Spatial and temporal patterns of soil salinization in shallow groundwater environments of the Bahia Blanca estuary: Influence of topography and land use

Soil salinization is considered an environmental threat as high salt content hinders plant growth. Soil salinity is usually associated with climate aridity at a regional scale, while topography, subsurface hydrology, and land use combine with climate to produce salinization patterns at landscape scale. In this study, the first such assessment for the study area, we investigated the relationship between climate, groundwater level (GWL) changes, and soil salinity. For comparison, two adjacent vegetation units used as marginal grazing lands were selected: thickets of Allenrolfea patagonica (Ap thicket), located at the base of a scarp, and bushes of Cyclolepis genistoides (Cg bush), located away from the topographic discontinuity. Electrical conductivity (ECrs) maps derived from LANDSAT-8/OLI were used to analyze salinity patterns. The results showed that GWL rose in coincidence with precipitation events and fell during dryer and warmer periods. GWL was always closer to the surface in the Ap thicket, and level changes were more likely to occur there. ECrs showed a seasonal pattern with significantly higher (p < 0.05) values in the Ap thicket during summer. Within the Cg bush, relatively higher ECrs appeared around a permanent water trough. Within this zone, ECrs values during summer were significantly higher (p < 0.05). Coupled evaluation of GWL dynamics and soil salinization patterns showed that GWL changes interact with land use practices to produce local-scale patterns of salinization. Topography played an important role in controlling soil surface properties through its influence on groundwater dynamics and small topographic changes produced largely different conditions for vegetation growth.