Annual winter wheat mapping datasets and dynamics in China from 2001 to 2020

As one of the largest producers of winter wheat worldwide, China contributes more than 19 % of the global production of winter wheat and playing a vital role in maintaining sustainable wheat production. Therefore, mapping the spatial distribution of winter wheat in China over long time scale precisely is of great importance for ensuring food security and investigating the spatiotemporal pattern of winter wheat at a national scale. Nevertheless, existing high resolution remote sensing datasets which can provide continuous observation for 20 years suffer from data gaps caused by cloud cover, making it difficult to map winter wheat area over long time scale. In this study, we used a phenology-based method to identify winter wheat area by integrated three key growing features of winter wheat into one variable for calculating the planting probability of winter wheat, which enlarged phenological differences between winter wheat and non-winter wheat fields. On this basis, we produced a long-term winter wheat mapping dataset at 30 m spatial resolution in China from 2001 to 2020 using the fusion dataset. Validations based on a total of 32,957 field survey samples displayed high accuracy, with the user’s, producer’s, and overall accuracies of 91.17%, 90.92%, and 91.6% in China, respectively. Furthermore, the identified winter wheat area aggregated to the municipal- and county-level exhibited good correlations with the agricultural statistical data. Based on this dataset, we found that the winter wheat planting condition in China exhibited a high frequency of continuous planting, with 54.45% of pixels having continuously planted winter wheat for over 10 years. During the period of 2001–2020, approximately 40% of the winter wheat pixels showed significantly increasing trends, which mainly concentrated in the major production area for winter wheat, such as Shandong, Henan, and Anhui province. Conversely, less than a quarter of winter wheat pixels showed significantly decreasing trends, which distributed in central and western provinces in China.