Dendroclimatology Study Of Salix Oritrepha Shrub In The Northeastern Tibetan Plateau

In this study,Salix oritrepha is one of the widespread tall shrub species on the northeast Tibetan Plateau which provides a unique opportunity to study the climate response of alpine biomes.Firstly,the climate responses across the gender in willow shrubs were examined.The radial growth responses to climate change were then investigated by using the chronology of basal area increment(BAI)along latitudinal sites locating at different elevations.Finally,the linear regression analyses were employed to detect the climate sensitivity along the altitudinal gradients.(1)The BAI in female shrub group is higher than that of male shrub group in our study area.The elevation factor plays an important role in controlling the BAI of willow shrubs in different regions.In the high altitudinal sites of Huashixia and Wulan(HSX-44,HSX-45,HSX-46 and WL-42),the BAI is lower than that of low altitudinal sites(HSX-40,HSX-41,HSX-42,HSX-43 and WL-38).The growth of shrubs at some sites(DL-40,DL-42 and WL-40)might be also affected by microecological conditions and shrub age,leading to higher BAI than those at low altitudinal sites.(2)The growth responses of female and male willow shrubs to climate factors were highly consistent.Radial growth in willow shrub was significant positive correlated with temperatures in July and January.In addition,radial growth in both female and male willow shrubs has negative correlations with winter precipitation,indicating that winter precipitation was not conducive to the growth of female and male shrubs in the study area.(3)In our study area,willow shrub growth was mainly driven by the July temperatures.However,the shrub growth in most of the sites was also affected by drought stress caused by high temperature in July.In addition,there are significant positive correlations between winter temperature and shrub growth at high altitudinal sites in Huashixia and Wulan regions(WL-40,WL-42,HSX-42,HSX-43,HSX-44 and HSX-45).However,negative effect of winter precipitation on the willow growth mainly occurred at the high altitudinal sites in Huashixia(HSX-43,HSX-44 and HSX-45).This is also consistent with the results of partial correlation analysis.Partial correlation analyses showed that the growth of willow shrubs in HSX-42 and HSX-45 sites was still positively correlated with winter temperature,and the growth of shrubs in HSX-43 and HSX-44 sites was negatively correlated with winter precipitation.Moreover,the sensitivity of shrub growth to July temperature increases with the elevation.