Geographic distribution of congeneric species with Betula halophila, flora regions and main geomorphology in Xinjiang, northwest China a geographic distribution of B. tianschanica b geographic distribution of B. microphylla c geographic distribution of B. pendula d geographic distribution of B. rotundifolia e geographic distribution of B. humilis f geographic distribution of five species of Betula genus in Xinjiang g geographic distribution of flora regions, IA2 Altai Region, IA3 Tianshan Region, IIC5 Junggar Region, IIC6 Kashgar Region, IIIF17 Tibet, Pamirs and Kunlun Region h geographic distribution of main geomorphology.