Abstract: To investigate the suitable canopy density and light intensity for the cultivation of Camellia nitidissima in the understory planting, the C. nitidissima saplings grown under Dalbergia odorifera with different planting densities, and the C. nitidissima seedlings under shading network of different aperture sizes were chosen as study materials, to study the photosynthetic physiological characteristics of  C. nitidissima. The results showed that the net photosynthesis rate decreased with decreasing the light intensity when the light intensity was below 700 μmol·m^-2·s^-1, stomatal conductance tended to increase at first and then decrease, intercellular CO₂ concentration increased, transpiration rate decreased, and water use efficiency varied nonsignificantly with decreasing light intensity. The correlation of leaf gas exchange parameters showed difference between seedlings and saplings, whereas there was no significant difference in the relationship of net photosynthesis rate with stomatal conductance between seedlings and saplings. The phenotypic plasticity of leaf gas exchange parameters of C. nitidissima saplings was high, being over 0.8. Our results showed that there was photoinhibition observed in C. nitidissima saplings under the light density of 700 μmol·m^-2·s^-1. So we suggest that the cultivation of C. nitidissima in the understory planting should be conducted in forest stands with above 30% canopy density to avoid growth inhibition by light stress.

Key words: species composition, Minjiang Estuary, diet composition, stable isotope