The Pattern of Variations of Hippophea gyantsensis(Rousi) Lian along an Elevation Gradient in Lhasa Valley,Tibet,China

Hippophea gyantsensis(Rousi)Lian is an endemic plant species of Qinghai-Tibet plateau,which distribute widely in the Lhasa valley with a distribution range of altitude about 3500-4200 m.Former research mainly focused on its utilization and exploitation,only a few studies on its ecological research.In this paper,based on the survey of H.gyantsensis(Rousi)Lian community along four altitudinal bands in Lhasa valley,three or two 10 m×10 m of plots was sampled in each altitudinal bands.In each plot all vascular plant species was recorded as percentage coverage,and height,base diameter,diameter of breast height,blade length of 20 individuals of H.gyantsensis was randomly measured.Environmental variables such as plot altitude and the distance of plot from river was also measured.DCA(detrended correspondence analysis) was performed to find major distribution pattern of H.gyantsensis.In order to detect how the height,base diameter,diameter of breast height,blade length of H.gyantsensis relate to the elevation the regression analysis was performed.The results showed that the habitat of H.gyantsensis was classified into four major types,which are forest side,meadow,river-side grasslands and sandy river side.Altitude is the most important environmental factor for influencing distribution and variation of H.gyantsensis.Height,base diameter,diameter of breast height H.gyantsensis decreases with increasing altitude,however,there is no significant relationship between the blade length and altitude,which may be more influenced by the microhabitats(light).