Abstract: Revealing the response of C, N and P contents and ecostoichiometric characteristics of leaves, stems and roots of Cyclobalanopsis gilva seedlings to the addition of slow-release fertilizer and inoculation of mycorrhizal fungi can provide scientific basis for improving nutrient use efficiency of Cyclobalanopsis gilva seedlings in the cultivation. In this study, 1-year-old seedlings of C. gilva were inoculated with mycorrhizal fungi (inoculation concentration of 36.28 mg·mL^-1 of Pisolithus tinctorius) under application of slow-release fertilizer (five levels of 1.50, 2.25, 3.00, 3.75, 4.50 kg·m^-3). The differences of nutrient concentration, nutrient accumulation, allocation proportions, and stoichiometric ratios in different organs of the seedlings of C. gilva under different treatments were analyzed. The results showed that the inoculation with mycorrhizal fungi primarily affected root N concentration and C∶N ratio and N∶P ratio of C. gilva seedlings. Following inoculation, root N concentration and N∶P ratio increased by 11.60% and 16.36%, respectively (P<0.01), while the C∶N ratio decreased by 10.46% (P<0.05). The addition of slow-release fertilizer mainly influenced P concentration, C∶P ratio and N∶P ratio in various organs. Fertilization had no significant effect on C and N concentration and C∶N ratio. The P concentration of all organs increased significantly with increasing fertilization level, and C∶P showed a decreasing trend. 3.00 kg·m^-3 was the most suitable level for slow-release fertilizer. The addition level higher than 3.00 kg·m^-3 of slow-release fertilizer could increase the P concentration, but would reduce the nutrient use efficiency and nutrient accumulation. Inoculation and fertilization had a positive interaction effect on stem C concentration and leaf C∶P in seedlings. Inoculation with mycorrhizal fungi reduced the difference of C concentration in stems and roots of seedlings among different fertilization levels, increased the accumulation of C, N and P in each organ, significantly increased the proportion of C and P in leaves and stems, and significantly decreased the proportion of C and P in roots. Inoculation reduced the correlation between nutrient concentrations in different organs, particularly between C and N concentration, while it increased the correlation between C, N, and P stoichiometric ratios in different organs. In conclusion, inoculation of mycorrhizal fungi can promote nutrient accumulation in seedlings, and reduce the influence of soil nutrients on seedling growth. The combination of fertilization and inoculation can alleviate the nutrient limitation of seedling growth. Our results can provide a theoretical reference for the efficient cultivation of C. gilva seedlings.

Key words: slow-release fertilizer, inoculation of mycorrhizal fungi, Cyclobalanopsis gilva, Pisolithus tinctorius, ecological stoichiometry