Chernozemic soils are associated with grassland vegetation that have a dark-colored chernozemic  Ah horizon (diagnostic horizon), which is > 10 cm thick (usually 20-40 cm), has 1-17% org. C, C/N <17, and base saturation > 80% with Ca as a dominant cation. The organic matter comes from the decomposition of leaves and grass roots and results in a dark colored surface Ah horizon.