Abstract
Water consumption patterns and leaf water relations obtained from P-V curves were compared to examine the suitability for afforestation among one-year-old seedlings of 4 tree species, Robinia pseudoacacia L., an introduced species native to north America, and 3 others indigenous to the Loess Plateau, Quercus liaotungensis Koidz., Pinus tabulaeformis Carr., and Platycladus orientalis (L.) Franco., under well-watered and drought treatments. The results showed that R. pseudoacacia consumed more water than indigenous species in both water conditions. In the condition of water deficiency, indigenous species decreased water consumption by stomatal closure, whereas R. pseudoacacia reduced water loss through leaf abscissions. Under well-watered conditions, values of ψwtlp and ψssat for P. tabulaeformis and P. orientalis were lower than those for R. pseudoacacia and Q. liaotungensis. These results indicate that P. tabulaeformis and P. orientalis have higher capacity to maintain turgor under drought conditions. Differences in the bulk elastic modulus (ε) were found between two conditions in P. tabulaeformis and Q. liaotungensis. The values of ψwtlp and ψssat decreased as water stress increased in R. pseudoacacia, Q. liaotungensis, and P. orientalis, indicating that these trees respond to water stress through osmotic adjustment. Q. liaotungensis and P. orientalis had a higher ability of osmotic adjustment than R. pseudoacacia. It is suggested that indigenous species has advantages over R. pseudoacacia in drought tolerance and can be applied to the afforestation practice in this region.
