The researchers studied the distribution of carbonate carbon in soil in a watershed with serious soil erosion. They collected soil samples from different locations and depths in the watershed and analyzed them using a geostatistical method. The results showed that carbonate carbon content in soil varies across the landscape, with higher levels on hilltops and lower levels in gullies. The change in carbonate carbon content is smaller on hill slopes compared to hilltops and gullies. Additionally, the depth at which carbonate carbon is found in the soil differs depending on the location, with lower levels in topsoil in gullies, similar levels on hill slopes, and higher levels on hilltops.