Plant species diversity of alpine grasslands on southern slope of Tianshan Mountain along altitude gradient.

Climate alteration due to altitude gradient makes mountain biota a hotspot of biological richness research. The study on the plant species diversity of Bayanbulak alpine grasslands on the southern slope of Tianshan Mountain showed that at 9 sampling sites along altitude gradient, a total of 34 species was recorded, belonging to 29 genera and 17 families. The species richness along altitude gradient presented partially unimodal pattern, being the maximal on the Alchemilla tianschanica grassland at 3 060 m, with 17 species belonging to 12 families and 17 genera. The Shannon-Wiener index also showed a partially unimodal pattern. Its variation range was 2.02-2.40, with the maximum on the A. tianschanica grassland at 3 060 m and the minimum on the Stipa purpurea grassland at 2 760 m. The Cody index along altitude gradient presented unimodal pattern. Shannon-Wiener index was negatively correlated with the temperature, while positively correlated with the relative humidity and soil moisture content in growing season.