Spatio-Temporal Soil Quality Dynamics of Ashtamudi: A Tropical Ramsar Wetland, India

Abstract

This study presents a spatio-temporal assessment of soil nutrient dynamics across five representative ecosites of Ashtamudi Lake, a tropical Ramsar-designated estuarine wetland on the southwest coast of India. Seasonal soil sampling was conducted during pre-monsoon, monsoon, and post-monsoon periods (2023–2024) at Neendakara, Puthenthuruthu, Asramam, Kidapram, and Cherikadavu. Key soil physicochemical parameters, including pH, electrical conductivity, organic carbon, and available nitrogen, phosphorus, and potassium, were analysed using standard methods. Statistical evaluation involved descriptive analysis, two-way ANOVA, Tukey HSD post-hoc tests, Pearson correlation, Principal Component Analysis (PCA), and development of a Soil Quality Index (SQI). Results revealed significant spatial and temporal variation in all soil parameters, with strong effects of season, site, and their interaction. Post-monsoon periods showed enhanced organic carbon and improved soil quality, while monsoon conditions were characterized by episodic nutrient enrichment, particularly phosphorus. PCA identified organic carbon, potassium, pH, and electrical conductivity as dominant drivers of soil quality variability, with the first two components explaining approximately 59% of the total variance. SQI values ranged from moderate to good (0.52–0.74), with consistently higher scores during the post-monsoon season. These findings provide a scientifically robust baseline for Ramsar site monitoring, nutrient management, and conservation planning, supporting sustainable ecosystem management of tropical estuarine wetlands.