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耕地复种是中国普遍的农业种植制度,对保障国家粮食安全和促进农村经济发展十分必要。本文基于1999-2013年1 km×1 km旬SPOT-NDVI数据和3期耕地数据,利用S-G(Savitzky-Golay)滤波方法,重建了农作物生长NDVI曲线;基于二次差分算法及相关阈值限定,提取了各时相复种指数;分析了1999-2013年中国耕地复种指数的时空变化过程。结果表明:1中国耕地复种指数从北到南逐渐增加,其中种植制度上43.48%的耕地实行一年一熟,56.39%的耕地实行一年两熟,仅有0.13%的耕地实行一年三熟。2 1999-2013年间,中国耕地复种指数整体上呈现显著上升趋势,年均增加约为1.29%(P<0.001);但空间差异明显,复种指数显著降低(P<0.1)的耕地仅占全国耕地的2.12%,主要分布在河北、北京、天津交界地区,安徽中部,四川的成都平原,江西的鄱阳湖平原,湖南的北部和南部以及广西的中部;16.40%的耕地复种指数显著上升(P<0.1),主要分布在甘肃的东部,陕西的渭河平原,山西的西部,河北、山东和天津交界处,山东的山东半岛和湖北的江汉平原。3耕地复种指数年际变化率与地形起伏和经济发展水平具有较好的相关关系:起伏度增强,复种指数上升;经济发展水平提高,复种指数降低。
Multiple cropping is a common system of agricultural planting in China and is necessary for ensuring national food security and promoting rural economic development. Based on the SPOT-NDVI data of 1 km × 1 km from 1999 to 2013 and the three-stage cultivated land data, the NDVI curve of crop growth was reconstructed by SG (Savitzky-Golay) filtering method. Based on the quadratic difference method and the correlation threshold, The multiple cropping index of each phase was analyzed. The temporal and spatial variation of cropland multiple cropping index in China from 1999 to 2013 was analyzed. The results showed that: 1 The index of cropland multiplication in China increased gradually from north to south, of which 43.48% of cultivated land was cultivated in one year, 56.39% of cultivated land was double-cropped in one year, and only 0.13% . 2 Between 1999 and 2013, the index of cropland multiplication in China showed a significant upward trend with an average annual increase of about 1.29% (P <0.001). However, the spatial difference was significant and the index of multiple cropping decreased significantly (P <0.1) Of the total population, 2.12% of which were mainly distributed in the border areas of Hebei, Beijing and Tianjin, the middle part of Anhui, the Chengdu Plain of Sichuan, the Poyang Lake Plain of Jiangxi, the northern and southern parts of Hunan and the central part of Guangxi. 0.1), mainly distributed in the eastern part of Gansu, the Weihe Plain in Shaanxi Province, the western part of Shanxi, the junction of Hebei, Shandong and Tianjin, the Shandong Peninsula and the Jianghan Plain in Hubei. The interannual variability of cropland multiple cropping index had a good correlation with topographic relief and economic development level: the fluctuation increased and the multiple cropping index rose; the economic development level increased and the multiple cropping index decreased.