Objective  To study the effect of five initial planting densities and different soil profile on soil nutrient contents of Chinese fir (Cunninghamia lanceolata) mature plantation.

Method  The soil nutrient contents (0-100 cm soil layers) of C. lanceolata mature plantation in Daqingshan Forest Farm under five different planting densities of A (1 667 trees·hm^-2), B (3 333 trees·hm^-2), C (5 000 trees·hm^-2), D (6 667 trees·hm^-2), and E (10 000 trees·hm^-2) were measured. One-way ANOVA and the least significant difference were applied to determine the soil nutrient contents in different densities and different soil layers.

Result  The results showed that: (1) The contents of organic matter, total N, P, available N and available Fe were the highest in most soil layers of stands with density A or B. In general, as initial planting density increased, the contents of organic matter, total N, P, available N and available Fe in upper soil layers (0-30 cm) decreased. While soil pH, total K and available K increased with initial planting density. Moreover, the initial planting density did not significantly influence the contents of exchangeable Ca and Mg; (2) Soil organic matter, total N, available N, P, K, exchangeable Ca, Mg and Fe contents obviously decreased with increasing soil depths. This pattern was particularly evident in the top 0-30 cm. The initial planting density had obvious effect on nutrient content in different soil depths.

Conclusion  The nutrients in 60 cm soil are affected by stand density in South Asia, while the low initial planting density is more conducive to the long term conservation of soil fertility in Chinese fir plantation.