[Grading of Robinia pseudoacacia and Platycladus orientalis woodland soil's water availability and productivity in semi-arid region of Loess Plateau].

With Li-6200 photosynthesis determination system and Li-1600 steaty state poro-meter, this paper studied the responses of Robinia pseudoacacia L. and Platycladus orientalis L. leaves' net photo-synthesis rate (Pn), carboxylation efficiency (CE), transpiration rate (Tr), water use efficiency (WUEL), stomata conductance (Cs), stomata resistance (Rs), intercellular CO2 concentration (Ci) and stomatal limitation (Ls) of Robinia pseudoacacia and Platycladus orientalis leaves to soil water content (SWC) in semi-arid region of Loess Plateau, and based on this, the soil water availability and its productivity of test woodland soils were graded and evaluated. The results showed that on Robinia pseudoacacia and Platycladus orientalis woodland, the SWC less than 4.5% and 4.0%, respectively belonged to "non-available water"; in the range of 4.5%-10.0% and 4.0%-8.5%, "low productivity and low efficiency water"; 10.0%-13.5% and 8.5%-11.0%, "middle productivity and high efficiency water"; 13.5%-17.0% and 11.0%-16.0%, "high productivity and middle efficiency water"; 17.0%-19.0% and 16.0%-19.0%, "middle productivity and low efficiency water"; and more that 19.0%, "low productivity and low efficiency water".