Stand structure and spatial patterns of trees in mixed Hyrcanian Beech forest, Iran

The mixed beach forests (Fagus orientalis) commonly dominate by shade tolerance species with irregular uneven age stand structure. The aim of this study was to analyze the stand structure and spatial pattern in order to identify specific structural patterns. Data was collected from a 16 ha permanent plot. We mapped all stems > 7.5 cm in diameter at breast height on permanent plot. The six main species were divided into two groups based on density and stand structure. Group A had higher density than group B, as well as L-shaped DBH distribution of live stems. Species in group B had bell-shaped DBH distributions. Species in group A have clump spatial distribution pattern in all layers but clump intensity is more than in understory layer and size of patch clump is small in this group. This phenomenon for group A may explaining by having numerous coppice, sucker and patch regeneration in the understory layer. Middlestory and understory stems of the six major tree species were patchily distributed throughout the plot but for Alder and Maple species common pattern in canopy layer was complete spatial randomness. The distribution of Beech and Hornbeam trees were negatively associated with other species. These results suggest species differences in favorable canopy condition.