西藏昌都县云杉天然林5个树龄梯度下的直径分布研究

Study on Diameter Distribution of Five Age Gradients of Picea asperata Natural Forest in Qamdo County

以昌都县云杉天然林林分为研究对象,选择Gamma分布、Logistic分布、Weibull分布和正态分布4种分布函数;对平均树龄在20~30 a,30~40 a,40~50 a,50~60 a和60~70 a这5个树龄梯度的15个样地的直径结构进行拟合研究。结果表明:随着西藏昌都县云杉天然林平均树龄的增长,其直径分布的范围逐渐变小;林分的偏度和峰度都随着林龄的增长由大变小,使得林分的直径分布也由相对集中变得较为离散;昌都县云杉天然林在20~70 a这段树龄中,林分结构的直径分布按先由Gamma分布转换为Logistic分布,再变为正态分布,最后趋向于Weibull的规律分布。

The distribution of Gamma distribution, Logistic distribution, Weibull distribution and normal dis- tribution were selected as the research methods, and the average age ware 20 -30 a, 30 -40 a, 40 -50 a, 50 - 60 a And 60 - 70 a of the five age gradients of 15 samples of the diameter structure for the fitting study. The results showed that with the increase of the average age of natural forests of Picea asperata in Qamdo county, the range of diameters was gradually smaller. The skewness and kurtosis of stand were greatly increased with the in- crease of age. The diameter distribution of the forest structure were as follows： the distribution of the Gamma distribution to the Logistic distribution was changed from the Gamma distribution to the Logistic distribution. State distribution, and finally tends to Weibull distribution.