Abstract: In order to explore the effects of planting densities on the growth and spatial utilization of young Cunninghamia lanceolata plantations, an investigation was conducted in 8 years old C. lanceolata plantations with different planting densities (2400, 3100, 3400, 4200 and 4400 trees·hm^-2). The average height, DBH, individual volume and stand volume all decreased after an initial increase. The average height reached the maximum (9.87 m) when the stand density was 3400 trees·hm^-2. The average DBH and individual volume were the highest at the stand density of 3100 trees·hm^-2. The maximum stand volume was found at the density of 4200 trees·hm^-2. With the increase of stand density, clear bole height increased, while the crown width, leaf area per plant and leaf area index all decreased. The root range and root biomass per plant increased with increasing the stand density, while root depth and coarse root density had the opposite pattern. The fine root density increased to the maximum of 46.19 g·m^-3 at the density of 3400 trees·hm^-2, and then decreased gradually. The competition for space among individuals became more intense with the increase of age, and higher stand density limited the individuals’ growth and development. By timely thinning and tending, the stand could keep reasonable spatial structure at different developmental stages to obtain the best timber yield.

Key words: carbon and nitrogen storage,  age dynamics, Cupressus chengiana plantation, arid valley.