Integrated monitoring and modeling activities in the Alento critical zone observatory as a lighthouse to support the implementation of the EU Soil Deal Mission in a Mediterranean agroforestry environment.

In arid to dry sub-humid Mediterranean climate regimes, significant pressure is exerted on soil and water resources of agricultural lands, especially during the dry season when the natural water supply is minimal and water demand for domestic use and irrigation is at its peak. Therefore, there is concern about the impacts of longer-than-normal dry spells as well as land-use/land-cover changes on the provision of ecosystem services (ESs). To address these challenges, a Critical Zone Observatory (CZO) was established in the Alento River basin, which is in Campania, an administrative region of southern Italy, and has a drainage area of approximately 411 km2. A hydraulic system of five dams store and supply water in the basin for irrigation, flood control, hydropower generation, and domestic uses. This basin belongs to the Cilento area, which is renowned worldwide for the presence of the Cilento and Vallo di Diano National Park (the largest in Italy), for the seat of the Mediterranean diet and the Velia archeological site, and is part of the UNESCO-IHP HELP (Hydrology for the Environment, Life and Policy) network. Therefore, the Alento CZO is an ideal lighthouse where the ongoing transdisciplinary research activities help provide inspiring solutions, training, and communication to enhance soil health and ecosystem services in representative Mediterranean agroecosystems. Our presentation focuses on integrated monitoring and modeling activities being conducted in two experimental catchments, which have different soil types and land uses. A leitmotif in these activities is the characterization of the hydro-geological responses of these test sites, as well as the entire basin, to the typical seasonality of the Mediterranean climate. Each catchment is equipped similarly with in-situ sensor networks and cosmic-ray neutron sensors for soil moisture monitoring. Thermo-gravimetric and time-domain reflectometry measurements were used to calibrate and validate soil moisture measurements on a seasonal basis. Environmental tracers (stable isotopes of oxygen and hydrogen) were measured fortnightly in water samples collected from rainfall, streams, water tables, xylem, and soil water during a 2-year-long field campaign. Spectral analysis and co-located soil physical, chemical, and hydraulic properties were carried out at 161 positions in a 25-m grid size. Remote sensing products from satellite and Unmanned Aerial Systems were used to estimate vegetation characteristics, soil moisture, and soil properties. The data collected thus far are being implemented in several hydrological models, including Hydrus-1D and HydroGeoSphere, to simulate water flow and solute transport in the critical zone at different spatial scales and elucidate questions about the resilience and vulnerability of current soil and water resources to global changes in these environments.