Effect of improvement cutting on quantitative and qualitative characteristics of Arasbaran Forests (Case study: Makidi Kaleybar Region)

Background and objectives: Silviculture is considered one of the most important activities of forestry and includes all issues related to training and improvement of forest stands. The main goal and purpose of forest treatment is to strengthen and improvement of the quantitative and qualitative of forest stand and to keep it in health condition during the long life of forest. Different cuts in the forest as forestry tools play an important role in guiding the forest stand towards the desired goals. These cuttings are done to improve forest stands and to achieve the development and sustainability of forest ecosystems. Investigation the importance and impact of these cuts in the target forests of the region is vital for forest management. This research conducted with the aim to compare the quantity and quality of mature forest stands and the regeneration of improvement cutting stand (improvement cutting operation for 14 years) and the control stand (adjacent to the improvement cutting stand) in Makidi area of Kalibar city.
Methodology: Makidi region located in the protected part of Arsbaran forests and in the southwest of Kalibar city. The altitude of this area is 1400-1500 meters above sea level and it is located in the western part of the middle Kliberchay river watershed. Both of the treatment areas were similar in terms of physiographic and ecological conditions and differed only in terms of the type of treatments. A total of 5% of the trees in the improvement cutting stand were harvested during the 14 years. In this operation, the trees that were weak or diseased in terms of their appearance, or the trunks of the trees that were attached to the elite trees or that had crown and root disturbances removed. The total surface area under study is 40 hectares, of which 20 hectares considered for each of the treatments. Using a 50x50 meter grid, 33 circular sample plots of 300 square meters were implemented in the control area (three sample plots located inside the uncovered area) 36 sample plots established in the improvement cutting area. Also, the regeneration of woody species in both stands investigated in circular sample plots with dimensions of 100 square meters centered on the main sample plot.
Results: The results showed that the average d.b.h of the trees was 11.35 and 10.98 cm, the average crown diameter was 2.48 meters and 2.11 meters in the improvement cutting stand and control stand, respectively. The average height of the trees in the improvement cutting stand was 9.22 meters and, in the control, stand was 9.61 meters, and the difference between the two stands was not statistically significant. Regarding the number of trees per hectare in both stands, the highest number recorded in the 10 cm diameter class, and in the higher diameter classes, the number of trees decreases. The results show that the stand is immature and fewer trees are in higher diameters. Observing the state of the two stands shows the youth of these stands, and considering that they are at the age of growth, they are high in number per hectare, and the competition between the stands to obtain soil nutrients and light is high and the demand for more treatment interventions can be felt. The height-to-diameter ratio of two improvement cutting stand and control stands shows that the average height-to-diameter ratio in the control stand is higher than in the improvement cutting stand, which indicates the improvement of the ratio due to cutting operations and the better stability of the stands after improvement cutting operations. Among the most important trees and shrubs observed in the study area, species such as Quercus petraea, Quercus macranthera, Acer compestre, Carpinus betelus, Cerassus avium were recorded. The results show that in terms of species composition, Quercus petraea was 56% and cypress species 0.31% more than the control population in the improvement cutting stand. The percentage of trees with a healthy crown is 93.4% and 93.9% and the upright trunk angle is 68.7% and 43.5% in the improvement cutting stand and control stands, respectively. Examining the tendency of the trees shows that trees in the improvement cutting stand has a more favorable position than the control stand, However, the control stand also have a favorable condition. The stand origin observed in the study area is seedling. The correlation between the diameter and height of trees in both the improvement cutting stand and control stands shows a significant exponential relationship, and the coefficient of determination for the improvement cutting stand is better than the control stand. In terms of the frequency of regeneration, the control stand has a more suitable state of regeneration compared to the improvement cutting stand, and the highest number of regenerations observed in the 5 to 7.5 cm diameter classes, followed by the 2.5 to 5 cm and 0 to 2.5 cm diameter classes.
Conclusion: The summary of the obtained results shows that these stands need more intervention and subsequent cuttings to increase the amount of light and nutrient to the remaining trees which causes more diameter growth increment. It is recommended that these studies be repeated every five years to understand better the impact of this operation.