Objective  To study the dynamic characteristics of stand density measures of Cunninghamia lanceolata plantation at different improved varieties and initial planting densities in order to select the appropriate density index and provide a basis for density management of Cunninghamia lanceolata plantation.

Method  Based on 8-year positioning observation data of interactive test forest, the dynamic characteristics of three stand density measures, including crown competition factor (CCF), stand density index (SDI), ratio of dominant height to nutrient area (Z), with different improved varieties and initial planting densities and the linear regression analysis between the three stand density measures and initial planting density and stand age were analyzed.

Result  The law of dynamic changes of the three stand density measures were consistent with age with same improved variety and different initial planting densities, which increased with age. Under lower initial planting density, the slope of the fitting line of stand density measures was small, and became larger with the increase of initial planting density. The results showed that the higher the initial planting density, the stronger the competition intensity. Under same stand age, all the density measures increased with the initial planting density. There were quite significant differences among planting densities. Under the same initial planting density and different improved varieties, the improved varieties had no significant effect on the three stand density measures, and there was no interaction between the improved varieties and initial planting densities.

Conclusion  The three stand density measures can reflect density information to some extent. In the density ranging from 5000 to 6 667 trees·hm⁻², the difference is not significant among initial planting densities in CCF and SDI, and it is difficult to reflect the difference between densities in this range. But the difference among densities reaches a significant level in Z in the whole density range. The Z can show the difference at different densities clearly, and has a larger applicable density, with no parameter and easy calculation. Therefore, it can be well applied to growth modeling and density management in Chinese fir plantation.