| چکیده انگلیسی مقاله |
Introduction: Forest volume stock is one of the most important quantitative characteristics of forests, which is estimated and monitored in national forest inventories to study the current situation and changes in forest resources. Therefore, its results can be used in forest management policies and plans. The purpose of this study was to estimate the volume stock of the Hyrcanian forests of Iran using permanent sample plots and a two-stage sampling method, which is specific for inventory in large areas.
Material and Methods: This forest inventory was conducted in the Hyrcanian vegetation region in northern Iran including 104 watersheds, using a two-stage sampling method. Based on this sampling method, 42 watersheds were randomly selected and sampling was carried out in randomly selected parcels of them using a regular grid with dimensions of 150×200 meters with circular permanent sample plots of 1000 m2 area. Inside each sample plot, the diameter at breast height (DBH) of all tree species greater than 7.5 cm, their distance and angle to the center of the plot, the height of the closest tree to the center, and the diameter of the thickest tree in each sample plot were measured and recorded.
Results: At the end of inventory, a total of 1195 circular sample plots (each 10 Ares) were established and 33517 trees were measured. Results showed that the mean quadratic mean diameter (QMD), basal area, standing volume and forest density in these forests, considering a minimum DBH of 7.5 cm, are 38 cm (arithmetic mean: 29.5 cm), 29 m2/ha, 359 m3/ha and 340 trees/hectare, respectively (The mean standing volume and tree density, considering a minimum DBH of 12.5 cm, are 355 m3/ha and 254 trees/ha, respectively). The highest and lowest standing volumes were observed in the middle land and lowland areas of these forests, respectively. In terms of volume distribution across diameter classes, the majority of volume stock was observed in the large and extra-large diameter classes, i.e., in the diameter range of 50 to 80 cm accounting for approximately 46% of the total volume stock. Furthermore, the highest forest density was found in the lowland and highland and the lowest in the middle land areas of these forests. Based on the obtained results, beech (Fagus orientalis Lipsky) and hornbeam (Carpinus betulus L.) together constitute 56.5% of total tree abundance and 71.2% of the total volume stock in the Hyrcanian forests of Iran.
Conclusion: By calculating the stock (density, basal area and standing volume) of these forests, in addition to obtaining important biometric information from this valuable vegetation region, the necessary data for resource management, biodiversity assessment, carbon storage estimation, stand quality improvement and planning silvicultural interventions to control both the quantity and quality of these forests are provided. |