关键词: NDVI, 时间序列, 种植制度, 物候期, 空间格局

Abstract:

【Objective】 Time series of NDVI dataset was used in this study to investigate spatial patterns of cropland phenology in North China region. 【Method】 A smoothing algorithm based on an asymmetric Gaussian function was firstly applied to the NDVI dataset to minimize the effects of anomalous values caused by atmospheric haze and cloud contamination. The cropping system and its related phenology in North China were then estimated based on the smoothed NVDI time-series dataset. 【Result】 The cropping pattern of cropland in North China is mainly characterized by double cropping system and shows a distinct spatial difference, gradually becoming complex as moving toward to the north from the south. Under this cropping system, the starting dates and the ending dates of first growth season in North China vary over space, and regions with double cropping system present a significant advance than those regions with single cropping. On the contrary, the phenology of second growth season including both the starting and the ending dates shows no much difference among regions. 【Conclusion】 Spatial patterns of cropping system and phenology in North China are highly related to its geo-physical environment. In addition, several anthropogenic factors such as crop variety, cultivation levels, irrigation and fertilizers can profoundly influence phenological status. How to discriminate the impacts of biophysical forces and anthropogenic drivers on phenological events of cultivation remains a great challenge for further studies.

Key words: NDVI, time series, cropping system, phenology, spatial pattern