Floristic composition and plant diversity in distribution areas of native species congeneric with Betula halophila in Xinjiang, northwest China.

Betula halophila, a wild plant with extremely small populations, is endemic to Xinjiang, northwest China. Its wild populations have declined severely in the field. Understanding the patterns of floristic composi tion where congeneric species of B. halophila are distributed and their determinants is a necessary step to restore the wild populations. Based on literature records, specimen information, shared public data and field survey data, the patterns of floristic composition, diversity and environmental conditions of seed flora within the distribution areas of five native species (i.e. B. tianschanica, B. microphylla, B. pendula, B. rotundifolia and B. humilis), congeneric with B. halophila, were examined. The results are as follows. (1) There were 3013 species, 693 genera and 108 families of seed plants in the distribution area of these congeneric species of B. halophila, which accounted for 86.16%, 94.54% and 93.91% of the total seed plants in Xinjiang, respectively.