Is potential cultivated land expanding or shrinking in the dryland of China? Spatiotemporal evaluation based on remote sensing and SVM

Chinese population growth has led to an increase in the demand for grain. Thus, it is of great importance to carry out spatiotemporal assessments of the dynamic of potential cultivated land in China, especially in dryland sensitive to climate change. Considering that previous assessments conducted at large scales were often dependent on abundant indicators, which are not easy to obtain or map at high spatiotemporal resolutions, this study combined remote-sensing images and support vector machine (SVM) model to identify the dynamics of potential cultivated land and non-cultivated land in the dryland of China. First, among several vegetation indicators during the growing season, the Enhanced Vegetation Index (EVI) in August was the most highly correlated with the yield (R2 =0.72). Second, the potential cultivated land that has not been cultivated was mainly distributed in the northwest and the northeast of the dryland of China, while the potential non-cultivated land that has been cultivated was mainly distributed in the Loess Plateau. According to different models, the area of potential non-cultivated land was 2.78 - 15.68 times that of potential cultivated land. Last, benefitting from the wetting trend, the potential cultivated land in the dryland of China expanded from 2001 to 2015. The area of potential cultivated in 2011-2015 was 34.39% more than that in 2001-2005. These findings provide both new methodological support for the simplified assessment of the potential cultivated land and quantitative evidence indicating the maximum potential capacity for cultivation in China's dryland.