LAUSR

A representative saline⁃sodic area measuring 300 m × 160 m was investigated to determine the salinity and sodicity levels in Lesheng Town, Da′an City, Jilin Province, northeast China on April 20, 2013. Apparent soil electrical conductivity was measured using EM38 ( electromagnetic induction) and GPS, and its spatial variability was studied by using classical statistics and geostatistics. Correlations between apparent soil electrical conductivity, including apparent soil electrical conductivity in horizontal direction(ECh) and apparent soil electrical conductivity in vertical direction (ECv), and salinity⁃sodicity parameters, including soil ions, EC1∶5, pH1∶5, sodium adsorption ratio ( SAR), and soil salinity content (SC) were analyzed in the saline⁃sodic upland soil of the Songnen Plain. The results indicated a moderate spatial variability for ECh and ECv in classical statistics. Frequency distributions and the Kolmogorv⁃Smirov test for normality showed that ECh and ECv were not normally distributed (P<0.05). Therefore, mathematical transformations were performed to convert the data to fit the normal distribution, which is a prerequisite for calibration of the theoretical model and generation of semivariogram parameters and kriged maps. After log⁃transformation, ECh and ECv showed normal distributions. The results of geostatistical analyses indicated that ECh has a strong spatial variability and dependence, and the spatial distribution of ECh is affected by structural factors, which might include topography, hydrology, and climatic