Community-driven invasion, also known as community coalescence, occurs widely in natural ecosystems. Despite that, our knowledge about the process and mechanisms controlling community-driven invasion in soil ecosystems is lacking. Here we performed a set of coalescence experiments in soil microcosms and assessed impacts up to 60 days after coalescence by quantifying multiple traits (compositional, functional, and metabolic) of the invasive and coalescent communities. Our results show invasion-triggered changes in the resident community's succession trajectory and functionality (carbohydrate metabolism), which were dependent on the invasive communities. Moreover, the invasion impact was mainly due to the high suppression of residents rather than the invaders’ survival. The short-term coalescence effect was predicted by the metabolic unevenness of the invasive community, indicating the direct competition between invaders and residents for labile carbon sources at the onset of coalescence. In contrast, the long-term impact was predicted by the compositional (phylogenetic) similarity between invasive and resident communities. Collectively, our results suggest that community coalescences in soil are primarily driven by resource competition – the lose-lose situation – between invaders and residents, and a multi-level trait-based approach could help predict the impact.