Spatial heterogeneity characteristics of soil-epikarst thickness in a typical karst dolomite small watershed

Abstract

Objective The thickness of soilepikarst is an important index affecting the hydrological process of critical zones. The spatial heterogeneity is critical understanding the structural evolution mechanism of the key zones of the Earth and the water conservation function of the key zones of the Earth. Methods Based on the 1.4 km2 area of the Mulian catchment in Huanjiang, Guangxi, the 1 731 soil-epikarst thickness samples were obtained through electrical resistivity tomography (ERT) with 45 sampling lines.The spatial distribution pattern of soil and epikarst thickness and its influencing factors were investigated. The results showed that the average thickness of soil and epikarst was 1.15 m and 6.44 m with strong and medium variance, respectively. Results The results of geostatistical analysis indicated that the spherical model and exponential model could reflect the spatial structure characteristics of soil and epikarst thickness, respectively. Soil thickness showed moderate spatial autocorrelation, a long range and good spatial continuity. However, the epikarst presented strong spatial autocorrelation and spatial dependence with a short range. Soil thickness was affected by multiple environmental factors (topographic wetness index, vertical curvature, curvature, aspect, slope, elevation, coverage, outcrop ratio and NDVI), while the thickness of epikarst was more affected by soil thickness and vegetation type. Conclusion These results are helpful for understanding the evolution of the soil-epikarst zone and provide a scientific basis for the spatial prediction of soil-epikarst thickness in karst areas.

Keywords

• karst critical zone
• spatial heterogeneity
• soil-epikarst
• vegetation type
• dolomite small watershed