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Subsurface flow at the hillslope scale is a critical process responsible for water redistribution and transport of nutrients to the stream. Despite its hydrological importance, understanding the mechanisms governing subsurface flow generation is still challenging. We investigated the case of a small forested catchment located in the Apennine mountains, Tuscany, central Italy, which experiences shallow lateral downslope water redistribution resulting in substantial differences in vadose zone water supply along the hillslope. We developed an integrated experimental and modelling approach in order to shed some light on the role of the subsurface structure on the generation of hillslope-scale subsurface flow in the study catchment. We used a combination of methods sensitive to different soil properties. Ground Penetrating Radar (GPR) surveys show a complex response reflecting the interplay of different factors such as the presence of rocks, banks and counterslope in the near-surface and thus highlighting the very heterogeneous soil that may control water flow patterns. Several Electromagnetic (EM) mappings were conducted and show top-down hillslope variations of soil electrical conductivity revealing that trees located at the footslope and that experience longer vegetative periods might benefit from larger soil moisture content compared to the smaller trees located on the hillslope top. Similar observations are made from the two parallel top-bottom hillslope Electrical Resistivity Tomography (ERT) transects. The geophysical results will be integrated into hydrogeological simulations using the CATHY model for different scenarios (e.g., initial soil moisture, preferential flow paths, drainable porosity, soil properties, bedrock topography or stratification of soils) to explore the main drivers for subsurface preferential flow.

*Corresponding author, email: diego.todini@iusspavia.it Stable isotopes are tracers used for the investigation of water flow paths, the quantification of the relative contribution of water sources to stream runoff or root water uptake, as well as to determine the spatial and temporal origin of water exploited by plants for transpiration. Previous studies have shown that uncertainties associated to samplings, soil and plant water extraction methods and the spatial variability in the isotopic composition of the water sources in a catchment can hamper the understanding of water cycling and the interactions between soil and plants.In this work, we used isotopic data collected during four growing seasons in a small forested catchment in the Italian pre-Alps to i) investigate the spatial and temporal variability of the isotopic composition of the sampled water sources, ii) determine the seasonal origin of the water sources, and iii) quantify the contribution of soil water to the root water uptake of beech and chestnut trees. The ecohydrological monitoring took place in the 2.4-ha Ressi catchment. Elevations are comprised between 598 and 721 m a.s.l., and the climate is temperate humid. The catchment is covered by a deciduous forest, with beech, chestnut, hazel and maple as the main tree species.Water samples for isotopic analysis were taken monthly from bulk precipitation, approximately bi-weekly from stream water, shallow groundwater and soil water by two suction lysimeter cups in the riparian zone. Plant water and bulk soil water samples were extracted by cryogenic vacuum distillation bi-weekly during summer. All water samples were analysed by laser spectroscopy, except plant water that was analysed by mass spectrometry. Results show that stream water, groundwater and soil water extracted by suction lysimeters were isotopically similar to precipitation, and on average they had an autumn or spring origin. Bulk soil water obtained by cryogenic vacuum distillation showed an evaporation signature, particularly on the hillslope sites where soil moisture was lower. At greater depths, bulk soil water extracted by cryogenic vacuum distillation was slightly less evaporated and less enriched in heavy isotopes compared to soil water extracted from shallow layers. Plant water was more similar to soil water extracted by cryogenic vacuum distillation, and mainly had a summer origin. Riparian trees tended to take up more water from shallow soil layers, whereas hillslope trees had a slightly larger preference for deep bulk soil water, particularly during the driest months.Our results suggest that, in the study area, trees likely use more bulk soil water than the mobile soil water, groundwater and stream water, and the preference for more shallow or deep soil water is likely due to the different rooting depth of the vegetation in the hillslope and the riparian zone. Keywords: stable isotopes; soil water; plant water; forested catchment; cryogenic vacuum distillation.

Conceptual models of catchment hydrological functioning are crucial to understand and predict runoff and the tracer responses during rainfall events, and thus for sound water resources management and pollution mitigation measures. In this study, we use hydrometric and tracer data (stable isotopes, major ions and electrical conductivity (EC)) collected in the Ressi catchment, a 2-ha watershed in the Italian pre-Alps, to test our existing conceptual model of runoff generation mechanisms. This model was based on previous hydrometric measurements and isotope data for selected events and highlights the importance of precipitation and antecedent conditions for hillslope-riparian zone-stream connectivity. More specifically, we determined if the temporal variability in the concentration-discharge relations can be explained by event characteristics, i.e., rainfall event size, intensity, and antecedent moisture conditions.The Ressi catchment is characterized by high seasonality in runoff response, due to the seasonality in rainfall (high in fall) and evapotranspiration (high in summer). Discharge and rainfall have been measured continuously since August 2012. Stream water, precipitation, shallow groundwater and soil water samples were collected for tracer analyses during 20 rainfall-runoff events between September 2015 and August 2018. All samples were analyzed for EC, isotopic composition (2H and 18O) and major ion concentrations. To investigate the possible controls on the concentration-discharge relations, we determined the main event characteristics (e.g., total event rainfall, rainfall intensity, antecedent soil moisture and depth to water table, runoff coefficient) for each event.Based on previous applications of isotope- and EC-based hydrograph separation in the Ressi catchment, we expected different dynamics of the major ions in stream water, depending on the magnitude of the rainfall-runoff events. For all major ions, we hypothesized a dilution effect, and a more marked response for large, long duration events with wet antecedent conditions. The temporal dynamics of calcium, magnesium, sodium and sulfate concentrations confirmed our hypotheses. On the contrary, nitrate, potassium and chloride concentrations sometimes increased at the onset of the event, before a later dilution. These temporal dynamics led to complex hysteretic relations with discharge that could not be explained by the event characteristics. We attribute the rapid increase in the concentrations of these solutes to a quick flushing from the dry parts of the stream channel and the near surface-soil layers of the riparian zone at the onset of the event. The revised conceptual model for the geochemical response of this catchment should, therefore, include a rapid flow pathway that leads to the mobilization of nitrate, chloride and potassium ions, and describe the rapid establishment of hydrological connectivity along the streambed and the near-channel zones. Keywords: concentration-discharge relation; major ions; electrical conductivity; stable isotopes; hysteresis; forested catchment.

