Altitudinal gradient and its correlation with plant diversity in Daral Valley, Swat in Pakistan using multivariate analysis.

Background: Biodiversity is facing direct threats due to climate change and anthropogenic disturbance. Daral Valley, Swat is not an exception and was selected based on its remote location and altitudinal variation, encompassing diverse ecosystems from moist temperate forest to alpine region. Starting at 1400 m a.s.l. (above sea level) through moist temperate region up to the alpine region at 5001 m a.s.l.

Methods: A quadrat sampling method was employed, taking 300 quadrats of varying sizes to record the necessary phytosociological data for herb shrub and trees. Importance value indices (IVI) for vegetation were calculated and subjected to ordination techniques, such as canonical correspondence analysis (CCA).

Results: The flora comprised 381 taxa from 224 genera and 81 families. The most represented families being Asteraceae, Rosaceae, and Lamiaceae with 46, 28, and 22 species, respectively. Therophytes were the dominant life form, followed by hemicryptophytes, and geophytes. Among the leaf spectra classes, microphyll was the dominant leaf form followed by nanophyll and mesophyll, respectively. Using Ward's agglomerative cluster analysis, we identified three floristically and ecologically distinct associations related with different topographic and edaphic variables, viz., alpine zone (Group I, 3582-5001 m), sub alpine zone (Group II, 2900-3580 m) and moist temperate forest (Group III, 1432-2900 m). The calculated values for evenness and species richness were 0.99 (with a variance of 16.0%). The Pearson's correlation coefficient was 0.99, indicating a significant portion of the data aligned with the ordination axes.

Conclusion: Based on the data, it is evident that the altitudinal gradient in Daral Valley, Swat significantly influences plant diversity, with varying biotic and abiotic stresses impacting local flora at different elevations. Lower altitudes experience higher anthropogenic pressures such as deforestation, overgrazing, and collection for medicinal purposes, while higher altitudes faces climate challenges like temperature fluctuations and snowfall. These stressors collectively threaten the sustainability of plant habitats across the gradient. To ensure the preservation of plant diversity, it is crucial to implement targeted conservation measures that address the specific challenges at each altitudinal zone. This will help mitigate anthropogenic interruptions and promote the long-term sustainability of the valley's unique ecosystems.