Species Turnover and Environmental Filtering Structure Plant Communities in Moist Temperate Forests.

Montane moist temperate forests are structured by steep elevational and edaphic gradients that drive plant community turnover over short spatial scales. However, integrated evidence linking community structure, diversity, and species turnover to environmental gradients remains limited for the Hindu Kush-Western Himalayan region. This study aimed to characterize plant community organization, quantify alpha and beta diversity, and evaluate vegetation-environment relationships in the moist temperate forests of northern Pakistan. Vegetation was sampled during 2022-2023 across 50 representative stands selected to capture environmental heterogeneity using nested quadrats, and phytosociological attributes were recorded. Soil samples were analyzed for texture and key physicochemical properties. Plant species were grouped into communities, and alpha diversity, beta diversity, and multivariate ordination were applied to examine compositional patterns. A total of 70 plant species were recorded, with herbs and hemicryptophytes representing the dominant growth and life forms. Five distinct plant communities were identified, each defined by significant indicator species. Ordination separated communities clearly, with the first two axes explaining 72.31% of total compositional variation. Alpha diversity was highest in the BRI community and lowest, with greatest dominance, in the QCL community. Beta diversity was driven primarily by species turnover, including complete replacement between high- and low-elevation communities, whereas nestedness was minimal. Communities differed significantly in altitude and soil texture fractions and also varied in pH, electrical conductivity, organic matter, nitrogen, and phosphorus. Community composition was most strongly associated with clay, sand, and slope, while within-community diversity related mainly to soil texture and nutrient availability. These findings demonstrate that environmental filtering promotes strong species replacement across environmental gradients, underscoring the importance of conserving edaphically and topographically heterogeneous habitats.