基于MODIS时序数据的湖南省水稻种植面积提取及时空变化分析

Extraction and analysis of spatiotemporal variation of rice planting area in Hunan Province based on MODIS time-series data

准确且及时获取大范围的水稻种植空间分布及其动态变化信息对科学指导水稻生产、合理分配水资源以及监测大气环境变化等具有重要意义。以湖南省为研究区,在提取MODIS陆地水分指数(land surface water content index,LSWI)和增强植被指数(enhanced vegetation index,EVI)时间序列数据集并对其进行去噪处理的基础上,根据水稻的LSWI和EVI时序变化特征建立了水稻种植面积决策树提取模型,并对模型精度进行了评价;基于该模型提取了湖南省2000—2016年间水稻种植面积信息,分析了其时空变化特征。研究结果表明,构建的研究区水稻种植面积提取模型总体分类精度为90.2%,Kappa系数为0.74;与统计报表数据相比,平均相对误差为13.6%,可适用于大范围长时间序列水稻种植面积的高效提取。湖南省年均水稻种植总面积为344.12万hm^2,其中单季稻面积为102.41万hm^2,主要分布在洞庭湖平原;双季稻面积为241.71万hm^2,主要分布在湘中偏北部地区(主要为岳阳、益阳、常德、长沙、株洲、湘潭、娄底等市县)。近17 a间,湖南省水稻种植面积变化情况可分为3个阶段,分别为在2000—2004年间减少了73.2万hm^2,在2005—2010年间呈相对稳定小幅度回升状态,在2011—2016年间增加了29.55万hm^2,但总体上呈减少趋势,共减少了58.22万hm^2。

It is essential to obtain a wide range of spatial distribution and dynamic change information of paddy rice timely and accurately for scientific guidance of rice production,rational utilization of water resources,and monitoring of atmospheric environmental changes.In this study,the decision tree extraction model of rice planting area in Hunan Province was constructed on the basis of time series variation characteristics of MODIS-derived LSWI and EVI in rice planting area,and the accuracy of the model was evaluated.In addition,the spatiotemporal variation characteristics of the rice planting areas in Hunan Province from 2000 to 2016 were investigated.The results are as follows:the total classification accuracy of rice planting area extraction model in the research area is 90.2%,the Kappa coefficient is 0.74 and;in comparison with agriculture statistics,the mean relative error is 13.6%.The proposed extraction model can be applied to the efficient extraction of rice planting area on a wide range and long time series basis.The average annual rice planting area in Hunan Province is 3441.2 thousand hectares,of which 1024.1 thousand hectares are single-cropping rice,mainly distributed in the Dongting Lake plain,and 2417.1 thousand hectares are double-cropping rice,mainly distributed in the north-central part of Hunan Province such as Yueyang,Yiyang,Changde,Changsha,Zhuzhou,Xiangtan and Loudi City.the rice planting area in Hunan Province was reduced by 732 thousand hectares from 2000 to 2004,reached a relatively stable level in 2005—2010 and increased by 295.5 thousand hectares in 2011—2016.Overall,there existed a decreasing trend from 2000 to 2016,with the rice planting area reduced by 582.2 thousand hectares.