[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]

Abstract

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.

Keywords: Changbai Mountain; Korean pine and broad-leaved forest; canopy crane; photosynthetic capacity; seasonal dynamic.