Alnus glutinosa (L.) Gaertn, a riparian forest species in Morocco, is declining due to habitat fragmentation and human disturbances. The Moroccan populations of Alnus glutinosa represent a climatic relic. These populations are isolated and threatened by both climate change and human activities. The status of this species in Morocco has been classified in the regional red list. Understanding its structure, regeneration dynamics, and vegetation composition is crucial for developing effective conservation strategies. This study assessed twelve populations, with 20 plots (30 x 30 m) sampled per population. In each plot, the density and diameter of all individuals were recorded, and vegetation composition was analyzed using thirty-six relevés. Significant variation in density and diameter was observed among populations (P<0.001). Although the regeneration status appeared satisfactory, population structure analysis identified five distinct patterns: a reverse-J shape, a broken reverse-J shape, a J-shape model, a bell shape, and an irregular shape, reflecting different demographic trends. A total of 218 species, from 161 genera and 74 families, were documented in Alnus glutinosa populations, with herbaceous species comprising 69% of the flora. The dominance of herbaceous vegetation may hinder seedling recruitment and survival, posing a challenge to population sustainability. These findings underscore the need for targeted conservation efforts, such as habitat restoration and seedling protection, to measure the long-term viability of Alnus glutinosa