Beech trees as a shade-tolerant and hardwood species experience inter and intra-specific competition in pure and mixed forest stands. The relationships between several tree traits and competition factor were studied on Oriental beech (Fagus orientalis L. Fagus orientalis Lipsky) in pure and uneven-aged stand in Hyrcanian region, northern Iran. Crown and stem characteristics were collected in 186 one-stemmed and healthy standing beech trees (target tree) randomly selected from the overstory strata. Results showed that competition index was positively correlated with crown length, crown volume, crown surface area, diameter at breast height, total height, basal area, and negatively related to height/diameter ratio and crown eccentricity. Crown eccentricity was negatively correlated to total height, crown length and diameter at breast height for target beech trees. The higher competition index values were observed in diameter at breast height and height classes equal to 46–100 cm and 26–40 m, respectively. The crown ratio was increased with increasing crown sizes. The findings showed that competition factor affect tree structure in beech stand that has not experienced main disturbances for long times in Hyrcanian (Caspian) forests.

山毛榉树作为一种耐阴和硬木树种，在纯林和混交林中经历种间和种内竞争。研究了东方山毛榉树的几个特点和竞争要素之间的关系（山毛榉侧柏L. Fagus orientalis Lipsky）在伊朗北部希尔卡尼亚地区的纯种和不均匀老化的林分中。从上层地层中随机选取 186 棵单茎健康立木山毛榉树（目标树），收集树冠和树干特征。结果表明，竞争指数与冠长、冠体积、冠表面积、胸高直径、总高、基部面积呈正相关，与高径比和冠偏心率呈负相关。树冠偏心与目标山毛榉树的总高度、树冠长度和胸高直径呈负相关。在胸高和身高等级分别等于 46-100 cm 和 26-40 m 处的直径中观察到较高的竞争指数值。冠比随着冠尺寸的增加而增加。