中文摘要：

以我国温带主要阔叶树种水曲柳幼苗为对象,在长白山自然保护区海拔740 m和1200 m布设两处试验地,分别进行增水30%（＋W）、减水30%（-W）和自然降水（CK）处理试验,分析植株生长和叶片光合作用参数、可溶性蛋白和光合色素含量,以及降水和温度变化对水曲柳光合作用的影响.结果表明：温度变化对水曲柳幼苗生长和光合生理指标的影响显著,与海拔1200 m样地相比,海拔740 m样地3个处理水曲柳幼苗的基径、株高、叶片叶绿素含量和可溶性蛋白含量显著增加,胡萝卜素含量降低;叶片净光合速率、气孔导度、蒸腾速率和气孔限制值均显著升高,而胞间CO2浓度和叶片水分利用效率显著降低.水曲柳幼苗光合能力的下降归因于非气孔因素限制.降水变化对水曲柳幼苗生长及光合作用的影响均不显著.

英文摘要：

Taking Fraxinus mandshurica,a main tree species in the temperate zone of Northeast China,as test material,two experimental sites were installed at the altitudes 740 m and 1200 m in Changbai Mountains,respectively,and three precipitation regimes including 30% precipitation enhancement（＋W）,30% precipitation deduction（-W）,and naturally occurring precipitation（CK） were designed,aimed to investigate the effects of the variations in precipitation and temperature on the photosynthesis in Fraxinus mandshurica seedlings,with their growth,leaf photosynthetic parameters,and leaf soluble protein and photosynthetic pigment contents examined.Temperature variation had significant effects on the growth and photosynthesis of the seedlings.For the seedlings grown at altitude 740 m,their stem basal diameter,plant height,and leaf chlorophyll and soluble protein contents under the three precipitation regimes had significant increase,leaf carotenoid content decreased,leaf net photosynthesis rate,stomatal conductance,transpiration rate,and stomatatal limitation all increased significantly,whereas leaf intercellular CO2 concentration and water use efficiency had significant decrease,as compared with the seedlings grown at altitude 1200 m.Non-stomatal factors limitation was the main reason for the decrease of the seedlings photosynthetic capacity.Precipitation variation had little effects on the growth and photosynthesis of F.mandshurica seedlings.