基于Landsat影像的鄱阳湖平原水稻主产区水稻熟制动态监测

鄱阳湖平原是我国重要的粮食生产基地,是华中单/双季稻作带,是基于遥感监测水稻多熟种植的典型区域。动态监测区域水稻熟制时空格局,对评估耕地利用强度、增强粮食供给功能以及保障国家与地区粮食安全具有重要意义。论文以鄱阳湖平原水稻主产区为例,首先结合水稻物候历、多年月均降水和Landsat影像云量特征,利用Landsat-5/7/8 TM/ETM+/OLI影像数据,在目视解译水田分布的基础上,基于合适时间窗口影像监测了主产区2005年和2013年水稻熟制变化格局;其次,通过农户访谈和调查问卷（677份）收集了主产区水稻种植及熟制变化的相关信息。研究表明：1）9月中旬到10月上旬是判别鄱阳湖平原单/双季稻的合适时间窗口。主产区9-10月处于少雨期,平均降水占全年的4%;云量覆盖小于等于10%的Landsat影像占20%,共484景,其中,9-10月占27%。2）2005-2013年,主产区水田面积减少2.68%,但复种指数增加9.0%,其中,单季稻减少1 061.35 km²,双季稻增加1 564.45 km²;2013年单季稻种植面积为4 795.63 km²,双季稻为11 617.13 km²,水稻复种指数为156.7%。3）空间上,双季稻主要分布在赣江河口三角洲、信江河口三角洲,而单季稻集中在鄱阳湖湖汊周边及市县（区）周围,总体上以赣江-饶河一线为界,界线以北以单季稻为主,以南则以双季稻为主。4）近3成受访农户近5 a调整了水稻熟制,其中“双改单”和“单改双”分别为14.2%和10.8%。另有4成多受调查县域存在主动弃耕现象,研究区弃耕或耕地他用比例占4.9%。

Monitoring Rice Cropping System Changes in the MajorRice-producing Area of Poyang Lake Plain UsingLandsat Images during 2005-2013

Poyang Lake Plain (PLP) is one of the important rice-producing regions in China, characterized by typical single-and double rice cropping systems (RCS), which are particularly suited for remote sensing monitoring. Investigation on the changes of the RCS in the major rice-producing area (MRPA) of the PLP is of great importance in evaluating farmland use intensity, enhancing food provision and ensuring regional grain security. Taking the MRPA as a study area, Landsat TM/ETM+/OLI images in 2005 and 2013 were used to classify the paddy fields and delineate the RCS within critical temporal windows which is defined by local rice calendar, cloud coverage percentage of scenes and precipitation data. Meanwhile, 677 valid questionnaires focusing on the changes of RCS during 2014-2015 were collected across the PLP. The results showed that: 1) The duration from middle September to early October is proved to be the critical time window for the differentiation of RCS in the PLP. There are 484 LandsatTM/ETM+/OLI scenes with cloud coverage less than 10% in the study area, accounting for 20% of the total observations during 1983-2015, in which 27% were acquired in September and October. Moreover, there is less rainfall in this period, only 4% of the annual precipitation. 2) During 2005-2013, the area of paddy field declined by 2.68% while the multiple cropping index of paddy rice increased from 147.7% to 156.7% accordingly. Specifically, the single cropping rice reduced by 1 061.35 km², and double cropping rice increased by 1 564.45 km². 3) Spatially, both rice types were distributed across the study area, but the single cropping rice mainly distribute to the north of Ganjiang and Raohe River, while the double cropping rice mainly distribute to the south of Ganjiang and Raohe River. Double-season rice is mostly cultivated in the delta plains of Ganjiang River and Xinjiang River, while single-season rice is generally distributed in the lowland around the Poyang Lake and the periphery area of the cities and towns. 4) About 30% of the interviewed households altered their rice cropping systems, and 14.2% of them changed double seasons to single season. Besides, there was farmland abandonment in about 44.4% counties. The areal ratio of abandoned farmland or occupied farmland in the study area was 4.9%.