[Water physiological characteristics and leaf traits of different aged Salix cheilophila on alpine sandy land].

Taking 4-, 11-, 25-, and 37- year old Salix cheilophila stands on the alpine sandy land of Gonghe basin in Qinghai of West China as test objects, a laboratory test was conducted on their relative water deficit, water holding ability, specific leaf area (SLA), leaf mass-based nitrogen concentration (N(mass)) and phosphorous concentration (P(mass)), and N(mass)/P(mass), aimed to understand the variation patterns of the water physiological characteristics and leaf traits of different aged S. cheilophila on alpine sandy land. No significant difference was observed in the relative water deficit of the four stands. The daily mean value of water potential of the 37-year old stand was significantly lower, as compared with that of the other three stands, and the 4- and 11-year old stands had a significantly lower daily mean water potential than the 25-year old stand. The water loss rate of the 4-year old stand was significantly lower than that of the other three stands, and the 25-year old S. cheilophila stand had a significantly lower water loss rate than the 11-year old stand. The 4-year old stand also had a significantly lower SLA than the other three stands, implying its higher water use efficiency. The N(mass) of the 11-year old stand was significantly higher than that of the other three stands, and the 25-year old stand had a significantly higher N(mass) than the 37-year old stand, implying that the 11- and 25-year old stands had a higher photosynthetic capacity. The P(mass) of the 11-year old stand was significantly higher than that of the 25- and 37-year old stands, and the 4-year old stand had a significantly higher P(mass) than the 25-year old stand. The N(mass)/P(mass) of the four stands was 5.16-6.28, and the 25-year old stand had a significantly higher N(mass)/P(mass) than the 4- and 11-year old stands. The N(mass) of the four stands was significantly positively correlated with P(mass) the P(mass) was highly significantly negatively correlated with N(mass)/P(mass) and significantly nega- tively correlated with stand age, and the N(mass)/P(mass) was significantly positively correlated with stand age. It was suggested that S. cheilophila at its different developmental stages could have different ecological adaptive strategies.