Abstract

The Khlong-Saeng durian (Durio spp.) of Surat Thani is undergoing a decline, leading to an investigation of environmental factors affecting its longevity. This study examined the relationship between soil properties and the age of native durian trees in Ban Khao Thep Phithak. Using geographic indices, correlation analysis, and preliminary phytochemical screening of peel waste, we identified factors influencing tree lifespan. Durian trees occurred in areas with temperatures of 26–31°C and relative humidity between 58.87% and 87.37%. A strong positive correlation was found between tree age and the dependent variable (r = 0.75, p < 0.05). All age groups were associated with silty soils, with significant variation in texture (p < 0.001, F(10, 22) = 42.96). Soil chemistry also differed significantly with tree age. Key parameters included soil pH (p < 0.001), organic matter (p < 0.001), nitrogen (p < 0.001), potassium (p < 0.001), phosphorus (p < 0.001), calcium (p < 0.001), and sodium (p < 0.001). Phytochemical screening showed antioxidant activity in the peels of trees over 50 years old, suggesting an age-related accumulation of bioactive compounds. Together, these results provide the first evidence linking soil nutrients and phytochemical markers to the longevity of Khlong-Saeng durian. The findings highlight the importance of maintaining optimal soil conditions and conserving high-elevation habitats to safeguard this unique genetic resource. Such knowledge is essential for sustainable cultivation strategies and long-term conservation of native durian in Southern Thailand.