遥感植被指数和CASA模型估算山东省冬小麦单产

准确估算区域尺度冬小麦单产对明确区域农业生产现状与保证国家粮食安全有重要意义。光能利用率模型是作物单产估算的常用模型之一，模型中最大光能利用率（ξ_max）是准确估算作物单产的关键参数，作物的ξ_max是否随时间发生变化需要深入探讨。首先使用Savitzky-Golay（S-G）对中分辨率成像光谱仪（MODIS）时序植被指数数据进行滤波，采用差分法结合光谱突变法提取了山东省2000年-2015年冬小麦种植面积，并使用市级尺度年鉴统计面积对提取面积进行验证，然后使用固定ξ_max和变化ξ_max分别驱动光能利用率模型（CASA），结合作物收获指数与冬小麦种植面积获取山东省2000年-2016年冬小麦单产时空分布特征，探讨最大光能利用率对作物单产模拟的影响。结果表明，滤波后的时序植被指数数据能够反映冬小麦生长的光谱特征，差分法与光谱突变法结合提取冬小麦面积具有较好的普适性，提取的多年冬小麦种植面积与年鉴统计冬小麦播种面积之间的决定系数（R2）达0.71；变化ξ_max情景下模拟的多年冬小麦单产与统计单产之间的决定系数更高，说明冬小麦ξ_max是随时间变化的，可能与冬小麦品种更替有关。基于统计与模拟的结果均显示山东省冬小麦单产在2000年-2016年间呈现增加趋势，两者表现出来的增加速率分别为93.12和149.79 kg·hm-2·a-1。在空间上，山东省冬小麦单产呈现西部高于东部的分布特征。

Estimations of Winter Wheat Yields in Shandong Province Based on Remote Sensed Vegetation Indices Data and CASA Model

Accurate estimation of regional winter wheat yields is of great significance for understanding the agricultural production status and ensuring national food security.Light use efficiency(LUE)model is one of the most used models for crop yield estimation,however an important parameter,maximum light use efficiency(ξmax),still remains large uncertainties,and whether the cropξmax changes along with time is also to be explored.In this paper,Savitzky-Golay(S-G)method is used to filter the time-series moderate resolution imaging spectroradiometer(MODIS)vegetation indices data,and a quadratic difference method and a spectral mutation method are used to extract the winter wheat planted areas during 2000—2015 in Shandong Province.Then a fixedξmax and a changedξmax are used to drive the CASA(the Carnegie-Ames-Stanford approach)model for years from 2000 to 2016 respectively.Using harvest index(HI)and winter wheat planted areas,the winter wheat yield during 2000—2016 in Shandong Province are obtained,to explore the effect ofξmax on estimating winter wheat yield.The results show that the filtered time-series vegetation indices data capture the spectral features of winter wheat during the growth stages,and the extracted method used in this paper shows a good universal property.The extracted winter wheat planted areas agree well with the planted areas from statistical yearbooks at the city level,and the determination coefficient(R^2)between those reaches 0.71,which indicates the extracted winter wheat planted areas are reliable in this paper.The R2 between statistical yields and yields estimated with a changedξmax is 0.32,which is higher than that between statistical yields and yields estimated with a fixedξmax.This indicates that theξmax of winter wheat is changed along with time,and the varieties replacement of winter wheat may be responsible for this.Both the statistical and estimated yields of winter wheat during 2000—2016 show increasing trends with increasing rates of 93.12 and 149.79 kg·hm^-2·a^-1,respectively.The winter wheat yields in the western Shandong province are overall higher than those in the eastern study area.