Principal Component Analysis of Environmental Factors Influencing Tribulus terrestris L. Distribution in Ninh Thuan Province, Vietnam

Abstract

This study investigated the ecological characteristics of Tribulus terrestris L., an endangered herbaceous perennial, in Ninh Thuan Province, Vietnam, to inform conservation efforts. Plant and soil samples were collected from Vinh Hai, Thanh Hai and Do Vinh in Ninh Thuan Province. Soil physicochemical properties were analyzed, and bioclimatic. The results showed that Ninh Thuan experiences a harsh tropical monsoon climate with a prolonged dry season and high temperatures; T. terrestris's growth cycle adapts to this seasonality. Soils were predominantly sandy (73.93-89% sand), with neutral to strongly alkaline pH (7.45-8.77) and generally low nutrient levels. PCA revealed site-specific environmental drivers. For instance, Vinh Hai showed positive correlations with silt and K₂O and negative with clay and organic matter. Thanh Hai had strong positive correlations with clay and K₂O, and negative with pH and sand. Do Vinh exhibited high positive loadings for pH, EC, and available-N, but negative for P₂O₅ and K₂O. Overall, EC and available-N were highly influential positive drivers, while pH and silt were limiting factors. These findings highlight T. terrestris's adaptability to arid, nutrient-poor, sandy environments and are crucial for conservation strategies.