Supplementary material 2 from: Huang J, Guo Z, Tang S, Ren W, Chu G, Wang L, Zhao L, Yu R, Xu Y, Ding Y, Zang R (2020) Floristic composition and plant diversity in distribution areas of native species congeneric with Betula halophila in Xinjiang, northwest China. Nature Conservation 42: 1-17. https://doi.org/10.3897/natureconservation.42.54735

Figure S2. The distribution frequency of Betula species varies with the environment gradients