[Natural regeneration of plantations with different densities and its influencing factors].

In this study, we analyzed the natural regeneration of pure plantations with stand densities of 128, 240, 320, 400, 480, 560, 640 and 720 trees·hm in the Guandi Mountains and its influencing factors. The results showed that the regeneration index first increased and then decreased with the increases of stand density, and that the regeneration performance of stand with medium density (400-560 trees·hm) was significantly better than other stands. Light conditions, herbaceous plants and litter of the understory had a dual effect on the regeneration of . Excessive light, herbaceous plant cover or over-thick litter was not instrumental to the regeneration. Soil organic matter promoted stand regeneration by providing soft soil texture, adequate water content, low phosphorus but high nitrogen. The effects of the examined factors on the regeneration index were as follows: soil water content (0.798) > total nitrogen (0.621) > litter thickness (-0.597) > soil porosity (0.504) > soil organic matter (0.493) > total phosphorus (-0.404) > transmitted total light (-0.274) > herbaceous plants cover (-0.021). In the plantation management, stand density could be controlled at about 480 trees·hm by thinning or replanting, while litter could be cleared properly to improve soil condition and to promote natural regeneration of .