Transpiration element is included in the integrated stomatal conductance photosynthesis model by considering gaseous transfer processes, so the present model is capable to simulate the influence of boundary layer con...Transpiration element is included in the integrated stomatal conductance photosynthesis model by considering gaseous transfer processes, so the present model is capable to simulate the influence of boundary layer conductance. Leuning in his revised Ball's model replaced relative humidity with VPD s (the vapor pressure deficit from stomatal pore to leaf surface) and thereby made the relation with transpiration more straightforward, and made it possible for the regulation of transpiration and the influence of boundary layer conductance to be integrated into the combined model. If the differences in water vapor and CO 2 concentration between leaf and ambient air are considered, VPD s , the evaporative demand, is influenced by stomatal and boundary layer conductance. The physiological responses of photosynthesis, transpiration, and stomatal function, and the changes of intercellular CO 2 and water use efficiency to environmental factors, such as wind speed, photon flux density, leaf temperature and ambient CO 2, are analyzed. It is shown that if the boundary layer conductance drops to a level comparable with stomatal conductance, the results of simulation by the model presented here differ significantly from those by the previous model, and, in some cases, are more realistic than the latter.展开更多
Based on potted plant experiment, BP-artifieial neural network was used to simulate crop evapotranspiration and 3 kinds of artificial neural network models were constructed as ET1 （meteorological factors）, ET2（ met...Based on potted plant experiment, BP-artifieial neural network was used to simulate crop evapotranspiration and 3 kinds of artificial neural network models were constructed as ET1 （meteorological factors）, ET2（ meteorological factors and sowing days） and ET3 （meteorological factors, sowing days and water content）. And the predicted result was compared with actual value ET that was obtained by weighing method. The results showed that the ET3 model had higher calculation precision and an optimum BP-artificial neural network model for calculating crop evapotranspiration.展开更多
HDS-SPAC,a new soil-plant-atmosphere continuum(SPAC) model,is developed for simulating water and heat transfer in SPAC.The model adopts a recently proposed hybrid dual source approach for soil evaporation and plant tr...HDS-SPAC,a new soil-plant-atmosphere continuum(SPAC) model,is developed for simulating water and heat transfer in SPAC.The model adopts a recently proposed hybrid dual source approach for soil evaporation and plant transpiration partitioning.For the above-ground part,a layer approach is used to partition available energy and calculate aerodynamic resistances,while a patch approach is used to derive sensible heat and latent heat fluxes from the two sources(soil and vegetation).For the below-ground part,soil water and heat dynamics are described by the mixed form of Richards equation,and the soil heat conductivity equation,respectively.These two parts are coupled through ground heat flux for energy transfer,root-zone water potential-dependent stomatal resistance,and surface soil water potential-dependent evaporation for water transfer.Evaporation is calculated from the water potential gradient at soil-atmosphere interface and aerodynamic resistance,and transpiration is determined using a Jarvis-type function linking soil water availability and atmospheric conditions.Some other processes,such as canopy interception and deep percolation,are also considered in the HDS-SPAC model.The hybrid dual-source approach allows HDS-SPAC to simulate heat and water transfer in an ecosystem with a large range of vegetation cover change temporally or spatially.The model was tested with observations at a wheat field in North China Plain over a time of three months covering both wet and dry conditions.The fractional crop covers change from 30% to over 90%.The results indicated that the HDS-SPAC model can estimate actual evaporation and transpiration partitioning and soil water content and temperature over the whole range of tested vegetation coverage.展开更多
文摘Transpiration element is included in the integrated stomatal conductance photosynthesis model by considering gaseous transfer processes, so the present model is capable to simulate the influence of boundary layer conductance. Leuning in his revised Ball's model replaced relative humidity with VPD s (the vapor pressure deficit from stomatal pore to leaf surface) and thereby made the relation with transpiration more straightforward, and made it possible for the regulation of transpiration and the influence of boundary layer conductance to be integrated into the combined model. If the differences in water vapor and CO 2 concentration between leaf and ambient air are considered, VPD s , the evaporative demand, is influenced by stomatal and boundary layer conductance. The physiological responses of photosynthesis, transpiration, and stomatal function, and the changes of intercellular CO 2 and water use efficiency to environmental factors, such as wind speed, photon flux density, leaf temperature and ambient CO 2, are analyzed. It is shown that if the boundary layer conductance drops to a level comparable with stomatal conductance, the results of simulation by the model presented here differ significantly from those by the previous model, and, in some cases, are more realistic than the latter.
基金Supported by the National Natural Science Foundation of China(50609022)~~
文摘Based on potted plant experiment, BP-artifieial neural network was used to simulate crop evapotranspiration and 3 kinds of artificial neural network models were constructed as ET1 （meteorological factors）, ET2（ meteorological factors and sowing days） and ET3 （meteorological factors, sowing days and water content）. And the predicted result was compared with actual value ET that was obtained by weighing method. The results showed that the ET3 model had higher calculation precision and an optimum BP-artificial neural network model for calculating crop evapotranspiration.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50879041 and 50939004)the National Hi-Tech Research and Development Program of China (Grant No.2011BAD25B05)
文摘HDS-SPAC,a new soil-plant-atmosphere continuum(SPAC) model,is developed for simulating water and heat transfer in SPAC.The model adopts a recently proposed hybrid dual source approach for soil evaporation and plant transpiration partitioning.For the above-ground part,a layer approach is used to partition available energy and calculate aerodynamic resistances,while a patch approach is used to derive sensible heat and latent heat fluxes from the two sources(soil and vegetation).For the below-ground part,soil water and heat dynamics are described by the mixed form of Richards equation,and the soil heat conductivity equation,respectively.These two parts are coupled through ground heat flux for energy transfer,root-zone water potential-dependent stomatal resistance,and surface soil water potential-dependent evaporation for water transfer.Evaporation is calculated from the water potential gradient at soil-atmosphere interface and aerodynamic resistance,and transpiration is determined using a Jarvis-type function linking soil water availability and atmospheric conditions.Some other processes,such as canopy interception and deep percolation,are also considered in the HDS-SPAC model.The hybrid dual-source approach allows HDS-SPAC to simulate heat and water transfer in an ecosystem with a large range of vegetation cover change temporally or spatially.The model was tested with observations at a wheat field in North China Plain over a time of three months covering both wet and dry conditions.The fractional crop covers change from 30% to over 90%.The results indicated that the HDS-SPAC model can estimate actual evaporation and transpiration partitioning and soil water content and temperature over the whole range of tested vegetation coverage.