Understanding hydrological flow pathways and spatio-temporal origin of surface and subsurface water in catchments with highly fractured geology is particularly challenging. In this work, we relied on the integration of hydrometric measurements with stable oxygen and hydrogen isotope data in two adjacent catchments in the Sibillini Mountains National Park, Central Italy, to better understand the drivers of the catchment hydrological response and the spatio-temporal origin of stream and spring waters. The Ussita catchment is 44 km2 and its highest elevation is 2204 m a.s.l. The Nera catchment is 110 km2 and its highest peak is 2233 m a.s.l. The two rivers merge at the Visso Village, at 615 m a.s.l.The area is characterised by heavily fissured and fractured calcareous rocks that foster the occurrence of several springs, some of them of karst origin. Both catchments host a dense hydrometerological network. The experimental apparatus is completed with one piezometer, soil moisture probes at five locations, lysimeters at two depths and four throughfall plots under beeches and oaks. Monthly samples for isotopic analysis are being collected since fall 2020 from precipitation at three different elevations and four locations, the streams at different sections, and four springs in the Nera catchment only.Preliminary results show a distinct hydrological behaviour in the annual streamflow regimes: the Ussita stream slightly reacts only to the largest storms and during intense snowmelt periods, whereas the Nera stream has a very damped response during all the year, revealing a clear buffer effect of the large subsurface reservoir, facilitated by the highly fractured nature of the geological setting. As expected, there is an elevation and seasonal effect in the isotopic composition of precipitation, although the seasonal effect is partly masked by the exceptionally high temperatures occurred in fall 2021. However, the time series of isotope data in stream water show a damped signal and very low seasonal variability in both streams, matching the observed low variability of streamflow. Only the Ussita catchment shows some more enriched outliers likely reflecting runoff response during large storm events. Interestingly, stream and spring samples from both catchments lie along but also above and below the Local Meteoric Water Line, suggesting that the sampled spring and stream water was either originated i) from precipitation fell, infiltrated, and stored well before the collection of the precipitation samples, and released; ii) and/or from areas outside the topographic catchments, and therefore not adequately characterized by the isotopic signal of sampled precipitation. The isotopic composition of the streams and springs is statistically the same, revealing that spring groundwater is the main component of stream runoff. Moreover, the isotope signature of both springs and streams is much closer to that of winter precipitation rather than summer precipitation indicating a major role of winter precipitation in recharging the catchments, consistently with the precipitation seasonal regime. On-going work is assessing the spatial difference in the isotopic composition and quantifying the temporal origin of stream and spring water of the two catchments.

Forests and trees are integral part to the global water cycle and therefore vital for water security. Forest and mountain ecosystems serve as source areas for more than 75% renewable water supply, delivering water to over half the world’s population.Throughfall generally represents about 70% of bulk precipitation, with a much smaller portion, less than 5%, delivered to the forest floor along tree trunks (i.e., stemflow), and the remainder (~25%) intercepted by the forest canopy and evaporated back to the atmosphere.The partitioning of water into these three pathways is largely controlled by seasonality, precipitation characteristics, meteorological conditions in addition to physiological and morphological traits related to forest composition.This study aims to determine the spatial and seasonal variability of throughfall in oak and beech trees growing on two hillslopes of contrasting aspect in the Ussita stream basin (44 km2), Apennine Mountains, central Italy.Throughfall was measured during 30 sampling periods between July 2022 and December 2022 at four locations by means of gutters connected to tipping buckets. characterized by different land cover, e.g., beech trees and oak trees. Specifically, two monitoring plots are located on a hillslope facing south and the monitoring two stations are located on a hillslope facing north. Moreover, two meteorological stations provide open-area precipitation measurements.The measurements show that the leafed canopy phase reduced the amount of throughfall in all four experimental sites. In particular, beech trees exhibited the largest inter seasonal differences in throughfall partitioning. This is mainly related to the rapid defoliation characterizing the beeches’ sites starting from September.The volumetric throughfall was higher during medium and severe rainfall events, while during low rainfall the forest canopy was found intercepting most of the precipitation. On the contrary, during severe events, the forest canopy storage capacity was saturated and most of the rainfall occurring after the saturation was converted into throughfall.The measurements carried out during medium rainfall events indicate that the differences between canopy structure in oak and beech trees, such as the number of canopy layers and branches orientation, can strongly affect the rainfall partitioning. Oak trees, with high number of canopy layers, low seasonal defoliation and roughness of the bark, have higher canopy storage values than beech trees and are able to generate less throughfall.Additional data to be collected during the next months will allow us to extend the results achieved in the first phase of analysis.

The Mediterranean region is considered a hotspot for climate change as it is expected to face more severe impacts compared to other regions of the world. To better understand these impacts and plan more effective adaptation strategies, integrated assessments should consider not only biophysical aspects, but also social, political, and economic ones. Plenty of models are available to simulate these various aspects, but certainly, the more models are included, the higher the complexity, which severely affects the reproducibility of the studies. Even when considering only biophysical aspects, related for example to water and food security, individual crop and/or hydrological models have intrinsic limitations. Integrated, distributed, agro-hydrological models such as the Soil and Water Assessment Tool (SWAT) might be the solution to overcome some of these drawbacks, including the point-scale nature of crop-growth models.We applied the SWAT+ model in a medium-sized agricultural watershed in Central Italy, the Ombrone watershed, in order to comprehensively assess climate change impacts on crop production and water management and evaluate autonomous agronomic adaptation strategies. By forcing SWAT+ with five bias-corrected EURO-CORDEX climate models, we assessed future precipitation and temperature in the study area. Moreover, we simulated the fluxes of different water balance components and evaluated how they were affected by the increasing CO2 concentration. Then, we simulated future crop yield and water footprint of three representative crops - durum wheat, sunflower and irrigated maize - and evaluated the adaptive capacity of the agricultural systems by simulating simple adaptation strategies such as shifting sowing dates and applying supplemental irrigation. Finally, we estimated the effects of these adaptation strategies on water balance components.While the temperature was predicted to increase, future precipitation showed much more uncertainty. Furthermore, considering the CO2 fertilization effect enhanced the uncertainty about future aridity conditions, with variables such as potential evapotranspiration that varied up to 50% when considering constant or increasing CO2 concentration. Crop yield was negatively affected mainly by the reduction of crop cycle length caused by increased temperatures, but with adaptation strategies it was possible to reduce losses or even obtain higher production. Finally, management changes such as the inclusion of cover crops in the crop rotation have a significant impact on some water balance components that cannot be neglected. The results of this study show the increasing need to adapt to climate change impacts in the Mediterranean cultivated catchments.

