Relations of salinity and soil physico-chemical and hydraulic properties in the Salar del Huasco, Chile

High-Andean wetlands in northern Chile are fragile arid ecosystems that sustain biodiversity, water resources, and cultural heritage. These systems are increasingly threatened by climate change, water scarcity, and mining activities. Despite their ecological relevance, soil properties and their spatial variability in these environments remain poorly characterized. This study investigates the relationship between soil salinity and physical, chemical, and hydraulic properties in the Salar del Huasco salt flat. A combined field and laboratory approach was employed. In-situ measurements were conducted during the dry season and included soil moisture, soil temperature, electrical conductivity, and saturated hydraulic conductivity at a depth of 5 cm. Laboratory analyses compromised pH, organic matter content, cation exchange capacity, soluble cations, and aggregate stability. Field results showed that, in general, soil water content and electrical conductivity were higher in areas closer to water bodies, while soil temperature was lower. In the eastern and western zones, located very close to water bodies, soil water content reached 0.17 and 0.23 m³ m⁻³, electrical conductivity values were 1,435.05 and 1,429.42 µS cm⁻¹, and soil temperatures were 16.72 and 15.86 °C, respectively. In contrast, the northern zone exhibited lower soil water content (0.14 m³ m⁻³) and electrical conductivity (444 µS cm⁻¹). Regarding hydraulic properties, the northern zone showed the highest saturated hydraulic conductivity (0.0043 cm s⁻¹), whereas the southern zone exhibited the lowest value (0.0002 cm s⁻¹). Laboratory results indicated predominantly saline soils, characterized by a mean pH of 9.73 (± 0.59) and an average electrical conductivity of 1,167.84 (± 1,288.72) µS cm-1. Among soluble cations, sodium was the dominant species, exhibiting the highest mean concentration (330.17 ± 208.27 meq L⁻¹), followed by potassium (67.65 ± 75.30 meq L⁻¹). In contrast, calcium and magnesium showed comparatively lower mean concentrations of 19.72 ± 15.15 meq L⁻¹ and 11.15 ± 13.44 meq L⁻¹, respectively. Regarding anions, chloride and sulfate were the most abundant, with mean concentrations of 203.51 ± 169.18 meq L⁻¹ and 214.46 ± 155.65 meq L⁻¹, respectively, whereas bicarbonate concentrations were markedly lower (9.23 ± 6.15 meq L⁻¹). Aggregate stability ranged from low to moderate, with an average value of 50 ± 17 %. Marked spatial differences were observed across the salt flat. The northern zone exhibits higher aggregate stability (72%), sand content (71%). In contrast, the southern zone showed higher electrical conductivity (10,486 µS cm-1), silt content (49%), and higher concentrations of soluble calcium (37 meq/L), magnesium (35.42 meq/L), sodium (425.67 meq/L), bicarbonates (11.2 meq/L), and chlorides (356.57 meq/L). The western zone presented the highest pH (10.06), while the eastern zone displayed intermediate values for most variables. These results revealed pronounced spatial heterogeneity in soil properties within the Salar del Huasco salt flat, suggesting differentiated hydro-saline dynamics at the sub-basin scale. Accounting for this variability is essential to support conservation strategies and the sustainable management of high-Andean wetlands under increasing environmental pressure.