Contribution à l'étude des paramètres dendrométriques et à la cartographie des peuplements relictuels d’une espèce septentrionale rare au Maroc : Alnus glutinosa (L.) Gaertn.

The common alder, Alnus glutinosa (L.) Gaertn. (Betulaceae), is a key species in certain alluvial and riparian formations in continental Europe. The alders found in Morocco are at the southernmost boundary of their range and represented there by relict formations in refuge zones to which the species had migrated during the glacial phases of the Pleistocene.  Despite its heritage value, there are very few data on its range of distribution or the condition of its populations. This study aimed to locate and map the main forest stands where this species occurs in the Rif region of northern Morocco. A typology of the stands was produced from surveys of twelve reference sites by determining their main characteristics, including stand composition, size, coverage, density and the nature of the forest regime. Stand structure and dynamics were determined from these dendrometric characteristics. The results contribute important quantitative and georeferenced data on the current distribution and dynamics of A. glutinosa populations in Morocco. Given their poor state of conservation, their degraded habitats and low regeneration rate, this species should be considered as endangered and urgently in need of protective measures.