Abstract. Fluvial sediment transport plays a key role in geomorphological and hydrological processes, influencing river morphology, watershed and coastal sediment balances, and the environmental response to climatic and anthropogenic changes. In Italy, the availability of homogeneous and long-term data is strongly limited due to the discontinuity of monitoring activities and the fragmentation of existing sources. This study presents the development of a relational database and web application specifically designed for the collection, storage, and consultation of sediment transport data, aimed at integrating and enhancing heterogeneous datasets from both historical and contemporary monitoring networks: the Italian Sediment Transport Database (ISTD). The database architecture, developed in PostgreSQL with the PostGIS extension, enables a direct link between observational data and their associated geographical, instrumental, and methodological metadata, ensuring traceability, interoperability, and the possibility to perform multi-temporal analyses. The web interface, built using open-source technologies, allows controlled data entry and interactive data exploration through maps, tables, and export functions. Analysis of the archived datasets highlights strong instrumental, temporal, and spatial heterogeneity: some physical-chemical parameters (e.g., pH and electrical conductivity) show standardized measurement protocols, whereas sediment transport variables exhibit high methodological variability. Time series range from sub-daily to annual observations, with denser coverage in northern Italian basins (e.g., Po, Adige, Piave, Tagliamento) since 1924. Despite these inconsistencies, integration within a unified relational framework enhances the value of a largely underused data heritage. The experience gained through this project enabled the identification of both the limitations and the potential of Italy’s sediment monitoring system, providing operational guidance for methodological standardization, metadata improvement, and data harmonization at the national scale. The ISTD represents a concrete step toward establishing a shared sedimentological archive that supports scientific research, environmental management, and sustainable river basin planning.

Study Region: We developed a new experimental nested catchment in the Eggen-Ega River basin, Eastern Italian Alps, comprising four 27 m2 hillslope plots and three watersheds draining 2.34, 42.4, and 166 km2. Study Focus: We aimed to understand scale-dependent magnitude and controls of turbid stormflow transfer across the Alpine catchments. We monitored runoff volume and turbidity at four spatial scales and assessed their dependence on the characteristics of 23-41 rainfall events between April and October 2024. New Hydrological Insights for the Region: Storm runoff coefficients exhibited a negative power-law scaling with drainage area (exponent:-1/10), suggesting stronger scale-dependent runoff fluctuations at finer scales, critically limiting the representativeness of small-scale, single-point stream gauging in the region. On the contrary, the mean runoff coefficients at 42.4 and 166 km2 were both 0.01, suggesting sufficient region-specific drainage sizes to average out the uniqueness of monitoring locations and timing. While rainfall intensity and saturation (event depth and duration) exerted primary controls on event-scale sediment delivery from 27 m2 plots to a 2.34 km2 headwater, turbidity in the larger 42.4 km2 catchment was more variable and less sensitive to rainfall predictors, likely due to sediment routing beyond the timescale of individual storm events. Our novel nested catchment approach highlights scale-dependent observations of turbid stormflow, calling for extended monitoring of nested catchments across the Alpine regions.

The hydrological and erosional impacts of dynamically decreasing deadwood cover in disturbed mountain forests are poorly understood. This study investigated hydrological-erosional responses to decreasing deadwood cover using the Water Erosion Prediction Project (WEPP) model, which was calibrated and validated with 4-year monitoring data from a 4.5 & times; 6.0 m plot in the Italian Alps. Three simulations were separately performed: uncalibrated (Sim #1); hydraulic conductivity and interrill erodibility calibrated (Sim #2); hydraulic conductivity, interrill erodibility, and residue cover parameter calibrated (Sim #3). Sim #1 significantly underpredicted runoff and sediment yield, highlighting the necessity of validation when extrapolating existing models to mountain forests. Sim #2 notably improved the prediction accuracy of both runoff (from 18.2% to 81.8%) and sediment yield (from 0% to 27.3%), whereas Sim #3 further improved runoff prediction accuracy to 90.9%, confirming the hydrological soundness of deadwood parameterization. Decreases in deadwood cover only marginally increased runoff and sediment yield (<1%) in grass-covered scenarios. Contrastingly, bare-soil conditions revealed dramatic increases (runoff: 13-263%, sediment yield: 139-3931%), emphasizing the protective role of vegetation cover. These results suggest that salvage logging can significantly accelerate runoff and erosion unless vegetation is restored, and properly calibrated models can inform low-impact deadwood management and post-windthrow recovery.

