Analysis of dendrometric diversity among natural populations of cork oak (Quercus suber L.) from Morocco

The cork oak (Quercus suber L.) has been the focus of research dealing with the conservation and reforestation of this species due to its economic importance and the problem of deforestation affecting it. The genetic diversity of this tree species, its main aspect of adaptation, has not been sufficiently studied. The Moroccan cork oak tree is found in the northern part of the country, where the fruits of the tree are soft corns. This forest tree species has undergone a strong decline due to many factors, including a significant loss of its biological diversity. While working within the national framework of protection and enhancement of this tree species, our research aimed to analyze and assess the phenotypic diversity of different provenances, using qualitative and quantitative dendrometric traits and geographical characteristics such as the total height of the tree (H), the height to the first branch (Hbr), girth (Gir), surface coefficient of the bole (K) (K = (H x Gir/200)), number of branches (NbrBr), vigor (V), foliage density (D), and altitude. The population of trees studied included 390 individuals from 6 regional provenances: the central plateau, Mamora, the Middle Atlas, the western Rif, the eastern Rif, and the Atlantic Rif. Univariate analysis showed a highly significant variability among these provenances. The highest coefficient of variation concerned K (62.79%) and Gir (42%), followed by NbrBr and Hbr with 32% and 30%, respectively. Hierarchical clustering led to the identification of 2 major groups, with the central plateau and eastern Rif representing the first group, and the Middle Atlas, western Rif, Atlantic Rif, and the Mamora forest representing the second group. The assembling of different groups as explained by dendrometric variation is mainly based on geographical traits.