Comparative research on the structure, chemistry, and physical properties of Turkey oak and sessile oak wood

Abstract

The objective of this research was to establish comparatively the anatomical, chemical, and some selected physical features of Turkey oak and sessile oak wood, in order to better understand the peculiarities of the drying behavior of these species. The analyzed samples were obtained from freshly harvested trees of the same age, originating from the same areal, namely the Southern Sub-Carpathians. All determinations were performed on sapwood and heartwood samples separately. The microscopic analysis revealed that Turkey oak has larger earlywood pores than sessile oak, both in sapwood (295m compared to 250m) and in heartwood (308m compared to 273m). In heartwood, they are partly filled with tyloses. The macroscopic analysis showed that Turkey oak wood has a much lower proportion of heartwood (only 50%) compared to sessile oak (which has around 90%). There is a distinctive color difference between the two zones in both species, but with all analyzed physical properties it was revealed that the Turkey oak sapwood and heartwood have similar values of oven-dry density, shrinkage coefficient, fiber saturation point, while in sessile oak, the values are clearly higher in the heartwood. A possible explanation is given by the high amount of extractives that were found in Turkey oak sapwood (5.34% in cold water, 7.77% in hot water, and 21.60% in NaOH), which were close to the ones obtained in sessile oak heartwood. The comparative FTIR analysis of the two species showed a similar qualitative chemical composition with regard to the main constituents. As far as the physical properties are concerned, the research showed that the density of Turkey oak wood is significantly higher (average 728kg/m3) than that of sessile oak wood (average 667kg/m3), but the volumetric shrinkage coefficient is lower (average 14.6% for Turkey oak, compared to 15.54% for sessile oak). This result can be also explained in correlation with the high contents of extractive substances in Turkey oak sapwood, which fill the spaces in the cellular walls, leading thus to a lower shrinkage of the respective wood. The fiber saturation point follows-up the same pattern, being lower in Turkey oak wood (23-24%), than in sessile oak wood (25-28%). The obtained results show that a slow drying is essential in case of this species.