Variance and regression analysis were used to analyze changes in C, N and P content and to assess stoichiometric characteristics of soil and leaves in Larix principis?rupprechtii plantations of different ages, including young stands (14 years), middle-aged stands (20 years) and near-mature stands (37 years) at the Saihanba Mechanized Forest Farm.

① Soil P content within the same soil layer showed significant differences among the differently-aged L. principis-rupprechtii stands (P < 0.05), with significantly lower concentrations in near-mature than in other stands; however, no significant differences in C and N content were observed among stands (P > 0.05); soil C and N content in stands of the same age decreased with increasing soil depth, while P content remained stable; soil C/N, C/P and N/P ratios first decreased and then increased with increasing forest age and soil depth; ② tree N content differed significantly among the differently-aged forest stands (P <0.05), whereas no significant differences in leaf C and P contents were observed among stand of different ages (P >0.05). Tree N content was significantly lower in 20-year-old than in 14- and 37-year-old stands. Tree C/N, C/P and N/P ratios differed significantly among stands of different ages (P <0.05); C/N ratios were highest in 20-year-old stands, and C/P and N/P ratios were highest in 37-year-old stands; ③ P content and C/P ratio of the trees showed significant positive correlations with those of soils in differently-aged stands (P < 0.05), while C/N ratios of leaves produced negative correlations with those of soil (P<0.05).

Soil N availability was the predominant factor limiting growth of L. principis-rupprechtii in the 20-year-old stands. In the 37-year-old stands, tree growth was mostly limited by P availability. However, neither N nor P were not major growth-limiting factorsin the 14-year-old stands. Fertilization may thus help promote growth of L. principis-rupprechtii at different growth stages.