Distribution pattern and environmental interpretation of plant species diversity in the mountainous region of Ili River Valley, Xinjiang, China.

Abstract

Aims Our major objective was to reveal the distribution pattern of plant species diversity in the mountainous region of Ili River Valley, Xinjiang, China and explore how environmental gradients influenced the pattern. Methods Based on a survey of 94 sample plots in the study area, DCCA was performed to analyze the relation- ships between diversity indices and environmental gradients and GAM was employed to model the response curve of diversity indices to elevation. Important findings We recorded 259 plant species, including 235 herbaceous species; the species of woody plants were very limited. Communities with complex vertical structure had higher values of diversity. The distri- bution pattern of species diversity on the northern slope was affected by elevation, slope aspect, slope gradient, total nitrogen, total potassium, soil water content, organic matter, etc., and that on the southern slope was mainly affected by slope gradient, elevation, available phosphorus, soil water content, etc. On the northern slope, Patrick index and Shannon-Wiener index had a bimodal pattern with elevation and Simpson index and Pielou index showed a partially unimodal pattern. On the southern slope all the distribution pattern of species diversity indices showed two peaks, though that of the Patrick index was not obvious. These patterns were formed by the synthetic action of a variety of environmental factors in which elevation played an important role.