Vegetation species diversity characteristics in relation to environmental factors along QinghaiTibetan Highway

QinghaiTibet Highway, a sensitive area to global climate change, passes through Tibetan Plateau from north to south. It is significantly important to study the characteristics of species diversity and its correlation to environmental factors along QinghaiTibet Highway. The characteristics of the roadside plant communities and its correlation with environmental factors of 29 samples whose number was 1 to 29 from Xining to Lhasa along QinghaiTibet Highway were investigated and analyzed. The results showed that the vegetation coverage of Tibetan Plateau decreased rapidly and then increased slowly from north to south, the lowest was sample plot 7 (AErCiTuoShan). The species richness firstly decreased and then increased, finally decreased rapidly, the lowest was sample plot 14 (Fenghuoshan Tunnel) and the highest was sample plot 26 (Jiachigang). The ShannonWiener index and Simpson index showed a decreasing trend excluding several sample plots. However, the Pielou index decreased slowly and then increased rapidly, the lowest was sample plot 22 (Tuo Qing Village). The Alatalo index had an opposite trend but a large fluctuation with Pielou index. The correlation and stepwise regression analyses between species diversity and environmental factors suggested that species coverage, species richness and species evenness index (Pielou index) were positively influenced mainly by the water factors. The species diversity index (ShannonWeiner index and Simpson index) and species evenness index (Alatalo index) had a significant correlation to shortwave radiation.