Characteristics of spatial distribution of soil water-air-heat parameters in typical oasis croplands at middle reaches of Heihe River

Using statistical methods for a study on the spatial variations of soil properties has become one of hot topics in the study of soil science. Due to the deep research on the spatial variation of soil hydraulic parameters, and the lack of research on the dynamic characteristics of soil air and heat transfer, we cannot compare the spatial variation characteristics of soil, water, air, and heat transfer kinetic parameters. As the interaction between the soil and the environment as well as the precise regulation of farmland soil moisture, air and heat condition problem is receiving more and more attention, the numerical model used to study the soil moisture, air and heat transport process, effectiveness and its impact on crop growth and ecological environment has gradually become a reality. But model accuracy depends largely on the accuracy of soil, water,air, and heat transfer kinetic parameters. Thus, seeking a simple and feasible method of determining the thermal dynamic parameters of soil moisture is the focus of research around the world. In order to define the dynamiccharacteristics of water conductivity、air permeability and heat conductivity's spatial variability, this paper examines the spatial variation of the above parameters in Linze County, an agricultural area in the middle reaches of the Heihe River Basin. PL-300 soil air permeability measurement and soil heat pulse meter were applied to measured soil air permeability and thermal conductivity. In this paper, we designed an experiment of four levels of moisture content and took the average of three replications. Hydraulic conductivity is measured by qdisc infiltration instrument, each measuring point design four suction head, based on a spatial analysis function of GIS, The results showed as follows: 1) simulate the spatial structure and variability of the water, air, and heat parameters using land statistics of a wheat field. The optimal fitting model for saturated hydraulic conductivity, air permeability, thermal conductivity are an exponential model, the sum of squared residuals are small, nearly zero, and the determination coefficient R2 reached more than 80%. The results show that the statistical method can better simulate the spatial structure and variation characteristics of soil moisture air and thermal parameters. Fractal dimension (D) was close to 2, illustrating that soil water conductivity, air permeability and heat conductivity have strong spatial variation characteristics in this region. 2) Saturated hydraulic conductivity, air permeability and heat conductivity's C / (C +C0)>75%, had a strong degree of spatial autocorrelation in the study scale. Recommend sampling distances of hydraulic conductivity, air permeability and heat conductivity both are 10m. And sampling distances of the other soil physical parameters are recommend to be 4m. 3) Kringing interpolation results show that soil water and gas parameters change was having a certain degree of consistency, Thermal conductivity has certain regional characteristics in the study area. The higher the moisture content, bulk density and the greater the sand content are, the greater the thermal conductivity is, and the thermal conductivity has certain regional characteristics. Among the soil, thermal conductivity is high, the north and south were on both sides of the lower tendency in the saddle. The research will be for the local soil moisture, air and thermal parameters field scale space mutation research to provide a certain reference basis.