Variation of leaf morphological traits in natural populations of Fagus orientalis Lipsky in the Caspian forests of Northern Iran.

Oriental beech (Fagus orientalis Lipsky) is a dominant tree species in the Caspian forests, where occupies approximately 18% of the forested area and produce more than 35% of the total wood stock volume in this region. However, little information is available about its variation along the Caspian forests of Northern Iran. This work studied the morphological vari- ation of five native oriental beech populations growing in the western Cas- pian region in Guilan province (Astara, Asalem, Fuman, Chere, Shenrud). Eight leaf morphological traits, including leaf length, leaf width, petiole length, leaf area, leaf dry mass per unit leaf area, leaf thickness and leaf den- sity were measured in 200 trees. The results showed that all measured leaf morphological traits were remarkably different among the populations, with the exception of distance between veins. A hierarchical classification of all populations led to the formation of three major groups: (i) Astara, (ii) Asa- lem, (iii) the rest of populations. Leaf morphological dissimilarities are pos- sibly attributed to the genetic variations, developed as a result of adaptation to diverse environmental conditions. However, multisite common garden experiments would be needed in order to completely separate environmen- tal and genetic factors explaining the observed level of natural variability. Keywords Caspian forest, leaf area, leaf morphological traits, natural popu- lation, oriental beech.