Stand structure and spatial pattern of trees in mixed Hyrcanian Beech forests of Iran

Mixed beech forests (Fagus orientalis) are the most important forests with the highest degree of naturalness in Hyrcanian forest of Iran. These forests commonly dominate by shade tolerance species with irregular and uneven-aged stand structure. The aim of this study is to analyze the stand structure and spatial pattern in order to identify specific structural patterns. We studied the stand structure and spatial pattern of trees in mixed beech forest in the Shastkolate Educational Forest to examine the coexistence strategies of different species. Data was collected from a 16.9 ha permanent plot on a 406×416m quadrate area. We measured all trees exceeded than 7.5cm 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 reverse J shaped DBH distribution of live standing trees. Species in group A have clump spatial distribution pattern in all layers. However, clump intensity is more than in understory and size of patch clump was smaller in this group. This situation 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. However, for Alder (Alnus subcordata) and Maple (Acer velutinum) common pattern in canopy layer was complete spatial randomness. The distributions of beech trees were negatively associated with other species. These results suggest species differences in favorable canopy condition.