This study presents a methodology to assess the spatiotemporal dynamics of water movement at the hillslope scale using geophysical techniques in order to identify preferential flow paths, estimate hydraulic conductivity, and ultimately understand runoff generation processes and predict streamflow response in small catchments. The study area is a 0.3 km2 forested headwater catchment in the Tuscan Apennines, central Italy. We used ground penetrating radar (GPR) and time-lapse electrical resistivity profiles (ERT) to respectively infer the soil bedrock depth and measure the movement of water through the subsurface and track its transit time along the hillslope. We applied these techniques during repeated infiltration experiments conducted over a 1m2 plot where more than 1m3 of water was applied in approximately 24 hours. We constructed a hydrological model simulating the observed infiltration events using multiple soil layers that corresponded with variations in bedrock depth, as revealed by the GPR data. The next step involves calibrating the hydrological parameters through a hydrogeophysical inversion framework, where the simulated resistivities will be compared with the measured ones. The model will then be applied over an extended period under natural atmospheric demands conditions, to the prediction of groundwater residence, and the conditions under which plants can access it.

A holistic understanding of ecohydrological processes that regulate the variability of tree water use, water flow pathways through the soil and to groundwater and the stream, and the transit time of water at the catchment scale is still challenging. In this work, we rely on an integrated dataset of isotope tracers and hydrometric data to show new evidence on the main ecohydrological processes and their controls that link runoff origin, sources of tree water uptake, and water transit time in a small mountain, forested catchment in central Italy.The Re della Pietra experimental catchment is located in the Tuscan Apennines. The catchment is 2 km2 in size and ranges in elevations between 650 and 1280 m a.s.l.. Forests cover more than 95% of the area, and the main tree species are beech and oak trees, with a much smaller proportion of conifers. Mean annual precipitation is around 950 mm. We collected water samples from April 2019 to January 2023 from precipitation, throughfall, soil, groundwater, springs, stream at different sections, and xylem of beech trees, and determined their isotopic composition. Weather data, streamflow, soil moisture, groundwater level, and throughfall were monitored in a 0.3 km2 headwater sub-catchment. Stream stage and electrical conductivity as additional tracer were measured in three stream sections from the headwater sub-catchment down to the Re della Pietra outlet. Streamflow, groundwater, spring flow, and soil moisture are characterized by a marked seasonality, reflecting the strong seasonal variability in the meteorological forcing, typical of the Mediterranean climate.Based on field observations and preliminary data analysis, we aim to test the following hypotheses:i) Trees growing along a steep hillslope in the headwater sub-catchment use different water sources (soil water vs. shallow groundwater) as a function of their topographic position. ii) Hillslope soil water is an important contributor to streamflow only during wet conditions (i.e., in winter, late fall, and early spring). iii) Spring water flows through shallow pathways and is a negligible contributor to streamflow, especially during dry conditions. iv) Water transit time increases as a function of increasing catchment size (i.e., increasing drainage area). The results will contribute to the conceptualization of the interrelated ecohydrological processes driving water fluxes in Mediterranean forested catchments.

Precision agriculture is a modern approach based on farm and irrigation management to improve the efficiency in the use of water resources. Precision agriculture, therefore, maximizes crop productivity and yield through technologies that identify, analyze, and monitor variability within a field and optimize profitability, sustainability, and land protection. This study proposes a combination of approaches to monitor a suite of environmental variables with the goal of improving agricultural management. We selected the experimental vineyard of Grignanello (Tuscany, Italy), located on a mild slope at 350 m.a.s.l in the famous Chianti wine region, where extensive ecohydrological data are available. In combination with this set of ground-based observations, the Environmental Policy Integrated Climate Model (EPIC) is adopted to model key variables for crop production, including soil temperature and soil water content. Using the EPIC model, we generate three sets of simulations based on three different parameterizations (i.e., original cosine, enhanced cosine, and pseudo heat transfer). By comparing model output against ground-based measurements and UAV-based soil temperature, we assess what model set-up is more accurate and for which environmental variable of interest. Furthermore, a new set of soil temperature and soil moisture estimates is obtained by taking the mean of the three EPIC simulations. Thus, we assess the possibility to improve the performance of the single models, as shown in previous studies across the Central Valley in California. Outcomes from this work will provide a solid basis towards developing a decision guidance system for precision agriculture management.

