DISTRIBUTION OF HYDRAULIC RESISTANCE IN SOIL-PLANT-ATMOSPHERE CONTINUUM
土壤-植物-大气连续体水流阻力分布规律的研究

Based on the measured data of soil water potential,leaf water potential, air water potential,and transpiration rate in winter wheat and summer corn fields and the application of them to the Van den Honert (1948) steady-state flow equation,the magnitude, the variation with time and depth, and the relative importance of various resistences to water flow in soil-plant-atmosphere continuum (i.e.SPAC) were estimated.The estimated results indicated that the main resistances to water flow in SPAC take place in the two symmetrical connecting "Chains" through which water enters the roots and emits out of the leaves of plants,the resis--tances from the leaves to atmosphere equal to 50 times that of soil-root system.So that the water flow in SPAC is controlled by leaf stomatal resistances and air boundary layer resistances.Discussed also were the leaf stomatal varing laws and the relationships between leaf stomatal and environmental factors, such as soil matric pcten-tial, air temperature, net radiation and air vapour pressure deficit.