Spatial Variability of Soil Moisture Content Based on Microrelief and Land Cover——A Case Study in Oasis in the Manas River Basin

The aims of this study were to explore the spatial heterogeneity of soil moisture content at depth of 0-70 cm and its affecting factors in oasis in the Manas River Basin.The relations between soil moisture content and microrelief as well as land use types were analyzed using the methods of traditional statistics and geo-statistics.The results show that soil moisture content was in normal distribution and moderate variability in the study area.The coefficient of variation of soil moisture content varied in a range of 0.293-0.371,in which that of topsoil moisture content was the highest.According to the highest r2 values,the best simulation model of soil moisture content above 50 cm in depth was exponential model,Gaussian model was applicable for soil layer of 50-70 cm,but the nugget effect was significant due to the structural and random factors.The spatial autocorrelation distance of all soil layers varied in a range of 40.2-489 km.The values interpolated with Kriging interpolation reveal that the spatial distribution of soil moisture content of all layers was similar and in strip and patch distribution patterns.Pearson correlation analysis shows that soil moisture content was positively correlated with elevation,and elevation affected significantly topsoil moisture content.Slope affected soil moisture content variability.Soil moisture content at soil layer of 0-70 cm increased with the increase of soil depth under different slopes.Soil moisture content above 30 cm in depth in farmland was higher than that in saline or alkaline land.The study results are of significance in vegetation regeneration and ecological balance in arid regions.