Three-Dimensional Mapping of Soil Organic Carbon by Combining Kriging Method with Profile Depth Function

Area of Science:

• Soil Science
• Geospatial Analysis
• Environmental Science

Background:

• Spatial variation of soil organic carbon (SOC) is critical for land management.
• Vertical SOC distribution is complex due to soil texture and depth, challenging traditional 3D mapping.
• Existing 3D ordinary kriging methods are limited by the non-stationary nature of SOC in the vertical dimension.

Purpose of the Study:

• To develop and apply a 3D kriging method combined with profile depth function (KPDF) for regional SOC mapping.
• To investigate the influence of soil texture and land use on the vertical distribution of SOC.
• To create a 3D spatial distribution map of SOC in Quzhou County, China.

Main Methods:

• Collected 605 soil samples from 121 profiles (0.0-1.0 m depth) in Quzhou County.
• Applied the Kriging with Profile Depth Function (KPDF) method to model and map 3D SOC distribution.
• Analyzed correlations between SOC content, depth, soil texture, and land use type.

Main Results:

• The KPDF method accurately predicted SOC content, with R²=0.52 and RMSE=1.82 g kg⁻¹.
• An exponential equation effectively described the vertical distribution of mean SOC content.
• Surface SOC was high in the mid-west and south, low in the southeast; land use impacted surface SOC more than texture, while texture dominated deeper layers (0.2-0.4 m).

Conclusions:

• The KPDF method is suitable for generating 3D SOC distribution maps at a regional scale.
• Soil texture and land use significantly affect SOC spatial distribution, particularly in vertical profiles.
• Understanding these factors is essential for optimizing land use and soil management strategies.