Objective Stand density is an important index to reflect the number and competition in a stand. It plays a critical role in stand growth models. It is of great significance to analyze the application value of stand density index in stand volume growth model for accurate prediction.

Method Based on the 28 years continuous observation data of the spacing trials of Chinese fir (Cunninghamia lanceolata) plantation in Shaowu, Fujian Province, the annual growth model of stand volume of Chinese fir including five different density indices respectively were developed based on the variable rate method, as well as the model without stand density index.

Result The R² values of the models including density indices were all larger than 0.979, and the model performance was higher than that of the model without density index. Among the five models including stand density indices, the model including living number of trees per ha (N) had the largest value of R², followed by the model with RS density. However, the two models are not feasible because of the parameter estimates of stand density index were not significant. The R² values of all models from high to low were: stand volume model including N (0.979 9), relative spacing RS (0.979 9), stand density index SDI (0.979 4), dominant high nutrient area ratio Z (0.979 3), Nilson density index model (0.979 0) and without density index (0.972 8).

Conclusion Accounting for significance of the parameter estimate, the model with stand density index SDI performed the best in the stand volume model of Chinese fir. In addition, stand volume in stands of planting density (1 667 ～ 3 333 trees·hm⁻²) was larger than the denser stands (5 000 ～ 10 000 trees·hm⁻²).