Spatio-temporal variability of throughfall (TF) in forested catchments depends on climatic forcing, forest stand parameters, and rainfall characteristics. Identifying and quantifying these controls is fundamental for a correct analysis and modelling of interception and catchment hydrological response. Despite many studies carried out at the stand and hillslope scale focused on the analysis of controls on TF variability, very little is known about the role of hillslope topography and the associated tree population characteristics in shaping throughfall spatio-temporal variability. In addition to ground-based measurements, satellite and unmanned aerial vehicle (UAV)-data can be explored to obtain a more robust assessment of the main drivers of TF variability. Therefore, this work aimed at i) identifying the dominant factors on throughfall variability in a European beech stand along a steep hillslope; and ii) quantifying forest interception at the hillslope scale and upscaling it at the small catchment scale using ground-level measurements and UAV-derived and satellite observations. The experimental activities were carried out in the upper part of the Re della Pietra catchment, Tuscany Apennines, Central Italy. The hillslope is roughly 110 m long and 60 m wide, has a mean slope of 30°, and is dominantly covered by European beech trees. The TF experimental plot consists of 126 throughfall collectors divided in two square grids of 144 m2 with 49 collectors at the bottom and the top of the hillslope, and a transect of 28 collectors from the bottom to the top grid. TF was manually measured from the collectors approximately monthly and compared with gross precipitation. Moreover, five automatic gauges were installed along the hillslope to increase the temporal resolution. Topographic surveys were conducted to measure the main physiological characteristics (diameter, height and age) of the trees in the TF plot. Leaf Area Index (LAI) was estimated using a ceptometer above each sampler in four dates in the dormant and in the growing season. The 40 manual measurements revealed a large spatial and temporal variability of the TF/precipitation ratio (mean 68%, standard deviation 37%). In the growing period, the TF/precipitation ratio showed higher spatial variability compared to the dormant season (66±29% and 85±31%, respectively), suggesting that the crown expansion can be an important control on TF variability. Moreover, TF was consistently lower in the bottom plot, characterized by larger tree size compared to the top grid indicating a control by trees size. Event-scale data from the gutter gauges show a rainfall intensity control on TF but showed no correlation between TF and hillslope position. To corroborate the preliminary observations on crown and tree size, in early March 2023 a UAV survey will be conducted to determine the crown architecture and lateral expansion, and relate this parameters to the observed TF. Furthermore, LAI ground measurements will be compared with LAI data derived from Sentinel-2 data to establish a relation between ground measurements and satellite observations. This relationship will be then use to upscale LAI and its possible associate control on TF variability from the hillslope to the small (0.3 km2) catchment scale.

Information and Communication Technologies (ICT) play a key role for improving the implementation of sustainable forest management at local, regional, and global level. The ICT potential to easily exploit a wider and more up-to-date set of information on the economic, environmental, and so- cial value of forests is of relevant help for the daily work of technicians, land owners, and companies in boosting the efficiency and effectiveness of forest management. The concept of “Precision Forestry” (PF) was developed from the early 2000s, as a branch of precision farming or precision agriculture. PF includes the use of ICT, remote and proximal sensing technologies, and other devices to coordinate and control several processes on a spatial scale (“Precision”) for monitoring, planning, and managing forest resources (“Forestry”). The aim of this monography is to collect and describe some of the most important PF experiences applied or potential- ly useful for the Italian forestry sector. It may represent a reference guide for the stakeholders, such as forest owners, professional technicians, public administrators, and policy makers. The book includes eleven chapters reviewing the main tech- nological tools available in the Italian context and the most recent advances of ICT in forestry, also focusing on the strengths and weaknesses of their practical implementation. The opportunities and challenges of implementing PF meth- ods, practices and technologies are also discussed. In the first two chapters the precision forestry concept and its historical development are introduced. In the third chap- ter some basic elements of ICT, GIS, Global Navigation Satellite Systems (GNSS), remote/proximal sensing, and related technologies which are essential for a better compre- hension of PF applications are recalled. In chapter 4 recent advances in large scale forest inventories with a focus on mapping and on the spatial estimation of forest variables integrating field surveys and multisource re- motely sensed data are described. Current advancements in the acquisition of field information including Terrestrial La- ser Scanning (TLS), new digital dendrometers, tree-talkers, terrestrial cameras, and APP for portable devices such as smartphones or tablets for dendrometric tree measures and new citizen science applications to support quantitative and qualitative spatial estimation of forest variables over large areas (i.e., forest health, fuel types) are also presented. The chapter ends up with the description of some experiences in the implementation of Forest Information Systems in Italy to provide a simple open-access to such new generation of spatial forest information. In chapter 5 PF tools, instruments, and technologies to sup- port sustainable forest management are illustrated. APPs developed to acquire field plots data to simulate manage- ment operations, the application of photogrammetric tech- nologies from Unmanned Aerial Vehicles and TLS data for monitoring with high-spatial scale forest monitoring and for acquiring indicators at single tree level are presented. A de- tailed description of new user-friendly tools for forest roadplanning, design and construction, as well as forest opera- tion planning is also included. Precision forest tree farming (with particular reference to poplar cultivation), useful to promote and increase the prof- itability and sustainability of forest plantations within the Italian context is described in chapter 6. The innovation and enhancement within the supply chain of wood plantations (from planting to harvesting, including monitoring and identification of stress) by soil proximal sensing techniques, Early Warning Systems, and specific software are highlight- ed. Considering the even higher market demands, promoted by the large-scale planting programs for climate changes mit- igation and the demands for propagation material for en- vironmental recovery, innovative techniques and methods supported by ICT in the forest nursery sector are described in chapter 7. In chapter 8 available technologies related to precision har- vesting are analyzed and described taking into consideration the wood chain efficiency, by means of improved commu- nications between the owner/buyer and operators as well as among machineries used in forest operations, health and safety of forest operators, environmental impacts mitigation and recovery, and operators training. Advanced communi- cation systems and sensors for the exchange of data and information between machines, machine-equipments and/or machine-operators, teleoperations and automation are also described. Chapters 9 and 10 are related to wood products traceabil- ity, timber quality assessment as well as the technologies for the optimization of wood transformation processes. The concepts of wood product traceability and tracing, togeth- er with latest digital technologies for the identification and tracking of the logs (i.e., fingerprinting and RFID), are de- tailly reported. Chapter 11 is finally dedicated to the relationship between the EU policy framework and the digitalization process in both agricultural and forestry sectors. The book summarizes, under a proactive and homogeneous framework, PF methods, tools and technologies in relation with the digital transition of the Italian forestry sectors. The authors hope this book will be useful for improving the implementation of sustainable forest management practic- es at all levels in Italy, providing a comprehensive review useful for policy makers, technicians, forestry owners and students.

