黄淮海地区耕地复种指数的时空格局演变

耕地复种指数是土地利用强度的重要表征,时空动态特征有助于理解人类活动与生态环境的耦合作用。以黄淮海地区2001—2015年MODIS(Moderate-resolution Imaging Spectroradiometer,中分辨率成像光谱仪)NDVI(Normalized Difference Vegetation Index,归一化植被指数)遥感影像为数据源,使用Savitzky-Golay滤波对时间序列曲线平滑重构后,结合研究区物候信息设置含有阈值的二次差分算法提取复种次数,最后在R环境下绘制复种指数空间分布图。结果表明:(1)河南省复种指数最高(169.3%),山东省次之,天津市最小;(2)各省市年际变化趋势大体一致,经历了升高-降低-升高的过程;从空间分布特征来看,耕地复种指数具有明显的地域性差异,二熟制主要集中于南部,东部和北部受地形和纬度影响,主要以一熟制为主。研究结果对于黄淮海农耕区的土地利用强度辨识、人类活动方式确定具有参考价值,同时也证明了该方法具有更大尺度推广的潜力。

Identifying the temporal-spatial pattern evolution of the multiple cropping index in the Huang-Huai-Hai region

The multiple cropping index is an important indicator of land utilization intensity, and the temporal-spatial dynamics can also help to understand the coupling effects of human activities and the ecological environment. In this study, MODIS(Moderate-resolution Imaging Spectroradiometer)NDVI(Normalized Difference Vegetation Index)remote sensing images in the Huang-Huai-Hai region from 2001 to 2015 were used as the source datasets. After a Savitzky-Golay filter was used to reconstruct the time series curve, the second-order difference method with threshold was used to extract the number of multiple cropping times, combined with the phenology of the study area. Finally, the spatial distribution map of the multiple cropping index was drawn using R language software. The result showed that: (1) the multiple cropping index of Henan Province was the highest (169.3%), followed by that of Shandong, and then Tianjin provinces; (2) during the study period, the inter-annual trends of the multiple cropping index showed a similar rising-decreasing-rising pattern in each province and city. From the spatial distribution characteristics, cultivation showed obvious regional differences. The two crops per year were mainly concentrated in the South. Owing to the terrain and latitude, the East and North showed mainly one crop per year. The results are valuable to identify land utilization intensity and human activities in the Huang-Huai-Hai cropland region. They also proved that this method could potentially be used at a greater scale.