Vegetation and climate changes in the western Chinese Loess Plateau since the Last Glacial Maximum

The climate was warmer and more humid in the loess areas east of the Liupan Mountains than in the west during both the LGM and Holocene Optimum. Likewise, a significant difference in specific plant types was observed between the east and west since the LGM. During the LGM, Pinus and some broadleaf trees emerged, but no Picea forest grew, while in the west, vegetation was characterized by desert shrub and desert steppe in situ, and by dark coniferous forests (mainly Picea) in nearby river valleys. During the Holocene Optimum, treeline advanced upward as a result of increased temperature. Picea thus withdrew from the western loess areas. Therefore, temperature is the major factor controlling the growth of Picea in the Chinese Loess Plateau.