基于Sentinel-2的海南耕地复种指数监测及时空变化分析

海南是发展热带特色高效农业的黄金宝地，开展高时空分辨率耕地复种指数遥感监测与时空变化分析对海南农业生产管理具有重要意义。基于Sentinel-2数据，利用最大值合成法和Savitzky-Golay滤波对NDVI时间序列曲线作平滑重构，结合二次差分法计算2016—2020年海南耕地复种指数，分析海南省耕地复种指数的时空演变特征。结果表明：通过2020年地面调查数据验证，海南耕地复种指数提取总体精度达91.94%，Kappa系数为0.88。海南省耕地复种指数从2016年1.53提升到2020年1.66，提高了0.13。从2016年到2020年单季种植面积占比增加了6.10%，两季种植面积占比减少了2.65%，三季种植面积占比增加了5.10%，休耕或抛荒耕地面积占比减少了5.60%。海南省各市县耕地复种指数在1.28—1.96区间内，其中海口市、三亚市、东方市、临高县等地区耕地复种指数上升，而琼海市、万宁市、琼中县等地区耕地复种指数下降。研究结果可为海南农业部门合理调整休耕、开垦方案等政策，实施热带高效农业可持续发展战略提供数据和决策支撑。

Monitoring and Spatial-temporal Variation of Multiple Cropping Index based on Sentinel-2 in Hainan

Hainan province is a golden place to develop tropical characteristic and efficient agriculture. It is of great significance to analyze the change of multiple cropping index with high spatial and temporal resolution. Based on Sentinel-2 data， maximum value composite and Savitzky-Golay filtering and smoothing were used to reconstruct NDVI time series curve. The second difference method was used to calculate the multiple cropping index of cultivated land in Hainan province from 2016 to 2020， and the spatial-temporal evolution characteristics of the multiple cropping index were analyzed. The results showed that the overall accuracy of multiple cropping index extraction in Hainan was 91.94% and the Kappa coefficient was 0.88， verified by the ground survey data in 2020. The multiple cropping index of hainan cultivated land increased from 1.53 in 2016 to 1.66 in 2020， an increase of 0.13. From 2016 to 2020， the single-season planting area increased by 6.10 percent， the two-season planting area decreased by 2.65 percent， the three-season planting area increased by 5.10 percent， and the fallow or abandoned farmland decreased by 5.60 percent. The multiple cropping index of all cities and counties in Hainan province is in the range of 1.28—1.96. The multiple cropping index of Haikou city， Sanya City， Dongfang City， Lingao County increases， while the multiple cropping index of Qionghai City， Wanning City and Qiongzhong County decreases. The results can provide data and decision-making support for agricultural departments in Hainan to adjust fallow and reclamation policies reasonably and implement sustainable development strategy of tropical efficient agriculture.