Interaction between competition index and some features of broad-leaved trees in Hyrcanian forest (Case study:beech forest of Savadkoh-Mazandaran)

Competition between trees has an impact on their structural features and it is very important to measure the competition index and determine the correlation with some of the characteristics of the trees. To conduct the research, circular sample plots (n = 24) with an area of ​​400 m ² were established in a 150 × 100 m grid in the forest, Savadkoh-Mazandaran. Within each sample plot, frequency, height, crown diameter and diameter at breast height (dbh) for each tree were measured in the overstorey. The richness and diversity index of trees and competition index for each plot were calculated. The results showed that there was a significant difference between the values ​​of competition index for the three tree species. Competition index with height, dbh and crown diameter had significant positive correlation for all tree species, but negative significant correlation with height and H/D for beech and alder and also positive correlation for hornbeam. There was a negative significant correlation between beech competition index and tree richness index and a positive correlation between alder competition index and tree diversity index. With increasing altitude, competition index values ​​decreased only for hornbeam species. Significant differences were observed among the three tree species in terms of crown diameter, dbh, height and H/D ratio in stand. In general, regarding the relationship between some tree variables and the index of competition in the stand, this information can be used in the selection and application of silvicultural operations such as thinning and remarking in temperate Hyrcanian broadleaf forest.