Seasonal and interannual dynamics of non-rainfall water inputs in a coastal mediterranean dune ecosystem

Non-rainfall water inputs (NRWI)—including dew, fog deposition, frost, and water-vapour adsorption (WVA)—can provide ecologically relevant moisture in water-limited environments, yet their long-term magnitude and partitioning remain poorly constrained. We present a three-year (2021–2024) assessment of NRWI in a Mediterranean coastal dune ecosystem in Doñana National Park (SW Spain), based on two large, high-precision weighing lysimeters under bare-soil and shrub-covered conditions. Hourly lysimeter mass changes during rain-free periods were combined with meteorological data to identify and classify NRWI components. Water-vapour adsorption dominated NRWI across all seasons and years, accounting for most events and cumulative inputs, while dew produced larger per-event gains but occurred less frequently. Fog deposition was negligible under conservative detection criteria. During the summer months, bare soil consistently accumulated more NRWI than shrub-covered surfaces, reflecting stronger nocturnal cooling and greater coupling to near-surface humidity. Dew showed pronounced interannual variability and was strongly reduced during the anomalously warm and dry hydrological year 2022, whereas WVA proved comparatively climate-resilient.