Effect of elevation gradient on morphological and physiological responses of Fagus orientalis Lipsky leaves in Guilan forests

Assessing the changes in plant functional traits along the gradients is useful to understand their adaptation and response to the global and local environmental drivers. In order to determine the effect of elevation on morphological and physiological responses of oriental beech (Fagus orientalis Lipsky), samples of leaves were collected from southern and northern parts of trees crown at 700 m, 1200 m and 1700 m a.s.l in Masal forests of Guilan province. Analysis of variance showed a significant difference among the morphological and physiological characteristics between the populations (p < 0.05). The results also showed that the leaf area, specific leaf area and relative water content of the samples collected from the two parts of crowns increased with the increasing elevation and decreased from 1200m to 1700m. Furthermore, Chlorophyll a, chlorophyll b, total chlorophyll and carotenoid content in three different altitudes were higher in northern part of the crown of the trees. The results of the mean comparison of carotenoid contents showed that with increasing altitude (from low to high altitude), the amount of carotenoid in both parts of the crown increased. Moreover, the plasticity in northern and southern directions of the crowns suggested that highest plasticity on the northern direction was observed for carotenoids (0.6), whereas it was 0.84 in the southern half for the ratio of Chl a/Chl b. In terms of morphological properties, the highest average impact of the plasticity in the northern and southern parts of the crown were observed in the relative water content (respectively, 0.81 and 0.9). The average physiological plasticity increased among elevation gradients and showed higher values than morphological traits. Conclusively, the results of this study showed that beach populations respond to environmental changes by changing in leaf traits at different altitudes.