Response of Leaf Morphology, Photosynthesis, and Light Induction of Species Seedlings from Different Functional Groups to Different Light Regimes in Evergreen Broad-Leaved Forest

This study focused on the response of the leaf morphology and photosynthesis traits of species seedlings from different functional groups to different light regimes (open, gap and understory) in evergreen broad-leaved forest in order to find out their succession status. The main results are as follows:1) There was a significant difference among the environmental factors under different light regimes in subtropical forests, especially photosynthetic active radiation (PAR), which made functional groups respond differently to environments;2) The seedlings of Cinnamomum camphora could capture more light energy with the lowest leaf dry mass per area(LMA), performing the most stomatal conductance and the lowest leaf intercellular CO₂ concentration(C_i) to improve carborxylation capacity and solar energy use efficiency (SUE), offsetting photoinhibition under higher regimes. These characteristics showed it could regenerate in high-light environment as a pioneer species;3) Seedlings of Gordonia acuminata showed photoinhibition due to the highest LMA and C_i but the lowest SUE under open light regimes. Otherwise it showed a relatively higher leaf net photosynthetic rate (Pn), SUE and water use efficiency (WUE) in gap and was more sensitive to light induction in understory. It belonged to intermediate shade-tolerant species;4) Although seedlings of Castanopsis fargesii could endure higher light with a relatively lower LMA and higher Pn than Gordonia acuminata under open light regimes, it probably experienced a big light stress for a lower sensitivity to abrupt high light induction. It also did not adapt to relatively high light regime of gap because of a lower SUE. However, it could not survive in understory for a 16% higher LMA than in gap either. It tended to regenerate better in sparse crown of Pinus massoniana forests and would replace intermediates such as Gordonia acuminata in succession.