Résumé.-La présente étude a été réalisée dans la chênaie verte du Moyen Atlas central marocain (Tafachna et Reggada), avec pour objectif la détermina-tion du stock de carbone organique dans les différentes couches des sols, de la litière et des différentes composantes de l'arbre (bois du tronc, écorce, branches, rameaux et feuilles). Il en ressort que le stock de carbone total (SCOT) dans cet écosystème est de 145 t C/ha pour Tafachna et 114 t C/ha pour Reggada. Le stock de carbone organique des sols (SCOS) représente plus de 50% du SCOT. Le SCOS varie considérablement avec la densité du peuplement, avec 80 t C/ha pour Tafachna (5192 pieds/ha) et 56 t C/ha pour Reggada (1584 pieds/ha). Au contraire, le stock de carbone dans la biomasse arborée (aérienne et racinaire) est plus important dans Tafachna que dans Reggada (64 t C/ha pour Tafachna et 58 t C/ha pour Reggada). Plus de 80% du stock de carbone organique des sols sont emmagasinés dans les trente premiers centimètres, où il est de l'ordre de 63 t/ha (43% du SCOT) pour Tafachna et 47 t/ha (41% du SCOT) pour Reggada.Mots clés : minéralisation -carbone organique -biomasse -sol -litière.Abstract.-The present study was carried out in Quercus ilex forest of the Middle Moroccan Central Atlas (Tafachna and Reggada). It aims at the determination of the organic carbon stock in the various layers of the soils, the litter and the various components of the tree (wood of the trunk, bark, branches, smal branches and leaves). It comes out from this study that the stock of total carbon (SCOT) in the ecosystem of the holm oak is of 145 t C/ha for Tafachna and 114 t C/ha for Reggada. The organic carbon stock of soils (SCOS) represents more than 50% of the SCT. This stock varies considerably with the density of peuplement with 80 t C/ha for Tafachna (5192 species/ha) and 56 t C/ha for Reggada (1584 species/ha). Contrary to the carbon stock in the phytomass which is equal 64 t C/ha for Tafachna and 58 t C/ha for Reggada. More than 80% of the organic carbon stock of the soils is stored in the first 30 centimeters, that is about 63 t/ha (43% of the SCOT) for Tafachna and 47 t/ha (41% of the SCOT) for Reggada.
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 × 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.
Morocco is one of the most important regions of the world in terms of L. number and variation. This species is in decline due to several factors, which can lead to permanent loss of this resource. It would be essential to evaluate the genetic diversity in order to conserve maximum genetic variability of this species. The genetic diversity and differentiation of 16 sites from five regions representing the entire range of Moroccan Cork Oak were assessed. Twenty-three ISSR primers used generated 985 polymorphic fragments with an average of 42.8 bands per primer and showed 100% of polymorphism. The 173 individuals revealed a moderate level of genetic diversity at species level (I = 0.27, He = 0.161). The AMOVA showed that the highest level of diversity occurred within populations (64%), this was also confirmed by the coefficient of differentiation (Gst = 0.47). The estimated gene flow (Nm = 0.56) and the Mantel test revealed a significant correlation between geographic and genetic diversity (r = 0.266; = 0.001). This genetic structure was further shown by the topology of the UPGMA, sPCA and STRUCTURE analysis. In addition, a core collection of 34 genotypes was established representing the essential diversity detected. This research advocates populations and individuals to preserve in order to improve and conserve this resource in the future.
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