Quantifying the structure of pure beech forests using spatial structural indices (case study: Hyrcanian forests of Mazandaran province, Iran)

Forest structure is a key element for assessing the ecological functions and services in forest ecosystems, which can be described and quantified using forest structural indices. This research was conducted with the aim of quantifying the structure of pure beech forests using spatial indices of forest structure in the Hyrcanian forests of Iran. For this purpose, 90 permanent sample plots of 1000m2 area in three pure beech forests (30 samples in each forest) were established based on a systematic-random grid of 150×200m and the variables of DBH, total height, species and spatial coordinates of all trees greater than 7.5cm in the sample plots were recorded. Then, the structural characteristics of the forests were quantified using O-ring statistic and indices of diameter and height differentiation, diameter and height dominance and Mingling. The results showed that the distribution patterns of trees in the pure beech forests is mainly random, the degree of diameter and height differentiation is average, the degree of species mixing is low, the top height is about 33.5m, the forests are two-storied, trees in terms of dominance indices are co- dominant and the average tree to tree distance is less than 3m. These spatial and quantitative indices of the forest structure can be used for management, planning and silvicultural interventions in the forests. Furthermore, by using these indices with permanent sample plots and assessing their changes over time, it is possible to long-term monitoring and comparing the forests.