Abstract:

The effects of different light regimes (such as open， gap and understory) on the phonotypic plasticity of the seedlings of Camptotheca acuminata and Gordonia acuminata were studied， based on the leaf traits. The results showed that： 1) Seedings of C. acuminata， as a deciduous broadleaf tree， mainly improved the self-shading， increased the midrib angle and ratio of root biomass to total biomass， and decreased the specific leaf area to adapt the full light in the open sites. Therefore those seedlings exhibited the highest relative growth rate in the open sites in compared with the other light regimes. However， the seedling of G. acuminata did not show the similar adaptability in the open light environment. 2) In order to receive more light energy in gap， the seedlings of G. acuminata developed more leaves， and larger single leaf area and specific leaf area， and increased the ratio of leaf biomass to total biomass. Therefore， the seedlings of G. acuminata could grow relatively higher in gap than that in open and understory. Compared with G. acuminata， the seedlings of C. acuminatain gap had larger single leaf area and total leaf area， longer petiole， and higher growth rates in height and total leaf area. 3) From March to August， the height of the seedlings of C. acuminata in gap increased by 35.3 cm，which was about 5.3 times of the height growth (6.6 cm) of the seedlings of G. acuminata. Therefore， in the gap， C. acuminata seedlings with a distinct competitive advantage of light resources showed a higher relative growth rate than G. acuminata， which was one of the major reasons why the deciduous broad-leaved tree of C. acuminata in evergreen broad-leaved forests. 4) Because of the lack of sufficient solar energy， the two trees’ seedlings could not grow well in the understory. 5) The phenotypic plasticity index based on leaf traits in different light regimes of C. acuminatawas much higher than the those of G. acuminata， which was another important reason for the existence of C. acuminata in evergreen broad-leaved forests.

Key words: light regimes, leaf traits, phenotypic plasticity, Camptotheca acuminata, Gordonia acuminata