Assessing the effects of forest gaps on beech (Fagus orientalis L.) trees traits in the logged temperate broad-leaf forest

Abstract

Silvicultural operations, including single-tree selection create gaps in forest canopies and these gaps impact on the forests structure. This study examines the influences of different harvest-created gap sizes on the oriental beech (Fagus orientalis L.) trees traits in temperate Hyrcanian forest, northern Iran. We selected three gap sizes (small, medium and large) and the adjacent unlogged closed canopies with five replications for each and measured some features of beech trees in overstory at the gaps-edge and closed stands. The results showed that gap size significantly influenced on crown length, crown surface area, crown ratio, bole, height/diameter (H/D) and minimum radius / maximum radius (CA) ratios of beech trees six years following gap creation (P < 0.05). Many beech tree traits in adjacent closed forest had no significant difference with gaps, except for crown asymmetric (P < 0.01).Statistically significant differences were observed in beech trees regarding to the clear bole, crown ratio, and CA among the four cardinal points of gaps. A significantly positive correlation was observed between crown ratio with crown length, crown width, crown area, crown volume, and DBH for trees. We found that crown ratio increased significantly with decreasing the bole and total height of beech trees. Results indicated that H/D ratio and total height, DBH, crown length and bole for beech trees were significantly negatively correlated. The CA ratio increased significantly with increasing the bole of trees. The crown radii of border beech trees towards gap center were significantly larger than those of forest-facing side of trees (P < 0.01). This study demonstrates that beech trees in overstory and at the edge of gaps respond differently to artificial gaps after 6 years of formation in oriental beech stand in temperate Hyrcanian forest.