Allocca, Carolina (2023) Impacts of climatic seasonality and land use on the ecosystem functions in a Mediterranean agro-forest environment. [Tesi di dottorato]

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Abstract

Mediterranean agroecosystems are experiencing rapid environmental changes due to natural and anthropogenic perturbations. According to the IPCC, the regions of the Mediterranean area are particularly vulnerable to global warming, and their vulnerability might increase to extreme events, i.e., more floods in winter and more droughts, fires, and water shortages in the future. The concepts of ecosystem vulnerability and resilience indicators have been recently used in environmental studies to describe an ecosystem's ability, in general, not only to cope with natural extreme events or anthropogenic disturbances but also to recover its functions at a greater or lesser rate. In this study, we identified two ecosystem vulnerability and resilience indicators at the regional scale. In this regard, we used an advanced geostatistical tool to map soil physical and hydraulic properties. Seven primary soil properties were estimated over 75-m ×75-m blocks by jointly analyzing more than 3,000 point-based soil measurements with gridded terrain attributes using multi-collocated block cokriging. Two compound soil indicators were then assessed from the maps of these soil properties: 1) the soil organic carbon stock (SOCS) in the entire region of Campania, which represents a resilience indicator, and 2) the groundwater recharge transit time in the Sele alluvial plain where information about the mean annual depth to groundwater is available. The recharge transit time represents an ecosystem vulnerability indicator. In the second part of this doctoral thesis, we carried out an intensive field campaign with a transdisciplinary approach to better describe and understand the dynamics of hydrological processes across different spatial scales in two experimental plots (MFC2 and GOR1) located in the Upper Alento River catchment (southern Italy). Sporadic (fortnightly to monthly frequency) measurements of stable isotopes (δ2H and δ18O) were sampled in water from the shallow aquifer (at MFC2 only), streamflow, and bulk precipitation. Water samples were extracted from soils and plant twigs using the CIRCE laboratory's cost-effective cryogenic vacuum distillation equipment (University of Caserta). The stable isotopes were used in Hydrus-1D to simulate isotope transport in the soil-plant-atmosphere continuum. In this regard, we exploited stable isotope measurements taken from a potted olive tree in a glasshouse and validated model simulations. We estimated the root water uptake transit time, which will be used at the plot scale in a follow-up study.

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