Canopy gaps characteristics and structural dynamics in a natural unmanaged oriental beech (Fagus orientalis Lipsky) stand in the north of Iran

Canopy gaps are one of the most important structural features of forest ecosystems, and studying of them can have useful results and implications for forest management. The aim of this study is investigation of characteristics and regeneration within canopy gaps in an intact beech stand in the Shastkalateh Experimental Forest of Hyrcanian region, north of Iran. All canopy gaps and related forest parameters were measured within a permanent plot 16ha. Considering the composition of the forest, the dominant tree species was oriental beech with 36.3% of the stem number and 56.6% of the stand volume. In total 54 canopy gaps were identified which covered about 5% of the forest area. An average of 4.32 gaps.ha-1 existed in the permanent plot and gap sizes varied from 48.3 to 622.7m2. More than three-quarters (77.7%) of canopy gaps were smaller than ≤200m2. Also more than half of the gaps (53%) were formed by a single tree-fall event and beech made up 52% of gap makers and 23.4% of gap fillers. Beech had the second largest proportion on standing deadwood of gap maker in the study area, while velvet maple was the most frequent gap filler in approximately 30% of the gaps. Despite the high frequency of small gaps 100m2, their proportion of the overall gap area reached only 25% that suggests the important role of intermediate and large gaps in the gap dynamics. Considering the recent occurring disturbances in the Hyrcanian Forests, the study analyzed the main characteristics of disturbance regime with the emphasis on the role of wind and longevity of trees. In general, findings of this study showed that the creating small and average gaps in intact beech forests could be based on natural disturbance regimes, And suitable conditions provides for successful regeneration of beech forests in close to nature silviculture.