Abstract: Platycarya strobilacea is widely distributed in the sub-tropical area of China. To study the potential effect of atmosphere nitrogen deposition on its seedling regeneration, the seedling leaf functional traits, biomass allocation, gas exchange and seedling carbon balance to low light (3.0%, 6.0%, 12.0% and 25.0% PAR of open sky light) and nitrogen (15.0 and 3.0 mmol·L^-1) treatments were determined in a greenhouse experiment. The results showed that light deeply affected leaf functional traits and biomass allocation. In contrast, nitrogen supply had no influence on them, though the interactions of low light and nitrogen supply could significantly affect RMR. We also found that the maximum photosynthesis rate (A_max) and apparent photon efficiency (Ф) decreased with increasing nitrogen supply under low light (3.0% and 6.0% of full sun light), vice versa in a relatively higher light (12.0% and 25.0% of full sun light). Hence, the interactions of light and nitrogen deeply influenced leaves gas exchange of seedlings of P.strobilacea. The results simulated with a whole plant carbon balance model indicated that light compensation point of P.strobilacea seedlings (LCP_-wholeplant) increased with increasing nitrogen under 3.0%, 6.0% PAR of open sky light, while it decreased with increasing nitrogen supply under 12.0% and 25.0% conditions. Therefore, we suggested that atmosphere nitrogen deposition would deteriorate P.strobilacea regeneration under lower light environment conditions, but increase its survival under disturbance and gap conditions.

Key words: Platycarya strobilacea, nitrogen deposition, photosynthesis, carbon balance