The aim of the present study was to analyze environmental effects (altitude, position of the trees, and orientation of the crown), on leaf traits of 18 deciduous, woody species in the Fandoglo forest region in Ardabil, NW Iran. We measured 9 leaf traits (leaf width, length, area, thickness, water content, relative water content, leaf mass per area, specific leaf area, and dry matter concentration). inWe used three positions of the treestrees' positions (forest edge, forest understory, and isolated trees) inat two altitudes (low and high) fromat 90 sites. A two-way ANOVA and t-test for independent samples were used to test differences in leaf traits betweenat the forest sites. The results confirmed that leaf traits of species were more strongly correlated with altitude and tree position than with the orientation of the crown. No direct link between leaf traits and the orientation was detected. However, patterns of leaf–orientation relationships changed across different orientations. All the values of the leaf traits here examined there were significantly higher in lowlower, rather than in high altitudehigher altitudes, thus indicating that environmental factors like atmospheric CO2 concentration, temperature, light, irradiance, and wind had a significant effect on foliar morphology and functionality. However, water relationsrelationships such as water content and specific leaf area, indicated an opposite trend. Furthermore, species with different positions havehad different responses to the range of altitudes. The research concluded altitude and positions of the trees formedtrees form environmental stressstresses that leadslead to the adaptation of functional traits (morphological and physiological) to thein forest habitats. Tree species can adapt to the environmental conditions bythrough different physiological mechanisms and morphological characteristics, which can provide a theoretical basis for afforestation and forest management in the Fandoghlo forest region.