ارايه مدل مناسب پراكنش تعداد در طبقات قطري كودهاي طبيعي و ناهمسان راش شمال ايران (جنگل هاي سنگده و شصت كلاته )

An Appropriate Model for Distribution of Diameter Classes of Natural Beech Stands in the Sangdeh & Shastkolateh Forests

This study has been carried out to obtain an appropriate model for the distribution of natural beech population in diameter classes in two different forest areas of Sangdeh and Shastkolateh in nothern Iran. Two different regions of beech forest were selected according to their varied age as well as varied growing conditions. These were separated from other sections and therefore four sample areas in one hectare selected for an overall sampling. Then, the numbers of points were plotted according to diameter class. Among different variants, diameter at breast height was shown to represent a reasonable distribution of points. Also statistical distribution of Beta, Weibule, Exponential, and Power were investigated in relation to distribution of points, their efficiency being concluded through chi-square. The results indicate that from among different methods, regression model bears the most suitable estimation for the mentioned regions. Power model for both selected areas and Beta distribution for Shastkolateh are expected to end up with reasonable results. Finally it can be concluded, although selective method is used as an approach for the distribution trend in forest stands, but, the above mentioned models can be recommended as more appropriate for the study areas.