Plant diversity enhances soil microbial activity and carbon storage. A long-term grassland experiment (The Jena Experiment) showed that higher plant diversity increases root carbon inputs, boosting microbial activity and carbon storage. This is due to the accumulation of recently fixed carbon in high-diversity plots, not just the decomposition of existing carbon. Soil carbon storage is directly linked to microbial activity, which is influenced by plant diversity through root exudates and other mechanisms. Legumes negatively affect soil carbon storage, possibly due to reduced root biomass. The study highlights the role of soil microorganisms in carbon storage, showing that increased plant diversity enhances carbon sequestration by improving microbial activity and carbon input. The findings suggest that soil microbial communities are key to carbon storage, with plant diversity driving this process through root exudates and microbial necromass accumulation. The study also indicates that the positive effects of plant diversity on carbon storage are more pronounced in the topsoil and decrease with depth. Overall, plant diversity enhances soil carbon storage by increasing microbial activity and carbon input, with soil microorganisms playing a central role in this process.Plant diversity enhances soil microbial activity and carbon storage. A long-term grassland experiment (The Jena Experiment) showed that higher plant diversity increases root carbon inputs, boosting microbial activity and carbon storage. This is due to the accumulation of recently fixed carbon in high-diversity plots, not just the decomposition of existing carbon. Soil carbon storage is directly linked to microbial activity, which is influenced by plant diversity through root exudates and other mechanisms. Legumes negatively affect soil carbon storage, possibly due to reduced root biomass. The study highlights the role of soil microorganisms in carbon storage, showing that increased plant diversity enhances carbon sequestration by improving microbial activity and carbon input. The findings suggest that soil microbial communities are key to carbon storage, with plant diversity driving this process through root exudates and microbial necromass accumulation. The study also indicates that the positive effects of plant diversity on carbon storage are more pronounced in the topsoil and decrease with depth. Overall, plant diversity enhances soil carbon storage by increasing microbial activity and carbon input, with soil microorganisms playing a central role in this process.