Ecohydrological characterization of a terraced hill vineyard in Corno di Rosazzo (Italy)

Climate change is causing more frequent heat waves and droughts in recent summer in the Mediterranean area. This phenomenon is posing risks for viticulture, regarding both the quantity produced and the quality of the wines. Adaptation and mitigation measures to climate change effects include the use of emergency irrigation and soil management practices. In this context, ecohydrological studies about the water dynamics in the soil, as well as the patterns and variability of vines root water uptake (RWU) depth throughout the growing season, can provide valuable insights for achieving more efficient and sustainable water resource use in viticulture. As part of the Interreg Ita-Slo IRRIGAVIT project, during the 2024 growing season, we conducted an ecohydrological characterization of a vineyard cultivated with Vitis vinifera cv. Ribolla Gialla (grafted on Kober 5BB) on a terrace in Corno di Rosazzo (Friuli Venezia-Giulia, Northeast Italy), using stable water isotope composition (δ18O, δ2H, d-excess) to track water fluxes in the soil-plant-atmosphere continuum. The site was chosen due to its soil composition, primarily consisting of flysch residuals (weathered alternations of marls and sandstones). We sampled monthly precipitation from February 2024 to January 2025, as well as individual precipitation from spring to late summer 2024. In the plot located on the highest terrace of the hillslope, we sampled soil and vines sap every two to three weeks, collecting three soil cores and nine sap samples per sampling date. Soil cores were divided into 10 cm segments down to 35 cm of depth and 20 cm segments from that to the maximum reached depth (more than 1 m). Soil water was extracted in the lab using a cryogenic vacuum distillation (CVD) line. Sap samples were extracted using a vacuum pump system in the field from three shoots of plants close to each drilling point. Rainwater and soil water samples were analysed using a CRDS laser spectroscope Picarro L2130-i in liquid mode, while the sap samples were analysed with the same instrument, coupled with a Picarro Induction Module to minimize the organic spectral interference. In addition, soil water content and water potential were measured, and soil mineralogy and particle size were assessed. Soil moisture and plant water potential were monitored in the field. The 2024 growing season was particularly challenging for viticulture in Northeast Italy: frequent rainfall in spring damaged vines’ flowers, the summer was hot and dry, while heavy rainfall occurred during harvest. Visual inspections of soil samples revealed roots reaching up to 1.50 m deep. Isotopic data indicated that vines RWU occurred mainly in the top 20 cm of soil, which retained sufficient moisture even during the hot, dry summer with high vapour pressure deficit (VPD) values. This may have been due to soil management practices, such as using shredded cover crops to create mulch, enriching the topsoil with organic matter and improving water retention.