Studies on Water Physiology of Main Afforestation Tree in East Qinghai

Ten water physiological indexes of seven main afforestation trees: Pinus tabulaeformis, Caragana microphylla, Populus cathayana, P. hopeiensis, Tamarix chinensis, Armeniaca sibirica, Hippophae rhamnoides grown in arid region of east Qinghai, were measured and analyzed in this paper. Principal component analysis on the ten water physiological indexes, cluster analysis and integrated drought resistance sort on the seven trees were made by using SAS software. The results indicated that ten water physiological indexes can be divided into three kinds:(1) water state factors (transpiration rate, free water content, bound water content, ratio of bound water and free water, reserved water content), (2) water content factors (tissue water content, water potential and time to constant weight), (3) water deficit factors (relative water content, water saturation deficit). The seven tree species can be divided into three categories: Populus hopeiensis, P. cathayana, Armeniaca sibirica, Hippophae rhamnoides; Tamarix chinensis, Caragana microphylla;Pinus tabulaeformis. Their droughtresistance abilities are:Pinus tabulaeformisTamarix chinensisCaragana microphyllaHippophae rhamnoidesArmeniaca sibirica Populus hopeiensisP. cathayana. The results provide some theoretical evidences for the selection of suitable tree species for afforestation in this region.