[Spatial Heterogeneity of Soil Carbon and its Fractions in the Wolfberry Field of Zhongning County].

It is important to accurately assess the regional spatial distribution and variation of soil carbon and its fractions due to its great significance in soil carbon cycling and soil quality. The objectives of this study were to investigate the spatial variability of soil carbon and its fractions using classical and geostatistical statistics. Topsoil samples (0-20 cm) from 119 sites in Wolfberry Field were collected from a grid of 100 m×100 m in Zhongning County. The GS+7.0 software was used to fit a semivariance model to determine the optimal theoretical model and parameters. The spatial distribution characteristics of soil carbon and its fractions were studied by ordinary kriging. The classical statistical analyses showed that the average concentrations of total carbon, inorganic carbon, organic carbon, active organic carbon, medium active organic carbon, and high active organic carbon were 28.74, 18.72, 10.09, 1.81, 1.48, and 0.73 g·kg ^-1 , respectively. The variation coefficient of total carbon and inorganic carbon were 7.69% and 9.13%, indicating a strong variation, while the other soil carbon fractions showed moderate variation with the coefficients of variations ranging from 14.77%-52.05%. The geostatistical analyses revealed that the semivariogram of organic carbon was best fit by the spherical model, while the other five kinds of carbon fractions were best fit by the exponential model. The nugget coefficients of total carbon and organic carbon were 48.99% and 34.35%, which demonstrated moderate spatial dependence. The nugget coefficients of inorganic carbon, active organic carbon, medium active organic carbon, and high active organic carbon were 8.17%, 0.25%, 12.18%, and 0.08%, which demonstrated strong spatial dependence. The ordinary kriging interpolation map indicated that the spatial distribution patterns were similar for total carbon, organic carbon, medium active organic carbon, and high active organic carbon, which increased from southeast to northwest. Inorganic carbon and active organic carbon presented an irregular plaque distribution in the study area. Spatial interpolation maps could provide useful information for environmental management and the sustainable use of land resources in this region.