Problem definition and objectives: The Zagros region is one of the most important natural forest ecosystems in Iran, where Amygdalus haussknechtii plays a significant ecological role. This study aimed to evaluate the effects of site conditions on the physical and biometric properties of this species’ wood in two distinct sites, Kareh-Bas and Cholicheh, located in Chaharmahal and Bakhtiari Province.
Methodology: Wood samples were collected from healthy, even-aged trees at breast height, and traits such as oven-dry density, basic density, volumetric swelling and shrinkage, as well as fiber characteristics (length, diameter, and cell wall thickness) were measured. To investigate the impact of habitat and environmental factors on the physical and biometric properties of A. haussknechtii wood, the data were first evaluated for normality. Pearson correlation coefficient was used to analyze relationships between variables, and principal component analysis was employed to reduce data dimensions and identify principal components. MANOVA was applied to examine multivariate separation among habitats. To identify the variables influencing dry density, multiple linear regression models were performed using stepwise forward.
Results: Results indicated that differences between the two sites were significant for most traits (P < 0.01). In Kareh-Bas, oven-dry density was 0.92±0.03 g/cm3 and basic density was 0.77±0.02 g/cm3, which were lower than the values recorded in Cholicheh (1.01±0.03 g/cm3 and 0.84±0.06 g/cm3, respectively). Fiber length in Cholicheh averaged 0.98 mm compared to 0.78 mm in Kareh-Bas (P < 0.01). Fiber diameter (20.75 µm) and cell wall thickness (6.02 µm) were also higher in Cholicheh than in Kareh-Bas (P < 0.01). The Pearson correlation pattern indicates that the dominant axis of variation aligns with dry density, fiber diameter, cell wall thickness, wet density, and fiber length. These same variables emerge as the dominant and habitat-separating components in the first principal component analysis. Therefore, the correlation structure provides an intuitive basis for explaining the PCA separation and the significance of the MANOVA. PCA results revealed that the dominant axis of variation in the data aligns with fiber and moisture-related traits (fiber diameter, cell wall thickness, dry density, wet density, and fiber length), and this same axis appeared as the primary habitat separator in the first principal component (PC1). The MANOVA statistically confirmed the separation observed in the biplot. Regression models showed that fiber diameter is the most significant predictor of dry density across the entire dataset. In the Choliche habitat, in addition to fiber diameter, shrinkage had a positive effect and swelling had a negative effect, whereas in the Kareh-Bas habitat, only the constant (intercept) was significant. These results indicate that in the Choliche habitat, a combination of fiber and dimensional traits determines wood quality, whereas in the Karebas habitat, wood density is primarily influenced by the overall tissue average.
Conclusion: Overall, wood grown in Cholicheh exhibited longer fibers, thicker cell walls, and higher density, whereas wood from Kareh-Bas showed lower density and greater porosity. These findings highlight the direct influence of environmental factors such as temperature, precipitation, and altitude on the wood structure of A. haussknechtii. It can be concluded that site-specific differences lead to substantial variations in the physical and biometric properties of this species, and such information is valuable for selecting optimal sites for industrial utilization and genetic improvement programs