Determining mathematical relations among important characteristics of Fraxinus excelsior (Case study: Research- Training Forest of Kheyroud)

In forest management, determining characteristics of trees is essential for assessing tree volume and providing other mathematical equations. In this study, the characteristics of 256 trees including stump diameter, diameter at breast height, total height, crown height, height of trunk with and without branch were measured in an even-aged Fraxinus stand at Chelir part of Kheyroud Forest in north of Iran. Results showed there are significant statistical correlations among various characteristics of Fraxinus excelsior trees, and mathematic-statistical equations were established among these characteristics. We found the incremental power relation between stump diameter (dst) and diameter at breast height (d), which can be used for estimating diameter at breast height of cut trees. Also, another equation was established between diameter at breast height and total height (ht) which is used for estimating total height of those trees for which diameter at breast height is available. An incremental logarithmic relation was found between diameter at breast height and crown height (hc) and an inverse one between diameter at breast height and trunk height (trh) for this species. Also, a sigmoid relation was found between stump diameter and total height. Results implied that trunk height decreases and crown height increases as total height increases. Trees with higher diameters have high height of trunk without branch. The relationship between Slenderness coefficient (h/d) and diameter at breast height of the trees was found to be a power type.