Abstract:

The responses of field-grown Fagus engleriana seedlings to light and soil nutrient availability were investigated. Two-year-old seedlings were grown for two growing seasons under six treatment conditions, including three light levels (L1: 1%-2% of full sunlight; L2: 18% of full sunlight; L3: 100% of full sunlight), with and without , fertilizer addition (F1 and F0) for each light level. The results showed that light and nutrients had significant effect on seedling growth as measured in terms of shoot height, stem basal diameter and biomass; the mean increments of shoot height over two growing seasons were significantly less in L1 than in L2 and L3 (P ＜0.001), and in L3 than in L2 (P ＜0.01), but the increments during the first growing season were not significantly different among the treatments; the increments of stem basal diameter and biomass components were significantly less in L1 than in L2 and L3 (P ＜0.001); the increments of stem basal diameter and whole plant biomass were not statistically different between L2 and L3; adding fertilizer did not affect the seedling growth under closed forest canopy, but had effect in the environments with more sunlight. The results suggest that (1) two-year-old F. engleriana seedlings could survive the conditions of closed forest canopy, but their growth might be severely inhibited; (2) the seedlings could grow as well as or even better in small forest gaps than in open sites; and (3) fertile soil might enhance seedling growth in forest gaps and open sites, but not under closed forest canopy.

Key words: Fagus engleriana, light, nutrient, shoot height, biomass, stem basal diameter, relative growth rates (RGR)