Land use-land cover gradient demonstrates the importance of perennial grasslands with intact soils for building soil carbon in the fertile Mollisols of the North Central US

•Long-term incubations used to study soil carbon kinetics in Wisconsin Mollisols.•Soil carbon differed across land use-land cover groups.•Grasslands had distinct carbon dynamics, cropping systems did not.•Tillage resulted in loss of carbon from active and slow cycling pools.•Remnant prairie had the most carbon in rapid and slowly mineralized pools.