Soil respiration is an essential component of carbon (C) cycling in terrestrial ecosystems. Despite increasingawareness of the signifificance of aboveground-belowground interactions, little is known about tree diversityeffffects on soil respiration and the underlying mechanisms. Here, we conducted a 105-day mesocosm experimentin a climate chamber to test the effffects of tree diversity (1, 2, and 4 species) and identity (with tree speciesdiffffering strongly in litter and growth traits) on soil respiration (comprising decomposition of soil organic carbonand root respiration). We expected tree diversity to affffect soil respiration through changes in tree growth andsurface litter decomposition (indicated by the litter mass loss). Our results show that soil respiration variedsignifificantly among the four tree species and increased with tree species richness. Path analysis revealed treegrowth as the main mechanism driving soil respiration and explaining the tree diversity effffect in this short-termexperiment. Our results indicate that tree diversity and particular traits related to tree growth regulate Cdynamics through changes in plant productivity and soil respiration.