Photosynthetic, spectral reflectance characteristics and primary productivity of main tree species in broadleaved Korean pine forest

Objective  This paper aims to explore the adaptability of five main tree species in different succession stages of mixed broadleaved Korean pine forests (MBKPFs) to light stress from the physiological perspective; to reveal whether different heights and canopy direction have influences on photosynthetic characteristics, spectral reflectance characteristics and related physiological functions of leaves; to evaluate the organic matter accumulation rate of various tree species in order to provide reference for the study of primary productivity of MBKPFs in northeastern China.

Method  Five species of arbor plants in the canopy of MBKPFs, Ulmus davidiana, Tilia amurensis, Juglans mandshurica, Quercus mongolica and Pinus koraiensis, were selected to determine the physiological index of photosynthetic characteristics, spectral reflectance characteristics and functional traits at different sample positions, conducting ANOVA and LSD test and establishing correlation between various physiological parameters, so as to estimate the primary productivity of each tree species with reference to the allometric biomass equation established by previous studies.

Result  (1) There were significant differences in the photosynthetic characteristics, spectral reflectance characteristics, specific leaf area, blade thickness and leaf nitrogen content and potassium content among varied species (P < 0.05). The lowest apparent quantum efficiency, specific leaf area, nitrogen content and potassium content were found in P. koraiensis, with higher dark respiration rate, light compensation point and blade thickness. (2) There were no significant differences in the photosynthetic characteristics, spectral reflectance characteristics, specific leaf area, leaf thickness, leaf nitrogen content and potassium content among different sampling positions within species (P > 0.05). (3) Among species, dark respiration rate and light compensation point were significantly negatively correlated with PRI with R² up to 0.96 and 0.94, respectively (P < 0.05), indicating that the adaptation of plants to light environment was reflected in both photosynthetic and spectral characteristics. (4) The maximum primary production rates of population were estimated with U. pumila of 4.806 kg/s, T. amurensis of 1.637 kg/s, J. mandshurica of 1.981 kg/s, Q. mongolica of 0.350 kg/s and P. koraiensis of 0.106 kg/s.

Conclusion  The adaptability differences of tree species to light stress are reflected both in photosynthetic characteristics and spectral reflectance characteristics, and the photosynthetic characteristics of leaves are closely related to the community succession, in the later stage of which the adaptability of plants in the canopy layer to the light environment determines the canopy species composition of the community; the difference of plant height below 15 m and canopy direction is not enough to cause adaptive changes in photosynthetic physiological characteristics of leaves; U. pumila contributes the most to the community productivity while P. koraiensis contributes the least.