Data for: Soil carbon sequestration benefits of active versus natural restoration vary with initial carbon content and soil layer

We systematically searched for the papers concerning 'Grain for Green program' in China and soil carbon restoration during 1900-2020, via Google Scholar, Web of Science and China Knowledge Resource Integrated Database. The reported studies were further screened to ensure data quality based on the following criteria. First, cropland, naturally and actively restored ecosystems must have experienced similar climate, soil conditions, history, and levels of disturbance at the same site. Second, restoration studies have been conducted with a paired comparison or chronosequence design. Third, paired comparisons of active restoration versus natural regeneration have started at the same time. Fourth, data on soil depth and restoration time have been clearly provided. Fifth, data on soil carbon at the cropland, naturally or actively restored sites have been reported by their mean values and sample sizes. Tabular data were manually copied from the identified papers, while graphical data were obtained using Engauge Digitizer (Free Software Foundation, Inc., Boston, MA). Finally, we screened 72 studies from 67 published papers.Our dataset (617 paired observations) covers a large spectrum of climate zones, with the mean annual precipitation and temperature spanning 263~1411 mm and -1.7 to 19.2 °C, respectively. The average, minimum and maximum of restoration time were 19.6, 1 and 60 years, respectively. The average, minimum and maximum of soil depth were 30.7, 2.5 and 100 cm, respectively.