Floral diversity, endemism, and environmental factors in Gebel Katrina, South Sinai, Egypt

Gebel Katrina, located in the Saint Catherine Protectorate of South Sinai (Egypt), is a biologically rich area with diverse plant communities shaped by factors such as elevation, slope, soil type, and precipitation. This study was designed to examine the vegetation structure, update the occurrence of endemic taxa, and investigate the impact of environmental conditions and landform types on plant disruption in the region. The primary objective of this study was to analyze the behavior and distribution of the most common species across major environmental gradients. Between 2022 and 2024, 49 stands were randomly collected within the study area characterized by relatively uniform vegetation and physiography and represent as much as possible the four major landform types (terraces, slopes, ridges, and gorges). The selected stands were distributed as follows: terraces (12 stands), slopes (9 stands), ridges (9 stands), and gorges (19 stands). For the analysis of the biological spectrum, a growth-form system with four categories was utilized: trees (T), shrubs (S), perennial herbs (PH), and annual herbs (A). Soil analyses were conducted for composite samples from the 49 stands. For each recorded species, nativity, species diversity measurements, endemism, and IUCN conservation status were depicted. Multivariate analysis techniques were used to assess the classification of the 49 stands in various landforms, and ordination with soil variables were applied using different software. A total of 137 taxa were recorded from Gebel Katrina area belonging to 39 families (1 Pteridaceae, 1 Ephedraceae, and 37 Angiospermae), of which 16 were endemics, which indicates the mountain's significance as a biodiversity hotspot. Of these endemic taxa, nine were classified as Endangered (EN) and four as Least Concern (LC), together accounting for over 80% of the endemic flora. The largest angiosperm families with the highest numbers of species included Asteraceae, Lamiaceae, Poaceae, Brassicaceae, Caryophyllaceae and Fabaceae. These six families constituted more than 30% of the recorded flora. Shrubs and perennial herbs were the predominant growth forms, collectively comprising over 70% of the total flora. Native taxa comprised the dominant component of the recorded flora, accounting for 80 species (58.4% of the total). In contrast, non-native taxa were limited to two annual grasses. Analysis of IUCN Red List proportions revealed a predominance of EN taxa, accounting for 52 taxa (37.9%), followed by Least Concern (LC) taxa with 36 taxa (26.3%). Together, these two categories constituted over 60% of the total assessed flora. Hierarchical cluster analysis of a presence/absence data matrix (49 stands × 91 species after removal of species with occurrences < 5%), using the Sørensen (Bray-Curtis) method, identified eight distinct vegetation clusters. Each cluster is characterized by one or more dominant species, distinguished by their highest percentage of occurrence (f) within their respective group. Apart from soil reaction (pH) and diversity indices (species richness and Shannon's index), ANOVA test showed high significant differences in most of the measured environmental variables among the obtained cluster groups (A-H). Canonical Correspondence Analysis (CCA) showed direct correlations between the 7 examined environmental variables and plant species composition in Gebel Katrina. The eight cluster groups were separated along axes 1 and 2 of the diagram. The species-environment correlations were high for the three axes explaining 63.0% of the cumulative variance. The stands of groups (E) and (G) were correlated with coarse sand, stands of group (B) were highly correlated with electric conductivity (EC), and stands of group (F) were correlated with elevation. The endemic flora of Gebel Katrina faces multiple anthropogenic and environmental threats. Overgrazing by livestock, excessive harvesting of plants for fuelwood and traditional medicinal uses, and habitat degradation due to land-use changes have led to significant depletion of vegetation cover and biodiversity loss.