Stand characteristics of gap formation phase through the development of oriental beech (Fagus orientalis Lipsky) stands in the Hyrcanian Forests, northern Iran

The quantification of forest stand dynamics and structural characteristics within the development phases can be useful in facing with new challenges in the close to nature forestry. The formation of gaps is known as a critical part of the natural dynamics of oriental beech stands. This research was carried out to describe the structural features of naturally regenerated oriental beech stands in the gap formation phase using a set of stand structure quantification indices. Our results revealed that gaps have an average size of 178 m² and are closed mostly by oriental beech and velvet maple, while gap formation is done exclusively by beech. Also stands have slightly heterogeneous diameter distributions and uniform tree height. The average number of trees per hectare and the average of stocking volume were 379 stem ha^-1 and 514.8 m3 ha^-1, respectively. Furthermore, the mean value of dead tree volume was 36.3 m3 ha^-1. The average mingling was 0.23 and tree-to-tree interval calculated and 4.87 m. Meanwhile, the mean value of diameter and height differentiation were 0.45 and 0.87 m, respectively. Knowledge on formation of natural gaps is useful for planning management interventions that are in accordance with natural process of development of the stands and exhibit minimum deviation from natural processes. We can conclude that harvesting in the gap formation phase led to shifting stand to the next phase and accelerate the natural gap phase scale disturbance. Removing trees in other phases does not emulate natural stand development pathways.