Revealing the scale- and location-specific relationship between soil organic carbon and environmental factors in China's north-south transition zone

•Wavelet identified the variations and controls of soil organic carbon (SOC).•SOC had a transition effect similar to that of plant types.•Controls of the variability in SOC differed with scale-location domain.•It was unnecessary to use too many variables to explain SOC variability.•Various types of combinations that control SOC enhanced with increasing scale.