In a warming climate, periods with lower than average precipitation will increase in frequency and intensity. During such periods, known as meteorological droughts, the decline in annual runoff may be proportionally larger than the corresponding decline in precipitation. Reasons behind this exacerbation of runoff deficit during dry periods remain largely unknown, and this challenges the predictability of when this exacerbation will occur in the future and how intense it will be. In this work, we tested the hypothesis that runoff deficit exacerbation during droughts is a common feature across climates, driven by evaporation enhancement. We relied on multidecadal records of streamflow and precipitation for more than 200 catchment areas across various European climates, which distinctively show the emergence of similar periods of exacerbated runoff deficit identified in previous studies, i.e. runoff deficit on the order of −20 % to −40 % less than what expected from precipitation deficits. The magnitude of this exacerbation is two to three times larger for basins located in dry regions than for basins in wet regions, and is qualitatively correlated with an increase in annual evaporation during droughts, in the order of +11 % and +33 % over basins characterized by energy-limited and water-limited evaporation regimes, respectively. Thus, enhanced atmospheric and vegetation demand for moisture during dry periods induces a nonlinear precipitation-runoff relationship for low-flow regimes, which results in an unexpectedly large decrease in runoff during periods of already low water availability. Forecasting onset, magnitude, and duration of these drops in runoff have paramount societal and ecological implications, especially in a warming climate, given their supporting role for safeguarding water, food, and energy. The outcome that water basins are prone to this exacerbation of runoff deficit for various climates and evaporation regimes makes further understanding of its patterns of predictability an urgent priority for water-resource planning and management in a warming and drier climate.

Higher temperatures, less reliable precipitation patterns, and increased occurrence of extreme events such as drought will significantly affect the sustainability of agricultural systems in the Mediterranean region. A multidisciplinary, participatory approach and a large amount of data are required to unravel the complexity of climate change and properly evaluate the impacts and the possible adaptation strategies. The European countries of the Mediterranean are interesting case studies for these processes since there are numerous institutions active on these topics, collecting a high amount of information. The study area selected for this research is composed of coastal watersheds of Central and Southern Tuscany, Italy. The main objective was to study the impacts of climate change and possible adaptation strategies, with a particular focus on drought. Therefore, a drought risk assessment was performed as a preliminary study to assess the hazard, exposure, vulnerability, and risk of agricultural systems. Free, ready- and easy-to-use data were obtained from public databases to calculate the forty-two indicators that were selected to estimate the various components of risk. Finally, archetype analysis, an emerging approach for identifying recurrent patterns within cases and supporting a context-specific generalization of insights, was used to link the study's results with possible adaptation strategies. Then, the hydrological model SWAT+ was applied to the Ombrone watershed, the largest and most representative of the study area, to estimate impacts on both hydrology and crop production and to evaluate possible agronomic adaptation strategies. By using a hydrological model that includes a module to simulate plant growth, it is possible to study these dynamics at a larger scale than the field scale; this is convenient, especially when dealing with the water resource which is better studied at the watershed level. Data from various public databases were used to set up the model; after that, it was calibrated with monthly streamflow and crop yield of the most representative crops of the area. The future risks for agricultural systems were then analysed by using a multi-model ensemble of EURO-CORDEX projections. The impacts related to the water resource were estimated by evaluating the components of the water balance, while those on agriculture by considering crop yield. Then, possible adaptation strategies such as conservation agriculture and supplemental irrigation were simulated. The presented research demonstrates the importance of integrating multiple data sources and methodologies for the study of climate risks in agricultural systems.

Tracer-aided studies to understand source water partitioning in tropical ecosystems are limited. Here we report dry season source water partitioning in five unique ecosystems distributed across Costa Rica in altitudinal (Adj. r=0.34, p

Estimation of young water fractions (Fyw), defined as the fraction of water in a stream younger than approximately 2?3 months, provides key information for water resource management in catchments where runoff is dominated by snowmelt. Knowing the average dependence of summer flow on winter precipitation is an essential context for comparing regional drought severity and provides the hydrological template for downstream water users and ecosystems. However, Fyw estimation based on seasonal signals of stable isotopes of oxygen and hydrogen has not yet explicitly addressed how to parsimoniously include the seasonal shift of water input from snow. Using experimental data from three high-elevation, Alpine catchments (one dominated by glacier and two by snow), we propose a framework to explicitly include the delays induced by snow storage into estimates of Fyw. Scrutinizing the key methodological choices when estimating Fyw from isotope data, we find that the methods used to construct precipitation input signals from sparse isotope samples can significantly impact Fyw. Given this sensitivity, our revised procedure estimates a distribution of Fyw values that incorporates a wide range of possible methodological choices and their uncertainties; it furthermore compares the commonly used amplitude ratio approach to a direct convolution approach, which circumvents the assumption that the isotopic signals have a sine curve shape, an assumption that is generally violated in snow-dominated environments. Our new estimates confirm that high-elevation Alpine catchments have low Fyw values, spanning from 8 to 11%. Such low values have previously been interpreted as the impact of seasonal snow storage alone, but our comparison of different Fyw estimation methods suggests that these low Fyw values result from a combination of both snow cover effects and longer storage in the subsurface. In contrast, in the highest elevation, glacier dominated catchment, Fyw is 3?4 times greater compared to the other two catchments, due to the lower storage and faster drainage processes. A future challenge, capturing spatio-temporal snowmelt isotope signals during winter baseflow and the snowmelt period, remains to improve constraints on the Fyw estimation technique.

Hydrological processes along mountain hillslopes involve complex interaction between soil storage and surface and subsurface flow, drainage and evapotranspiration. To capture this complexity, time-lapse extensive and intensive measurements are needed, potentially capable of providing spatially dense information in 3D and time frequent data. To this end, hydro-geophysical methods (ground penetration radar, GPR, electromagnetic induction, EMI and electrical resistivity tomography, ERT) based on electrical and electromagnetic laws are widely used as they naturally link to the electrical properties of soil moisture. ERT produces, especially in time lapse mode and using permanent installations, very detailed images of the water dynamics along hillslopes. While ERT requires galvanic contact with the ground, and thus relatively slow operations, EMI can be applied over large areas in a very short time. This method has been used for decades, mainly to produce apparent electrical conductivity (ECa) maps. Only recently, inversion of EMI data as a function of depth has become a viable practice.In this work, we present two cases of hillslope monitoring using non-invasive methods, both performed as part of the WATZON project, funded by the Italian Ministry of University and Research (MIUR). The first case is the Mediterranean catchment of the Alento River, in southern Italy. The monitoring was carried out using 7 different EMI surveys, acquired in multifrequency mode (FDEM) between August 2020 and December 2021. The purpose of this survey was to characterize the structure of the basin’s subsoil within the first few meters, as well as to record the variation of electrical conductivity (EC) associated with seasonal variations. The second case is related to the Apennines catchment of the Re Della Pietra, located at the border between Tuscany and Emilia-Romagna in central Italy. The monitoring was carried out through 6 different EMI surveys, acquired in multifrequency mode (FDEM) between August 2020 and May 2021. The purpose of this survey was to characterize the structure of the basin’s subsoil within the first few meters, as well as to record the variation of electrical conductivity (EC) associated with seasonal variations. Furthermore, ERT measurements were carried out along a fixed line on the ground, according to the direction of the maximum slope. The combination of EMI and ERT proved particularly effective in delineating the hydrologic dynamics of the hillslope.

