Photosynthetic ecophysiological study on the growth of korean pine (Pinus koraiensis) afforested by the edge-effect belt method
边缘效应带促进红松生长的光合生理生态学研究

A 14 year old Korean pine ( Pinus koraiensis ) forest (as of 1998), afforested after clear cutting of 4 m , 6 m and 8 m width edge effect belts in an oak ( Quercus mongolica) secondary forest in 1986 (with a 10 m width undisturbed belt close to each edge effect belts, namely reserved belts), was studied. In each edge effect belts and reserved belts, growth status parameters (basal diameter, canopy projection area) and diurnal course of net photosynthesis, daily carbon accumulation, and other ecophysiological parameters, such as photosynthetic active radiation, stomatal conductance, xylem water potential of current year branch, leaf temperature, vapor pressure deficit of leaf, were measured to discover the photosynthetic ecophysiological reason responsible for the growth differences in different treatment plots. The results indicate that the lower photosynthetic active radiation and subsequent lower carbon daily accumulation induced the lower potential of growth in the 4 m edge effect belt, while the lower stomatal conductance and subsequent photosynthesis noon depression and lower daily carbon accumulation induced the lower potential of growth in the 8 m edge effect belt. In comparison to the 4 m and 8 m edge effect belt, the 6 m edge effect belt showed the best photosynthetic capacity, which was responsible for the best growth status of Korean pine in this treatment plot. Leaf water potential, leaf temperature, vapor pressure deficit of leaf were positive correlated with the stomatal conductance. Thus, the high light in the 8 m edge effect belt induced the higher leaf temperature, vapor pressure deficit of leaf and lower water potential may be responsible for the sharp decrease in 8 m edge effect belt. Therefore, based on our present study, too wide (8 m) and too narrow (4 m) width can result in the photosynthetic ecophysiological maladjustment (as discussed above). The optimal candidate width of edge effect belts in afforestration of Korean pine in the secondary oak forest may be 6 m.