Satellite-based observations of the green depressing cropping system in a farming-pastoral ecotone of northern China

The green depressing cropping system (GDCS) has existed in the farming-pastoral ecotone of northern China (FPENC) for hundreds of years. This ancient practice aims to promote an agricultural system that is both green and sustainable at the same time. However, there is a knowledge gap regarding the extent and implementation of the GDCS in China. Here we present a study that analyses GDCS fields and their related farmland use patterns in Ulanqab, China. This study takes into consideration satellite imagery, ground truth data, phenological records, and other ancillary data from 2015 to 2019 at the Ulanqab region. The integration of the former datasets, combined with visual interpretation and a random forest classification approach, successfully mapped the distribution of GDCS fields, GDCS frequencies, GDCS-crop rotation, and the determinants (terrain, irrigation) of the distribution of the GDCS practice. Our results suggest that GDCS is still prevailing and relatively widespread in Ulanqab, especially in the Houshan area, where a total of 10.29% of farmlands in the study region have adopted the practice. Cereal crops, potato, and other drought-resistant crops were the preferred previous and subsequent crops of GDCS, rather than maize and sunflowers. According to our results, 91.5% of the GDCS fields were rainfed in Ulanqab, suggesting that the practice is associated with dry farming. We also found that the practice is particularly prevalent in the fields with a steeper slope. Our findings provide empirical evidence for the importance of remote sensing towards the implementation of pilot programs that involve crop rotation and fallow systems.