Recent studies applying stable isotopes of hydrogen and oxygen showed that different methods for extracting water from plant tissues can return different isotopic composition. One of the most used methods to extract plant water is the cryogenic vacuum distillation (CVD), which tends to extract total plant water. Conversely, the Scholander pressure chamber (SPC), which is commonly used by tree physiologists to measure water potential in plant tissues, likely accesses only the mobile plant water (i.e., xylem and inter-cellular water). However, only few studies reported the application of SPC to extract plant water for isotopic analyses, and therefore, an inter-method comparison between SPC and CVD is needed.In this study, we analyzed the variability in the isotopic signature of plant water extracted by SPC and CVD. Furthermore, we considered the potential variability in the isotopic composition of the plant water extracted from various tissues by CVD (i.e., leaves, twig without bark, twig with bark, twig close to the trunk of the tree, and wood core), and from different tree species (i.e., alder, apple, chestnut and beech) located in three different study areas in northern Italy.Results indicate that plant waters extracted by SPC and CVD were significantly different, likely due to the extraction of different plant water domains. The difference in the isotopic composition obtained by the two extraction methods was smaller in the beech samples compared to alder, apple and chestnut samples. The signature of alder, apple and chestnut plant water extracted by SPC was more enriched in heavy isotopes than the samples obtained by CVD (except for the leaf water obtained by CVD, which also had a marked evaporative signature). We conclude that plant water extraction by SPC does not represent an alternative for CVD, as SPC likely extracts mostly the mobile plant water, whereas CVD tends to retrieve all water stored in the sampled tissues. However, studies aiming to quantify the relative contribution of the water sources to transpiration should rely more on the isotopic composition of xylem water transpiring during the sampling day (theoretically sampled by SPC), than the isotopic composition of total plant water (sampled by CVD), which also contains a fraction of water that could be stored in plant tissues for a long time. Keywords: stable isotopes of hydrogen and oxygen; cryogenic vacuum distillation; Scholander pressure chamber; plant water; xylem water.

Understanding water availability and sources for crop transpiration is essential for sustainable management of water resources in agriculture, especially under changing climatic conditions. Identifying the origin of water accessed by crops is particularly critical in typical rain-fed agroecosystems, such as vineyards in Mediterranean regions where viticulture is one of the mainstays of the local economy.As far as we know, no study so far has attempted to analyse root water uptake dynamics on hilly vineyards where the hillslope topography plays a role on water redistribution and availability for grapevine uptake. For this reason, we instrumented two plots within a vineyard in the famous Chianti wine region in Tuscany, Italy. The vineyard is cultivated with 11-year-old grapevines either on 1103 Paulsen or 420A rootstocks, which are typically characterized by a deeper and shallower rooting system, respectively. We aimed to test the hypothesis that i) grapevines located at the hillslope bottom took up water from shallower soil layers compared to grapevines located at the hillslope top due to lateral downslope redistribution of infiltrated rainwater; and that ii) grapevines with rootstock 1103 Paulsen took up water from deeper soil layers compared to the grapevines with rootstock 420A.We monitored precipitation and temperature as well as soil moisture at 30 and 60 cm depth at two hillslope locations (top and bottom, 140 and 115 m asl, respectively) from April to October 2021. We collected samples for isotopic analysis from rainfall, soil at 30 and 60 cm, shoots and leaves from two adjacent grapevines for each rootstock at the two hillslope locations. Additional water samples were taken through the application of sealed plastic bags around some top branches and collection of water that had transpired and condensed on the bag walls. Water from soil samples, leaves and shoots was extracted though cryogenic vacuum distillation. The isotopic composition was determined through laser spectroscopy or, for organically-contaminated samples, mass spectrometry.Preliminary results show that soil moisture was higher at the hillslope bottom than at the top, and higher at 60 than 30 cm depth. The isotopic composition of soil water was statistically different at the two depths with more enriched values in the shallower layer, as expected in Mediterranean climates; however, no statistical difference was observed between soil water at the two hillslope locations. The isotopic composition of plant water between the two locations was statistically different for bag (transpired) water and leaf water (although the latter was highly fractionated), but not for shoot water, allowing us only to partially accept hypothesis i). However, the isotopic composition of bag, leaf, and shoot water was always similar for 1103 Paulsen and 420A grafted plants, suggesting that grapevines with different rootstock took up soil water from the same depth in the study vineyard, and leading us to reject hypothesis ii).These results contribute to better understand water uptake sources in economically-valuable agroecosystems such as vineyards.

The WATSON COST Action (CA19120; https://watson-cost.eu/) started in September 2020. It aims to integrate and synthesize current interdisciplinary scientific knowledge on the use of the stable isotopes of water to understand the mixing and partitioning of water in the Earth’s Critical Zone. The network is organized into working groups that focus on a major scientific challenge: 1) groundwater recharge and soil water mixing processes; 2) vegetation water uptake and transpiration; and 3) catchment-scale residence time and travel times. A fourth working group organizes the network and dissemination activities.WATSON aims at better connecting academia and stakeholders from industry, non-profit organizations, and government agencies. WATSON fosters the exchange of information and expertise among scientists and stakeholders, builds capacity in the use of the latest isotope approaches and translates scientific cutting-edge knowledge into tangible outputs and recommendations on how to use stable water isotopes to effectively address water management needs. Our poster describes the WATSON network, as well as its activities. These include the preparation of an open-access database of water isotope-based studies in the Critical Zone, the development of protocols for water sampling and stable isotope analysis, the organization of virtual and in-person meetings, seminars, training schools, and the exchange of students, researchers, and technicians via short term scientific missions.

