Alpha and beta diversity of birds along elevational vegetation zones on the southern slope of Altai Mountains: Implication for conservation

Abstract

1Understanding species diversity patterns is important for conservation planning. We studied birds’ alpha and beta diversity along vegetation gradients in three watersheds in the Altai Mountains, a global biodiversity hotspot; and tested whether environment-based hypotheses could explain these patterns. 2In Daxiaodonggou (DXDG), Jiadengyu (JDY) and Liangheyuan (LHY) watersheds, alpha diversity varied strongly along elevational vegetation zones. In DXDG, bird species richness displayed a double-hump pattern and increased slightly at the highest elevations. In JDY and LHY, bird species richness increased gradually with elevation but dipped in certain vegetation zones. The Shannon-Wiener index and Simpson's index showed consistent patterns in each watershed, and were higher in forest habitats. Bird species richness was affected by Human Footprint Index, elevation, temperate and precipitation in LHY, but only affected by Compound Topographic Index in JDY, and only affected by elevation in DXDG. 3High beta diversity and high turnover component were found in all of the three watersheds, revealing distinct bird assemblages between various vegetation types. In contrast to previous studies, beta diversity of the Altai Mountains was not lower than those reported in tropical mountains. Simplified models by Canonical Correspondence Analysis explained 34–41% variation of bird species composition along vegetation zones among three watersheds, and environmental factors in the three models were inconsistent. Mantel test revealed beta diversity of the bird communities were lower in the two vegetation zones with more similar environmental conditions. 4The variety of bird diversity patterns and various influential environmental factors among longitudinally-separated watersheds in the Altai Mountains indicate the complexity of environmental filtering mechanics. Though some vegetation zones contain higher bird species richness than others, high species composition turnover in the whole area suggests conservation strategies should consider multiple watersheds and multiple vegetation types in the Altai Mountains when aiming to conserve avian diversity.