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土壤水分是制约作物产量和品质的主要环境因素之一,估算不同水分条件下的蒸腾速率(T r)对于作物的优质高产和节水灌溉等具有十分重要的意义。通过构建蒸腾-气孔-光合耦合模型可模拟出不同水分条件下苹果树的蒸腾动态,模型参数根据逐步干旱条件下盆栽‘富士’苹果树试验获取。结果表明,T r主要由饱合水气压差和气孔导度(G s)驱动,同时气象因子和土壤水势对其有强烈的交互作用影响。T r随土壤水势的下降而减小,当土壤水势低于0.4 MPa时减小幅度更加显著。晴天时,G s在一天中呈双峰曲线,而T r呈单峰曲线,最大值出现在13:00左右,约为3.6 mmol·m-2·s-1。根据该模型可计算出不同水分条件下1株盆栽苹果树(总叶片积为0.26 m-2)全天的蒸腾总量,供水充足时为652.1 g,严重干旱时(土壤水势为1.5 MPa)为85.4 g。实测值和模拟值的比较表明,该耦合模型能够模拟出不同土壤水分条件下盆栽苹果树的蒸腾动态以及土壤的含水量。
Soil moisture is one of the main environmental factors restricting the yield and quality of crops. Estimating the transpiration rate (T r) under different water conditions is of great significance for high yield and water-saving irrigation of crops. The transpiration dynamics of apple trees under different water conditions can be simulated by constructing a model of transpiration - stomatal - photosynthesis. The model parameters were obtained from pot experiments of ’Fuji’ apple tree under the condition of gradual drought. The results show that T r is mainly driven by the pressure difference of saturated water vapor and the stomatal conductance (G s), and the meteorological factors and soil water potential have a strong interaction with T r. T r decreases with the decrease of soil water potential, and decreases more obviously when soil water potential is lower than 0.4 MPa. On sunny days, G s showed a bimodal curve in one day, while T r showed a single peak curve with the maximum at about 13:00, which was about 3.6 mmol · m-2 · s-1. According to the model, the total transpiration amount of one potted apple tree (total leaf product of 0.26 m-2) under different water conditions was calculated, which was 652.1 g when the water supply was sufficient and 1.52 MPa when severe drought (soil water potential was 1.5 MPa) 85.4 g. The comparison of the measured data and the simulated data shows that the coupled model can simulate the transpiration dynamics and soil water content of potted apple trees under different soil moisture conditions.