冬小麦叶片和冠层尺度的光合-蒸腾模拟

Photosynthesis-transpiration coupling simulation in leaf and canopy scales of winter wheat

利用气孔导度-光合-蒸腾耦合模型(SMPT-SB),选取冬小麦关键生育期的典型日,模拟了冬小麦叶片和冠层尺度的光合与蒸腾速率日变化,并借助光合仪和涡度相关系统获得的观测数据进行了验证。研究结果表明:模型模拟的叶片和冠层尺度光合及蒸腾速率与实测值变化趋势具有较好的一致性,光合速率日均绝对误差不超过1μmol·m^(-2)·s^(-1),蒸腾速率日均绝对误差不超过0.41 mmol·m^(-2)·s^(-1);叶片尺度光合和蒸腾速率模拟值与实测值的决定系数R^(2)均在0.90以上,冠层尺度也分别达到了0.96、0.88。此外,模型中水汽响应函数以f(D_(s))=RH表示时,相对湿度(RH)变化较大会导致参数m值不能准确量化气孔导度(g_(s))的变化,从而降低模拟效果;若分时期率定m值,会大幅提高模拟精度。该模型适用于冬小麦叶片及冠层尺度的土壤-植物-大气之间水碳交换的模拟。

Synthetic model of photosynthesis-transpiration based on stomatal behavior(SMPT-SB)was used to simulate the diurnal variation in photosynthesis and transpiration rate of winter wheat at leaf-and canopy-scales.The results were validated by in-situ measurements from photosynthesis instrument and eddy covariance.The results showed that the simulated leaf-and canopy-scale photosynthesis and transpiration rate were in good agreement with in-situ measurements.The daily average absolute error of photosynthesis rate was less than 1μmol·m^(-2)·s^(-1),and that of transpiration rate was less than 0.41 mmol·m^(-2)·s^(-1).The determination coefficient of linear regression(R^(2))between the simulated and measured leaf-scale photosynthesis and transpiration rate were all larger than 0.90,and R^(2) also reached 0.96 and 0.88 on the canopy scale,respectively.In addition,when the water vapor response function in the model was expressed as f(D_(s))=RH,large changes in relative humidity(RH)caused inaccurate simulation of the stomatal conductance(g_(s))variation through the parameter m.If m was calibrated according to the crop growth periods,the simulation accuracy was greatly improved.As the calculation method of the model was relatively simple and most parameters were easy to access.The model can be used to simulate water and carbon exchange between soil-plant-atmosphere at leaf and canopy scales of winter wheat.