Abstract: Abies faxoniana coniferous forests play important roles such as conserving water and soil and maintaining habitat stability for the giant panda in the eastern Tibetan Plateau and the upper reaches of the Yangtze River. Canopy gap disturbance drives successional dynamics of forest communities and shapes forest structure, dynamics and biodiversity in the A. faxoniana forests. The objective of this study was to elucidate the growth dynamics of dominance and periodic fluctuation of seedling population and evaluate the effects of canopy gaps on A. faxoniana regeneration. There strip transects (300 m×2 m), including forest canopy(FC) and canopy gaps (CG), were established in a subalpine coniferous forest in the Wanglang National Nature Reserves, Pingwu County, western Sichuan Province. We investigated the diameter, height and biomass of A. faxoniana seedling (H≤100 cm) and used the Logistic model and spectra analysis for data analysis. The results showed that the Logistic model fitted well with the dynamic adjustment process of the growth dynamic of dominance of A. faxoniana seedling population. The habitat carrying capacity based on basal area and total biomass were 11.34 mm²·m^-2, 4.64 g·m^-2, respectively, and the intrinsic rate of increase were 0.60 and 0.62, respectively. The ratios of the habitat carrying capacity and the intrinsic rate of increase of CG and FC seedling populations were 4.2:1 and 1.4:1 , and the biggest absolute growth rate of CG seedling population was two age classes in advance of FC seedling population. The spectra analysis showed that the fundamental wave regulated the periodic fluctuation of A. faxoniana seedling population and the harmonic wave affected the fluctuation. The fundamental wave of CG population had higher amplitude than the fundamental wave of FC population, and the ratio amplitude was 3:1. The harmonic wave effects on CG population appeared earlier. CG are an important impetus for growth dynamics of dominance, e.g., they improve habitat carrying capacity and intrinsic rate of increase, and advance the appearance of the biggest growth rate. CG can also affect the periodic fluctuation of seedling population, which enhance the regulation of the fundamental wave, and advance the time of the harmonic effect. After the beginning of the highest absolute growth rate, the A. faxoniana seeding population growth was inhibited by intraspecific competition in CG and environmental resource constraints. The influence of CG seeding population on the growth dynamics of dominance and fluctuation of global seeding population was not strong, so we should pay attention to the role of the forest gap in the process of A. faxoniana forest ecosystem management.

Key words: Abies faxoniana seeding, growth of dominance, Logistic model, population fluctuation, population growth, spectra analysis