Droughts have huge negative impacts on livelihoods and economies throughout the world, and climate change is expected to increase their future frequency and severity. For an effective drought management, drought risk assessment is considered of major importance. However, despite the high number of studies, shared and clear guidelines to perform drought risk assessments are missing, undermining the overall reliability of this procedure. A significant limitation common to most drought risk assessments is the lack of any form of validation. Moreover, checking the robustness of the assessment tools is of paramount importance, but appropriate data are usually not available for external validation; hence, internal validations are in many cases the only option. For this scope, we propose a simple but robust uncertainty analysis, using the methodology presented in the “Handbook on constructing composite indicators” of OECD (2008). An additional deficiency of most drought risk assessments is the missing link between the results and possible adaptation strategies. To address this limitation, we propose to use archetype analysis, which is an emerging approach for identifying recurrent patterns within cases and supporting a context-specific generalization of insights. The innovations introduced were applied to a drought risk assessment performed for the agricultural systems of five coastal watersheds of central and southern Tuscany, Italy. These watersheds are particularly prone to drought impacts because of the high concurrent water demand for domestic and agricultural uses during the summer months. To allow a better discretization, municipalities were selected as units of analysis. A total of 42 indicators were used to represent drought hazard, exposure, and vulnerability. Multiple drought hazard indicators were selected to estimate both past and future drought hazards, using ready-to-use data from public institutions. Overall, the southern part of Tuscany showed to be the most at risk, in particular the Grosseto province. For the robustness evaluation, we (1) excluded individual exposure and vulnerability indicators, (2) included the excluded indicators with the multicollinearity analysis, (3) assigned different weights, and (4) used an alternative aggregation method to calculate the composite risk indicator. Results in terms of average shifts in rankings and new rankings assigned revealed that the most uncertain parts were the selection of exposure indicators and the assignment of weights, but overall, the rankings were confirmed. The archetype analysis yielded as result seven clusters of municipalities; their characteristics were analysed and tailored adaptation strategies were proposed according to their specific drought risk profiles.

Understanding the role of forest on rainfall interception is fundamental for a correct analysis and modelling of runoff generation and catchment hydrological response. Despite many studies were carried out at the stand and hillslope scale, very little is known about the role of hillslope topography and the associated tree population characteristics on throughfall spatio-temporal variability. Therefore, this work aimed at better understanding the dominant factors on throughfall variability and on the temporal persistence of throughfall spatial patterns along a transect on a steep hillslope characterized by trees with different size and density.The experimental activities were carried out in the upper part of the densely-forested Re della Pietra catchment, Tuscany Apennines, Central Italy. The hillslope is roughly 110 m long and 60 m wide, has a mean slope of 30°, and is dominantly covered by beech trees and by sparce individuals of oak trees. A grid of 126 throughfall collectors was installed in July 2020 and divided in three sub-plots: two plots of 144 m2 with 2-m spaced 49 collectors at the bottom and the top of the hillslope, and a transect of 28 1-m spaced collectors from the bottom to the top of the hillslope. A survey was conducted to measure the diameter and basal area of the stand. Throughfall was manually measured from the collectors approximately monthly from June 2020 to November 2021, and compared with gross precipitation measured by a rain gauge placed outside the vegetation cover. Moreover, five automatic gauges connected to 1.5 m-long gutter to increase the collection area were installed in November 2021 along the hillslope to measure throughfall at high temporal resolution.Preliminary results from 25 manual measurements over the experimental grid highlighted a large temporal variability of interception (mean: 17%, standard deviation: ±31%), reflecting the variable seasonal precipitation pattern of Mediterranean areas and the phenological stage of trees (leaves/no leaves). Overall, the spatial variability in throughfall increased with increasing gross precipitation. Particularly, the bottom plot, characterized by lower tree density and larger tree size compared to the top plot, showed a lower spatial variability with respect to the top plot, while the longitudinal transect exhibited an intermediate variability. Analogously, the temporal stability analysis revealed that the most temporally-stable and representative measurement points laid on the transect that, overall, captured the different tree characteristics along the hillslope.Future work will make use of the high-resolution measurements of the five gauges to assess their representativeness compared to the manual grid and to test and validate an interception model at the hillslope scale to be possibly upscaled to the entire catchment.

Vegetation exhibits critical feedback with runoff generation. Trees show distinct water uptake patterns relying on soil water from different depths and groundwater with a mixture of water sources that is commonly very different from runoff in terms of age distribution and isotopic composition. Here we present a multi-method and multi-model approach to study the spatio-temporal patterns of sap flow and age distribution of tree water uptake and streamflow in a headwater catchment (mixed forest, 43 ha). For this, we monitored sap flow spatially distributed at >30 trees over two years, sampled 2H and 18O bi-weekly and spatially distributed in xylem for two years and in streamflow sub-daily for four years. This was supplemented by tritium sampling in streamflow over two years for different flow stages. We used statistical modeling to determine spatio-temporal patterns of transpiration and isotopic composition of xylem water and their drivers. We used a multi-model approach to derive catchment travel times through (i) composite Storage Selection (SAS) functions, (ii) conceptual hydrological modeling, and (iii) coupled land surface-subsurface modeling (ParflowCLM) combined with particle tracking. Statistical data analysis revealed that tree species, tree diameter, and topographic wetness index at the tree location were the main driver of spatial variability of sap flow, while soil water was the main source of xylem water with little groundwater influence. The travel time modeling showed a strong seasonal and event-based variability of travel times and allowed to include information on vegetation behavior with different complexity. Last, our detailed sampling of vegetation offers a blueprint for a sampling strategy of isotopes in xylem water for travel time studies. Our data revealed that approximately 20 sampled trees are sufficient to capture the mean isotopic value of xylem water of a species at our study site, while we needed around 100 samples to detect landscape influence on the xylem isotopes needed for considering spatial patterns in the travel time analysis. Our results underline the feedbacks between vegetation and runoff generation and show their relevance for better simulating catchment travel times.

