Modelling of diameter distributions of Douglas (Pseudotsuga menziesii (Mirb.) Franco) stands

Abstract

In this study, Diameter distributions of Amance and Vallombrosa origin stands of Douglas were intendent modelling with two parameter Weibull probability density function having shape and scale parameters for different age periods. Periodic diameter at breast height measurements measured in different age periods in permanent plots of planted Amance and Vallombrosa origin stands of Douglas in Belgrade forest Topuzlu Bend location for cultivating and investigating yield with periodic measurement of Douglas in Turkey by Istanbul University Faculty of Forestry Forest Yield and Economics Department were based on modelling diameter distributions. Theoretical Weibull diameter distributions were obtained with estimating the parameters of Weibull probability density function by maximum likelihood method for each origin and age periods. The suitability of observed diameter distribution of plots to theoretical Weibull diameter distribution was tested by method of Komogorov-Simirnov at 0.05 significant level. Diameter distributions obtained from plots are suitability to two parameter theoretical Weibull probability distribution, in other words it was concluded that diameter distribution of Amance and Vallombrosa origin stands of Douglas can be represented by Weibull distribution for each periods.

Keywords

• Weibull distribution
• scale parameter
• shape parameter
• Belgrad Forest
• Kolmogorov-Simirnov