Height and Crown Area Distribution of Cionura erecta Shrub lands in chaharmahal and Bakhtiari Province, Using Probability Distribution Functions

Importance of probability distribution functions in natural resource studies is increasing due to their effective roles in better understanding of vegetation structure and providing conceptual models of quantitative indices of plant species. The present study was performed to model the distribution of height and canopy area of Cionura erecta L. shrub, using probability distribution functions in Chahar-Tagh forest reserve in Chaharmahal and Bakhtiari Province. Height and crown cover (the largest and smallest diameters) of the studied species were measured by a strip meter in 35 sample plots of 10r area. The area of canopy cover was calculated by considering the crown shape of the studied species as a circle. Normal, Log-normal, Beta, Gamma, Weibull and Exponential probability distribution functions were used to model the height and canopy cover of the studied species and their goodness of fit were examined by Kolmogorov–Smirnov and Anderson Darling tests. Results showed bell-shaped distributions skewed to the right for height classes and in the case of the canopy cover it was decreasing. Beta and Gamma distribution functions were identified as the most appropriate functions for fitting to the height curve and Log-normal and Weibull functions were the most suitable ones for modeling the canopy cover. The present study showed that the quantitative characters of the studied species are far from a normal distribution under the influence of human activities.