Floristic Diversity and Taxonomic Composition of Mount Allahoum, Souk Ahras, Northeastern Algeria

Abstract

Floristic inventories provide essential baseline information for documenting biodiversity, assessing ecosystem value, and supporting conservation planning. Mountain ecosystems are particularly important because their environmental heterogeneity can support diverse plant communities over relatively short spatial distances. This study was conducted on Mount Allahoum, the highest mountain in Souk Ahras Province, northeastern Algeria, to provide the first comprehensive assessment of its flora and its organization along an elevational gradient. Field surveys were conducted over three consecutive years (2023–2025), covering all seasons and the main habitats and elevations of the mountain. A total of 130 plant species belonging to 49 families were recorded. For the standardized elevational analysis, the mountain was divided into 15 successive 20-m elevation belts between 800 and 1100 m a.s.l. Species richness was highest at 840–860 m, where 48 species and 28 families were recorded, and declined markedly with increasing elevation. Species richness showed a strong negative relationship with elevation (Spearman's ρ = −0.913, p < 0.001; linear model R² = 0.834). Floristic dissimilarity among adjacent elevation belts was particularly pronounced between 880 and 980 m, indicating substantial changes in species composition along the elevational gradient. Jaccard-based non-metric multidimensional scaling (NMDS) provided a good two-dimensional representation of floristic dissimilarity among the elevation belts (stress = 0.063), revealing a clear compositional pattern along the elevational gradient, while distance-based permutation analysis confirmed a significant association between elevation and floristic composition (R² = 0.319, p = 0.0001). These results demonstrate pronounced elevational structuring of the flora and highlight the importance of the lower–middle elevations, particularly the 840–860 m belt, as a zone of high floristic richness, while the 880–980 m interval represents a major compositional transition. This first comprehensive assessment establishes a detailed botanical baseline for Mount Allahoum and provides essential information for future biodiversity monitoring, ecological research, and conservation planning. Given its floristic richness and elevational differentiation, the study also provides an evidence base for considering Mount Allahoum for future protected-area designation, while supporting carefully managed nature-based activities that maintain ecosystem integrity.