An Investigation of the Relationship between Stem Size and Longitudinal Growth Strains in Hornbeam Species (Carpinus betulus)

Growth stresses are one of the major problems in conversion of trees to timbers especially in hard wood trees. They can cause severe timber degradation such as end split in logs and stems, warp and end checks in lumbers or even difficulties in cutting process like pinch of saw blade. It has been demonstrated that growth stresses are under the control of genetics and the influence of environmental factors. But, the fact that up to which level the impact of environmental factors on various species could result in higher levels of growth stresses is still under investigation due different properties that numerous species show in response to these conditions as well as different reactions in one species or even at one stand. The aim of this study was to focus on the stem size parameters and make a link with the levels of growth stresses in Hornbeam species. In doing so, 11 trees from Iran Northern Forests located close to Nowshahr, were used for the DBH, height, age, pith eccentricity, and longitudinal growth stress measurement. Results showed that by the application of single factor regression analysis to consider only one factor as a result of higher intensity in growth stress indicator (GSI), the obtained correlation could not be significant. But, through a step-wise regression modeling by a multiple factor linear regression analysis, GSI could be predicted as a function of age, height, and DBH up to 84% with a high significant correlation. This reveals that growth stresses are significantly under the influence of stem size specifically on the Hornbeam species as one of the hardwood trees and also shows that the nature of growth stresses are very complex.