Composition change and vegetation degradation of riparian forests in the Altai Plain, NW China

Riparian forests of the Altai Plain in China were studied using Detrended Canonical Correspondence Analysis (DCCA) and Two-way Indictor Species Analysis (TWINSPAN). The species could be divided into hydrophytes, hygrophytes, hygro-mesophytes, xero-mesophytes, xerophytes, and high xerophytes. River run-off, water table, and physical components of the soil decided the distribution of the species. The forests could be classified into wood swamp, hygro-mesic forest, mesic forest and xeric forest. As a specific habitat in the desert of northwest China, the river valleys harbored most of the Populus and Salix species recorded in China. However, the forest has been gradually invaded by adjacent desert species. Meanwhile, the native species diversity of the forest has been declining as the soil has become more saline and more xeric through intensive irrigation practice and dam construction in the upper rivers.