A preliminary study on estimating soil thickness on karst dolomite slopes using ground gamma radiation dose rate in Southwest China

Abstract

Karst landscapes, which occupy ∼15 % of the global terrestrial surface, are characterized by shallow, discontinuous soils that strongly influence vegetation dynamics and ecological processes. However, accurately estimating soil thickness in such heterogeneous environments remains a challenge, as existing methods are often labor-intensive, inefficient, or prone to substantial errors. This study introduces a novel approach to estimating soil thickness on karst dolomite slopes using ground gamma radiation measurements. The method is based on the principle that dolomite bedrock contains low concentrations of natural radionuclides, whereas overlying soils are comparatively enriched in radioisotopes, producing higher gamma dose rates. Calibration experiments at 15 depths revealed a positive correlation between soil thickness (y, cm) and gamma dose rate (x, µSv/h) within the range of 0–35 cm, from which a power function model was further developed with R² of 0.99. Field tests of 18 locations showed average soil thicknesses of 11.22 cm in shrublands and 0.47 cm in grasslands, consistent with results from prior large-scale excavations. This technique offers a simple, non-invasive, and accurate tool for assessing shallow soil distribution in karst regions, with implications for soil mapping, ecological restoration, and land use planning.