Variation of Plant Species Diversity Along an Altitudinal Gradient in Subtropical Pine Forest, Swat, Pakistan

This study investigates plant species diversity patterns in Chir pine (Pinus roxburghii) forest along an altitudinal gradient in the Karakar Valley, Swat, Pakistan, covering an area of 97,339 hectares around Karakar village at 1,336 meters above sea level.

Field studies were conducted across various high-altitude regions to assess plant species diversity, composition, and richness along slopes and altitudinal gradients within four forest management units (compartments). Data were collected systematically from 39 plots using a systematic sampling technique along transects: 30×30m plots for tree species, 5×5m plots for shrubs, and 1×1m plots for herbs.

Results indicate a significant decline in tree species diversity with increasing altitude, especially in Compartment 36, compared to Compartment 37, which shows an increase in species diversity with altitude. Compartment 48 exhibits a less pronounced increase in diversity with elevation. Shrub species density per hectare consistently decreases across all compartments, indicating a decline in shrub diversity with elevation. In contrast, herbaceous plant species diversity increases with altitude in all compartments, except for a notable decrease at higher elevations in Compartment 48.

Tree species diversity, measured by the Simpson index, shows an overall decline, while the Shannon index indicates an increase. The Margalef index highlights general trends in tree species diversity. Shrub species diversity trends upward according to the Simpson index but downward according to the Shannon and Margalef indices. Herbaceous species diversity increases in all regions, corroborated by all three diversity indices.

This study underscores the importance of conserving Chir pine forests. The findings provide critical insights for sustainable land use planning and biodiversity conservation in the Karakar Valley and similar ecosystems. The study advocates for the protection of natural habitats to preserve native species diversity and emphasizes active community participation in conservation efforts.