2001—2017年中国不同耕作区重建MODIS LAI时空动态

叶面积指数Leaf Area Index （LAI）作为植被生物量指标之一,耕作区LAI不仅能反映作物的长势动态,且与农业生态、作物产量密切相关。本文通过对2001—2017年中国农田区域的MODIS-LAI长时序数据进行重建,利用Mann-Kendall检验、变异系数、重心迁移模型等方法分析了中国耕作区LAI的时空变化特征。结果表明：① 中国耕作区LAI在2001—2017年显波动式上升,且与农作物单产相关系数高达0.91;② 不同耕作区季节差异显著,夏季>秋季>春季>冬季,夏季平均为1.54,生长季平均为1.13,秋季平均为0.78,春季平均为0.63,冬季平均为0.31;③ 2001—2012年二熟、三熟区LAI变化平缓,2012年后有上升趋势但未发生明显突变;一熟区2006年之前处于平稳上升状态,2006年之后发生突变上升趋势显著;④ 研究时段内我国长江以北的耕作区LAI变异程度较为突出,最高达4.12; 农田面积重心经历了先向西南迁移,后再向西北迁移过程,农田生长季LAI重心相对于农田面积重心变幅较大,经历了南北波动式向西部迁移过程,迁移距离分别为82.78 km、90.53 km。

Spatiotemporal Dynamic Analysis of MODIS LAI Reconstructed in Different Cultivation Areas in China from 2001 to 2017

Leaf Area Index (LAI), one of the vegetation biomass indicators, not only change with growth of crops, but also closely related to agroecology and crop yield in cultivation areas. In this study, the long time series of MODIS-LAI data were reconstructed in China's cultivation areas from 2001 to 2017. The spatial and temporal changes of LAI were further analyzed by Mann-Kendall test, coefficient of variation, and gravity center migration model. The results show that LAI significantly increased wavelike from 2001 to 2017 in cultivation areas of China. The correlation coefficient between LAI and crop yield was as high as 0.91. There were significant differences in mean LAI between different seasons, with summer (1.54) > autumn (0.78)> spring (0.63) > winter (0.31) and an average of 1.13 for the growing season. LAI changed little from 2001 to 2012 in the double and triple cropping regions but showed an increase trend after 2012. It was very different that LAI in the single cropping region showed a steady increase before 2006 and an abrupt increase after 2006. The coefficient of variation of LAI was large in cultivation areas in the north of the Yangtze River in China with a maximum of 4.12. Moreover, the gravity center of cultivation areas first migrated forward southwest and then forward northwest. The migration range of LAI gravity center during farmland growth season was larger than that of cultivation area. It migrated to the west after the north-south transfer, with a migration distance of 82.78 km and 90.53 km, respectively.