Priority effects largely determine the consequences of soil microbial community coalescence

Priority effects play critical roles in microbial community assembly but remain underexplored in soil systems. Here, we investigated their influence on soil microbial community coalescence via microcosm experiments based on soils collected from six sites across southwestern China. Results showed that priority effects dominantly determined soil microbial community coalescence outcomes, with pre-inoculated communities maintaining high similarity to their independently inoculated counterparts. Notably, at most study sites, the microbial taxa that showed strong responses to the treatments exhibited remarkably higher niche overlap than those that remained stable. Additionally, priority effects altered many soil properties that strongly correlated with microbial community composition. Collectively, these findings suggest that priority effects govern soil microbial community coalescence outcomes via niche preemption and modification.