Monitoring spatial patterns of cropland phenology in North China plain based on time-series NDVI data

This study used SPOT/VEGETATION NDVI time-series data to investigate the spatial patterns of cropland phenology in North China Plain (NCP). To do so, a smoothing algorithm based on an asymmetric Gaussian function was first performed on NDVI dataset to minimize the effects of anomalous values caused by atmospheric haze and cloud contamination. Subsequent processing for identifying cropping systems and extracting phenological parameters (SGS and EGS) was based on the smoothed NVDI time-series data. The results show that the cropping systems in NCP become complex as moving toward to the south from the north of NCP. Under these cropping systems, the SGS and the EGS of the first growing season vary largely over space, and those regions with multiple cropping systems generally present a significant advanced SGS and EGS than the regions with single cropping patterns. On the contrary, the phenological events of the second growing season including both the SGS and EGS show little difference between regions. The spatial patterns of cropping systems and phenology in cropland are highly related to the geophysical environmental factors in NCP.