Floristic Diversity and Indicator Species Analysis Along Altitudinal Gradients of the Upper Indus Basin, Northern...

Understanding how altitudinal gradients influence floristic diversity and indicator species is essential for unlocking the ecological dynamics of biodiversity-rich regions. We examined the floristic diversity, communities' formation and their respective indicator species across defined altitudinal zones of the Upper Indus Basin region in Indus Kohistan Valley, northern Pakistan. Vegetation was sampled along transects ranging from 1957 to 3380 m using quadrat, with a total of 600 quadrats from 30 different sites surveyed during the summer season (June-August). Most plants belonged to family Asteraceae, Pinaceae, Lamiaceae and Berberidaceae, with chamaephytes as the dominant life forms, followed by geophyte and phanerophytes. Cluster Analysis classified the vegetation into three communities: Taxus-Rumex-Mentha (TRM), Pinus-Indigofera-Leontice (PIL), and Pinus-Phyllanthus-Valeriana (PPV). Species attributes plots identified based on Canonical Correspondence Analysis demonstrated that TRM community is primarily influenced by calcium, pH and salinity. The PIL community is limited by potassium, oxygen reduction potential, sand and silt while the PPV community by sodium, MWHC, soil moisture and carbon content. Tukey showed that the TRM community had the highest mean dominance, the PIL community exhibited the highest Simpson, Shannon and Evenness indices, and the PPV community had the lowest values, indicating that soil properties and microclimatic factors along the altitudinal gradients shape the species composition and association. Detrended correspondence analysis explained a total of 23.89% of the variance, as the first axis illustrated the maximum gradient length (3.07) further strengthening the influence of environmental variables on species distribution and association. The DCA indicated that environmental variables such as salinity, pH, carbon content, soil texture, and calcium substantially influenced species distribution and association, a pattern supported by the Mantel test. It is recommended that reforestation efforts should prioritize the PPV community at high-altitude zone (2390-3380 m) and consider sodium, MWHC, soil moisture and carbon content when selecting suitable indicator species for restoration.