基于电磁感应研究新疆土壤盐分三维空间变异对季节的响应

    Response of three-dimensional spatial variability of soil salinity to change of season of Xinjiang based on electromagnetic induction

    • 摘要: 为了获得新疆典型区域不同季节土壤盐分的三维特征,该研究以新疆伊犁地区典型地块为研究区域,将电磁感应式土壤表观电导率快速测定技术作为基础,建立了基于土壤表观电导率数据不同季节的区域尺度剖面分层土壤盐分精确解译模型,获得了剖面土壤盐分含量信息,并以此为数据源采用反距离权重空间数据插值方法评估了研究区不同季节三维土壤盐分空间变异特征,探索了三维土壤盐分变化对不同季节的响应特征。研究表明:研究区秋、春两个季节各土层土壤盐分含量的变异系数在1.223~1.636之间,均表现为强度变异性,秋季土壤盐分含量的变异性随着土层深度的增加而减小,而春季土壤盐分含量的变异性随着土层深度的增加而增大。秋、春两个季节研究区大部分区域土壤盐分含量比较低,土壤盐分含量高值区域主要集中在研究区的西北、西南及中部地区,并且表现出次年春季的盐渍化程度及盐土所占比例比前一年秋季明显加重。利用电磁感应式土壤表观电导率快速测定结合三维反距离权重方法,对区域不同季节土壤盐分三维空间变异特征解析的精度分别达到相关系数为0.887和0.862。研究结果将为解译与评估干旱区三维土壤盐分特征随季节变化提供可靠的理论依据和技术方法。

       

      Abstract: Abstract: Salinization and alkalinization are the prominent land degradation processes in arid areas. In this study, our objective was to demonstrate the three-dimensional distribution of the regional soil salt responding to the change of season in typical zone of Xinjiang Automonous Region. The studied areas are located in typical area of the YiLi district in Xinjiang. The apparent electrical conductivity (ECa) was measured at each site using a Geonics ElectroMagnetic (EM38) instrument in different season. The ECa data collected included measurements using both horizontally and vertically modes. Soil samples were collected at selected sites immediately after the EM38 surveys. A field study was conducted, which was consisted of 70 measurement sites visited in different seasons. In addition, soil samples were also collected between 0 to 0.3 m, 0.3 to 0.6 m and 0.6 to 1.0 m depth increments at the location of the deep cores. Prior to laboratory analysis samples were air-dried and ground to pass a 2-mm sieve. The profile soil salinity was determined from the electrical conductivity of a saturated soil paste extract (ECe) according to standard methods. The profile soil salinity was obtained by regression model using apparent electrical conductivity. The model correlation coefficient differed from 0.875 to 0.952 that indicated high precision accuracy for each model. Three-dimensional soil salt distribution was characterized by inverse distance weighting method for different season. The results showed that average of soil salinity all decreased with increasing depth in the study area in different season. But average of soil salinity moderately decreased with increasing depth in autumn than in spring. The coefficient of variation of soil salinity, an indicative of strength intensity variation for different seasons, ranged from 1.223 to 1.636. Variation of soil salinity decreased with the increase of soil depth in autumn, but variation of soil salinity increased with the increase of soil depth in spring. Map of three-dimensional distribution of the regional soil salt demonstrated that sever soil salinity located in northwest corner of the studied area in autumn and spring. But the area and degree of salinization indicated more serious in spring than in autumn in northwest corner of the studied area. The soil salinity of total profile was more than 6 g/kg soil in northwest corner of study area in spring. Non-saline soil mostly distributed in the studied area in autumn of 2015. Area ratio of non-saline soil for each depth differed 65%, 69% and 81%. Area ratio of non-saline soil increased with increasing depth, area ratio of salinization soil decreased with increasing depth in the study area. Area ratio of different degree salinization soil had slight difference with increasing depth. Area ratio of mild salinization was more than moderate salinization and severe salinization, and area ratio of saline soil (soil salt content more than 6 g/kg soil) was least in 0 to 60 cm depth. Area ratio of moderate salinization was more than mild salinization, and area ratio of severe salinization was least in 60 to 120 cm depth. Non-saline soil mostly distributed and area ratio of non-saline soil increased with increasing depth in study area in spring of 2016. But ratio of saline soil became more than 5% for each depth. The degree of soil salinization and proportion of the severity salinization was significantly increased in the spring of next year than the previous year in autumn. The synthesized method based inverse distance weighting (IDW) method combining electromagnetic induction technique in this study had 0.887 and 0.862 of high correlation coefficient for different season assessment of regional soil salinity. Thus the application of this technique provides a new method to interpretation and evaluation of regional soil salinity response to different season in the three-dimensional spatial distribution characteristics in Xinjiang province.

       

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