基于冠层塔吊原位测定长白山温带阔叶红松原始林群落主要树种的光合特征

为了更好地理解温带阔叶红松原始林群落主要树种的生理生态学特征,为森林生态系统碳动态的模拟预测提供基础数据,本研究依托中国科学院长白山森林生态系统定位站,首次利用冠层塔吊原位测定了阔叶红松原始林群落4个主要树种成熟大树的CO₂响应曲线,并利用FvCB模型计算了一些重要的光合生理参数.结果表明: 红松的光合速率(A)、最大羧化速率(V_{c max})和气孔导度(g_s)均最小,而其气孔对光合的限制性(L_s)最大.水曲柳、蒙古栎和紫椴这3个阔叶树种的光合特征也存在显著差异.基于叶片面积的V_{c max}大小顺序为:水曲柳(83.2 μmol·m^-2·s^-1)、蒙古栎(89.3 μmol·m^-2·s^-1)>紫椴(68.4 μmol·m^-2·s^-1)、红松(68.8 μmol·m^-2·s^-1)(P<0.05),而基于叶片质量的V_{c max}大小顺序为:水曲柳(1.36 μmol·g^-1·s^-1)>蒙古栎(1.03 μmol·g^-1·s^-1)>紫椴(0.90 μmol·g^-1·s^-1)>红松(0.42 μmol·g^-1·s^-1)(P<0.05).7—9月,水曲柳和蒙古栎的A值显著降低,而紫椴和红松的A值变化不显著;所有树种V_{c max}都随季节发生显著下降.在温带阔叶红松林生态系统碳动态的模拟预测中,应该考虑V_{c max}的季节变化.

In-situ measurement of photosynthetic characteristics of dominant tree species based on canopy crane in a Korean pine broad-leaved forest in Changbai Mountain,northeastern China.

To better understand the eco-physiological characteristics of dominant tree species in Korean pine broad-leaved forests, and to provide fundamental data for modelling and predicting carbon dynamics of forest ecosystems, we measured leaf CO₂ assimilation rate versus intercellular CO₂ concentration curves of four canopy dominant tree species in a Korean pine broad-leaved forest, in situ, for the first time, using a canopy crane in the Changbai Mountain Forest Ecosystem Research Station. Several important photosynthetic parameters were fitted with the FvCB model. Photosynthe-tic rate (A), maximum carboxylation rate (V_{c max}) and stomatal conductance (g_s) were lowest in Pinus koraiensis (Pk), while stomatal limitation on photosynthesis (L_s) was highest in Pk. There were significant variations of photosynthetic characteristics among the three broad-leaved tree species [i.e., Fraxinus mandshurica (Fm), Quercus mongolica (Qm) and Tilia amurensis (Ta)]. The rank of tree species with respect to area-based V_{c max} was: Fm (83.2 μmol·m^-2·s^-1) and Qm (89.3 μmol·m^-2·s^-1) > Ta (68.4 μmol·m^-2·s^-1) and Pk (68.8 μmol·m^-2·s^-1) (P<0.05), and their rank with respect to mass-based V_{c max} was: Fm (1.36 μmol·g^-1·s^-1) > Qm (1.03 μmol·g^-1·s^-1) > Ta (0.90 μmol·g^-1·s^-1) > Pk (0.42 μmol·g^-1·s^-1) (P<0.05). From July to September, A value significantly declined in Fm and Qm, but remained stable in Ta and Pk. By contrast, V_{c max} significantly decreased in all tree species from July to September. Our results indicated that seasonal variation of V_cmax should be taken into consideration in the modelling and predicting of forest ecosystem carbon dynamics in northeastern China.