Desert shrublands extend from the Altai Mountains in the north and west across the Junggar Basin and Alashan Plateau of southern Mongolia and northern China. The area is bounded to the northeast by the Mongolian Gobi Desert and to the south by the Tibetan Plateau and Tian Shan Mountains. The areas have low, variable precipitation with an average 80 mm (3 in) in the central desert regions to 250 mm (10 in) in the periphery. Shifting sand dunes cover extensive areas of the Alashan Plateau, but are also encroaching and expanding within the Junggar Basin creating more desertified expanses.