Changes in forest stand structure in a permanent plot established in Neka-Zalemroud forest plan

A permanent sample plot with an area of 6 ha is located on mid elevation of the Neka-Zalemrood forest, south of Sari in northern Iran. After fencing the plot, a metal tag indicating tree number was installed on each tree. A full calipering was conducted, which was followed by measuring the diameter at breast height (DBH) and height of selected trees. Forest structure, proportion of dead wood, and proportion of tree species were studied for a period between 2006 and 2012. Results of the inventory of the total 2375 trees in 2012 showed three storeys and an uneven-aged structure in Fagus orientalis-Carpinus betulus forest type. Further results included mean tree number of 389 ha-1, mean basal area of 43 m2ha-1, mean stand volume of 538 m3ha-1, and De' Liocourt factor of 1.38. Dead trees accounted for 3.1% of the total tree number and 5.7% of the stand volume. Comparison between the two inventories (2006 and 2012) showed that beech trees gained a higher proportion among the tree species in almost all diameter classes, while hornbeam lost more of its presence in the diameter classes. Amongst the DBH classes