Spatial pattern and intra-specific competition of beech trees in the development stage of volume accumulation in Hyrcanian forest (Case study: Kheyroud forest, Nowshahr)

Spatial patterns of tree species can provide valuable insights into forest dynamics, including processes such as forest establishment, tree growth, species competition, and mortality. This study aimed to investigate the structure, spatial pattern, and interactions of beech trees during the volume accumulation stage of forest evolution in the climax stage of succession. Three one-hectare sample plots with characteristics representative of this stage were selected, and tree characteristics, including species type, DBH, and location, were measured and recorded for all living trees. The results of the uniform angle index indicated a regular pattern among neighboring trees. The average mingling index was 0.08, suggesting intense intra-species competition and a low tendency for beech trees to be located near other species. The mean diameter and height differentiation indices were 0.36 and 0.28, respectively, indicating an average difference between neighboring trees. According to the results of the univariate L11 function, in sample plots one, two, and three, trees exhibited a regular pattern up to distances of 7, 4, and 6 meters between trees, respectively. At greater distances, trees were located within the Monte Carlo range. Based on the results of the L12 bivariate function, in all three sample plots, small diameter trees had a negative interaction with medium and large diameter trees up to a distance of at least 5 meters. Any intervention based on silvicultural programs should take into account the preservation of the structural features of stands at this stage of beech evolution.