Objective To study the economic benefit of Eucalyptus plantations with different initial planting densities by monitoring their growth.

Method Three initial planting density treatments were tested, i.e. 1250 tree·hm⁻², 883 tree·hm⁻² and 667 tree·hm⁻². The data of 16 years' growth were collected and analyzed to calculate the timber yield, mean annual increment (MAI), internal rate of return (IRR) and net present value (NPV).

Result It is showed that the DBH of the plantation with initial planting density of 1250 tree·hm⁻² was significantly different from that with the initial planting densities of 883 and 667 tree·hm⁻² in the growth process (p < 0.05). Meanwhile, there was no significant difference in stand volume among different initial planting densities (p > 0.05). The largest timber yield and MAI of middle diameter timber were at the plantation with initial planting density of 883 tree·hm⁻² in the range of 7th to 12th years and the 16th year, followed by the plantations with initial density of 667 tree·hm⁻² and 1250 tree·hm⁻². At the 16th year, the timber yield of middle diameter timber of the plantation with initial planting density of 1250 tree·hm⁻² exceeded that of the plantation with initial planting density of 667 tree·hm⁻². Large diameter timber began to appear at the plantation with initial planting density of 883 tree·hm⁻² at the 16th year. The harvesting rotations of the plantations with initial planting densities of 1250, 883 and 667 tree·hm⁻² were 7, 9 and 9 years respectively. At the 9th year, The NPV of the plantations with initial planting densities of 1250 and 883 tree·hm⁻² reached the peak, while that of 667 tree·hm⁻² was at the 8th year, The peak NPVs of the plantations with initial planting densities of 1250, 883 and 667 tree·hm⁻² were 30994, 40193 and 31288 CNY·hm⁻² and the peak IRRs were 37%, 41%, 42% respectively.

Conclusion Overall, the plantation with initial planting density of 883 tree·hm⁻² has the highest NPV and IRR, as well as higher growth potential, followed by that with initial planting densities of 667 tree·hm⁻² and 1250 tree·hm⁻².