soil organic carbon (soc) is a valuable natural resource, supplying goods and services for human benefits, including mediating global climate change and securing food production and environmental quality. biodiversity loss across multi-taxa is at an alarming rate globally. recent advances have been made in our understanding of the negative impact of biodiversity loss on ecosystem production. the higher biomass production in species-rich communities is expected to enhance plant litter inputs to soils for soc formation. despite the critical importance of soc and rs in the global carbon and nutrient cycles, our understanding of the effects of plant diversity on soc and soil respiration (rs) remains equivocal. the purpose of this dissertation is to provide the first global-scale estimates of changes in rs and soc storage in response to global plant diversity loss, and to mechanistically understand the effects of plant mixtures on soil carbon dynamics. in my first study, i examined the global effects of plant litter alterations on soil carbon release. by presenting a meta-analysis of 100 published studies to examine the responses of rs to manipulated aboveground and belowground litter alterations. i found that aboveground litter addition increased rs, while aboveground litter removal, root removal and litter + root removal reduced rs, respectively. estimated from the studies that simultaneously tested the responses of rs to aboveground litter addition and removal and assuming negligible changes in root-derived rs, “priming effect” on average accounted for 7.3% of rs and increased over time. my meta-analysis indicates that priming effects should be considered in predicting rs to climate change-induced increases in litterfall. this analysis also highlights the need to incorporate spatial climate gradient in projecting long-term rs responses to litter alterations.