雪被-农田土壤复合系统水热时空分异特征及互作效应研究

Aiming at ignoring some factors like snowcover thickness and snowcover density to affect energy distribution and transformation between water and heat that leading to unfulfill the function of water conservation of frozen soil, snowcover, soil and coverage between them can be seen as a complex system. Firstly, the main part of each system can be generalized with the help of CAS theory, behavior function and behavior parameters can be fixed and the key driving factor, that its driving force comprehensive index can be calculated can be distinguished. Then the spatial-temporal variation feature of water and heat of snowcover-farmland combined system can be revealed. Secondly, through building the water and soil relation function of snowcover-farmland combined system on the condition of different cover, the spatial-temporal variation pattern of water and heat can be fixed and the variation index, variation function and variation model can be built, and then the spatial-temporal variation degree and spatial-temporal designability can be fixed. The spatial-temporal variation law of water and heat of snowcover-farmland combined system can be revealed. Finally, the influence mechanism of different freeze-thaw period, different coverage and snow thickness to heat and water process of soil activities can be analyzed. Through building the system mutual impact function the key influence factor can be fixed, and then the technology of keeping farmland soil moisture content can be presented. The results have great significance for revealing water and heat action mechanism on the condition of snowcover and coverage and solving some problems, such as fixing "stream" transitive relation among different factors of snowcover-farmland combined system, distinguishing the spatial-temporal variation pattern of water and heat and fixing the water and soil relation function.

针对以往研究忽视雪被厚度、雪层密度等因素对水热间能量分配与转换的影响，难以充分发挥冻土蓄水保墒作用，将雪被、农田土壤及中间覆盖视为一个复合系统，运用复杂适应系统理论概化各子系统主体，确定其行为函数及行为参数，识别水热时空分异关键驱动因子，计算其综合驱动力指数，揭示水热时空分异驱动机制；进而建立不同覆盖条件下雪被-农田土壤复合系统水热联系方程，确定水热时空分异分析模式，建立适宜的水热时空分异指标、分异函数和分异模型，确定水热时空分异程度和时空结构性，揭示水热时空分异规律；最后，分析不同冻融期、不同覆盖及雪被厚度对土壤活动层水热过程的影响机制，建立系统互作效应函数，确定农田土壤墒情诊断关键影响因子，提出适宜的农田土壤墒情保持技术。研究成果为揭示雪被及覆盖条件下水热作用机理，解决雪被-农田土壤复合系统不同要素间"流"传递关系确定、水热时空分异模式识别和水热互作效应函数确定等问题具有重要意义。

本项目针对寒区农业水土资源高效利用问题，将雪被、农田土壤视为一个复合系统，运用系统工程的思想，研究了土壤水热时空分异特征、水热运移驱动机制、水热耦合互作机理、水热复杂适应性、水热响应传递函数、土壤水热动态模拟以及土壤墒情识别等内容。从土壤冻融循环机理以及水热传递方式阐述了雪被-农田土壤复合系统水热之间相互交流、协同和反馈关系；借助灰色关联分析，筛选了与土壤水热迁移转化影响较为密切的环境因子，解释了土壤水热运移的驱动机制；从冻结期和融化期分别建立了土壤水热耦合模型，提出了雪被覆盖保温和融雪水入渗对土壤温度和液态含水率之间转化关系的响应特征；采用小波变换信息量系数、近似熵、符号动力学等方法对雪被-农田土壤复合系统水热时间序列进行了复杂性测度，解决了寒区冻土水热资源的复杂性诊断问题；利用筛选出的土壤水热空间分布变异影响较大的环境因子，建立了大气-土壤水热响应传递函数模型，明确了环境因子与土壤水热变化的关联响应关系；借助粒子群算法、改进的萤火虫优化算法等工具优化了土壤特性参数，利用SHAW模型对不同上边界条件下冻融土壤水热变化进行了数值模拟，实现了雪被覆盖条件下冻融土壤水热迁移动态模拟；根据雪被-农田土壤复合系统的水热效应机制，建立了不同覆盖处理条件下土壤墒情影响模式，确定了适宜的农田土壤墒情保持技术。此外，本课题还进行了拓展研究，将大气、雪被、农田土壤作为一个联合体，结合大气环境驱动机制和土壤水动力学理论，初步探究了大气-雪被-土壤之间的水热协同效应及能量传递机理，分析了大气-雪被-冻融土壤系统的水热蒸发入渗规律，识别了融雪水入渗蒸发的关键性驱动因子，研究成果对于合理开发利用农田土壤水热资源、高效利用寒区冻融土壤以及科学合理的指导农业生产具有重要的理论价值和现实意义。