[Variations of water use efficiency and its relationship with leaf nutrients of different altitudes of Wuyi Mountains, China]. / æ­¦å¤·å±±ä¸åŒæµ·æ‹”æ¤ç‰©æ°´åˆ†åˆ©ç”¨æ•ˆçŽ‡çš„å˜åŒ–åŠå ¶ä¸Žå »åˆ†å˜åŒ–çš„å ³ç³».

We determined the water use efficiency and nitrogen and phosphorus concentrations of plants at different altitudes (600, 900, 1300, 1500, 1800, 2000, 2100 m) in Wuyi Mountains to understand the relationship of water use efficiency with foliar nutrients. The results showed that plant water use efficiency increased with altitude, and the leaf δ18O of tree showed no significant variance with altitude. On the whole, leaf nitrogen concentration showed no obvious trend, while leaf phosphorus concentration at high altitude was significantly higher than that at low altitude. No significant relationship between water use efficiency and foliar nitrogen concentration was found in this study, but water use efficiency had a positive correlation with foliar phosphorus concentration. In conclusion, the change of water use efficiency was mainly caused by the difference in photosynthetic rate. The effect of water status on plant water use efficiency was not significant. The variances of leaf phosphorus concentrations along the altitudinal gradient may affect photosynthetic rate and in turn the water use efficiency of plant in this area.

[Variations of water use efficiency and foliar nutrient concentrations in Cunninghamia lanceolata plantations at different ages]. / ä¸åŒæž—é¾„æ‰æœ¨äººå·¥æž—çš„æ°´åˆ†åˆ©ç”¨æ•ˆçŽ‡ä¸Žå¶ç‰‡å »åˆ†æµ“åº¦.

We studied water use efficiency (WUEi), nitrogen (N) and phosphorus (P) status of leaves at different leaf ages (current year, 1-, 2-, and 3-year-old foliage) as well as their relationships in a subtropical chronosequence of Chinese fir (Cunninghamia lanceolata) forests (3-, 8-, 14-, 21- and 46-year-old). The results showed that foliar WUEi varied significantly with foliar age in the order of current year foliage > 1-year-old foliage > 2-year-old foliage > 3-year-old foliage, while stand age had no significant impact on foliar WUEi. Foliar N/P ranged from 11.4 to 19.6 and was higher in younger and older stands than in stands at the fast-growing stage. The foliar N and P concentrations tended to display similar trends with foliar ages in the order of current year foliage>1-year-old foliage>2-year-old foliage>3-year-old foliage. WUEi did not change significantly with stand ages, probably because the photosynthetic rates and stomatal conductance decreased simultaneously with stand age. There was no relationship between WUEi and foliar N. WUEi had significant positive correlation with foliar P and significant negative correlation with foliar N/P. It is indicated that foliar P concentration would be a key factor affecting WUEi with increasing atmospheric N deposition in subtropical forests.