Abstract:

Plant physio-ecological characteristics at different stages of vegetation succession are a foundation to demonstrate the inner mechanism of vegetation succession and to rehabilitate the deteriorated ecosystem. Leaf long-term water use efficiency (WUE) and hydraulic characteristics (specific conductivity K_s, specific leaf conductivity K_l, Huber value HV, xylem pressure corresponding to 50% loss of conductivities P₅₀ and wood density WD) of seven naturally generated dominant trees and shrubs (three trees:Populus davidiana, Pinus tabulaeformis, Quercus liaotungensis；four shrubs:Amygdalus davidiana, Vitex negundo var. heterophylla, Rosa xanthina, Sophora viciifolia) and a planted species Robinia pseudoacacia were determined in this study research. Results indicated that: 1) Averaged leaf WUE of four shrubs was higher than that of four trees. Leaf WUE of planted Robinia pseudoacacia was the highest among the four trees, and leaf WUE in the early succession species Populus davidiana was higher than in the late succession species Pinus tabulaeformis and Quercus liaotungensis. 2) Four trees species had a higher averaged K_s and a lower HV than four shrubs, thereby the averaged K_l showed little difference. Populus davidiana had higher K_s, K_l and a lower WD when compared with Pinus tabulaeformis and Quercus liaotungensis. The P₅₀ of Populus davidiana was higher than that of Quercus liaotungensis but lower than Pinus tabulaeformis. Exotic Robinia pseudoacacia had a relatively lower K_s and K_l, and its xylem was more vulnerable to embolism than the other tree species. 3) No correlation was found between leaf WUE and hydraulic characteristics，indicating the change of leaf WUE during vegetation succession was mainly caused by other physiological processes rather than the studied hydraulic properties.

Key words: leaf water use efficiency, hydraulic characteristics, trees and shrubs, succession