Abstract: From June 2010 to July 2011, a pot experiment was conducted to explore the effects of nitrogen deposition on the leaf physiological and ecological characteristics of Lindera aggregate seedlings. Three levels of NH₄NO₃, i.e., lowN (2 g·m^-2·a^-1), mediumN (8 g·m^-2·a^-1), and highN (32 g·m^-2·a^-1), were added to simulate nitrogen deposition, and the seedling leaf photosynthesis, relative chlorophyll content, chlorophyll fluorescence parameters, membrane lipid peroxidation, and antioxidant enzyme activities were determined. After oneyear treatment, the daily mean values of the net photosynthetic rate (P_n) and the maximum net photosynthetic rate (P_{n max}) at low, medium and high levels of NH₄NO₃ addition were 47.0%, 117.8% and 41.2%, and 82;6%, 191.3% and 152.2% higher than those of the control (no NH₄NO₃ addition), respectively, with the highest values at medium level of NH₄NO₃ addition. The intercellular CO₂ concentration, daily mean stomatal conductance, light saturation point, and apparent quantum yield in the three treatments of NH₄NO₃
 addition were all higher than those of the control, and the dark respiration rate was the highest in treatment high-N. The relative chlorophyll content was the highest in treatment medium-N, followed by in treatment highN, and had no significant difference between treatment lowN and the control. The chlorophyll fluorescence parameters varied with the levels of NH₄NO₃ addition. The PSⅡ primary chemical efficiency (F_v/F_m) and PSⅡ potential activity (F_v/F_o) were the lowest in treatment high-N, the superoxide dismutase activity was higher in nitrogen addition treatments than in the control, and the peroxidase activity, malonydialdehyde content, and membrane permeability were the highest in treatment high-N. All the results suggested that nitrogen deposition enhanced the photosynthetic ability of L. aggregata seedlings, with the most obvious effects in treatment medium-N, and altered the other physiological traits of the seedlings to different degrees.