Trend Effect and an Isotropy of Soil Particle Composition in the Chengdu Plain

This paper studies the spatial variation characteristics of soil particle composition on both sides of Qingbaijiang River (Chengdu Xin Du District of Sichuan province) by using the geostatistical component of ArcGIS and GS software. The results have shown that the trends of sand contents in the east-west direction and the north-south direction were first order and second order, respectively. And the trends of both silt particle and clay particle contents were first order in the east-west direction, and second order in the north-south direction. The anisotropy semi variance models of sand particle content showed that the ranges in the long axis direction were 718.77 m and 677.01 m and the ranges in the short axis direction were 273.78 m and 276.63 m with first order and second order. The results showed that the difference between the ranges in the short axis direction and the ranges in long axis direction changed little, while the anisotropy semi variance model had longer ranges than the isotropy model with the trend parameters of first order. From the error analysis and the result that reflect regional and local trend, it indicated that Kriging interpolation method considering the study about soil particle composition along Qingbaijiang River with the second order trend effect was the best, comparing the contour maps of sand particle content under different trend effects and anisotropy parameters.