Fig. 5: The temporal trends of soil organic carbon (SOC) stocks in the Contiguous United States (CONUS) across different soil depths from 1955 to 2014.

Each panel represents a specific depth interval: 0–15 cm, 15–30 cm, 30–60 cm, and 60–100 cm. The gray area around each trend line represents the 95% confidence interval of the linear regression model.