Abstract

The Yungay Oasis is a unique area within the hyper-arid Atacama Desert where native plants still thrive. This study aimed to evaluate how Suaeda foliosa and Distichlis spicata influence soil physicochemical and mineralogical properties and potentially induce the formation of "fertile islands". Soil samples were collected along horizontal direction extending from 0 to 50 cm away from the plants at 10 cm intervals, and along vertical directions between 0 and 25 cm depth at 5 cm intervals. Unvegetated soils were also sampled for comparison. The results show that both plant species influenced soil physicochemical parameters by reducing soil alkalinity (from 7.8-8.5 to 6.9-7.2 and 6.6-7.6 in S. foliosa and D. spicata, respectively) and increasing phosphorus and different carbon fractions, primarily in S. foliosa soils, compared with unvegetated soils. In contrast to previous fertile island studies, nitrogen contents showed lower values, especially in S. foliosa soils, suggesting processes related to N losses driven by vegetation presence. These results were accompanied by mineral formation inside and outside D. spicata roots observed by SEM analysis, suggesting changes in physicochemical conditions driven by the roots in the soil, together with the formation of calcium carbonates such as vaterite. Additionally, weathering indices, including the Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW), and Vogt's Residual Index (V), indicated an increase in chemical weathering in soils under D. spicata. These findings indicate that S. foliosa and D. spicata potentially influence soil development, fostering a fertile island-like effect that enhances soil nutrient content and structure within the Yungay Oasis, making these species vital to ecosystem resilience in hyper-arid environments.