[A comparative study on nutrient accumulation and distribution of different generations of Chinese fir plantations]

The nutrient accumulations and distribution of different generation of Chinese fir plantations in central production areas of China were studied through the investigation of plantation with different generation(first, second and third), ages (5, 10, 15, 20 years old) and sites(site index 14, 16 and 18). The nutrient accumulations and distribution of Chinese fir plantations were greatly influenced by the number of planting generation. Nutrient accumulation and utilization efficiency in tree layer of Chinese fir plantations declined with the increasing planting generation number, with the first generation > the second > the third; while the nutrient accumulation of understory vegetation was increased with the increasing of planting generation number. Compared with the first generation plantations, nutrient accumulation of tree layer of the second and the third generations decreased by 17.56% and 36.24% respectively, and the third generation platation decreased by 22.65% than the second generation. Meanwhile, successive planting resulted in a decreasing nutrient utilization efficiency of Chinese fir plantation, and an increasing nutrient necessary for dry matter production per unit, which is disadvantageous to the maintaining of soil fertility, but beneficial to the nutrient accumulation of understory vegetation.