Understanding how catchment streamflow response varies in time and at different spatial scales is critical to assess runoff production and water availability in mountain areas. Very little work on comparing runoff generation processes in catchments of increasing size has been done in Dolomitic areas. In this research, we adopted a nested catchment (0.14–109 km2) approach to i) assess whether and how streamflow response at the seasonal and the rainfall-runoff event time scale varies with increasing spatial scale, and ii) identify the main factors controlling the temporal variability of streamflow response in three mountain catchments in the Italian Dolomites. We used precipitation and streamflow data from June to September of 13 consecutive years (2005–2017) available for all three catchments, and computed runoff coefficients, stormflow volumes, streamflow peaks and lag times between the rainfall centroid and the streamflow peak for 203 rainfall-runoff events occurred during the study period. Results show that, overall, specific streamflow and runoff coefficients decreased with the increasing spatial scale. However, this pattern was disrupted at the end of spring-beginning of summer due to the relevant snowmelt contribution to streamflow in the intermediate catchment characterized by the largest fraction of high-elevation areas, where deep snowpack accumulated during the winter. The probability distribution of runoff coefficients was very well represented by a Beta-distribution for all three catchments, suggesting that analogous factors controlled the variability of runoff coefficients. This was confirmed by multiple regression analysis that revealed that event rainfall amount, storm duration and 3–12 days antecedent precipitation (assumed as a proxy for antecedent wetness conditions) explained up to 0.81 of the variability of streamflow response, with a minor role of rainfall intensity. Further research is needed to assess whether detailed measurements of hydrological variables collected at the small catchment scale (

In a warming climate, periods with below-than-average precipitation will increase in frequency and intensity. During such periods, known as meteorological droughts, sparse but consistent pieces of evidence show that the decline in annual runoff may be proportionally larger than the corresponding decline in precipitation (e.g., −40 % vs. −20 %). Reasons behind this exacerbation of runoff deficit during dry periods remain largely unknown, which challenges generalization at larger scales (i.e., beyond the single catchment), as well as the predictability of when this exacerbation will occur and how intense it will be. Here, we tested the hypothesis that runoff-deficit exacerbation during droughts is a common feature of droughts across climates and is driven by evapotranspiration enhancement. We support this hypothesis by relying on multidecadal records of streamflow and precipitation for more than 200 catchments across various European climates, which distinctively show the emergence of similar periods of exacerbated runoff deficit identified in previous studies, i.e., runoff deficit on the order of −20 % to −40 % less than what expected from precipitation deficit. The magnitude of this exacerbation is two to three times larger for basins located in dry regions than for basins in wet regions and is qualitatively correlated with an increase in annual evapotranspiration during droughts, on the order of 11 % and 33 % over basins characterized by energy- and water-limited evapotranspiration regimes, respectively. Thus, enhanced atmospheric and vegetation demand for moisture during dry periods induces a nonlinear and potentially hysteretic precipitation-runoff relationship for low-flow regimes, which results in an unexpectedly large decrease in runoff during periods of already low water availability. Forecasting onset, magnitude, and duration of these drops in runoff availability has paramount societal implications, especially in a warming climate, given their supporting role for water, food, and energy security. The outcome that water basins are prone to this exacerbation of runoff deficit for various climates and evapotranspiration regimes, compounded by the lack of specific parametrizations of this process in the majority of hydrological and land-surface models, make further understanding of its patterns of predictability an urgent priority for water-resource planning and management in a warming and drier climate.

Understanding the internal functioning of natural systems often requires interdisciplinary approaches and competences that allow encompassing and disentangling different and strictly intertwined physical and biological processes. Hydrology and ecophysiology are examples of complementary and highly interconnected disciplines that share water as a common analysis element when investigating the functioning of vegetated ecosystems. In this discussion paper, we call for more frequent and active dialogue and collaboration between (field) hydrologists and ecophysiologists to study natural processes at the boundary between the two disciplines. We report some examples of the specific approaches of hydrologists and ecophysiologists to analyse water movement in the soil-vegetation-atmosphere continuum at increasing spatial scales, highlighting how the same mechanisms can be seen from different, but largely complementary, points of view. We argue that these different perspectives can and should be merged in order to overcome possibly fragmented vision of complex processes and provide a more holistic comprehension of ecohydrological mechanisms in forest ecosystems.

Background To determine whether artificial intelligence (AI) processed PET/CT images of reduced by one-third of 18-F-FDG activity compared to the standard injected dose, were non-inferior to native scans and if so to assess the potential impact of commercialization. Materials and methods SubtlePET™ AI was introduced in a PET/CT center in Italy. Eligible patients referred for 18F-FDG PET/CT were prospectively enrolled. Administered 18F-FDG was reduced to two-thirds of standard dose. Patients underwent one low-dose CT and two sequential PET scans; “PET-processed” with reduced dose and standard acquisition time, and “PET-native” with an elapsed time to simulate standard acquisition time and dose. PET-processed images were reconstructed using SubtlePET™. PET-native images were defined as the standard of reference. The datasets were anonymized and independently evaluated in random order by four blinded readers. The evaluation included subjective image quality (IQ) assessment, lesion detectability, and assessment of business benefits. Results From February to April 2020, 61 patients were prospectively enrolled. Subjective IQ was not significantly different between datasets (4.62±0.23, p=0.237) for all scanner models, with “almost perfect” inter-reader agreement. There was no significant difference between datasets in lesions’ detectability, target lesion mean SUVmax value, and liver mean SUVmean value (182.75/181.75 [SD:0.71], 9.8/11.4 [SD:1.13], 2.1/1.9 [SD:0.14] respectively). No false-positive lesions were reported in PET-processed examinations. Agreed SubtlePET™ price per examination was 15-20% of FDG savings. Conclusion This is the first real-world study to demonstrate the non-inferiority of AI processed 18F-FDG PET/CT examinations obtained with 66% standard dose and a methodology to define the AI solution price.