Effects of Light Intensity on Seedling Emergence and Early Growth of Liquidambar formosana Hance

Liquidambar formosana Hance is a common deciduous broad-leaved tree known for its fast growth rate and adaptability. However, excessive logging has substantially reduced the area of natural forest patches of L. formosana, and seedling regeneration is essential for the long-term continuation of L. formosana populations. To explore the effects of light intensity on the seedling emergence and early growth of L. formosana, a controlled experiment was conducted under three light-intensity treatments (20%, 60%, and 100% of full sunlight, i.e., the photosynthetic photon flux densities (PPFDs) were 223.93 ± 7.54, 670.94 ± 30.14, and 1119.61 ± 23.19 μmol·m−2·s−1, respectively). The seedling emergence percentage, mean germination time, germination synchrony, vitality index, survival percentage, emergence index, morphological characteristics, and biomass allocation under different light intensities were analyzed. The seedling vitality index and survival percentage significantly differed among the treatments and were the lowest under 20% light intensity. With increased light intensity, the seedling mean germination time and germination synchrony increased and then decreased, and the opposite was true for the emergence index. With the increased light intensity, the seedling height, stem diameter, and root length significantly increased. The total, root, stem, and leaf biomasses reached maximum values under full sunlight. With the increased light intensity, the leaf biomass ratio increased, whereas the root biomass, stem biomass, and root–shoot ratios decreased. Our results indicated that the poor light environment under the canopy is not conducive to the survival and growth of L. formosana seedlings and may be among the primary reasons for low seedling establishment.