposition of oak leaf litter, a high-quality substrate in forest ecosystems. Over a one-year incubation, we observed a significant reduction in mass loss in colonized litter (46%) compared to non-colonized litter (80%), indicating an inhibitory effect of endophytes on decomposition. Structural equation modeling revealed a bimodal impact of endophytic microbes, with an initial enhancement followed by a pronounced inhibition as decomposition progressed. Extracellular enzyme stoichiometry showed phosphorus limitation became significant, particularly with endophytic colonization, contributing to reduced decomposition rates. Microbial diversity analyses exposed the variable impacts of endophytic colonization on fungal and bacterial communities, with taxa such as Helotiales (order) and Burkholderia–Caballeronia–Paraburkholderia (genus) significantly affected. The identification of 16 keystone species, mostly endophytic bacteria, underscored their pivotal influence on decomposition processes. Despite initial endophytic impacts, abundant carbon resources promoted stochastic colonization, potentially surpassing the effects of early endophytic establishment. This study provides insights into the priority effects of endophytic colonization and niche differentiation, offering a foundation for further research into the mechanisms underlying these processes and their ecological consequences in various ecosystems.