Tham khảo luận văn - đề án 'báo cáo lâm nghiệp: "evaluation of three methods for estimating the weibull distribution parameters of chinese pine (pinus tabulaeformis)"', luận văn - báo cáo phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | JOURNAL OF FOREST SCIENCE 54 2008 12 566-571 Evaluation of three methods for estimating the Weibull distribution parameters of Chinese pine Pinus tabulaeformis Y. Lei Research Institute of Resource Information and Techniques Chinese Academy of Forestry Beijing China ABSTRACT Weibull distribution was used to fit tree diameter data collected from 86 sample plots located in Chinese pine stand in Beijing. To estimate the Weibull distribution parameters three methods namely maximum likelihood estimation method MLE method of moment MOM and least-squares regression method LSM were compared and evaluated on the basis of the mean square error MSE and sample size. For these sample plots the moment method was superior for estimating the parameters of Weibull distribution for tree diameter distribution. Keywords Weibull distribution diameter distribution parameter estimation Tree diameter distributions play an important role in stand modelling. A number of different distribution functions have been used to model diameter distributions including Beta Lognormal Johnson s Sb and Weibull ones. The Weibull distribution introduced by Bailey and Dell 1973 as a model for diameter distributions has been applied extensively in forestry due to 1 its ability to describe a wide range of unimodal distributions including reversed-J shaped exponential and normal frequency distributions 2 the relative simplicity of parameter estimation and 3 its closed cumulative density functional form . Bailey Dell 1973 Schreuder Swank 1974 sChreuder et al. 1979 Little 1983 Ren-nolls et al. 1985 Mabvurira et al. 2002 and 4 its previous success in describing diameter frequency distributions within boreal stand types . Bailey Dell 1973 Little 1983 Kilkki et al. 1989 Liu et al. 2004 Newton et al. 2004 2005 . It is important that different estimation methods are compared to fit parameters of the Weibull probability density function PDF from given tree diameter breast height dbh data in forest inventory .
