Abstract: With locust (Robinia pseudoacacia),the main tree species in afforestation,as test material,this paper studied the characteristics of its water physiological ecology and productivity under four habitats,i.e.,sunny,shady,semi-sunny and semi-shady hillsides,in the North Shaanxi gully areas of Loess Plateau.The mean water content in 0～500 cm soil layer was 8.87% (shady),8.06% (semi-shady),7.62% (semi-sunny),and 6.96% (sunny),respectively.There was a significant discrepancy between shady,semi?shady,semi-sunny and sunnyhillsides (α=0.01),and the difference between shady,semi-shady and semi-sunny,as well as between semi-sunny and sunny hillsides was also significant (α=0.05).Remarkable relationships were found between leaf RWC,locus WSD and soil water content (SWC).The leaf RWC and locust water potential under sunny hillside were lower,but those under shady hillside were higher.The daily mean transpiration was in order of shady (4.07 μg·cm^-2·s^-1) > semishady (3.89 μg·cm^-2·s^-1) > semi-sunny (3.05 μg·cm^-2·s^-1) > sunny (2.70 μg·cm^-2·s^-1) hillside.The remarkable difference of transpiration appeared at 11:00 and 13:00,and there existed a remarkable relationship between transpiration and light intensity,RH and soil water content.All of these resulted in a diversity of locust biomass under different habitats,the highest under shady hillside,and the lowest under sunny hillside,and the differences between different habitats were all significant.It could be concluded that soil water content was the main factor affecting locust growth.

Key words: Quercus mongolica community, Leaf size spectra, Leaf edge