新疆棉花亏缺灌溉叶面积指数模拟研究

Simulation of Cotton Leaf Area Index under Deficit Irrigation in Xinjiang

建立了充分灌溉和亏缺灌溉条件下新疆棉花叶面积指数的动态模拟模型。模型以基于beta函数的每日热效应为时间尺度,在考虑土壤水分胁迫效应的基础上,使用Logistic函数的一阶导数描述叶面积指数的变化速率,叶片衰老过程同样采用Logistic函数的一阶导数,并假设从初花期开始发生。该模型还考虑了土壤水分胁迫和温度对叶片衰老的加速效应。最后使用石河子棉花灌溉试验观测结果对模型进行了参数率定、验证和敏感度分析。验证结果显示:充分灌水条件下叶面积指数的均方根误差(RMSE)为0.22 m2/m2,残差聚集系数(CRM)为-0.01;20%和40%亏缺灌溉条件下叶面积指数的RMSE和CRM分别为0.37 m2/m2、-0.05和0.23 m2/m2、0。此外,叶面积指数的模拟值与实测值间R2为0.96。说明该模型准确地模拟了新疆棉花叶片全生育期的动态变化过程。敏感度分析结果表明,在充分灌水条件下,叶片潜在衰减面积、叶片日最大增加面积和衰减面积、初花期开始时间是影响模型的主要参数。

A leaf area index simulation model of cotton was developed under full and deficit irrigation in Xinjiang. The model was based on beta function of daily heat effect as time scales, and the effect of soil water stress was considered. One ordered derivative of the Logistic function was used to describe the changing rate of leaf area index. One ordered derivative of the Logistic function was also used to describe leaf senescence process and assumed that leaf senescence occurred since the early flowering. The acceleration effects of soil water stress and temperature on leaf senescence were also considered in the model. Finally field observations from Shihezi were used for model parameter calibration, evaluation and sensitivity analysis. Evaluation results showed that under the condition of full irrigation the root mean square error （RMSE） between simulated and observed leaf area index （LAI） values was 0.22 m^2/m^2 and the residual accumulation coefficient （CRV） was - 0.01. Under the condition of 20% and 40% deficit irrigation RMse and Cnu were 0. 37 m^2/m^2, 0.05 and 0.05 ma/m^2, 0, respectively. In addition, the determination coefficient of linear relationship between simulated and observed LAI was 0.96. Simulation results showed that the model was accurate in describing the dynamic changing process of cotton LAI during the whole growth period in Xinjiang. Sensitivity analysis results showed that under the condition of sufficient water, potential leaf aging area, maximum daily leaf extension area and aging area, early flowering start time were the main parameters affecting the model. The model had a few parameters and it can be used to supply the LAI dynamic information for establishing the Xinjiang cotton growth model and evapotranspiration model.