Thermo-TDR技术监测根区土壤物理性状：根系的影响机理及校正

Thermo-TDR是目前唯一能够在相同体积土壤上原位监测土壤温度、含水量、热特性、电导率和容重的技术，在研究土壤结构以及SPAC系统的水分运动和能量转化中具有很大潜力。常规thermo-TDR技术的理论基于土壤是无限大均匀多孔介质的假设，而植物根区土壤结构复杂且变异性强、能量和物质交换强盛、生物活动活跃，导致该技术难以提供可靠的根区土壤物理性状信息，限制了其发展与应用。本项目采用模型分析和室内外实验相结合的研究方法，探讨根系对thermo-TDR技术测定土壤物理特性的影响机理，发展根区热容量和介电常数混合模型，建立thermo-TDR监测根区土壤热容量、含水量和容重的理论和技术，阐明作物生育期内根区土壤容重和水热特性的时空变异规律。研究结果对根区土壤结构和水热特性定量化、揭示根系对土壤结构、孔隙度和水热过程的影响机理具有重要意义。

The thermo-TDR technique is capable of monitoring soil temperature, water content, thermal properties, electrical conductivity and bulk density continuously and in the same soil volume. This method has a big potential for studying soil structure and heat and water transport in the SPAC system. However, due to the assumption of an infinite and uniform porous medium, thermo-TDR sensors provide biased measurements in the root zone, in which there are complicated and heterogeneous soil structure, strong heat and mass exchange, and a lot of bioactivities. The objectives of this program are: 1) to quantify the influences of plant roots on thermo-TDR measured volumetric heat capacity, water content, and bulk density in the root zone; 2) to expand the traditional heat capacity model and the dielectric model that treat soil as a three-phase system; 3) to advance the thermo-TDR technique for monitoring soil bulk density, water content, and thermal properties in the root zone, and 4) to understand the spatial and temporal changes of soil bulk density and water content, and thermal properties during crop growth period. These results have important applications for quantify soil structure and thermal and hydraulic processes, and for understand the interactions between plant roots and soil structure, porosity, and physical processes.