Study sites
The transect study was conducted across a 3200-km scale of northern China’s grasslands (Wang et al. 2017), extending from the Xinjiang Uygur Autonomous Region in the west to eastern Inner Mongolia (83.45° E to 120.36° E, 42.89° N to 49.19° N; Fig. 1). There are four vegetation types along this transect, including alpine-, desert-, typical- and meadow-steppe from west to east. Information on dominant species observed at each study site is supplied in Supplementary Dataset 1. Species richness decreased when moving from the eastern to the western end of the transect. Dominant soil types are classified as aeolian chestnut soil in the east to brown calcic soil, grey desert soil and sandy soil to the west.