Assessing the intra-specific competition and its relation with tree structure in a beech forest (Fagus orientalis Lipsky)

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.