Quantitative and qualitative characteristics and altitudinal zonation of Arasbaran forest protected area, northwestern Iran

Knowledge on silvicultural characteristics of forest stands is prior to any forest management practice. The objectives of this study were to determine the forest types and to explore some quantitative and qualitative characteristics of Arasbaran forest protected area along an altitudinal gradient. Therefore, circular plots of 400 m2 at 50-meter elevation intervals were established along five altitudinal transects, 100 meters apart, from the lowest (1100 m a.s.l) to the highest (1725 m a.s.l) forest limit. In each plot, the physiographic conditions including slope gradient, altitude and geographic coordinates were determined. Woody species were identified and the diameter at breast height (dbh) of all trees above 7.5 cm dbh, as well as origin, health status, number of stems and tree leaning were measured. In addition, the regeneration frequency of each individual tree taller than 1.30 m in three diameter classes (0-2.5, 2.5-5 and 5-7.5 cm dbh) and shorter than 1.3 m in three height classes (0-10, 10-50 and 50-130 cm) were examined within 100 m2 regeneration plots. Four forest types including Carpinus betulus - Quercus petraea (1100-1400 m a.s.l), C. betulus - Q. petraea - Acer campestre- Fraxinus excelsior (1400-1500 m a.s.l), C. betulus - Q. petraea - A. campestre (1500-1650 m a.s.l) and C. betulus - Q. macranthera (1650-1725 m a.s.l) were distinguished along the altitudinal gradient. The highest number of stems per ha (mature and regeneration stands) and average basal area were observed in C. betulus - Q. macranthera type, whereas the highest average dbh was recorded in C. betulus - Q. petraea forest type. Finally, seed regeneration was most common in C. betulus - Q. petraea - A. campestre forest type.