Mowing enhanced grassland belowground carbon stocks through species reordering

Grasslands are vital for global carbon (C) cycling, with belowground organs crucial for C sequestration. Mowing, a common practice in nutrient‐enriched grasslands, affects biodiversity positively but reduces aboveground biomass. Its impacts on belowground C stocks remain unresolved, posing knowledge gaps in understanding community assembly and belowground C responses due to limited species‐level belowground biomass data. With a long‐term field experiment in temperate steppe of northern China, we investigated the impacts of annual mowing on belowground biomass C stocks at both species and community levels under ambient and N addition conditions. Mowing significantly increased belowground C stocks but not aboveground C stocks. Mowing induced reordering of plant species in the community, and facilitated the growth of a sedge Carex duriuscula with the highest belowground:aboveground biomass ratio, which accounted for the positive responses of belowground C stocks. Under projected warmer and drier climate and more frequent fire across global grasslands, mowing would be one of the important nature‐based solutions to boost grassland C storage by moving C from vulnerable aboveground pools to the long‐lasting belowground pools.