Abstract: Cunninghamia lanceolata plantations of 4 different age classes were compared and analyzed. These plantations lie in Youxian County of Zhuzhou city, Hunan province. In this research, space is studied as the object instead of time. The result shows that compared with different stand age gradations, the diversity of under-storey species richness is not so obvious. There are about 22~33 plant species per 2700 m² in plot. However, the bio-ecological characteristic differences among dominant species are evident. The dominant under-storey species at different age levels of Cunninghamia lanceolata plantations were respectively Pueraria thunbergiana and Dicranopteris dichotoma, Gelsemium elegans and Pteridium aquilinum, Desmodium elegans and Pteridium aquilinum, Serissa serissoides and Pteridium aquilinum. Under-storey species diversity index of different stand ages is almost the same. The species diversity index in Cunninghamia lanceolata plantations of Guanghuang is best, with the average species being 18.3, 11.3 and Shannon-wiener index (H) 2.136 3,1.961 0 of shrub layer and herb layer under Cunninghamia lanceolata plantation. So, both canopy density and crown structure of plantation dominate under-storey species composition and distribution.

Key words: Cunninghamia lanceolata, under-storey, important value, diversity index