极端干旱区胡杨生长季水分利用效率变化特征研究

 在干旱区的极端环境，植物能否适应当地的极限环境条件，最主要的是看它们能否很好地协调碳同化和水分耗散之间的关系，也就是说植物水分利用效率是其生存的关键因子之一。 就生长季胡杨叶片稳定碳同位素组成(δ13C)、胡杨叶片水分利用效率及其影响因素进行了研究。结果表明,生长季胡杨叶片δ13C值在-28.16‰±0.23‰～-26.82‰±0.22‰间变化，平均值为-27.70‰±0.13‰。胡杨各月水分利用效率在84.81±2.23～(70.97±2.40)μmolCO2·mmol-1H2O间变化，平均值为(75.69±1.31)μmolCO2·mmol-1H2O；胡杨水分利用效率变化趋势是逐渐降低。最高值出现在5月，而后不断降低，7月达到最低值。造成这种变化的原因是叶片营养物亏缺导致的叶片光合速率的减小和气温升高、土壤含水量减小以及地下水埋深加深共同导致的气孔导度的变化。

Research on Characteristics of Water Use Efficiency Variations of Populus euphratica during the Growing Season in Extremely Arid Region of China

In extremely arid environment,whether plants can adapt to the extreme environment or not depends mainly on whether they can finely harmonize the relation between carbon assimilation and water evapotranspiration.That is,water use efficiency is a key factor.We studied the variations of foliar δ13C values,water use efficiency and their affecting factors during the plant growing season.Results showed that the foliar δ13C values ranged from-28.16‰±0.23‰ to-26.82‰±0.22‰,and the means were-27.70‰±0.13‰.The monthly water use efficiency of P.euphratica ranged from(84.81±2.23)μmolCO2·mmol-1H2O to(70.97±2.40)μmolCO2·mmol-1H2O,and the mean was(75.69±1.31)μmolCO2 mmol-1H2O.The water use efficiency of P.euphratica decreased continuously during the growing season.The highest value of water use efficiency appeared in May,and the lowest value appeared in July.The causes for this trend were reduction of photosynthetic rates resulting from foliar nutrimental deficit and variations of stomata conductance caused by air temperature raising,soil content water decreasing and groundwater level falling.