Modeling of Frequency Distribution of Tree: s Height in Uneven-)aged Stands (Case study: Gorazbon district of Khyroud forest)

To study the frequency distribution of the data for the height of trees in uneven-aged stands in Gorazbon forest and its modeling، some statistical distribution were used. The utilized data belong to 196 trees (Fagus orientalis، Betulus carpinus، Quercus castaneifolia، Alnus subcordata، Acer velutinum etc.) that were extracted from the data related to the forest management plan of Gorazbon district located at Khyroud forest. The range of the trees’ height measured was between 5 and 51 meters which is an indication of height variable in the northern forests. After initial calculations، four distributions Weibull، Gamma، Normal and Lognormal for frequency distribution modeling of height variable were selected and related pertinent calculation were done. The results of Anderson-Darling test and P-P plot showed that lognormal distribution is not an appropriate model for frequency distribution modeling of trees’ height. Among the other three distributions، Weibull، Gamma and Normal are respectively more suitable.