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水曲柳、胡桃楸和黄波罗是东北东部山区天然次生林的主要组成树种。采用红外气体交换分析仪，分别在叶片生长初期、中期和末期，同步测定了净光合速率（Ａ）、气孔导度（ＧＳ）、蒸腾速率（Ｅ）及其相关的外界环境因子的日变化。三大硬阔的Ａ和Ｅ的日变化格局随树种、生长季节和天气状况而表现为单峰、双峰和多峰曲线等三种类型。水曲柳、胡桃楸和黄波罗单位面积叶片的最大净光合速率（Ａｍａｘ）分别为１５１１、２１５４和２３０３μｍｏｌ·ｍ－２·ｓ－１；但测得的日平均净光合速率峰值（Ａｍｅａｎ）以胡桃楸最大，为１１０７μｍｏｌ·ｍ－２·ｓ－１，水曲柳和黄波罗分别为８５１和８６５μｍｏｌ·ｍ－２·ｓ－１。在所测定的日期中，三大硬阔的光合作用变化主要是由非气孔限制引起的。三个树种的蒸腾速率的差异及其变化均不大，平均Ｅｍｅａｎ为２０ｍｏｌ·ｍ－２·ｓ－１左右。
Ash, Juglans mandshurica and Huangpoluo are the major tree species of natural secondary forests in the eastern mountainous areas of northeastern China. Infrared gas exchange analyzer was used to measure diurnal variation of net photosynthetic rate (A), stomatal conductance (GS), transpiration rate (E) and their related environmental factors simultaneously at the early, middle and late leaf growth stages. The three broad and hard A and E diurnal variation patterns with tree species, growing season and weather conditions showed unimodal, bimodal and multi-peak curves and other three types. The maximal net photosynthetic rate (Amax) of leaves per unit area in Fraxinus mandshurica, Juglans mandshurica and Huangpoluo were 15.11, 21.54 and 2303 μmol · m-2 · s-1, respectively. However, The peak of photosynthetic rate (Amean) was the largest in Juglans mandshurica, which was 1107μmol · m-2 · s-1, while that in Fraxinus mandshurica and Huangporo was 851 and 865μmol · m-2 · s-1, respectively. Changes in photosynthesis in the three broad and broad spikes were mainly caused by non-stomatal limitations on the date measured. The differences of transpiration rates among the three species and their changes were not significant. The mean Emean was about 2.0 mol · m -2 · s -1.