Study on Change Laws of Biomass and Productivity of Masson Pine Forest Plantation Ⅱ.Biomass and Productivity of Stand at Different Ages

Stand biomass and productivity of five stands with different ages from young growth to mature forest had been studied by the methods of diameter class sample tree in which we substitute space distribution of stand for progress of time. The results showed that tree biomass was allocated to each organ according to definite percentage, the percentages were not relative to diameter class, but relative to stand age. With stand age increasing, biomass of stand average tree and each organ increase. The annual growth speed of biomass is the biggest at 18 22 year for stand average tree, but the biggest at 12 18 year for the stand. With stand age increasing, the percentage(above 48%) of stem biomass increases, but that of branch, leaf and bark are on the contrary. When time is shorter than 18 year, with stand age increasing, the percentage of root decreases, then it tends to be stable. The percentage orders of each organ biomass are stembranchrootbarkleaf. Stand(stem) tree stratum biomass and net productivity of stands at the age of 8, 12, 18, 22, 30 are 33.94(16.39),89.94(52.60),204.51(134.52), 223.71 (150.96),234.12(158.94) t·hm-2 and 6.24(2.05),11.14(4.38),15.63(7.47),14.07 (6.86),11.93(5.30) t·hm-1 ·a-1 individually. The diameter class distribution laws of biomass are similar to that of tree, many of them are left offset prior to hail mature forest, since then it tends to right side, its peak is moved 1 2 diameter class to right. Pulewood stand should be cut by 18 years old.