新疆包头湖灌区农田土壤水盐热特性空间变异特征

土壤作为高度变异体,其大尺度下的土壤水盐热分布特征具有空间变异性。为了探究大尺度下的土壤水、盐、热的空间分布特征及空间变异性,以新疆包头湖区域为例,采用经典统计学和地统计学相结合的方法,对土壤水盐热参数的空间分布特征进行分析。结果表明:土壤含水率、导热率及热容量均属于中等偏弱变异程度,土壤含盐量为强变异程度;土壤含水率、含盐量、导热率的半方差函数均可用高斯模型进行拟合,热容量的半方差函数可用指数函数进行拟合;含水率、含盐量、导热率、热容量同一深度各自变量之间均具有较强的空间依赖性,随机因素占总变异程度较低,最大相关距离在2 600~3 900 m。该研究为当地农业灌溉及精细农业的生产提供一定参考。

Spatial variability analysis of large-scale soil water, salt and heat characteristics in Baotou lake irrigation area of Xinjiang

Abstract: As a highly heterogeneous soil, its spatial variability has seriously affected the formulation of precise management measures for water and salt in farmland and the efficient use of farmland water and soil resources. The purpose of this paper was to study the spatial distribution characteristics and spatial variability of soil water, salinity and heat in large scale region. Taking the Baotou Lake region of Xinjiang as an example, the soil samples were taken about 1 week after the spring irrigation, and soil moisture, salinity, bulk density, and particle composition were measured. The spatial distribution characteristics of water, salt, thermal parameters were analyzed by using a combination of classical statistics and geostatistics and GS+ software and ARCGIS software were used to process the data. The soil moisture, salinity, and soil texture were analyzed. The soil thermal conductivity and soil heat capacity were calculated. The spatial distribution feature maps were plotted. The results showed that soil moisture and salinity gradually increased with the increase of soil depth. According to the classification standard of Xinjiang Soils, the soil in the studied area belonged to the moderate salinized soil. The overall thermal conductivity of the soils were low, with a minimum value of 0.134 W/(m·K) and a maximum value of 0.732 W/(m·K). The soil thermal conductivity averaged around 0.5 W/(m·K). The soil heat capacity increased with the increase of soil depth. The maximum value was 3.004 J/(m·K) and the minimum value was 1.321 J/(m·K). The soil bulk density had a weak variability; soil moisture content, thermal conductivity and heat capacity all had moderately weak variability; soil salinity had a strong variability. The semivariogram functions of soil moisture, soil salinity and soil thermal conductivity could be fitted by Gaussian models. The semivariance function of soil heat capacity could be fitted by an exponential model. There was a strong spatial dependence between the soil moisture at the same depth. The random factors accounted for low degree of total variation. The maximum correlation distance was 2 600 m-3 900 m. The sampling distance was about 1 500 m, which was reasonable. The spatial distribution maps of salt salinity interpolated by Kriging interpolation showed that the soil moisture was low in the middle area of the study area and increased from the east to the west. The Kriging interpolation showed that the soil salinity had an increasing trend from north to south. With the increase of soil depth, the peak area of the "circular" peak area gradually decreased and the shape formed a strip distribution area. And the lower values of the thermal conductivity of the surface soil were mainly distributed in the northeast-southwest direction, and the distribution belt with lower values gradually shifted westward as the soil depth increased. At the soil depth of 20-40 cm, there was a relatively significant positive correlation between soil moisture and salinity, and the range of positive correlation was about 1 km. This research results could provide valuable information for local agricultural irrigation and precision agriculture production.