土壤-植物系统水分运移过程的阻容电模拟

Electric resistance-capacitance model of water flow through soil-plant system

把土壤-植物系统水分运移作为一维水流运动由阻容电路进行模拟,在于将D arcy-R ichards方程从对单点的描述扩展到对一段流路的描述。由此出发,考虑到水流的非稳态性,某一流路的水阻定义为其水势差与平均流量之比,水容为其贮水量对平均水势的导数。与D arcy-R ichards方程相对应,水阻、时间常数分别为导水度、水分扩散度的倒数,相应地单位化的水阻率、比时间常数分别为导水率、水分扩散率的倒数。把SP系统沿水流通道分为若干部分,每一局部的水阻与其水容相并联,各局部间相串联。在此基础上,文章给出了土壤-植物系统水流模拟通式、总水容与分水容间的关系式、总水阻与分水阻间的关系式及特定条件下叶水势随时间变化的关系式。

Water flow through a soil-plant system can be simulated by an electric resistance-capacitance circuit when the flow is considered as one-dimensional Darcy-Rechards flow. The hydraulic resistance is a ratio of the water potential difference to the average rate of outflow and inflow, and the water capacitance is a derivative of the water storage with respect to the average water potential because of the nonsteady nature of water transport. Corresponding to the Darcy-Richards equation, hydraulic resistance and resistivity are the reciprocals of conductance and conductivity respectively; time constant is the reciprocal of the diffusancel and time constant per unit squared length is the reciprocal of diffusivity. If the soil-plant system is taken as a catenary series of segments along the water flow path, the hydraulic resistance and water capacitance are connected in parallel with each other in each segment, and all segments are connected in series. The study gave universal formula of water flow through the soil-plant systems, formula of the relationship between the total capacitance and partial capacitances of individual segements, formula of the relationship between the total resistance and partial resistances, and formula of temporal change of leaf water potential under a certain condition.