Abstract: To examine the effects of phosphorus (P) addition on ecological stoichiometry of Chinese fir (Cunninghamia lanceolata) plantation under the context of increasing atmospheric nitrogen (N) deposition and thus to provide preference for improving productivity through reasonable fertilization, we carried out a field experiment with nine fertilization treatments in a 10-year-old Chinese fir plantation, including low N level (30 kg·hm^-2·a^-1, N30), high N level (60 kg·hm^-2·a^-1, N60), low P level (20 mg·kg^-1, P20), high P level (40 mg·kg^-1, P40), four combinations (N30+P20, N30+P40, N60+P20, and N60+P40) and a control (CK). Ourresults showed that P addition alone had no effect on leaf carbon (C), N, P concentrations and the ratios of C∶N, C∶P, and N∶P in summer. Leaf N concentration and N∶P significantly increased after N addition (P<0.05), but leaf C and P concentrations had no significant change (P>0.05). In autumn, leaf N and P concentrations and N∶P ratio increased first and then decreased with the increases of P addition alone (P<0.05), while leaf C concentration and the ratios of C∶N and C∶P exhibited an opposite trend (P<0.05). Nitrogen addition significantly increased leaf N and P concentrations but decreased leaf C concentration and the ratios of N∶P and C∶P (P<0.05), indicating that N deposition would decrease nutrient use efficiency of Chinese fir under P stress. The interactive effects of N deposition and P addition foliar nutrient concentration and stoichiometric ratios in Chinese fir changed with the duration of the experiment. According to our results, nutrient limitation of young Chinese fir trees varies with season, which provides a scientific basis for the precision fertilization of Chinese fir.

Key words: Nutrient leaching, Paddy field, Taihu Lake area