SUMMARY
Aim of the study: This study aimed to investigate the effect of altitude difference on the wood dry density, fiber dimensions, and morphological properties of hornbeam wood (Carpinus betulus L.).Area of study: The study area was located in the province of Mazandaran, north of Iran.Material and method: 18 mature trees were randomly selected and harvested at six altitude levels (300, 500, 700, 900, 1100, and 1300 m) in the north of Iran. The clear test samples? were prepared? at diameter at breast height (DBH) to measure the wood dry density, fiber length, fiber diameter, cell wall thickness, Runkel coefficients, flexibility coefficients, and slenderness coefficients. Further ?analyses included the relationships between the wood properties and site conditions (temperature, ?precipitation, crown canopy, ?and understory herb layer) as well as tree’s main dimensions ?(tree height and the DBH).Main results: The results indicated significant effects of altitude variations on the studied ?properties. The pattern variations of wood properties were very regular at different levels of height. The average fiber length and fiber diameter decreased while the wood dry density and cell wall thickness increased with increasing the altitude levels. The average values of wood dry density, fiber length, fiber diameter, cell wall thickness, slenderness coefficients, flexibility coefficients, and Runkel coefficients of hornbeam wood were 698 kg/m3, 1.42mm, 25.58 µm, 5.72µm, 55.55, 54.04%, and 0.93, respectively, in the above six altitudes. Pearson matrix correlation showed that there were significant relationships between temperature, crown canopy, tree height and DBH ?with the studied wood properties (except the slenderness coefficients)?.Research highlights: The hornbeams grown at altitudes above 900-1300 m were not suitable for pulp and ?paper production? due to relatively higher Runkel coefficients, the lower flexibility coefficients, as well as smaller fiber length than other altitude levels.Additional Keywords: Carpinus betulus; altitude variation; density; fiber dimensions; morphological properties.Abbreviations used: WDD (wood dry density); FL (fiber length); FD (fiber diameter), CWT (cell wall thickness); FC (flexibility coefficient); RC (Runkel coefficients); SC (slenderness coefficient).