干旱区生态环境知识资源中心

We investigated the effects of overstory canopy openness and seedling density on seedling morphology and growth in the mid-successional species Acer nipponicum Hara in a cool-temperate forest. Studied seedlings were 46 seedlings of 30-160 cm height, and their overstory canopy openness ranged between 7.2% and 17.0%. Seedling density, measured as the number of conspecific neighboring seedlings within a 50 cm radius of the target seedling, ranged between 0 and 19. There were no significant correlations between seedling height, canopy openness, and seedling density. Multiple regression analysis showed that crown depth, leaf mass fraction, and leaf area index decreased with decreasing canopy openness and increasing seedling density, while the ratio of trunk-lateral branches mass increased. Overstory canopy openness did not affect crown area, leaf size, or petiole length, all of which decreased with increasing seedling density. Standardized regression coefficients indicated that seedling density affected morphology and growth more than canopy openness did. The morphological responses to canopy openness cannot be considered as adaptive plasticity, as total leaf area and leaf mass fraction decreased with decreasing light levels. In contrast, responses to seedling density indicate adaptive responses to neighborhood competition. The results highlight the importance of seedling density that influenced seedling growth and morphology independently of overstory canopy openness.