Tree diversity regulates soil respiration through accelerated tree growth in a mesocosm experiment

Soil respiration is an essential component of carbon (C) cycling in terrestrial ecosystems. Despite increasing awareness of the significance of aboveground-belowground interactions, little is known about tree diversity effects on soil respiration and the underlying mechanisms. Here, we conducted a 105-day mesocosm experiment in a climate chamber to test the effects of tree diversity (1, 2, and 4 species) and identity (with tree species differing strongly in litter and growth traits) on soil respiration (comprising decomposition of soil organic carbon and root respiration). We expected tree diversity to affect soil respiration through changes in tree growth and surface litter decomposition (indicated by the litter mass loss). Our results show that soil respiration varied significantly among the four tree species and increased with tree species richness. Path analysis revealed tree growth as the main mechanism driving soil respiration and explaining the tree diversity effect in this short-term experiment. Our results indicate that tree diversity and particular traits related to tree growth regulate C dynamics through changes in plant productivity and soil respiration.