Extensively disturbed catchments undergo heterogeneous vegetation recovery trajectories due to complex disturbance-intervention interactions. Windstorms are one of the major disturbance agents in intensively managed mountain forests of the European Alps; however, little is known about how post-windthrow runoff and erosion processes change in time and space due to limited empirical studies covering multiple disturbances and interventions. Between vegetation periods 2021-2023, we monitored water and sediment fluxes from four 4.5-m- wide x 6.0-m-long plots in a headwater catchment of the Eastern Italian Alps, characterized by deadwood (salvaged/unsalvaged), time since windthrows (3-5 and 21-23 years), and regeneration (natural/artificial). Our monitoring data suggested unsalvaged deadwood has a minimal effect on storm runoff generation for 3-5 years after disturbances, whereas legacy deadwood seemed to offer better soil protection during erosive storms (maximum 5-min intensity > 40.2 mm h(-1)). Recently disturbed plots presented slightly yet significantly 1-2 % higher mean runoff coefficient after prolonged dry periods (30-45 days), implying the importance of disturbance history in better accounting for current hydrological responses. Saplings and trees artificially regenerated after windthrows marginally facilitated quicker runoff transfer, seemingly due to scale-dependent preferential flow pathways (microrelief and litter). Our continuous monitoring efforts underscore the critical need to recognize upstream vegetation recovery trajectories to advance our understanding of catchment-scale responses to major forest disturbances.

Wind-disturbed mountain forests are often subject to artificial deadwood extraction and tree planting to accelerate the recovery of timber resources. However, little is known about to what degree and extent those post-storm silvicultural treatments modify the surface processes of wind-affected hillslopes. This study aims to understand how post-storm silvicultural treatments affect soil erosion from wind-disturbed mountain forests by coupling monitoring and modeling approaches. We continuously collected and measured soil losses from four 4.5-m-wide and 6.0-m-long bounded field plots located on wind-disturbed hillslopes with a slope angle of 45 % in a subalpine headwater of the Italian Alps during the vegetation periods from 2021 to 2023. The dominant ground cover of four plots resulting from altered post-storm interventions is characterized by residual deadwood, native herbs, 20-year-old plantation, and 5-year-old plantation, respectively. During 75 analyzed storm events, average soil loss from the native herbs-covered plot (2.4 t ha-1; SD: ±3.5 t ha-1) was the smallest, followed by plots covered with residual deadwood (mean±SD: 3.1±2.9 t ha-1), 20-year-old plantation (mean±SD: 3.5±5.2 t ha-1), and the 5-year-old plantation (mean±SD: 4.5±4.2 t ha-1). Moreover, linear regression models (p-value < 0.001) indicated that two plantation plots potentially yield 2-fold sediment of naturally regenerating deadwood and herbs-covered plots as storm rainfall depth increases. Our three-year field observations highlight the persistent impact of post-storm forest management activities in accelerating soil erosion potentially even 20 years after their implementation. In the next step, the Water Erosion Prediction Project (WEPP) model will be used to further investigate the effect of human treatments on hydrology and sediment transport in storm-affected mountain areas.

The use of eco-hydraulic physical habitat models at the meso-scale for river management and restoration design has grown in recent years. Consolidated approaches mostly rely on extensive field data collection to describe species- and life stage-relevant environmental characteristics to assess habitat suitability. This restricts their applicability to smaller wadable rivers and short reaches representative of the hydro-morphological conditions of the longer section. It also makes their use challenging in rivers subject to limited flow variability or when channel morphology changes during the data collection period. To address these limitations, complementary approaches involving remote sensing and hydraulic modeling are increasingly used alongside field methods. However, a review of the potential offered by these rapidly evolving methods is lacking, with the related gap in the availability of unified, integrated mesohabitat modeling frameworks. Here, we comprehensively review the state-of-the-art of a wide set of remote sensing-based techniques and methods used to process outputs of 2D hydraulic models for mesoscale habitat modeling in the wet channel, with a focus on gravel-bed rivers. Based on that, we conceptualize a general and flexible 5-step framework for integrating these complementary methods into mesoscale habitat assessment and illustrate its application with reference to the Aurino River (NE Italy). The outcomes of the literature review provide an overview of the present potential and limitations of the examined techniques, supporting the choice of which specific methods can be effectively adopted within each framework step given the specific conditions of the river of interest for a certain application.

Ground surface temperature (GST), measured at a depth of around 5 cm below the ground surface, is essential for understanding the climate change impacts in the Earth Critical Zone. Large spatiotemporal variations of GST have been reported in mountain regions due to the heterogeneity of surface cover and topography. This work aims to improve the monitoring of GST using a physical land-surface model driven by satellite-based land surface temperature (LST). In this regard, GST was simulated using the physical GEOtop model at 1500 m elevation in Matsch Valley, north-eastern Italian Alps, from 2014 to 2017 during the phenological cycle, between April and October. The model was forced only by the LST derived from the Terra MODerate resolution Imaging Spectroradiometer (MODIS). The 1-km MODIS LST was first downscaled to a finer spatial resolution of 250-m using data-driven sharpening from random forest algorithm. The simulated GSTs correlate well with the in-situ observations with a Pearson correlation of 0.88 and a coefficient of determination of 0.77. However, the model overestimated the GST for the whole period with a mean bias of 8.72 °C. These overestimations are similar to the differences between in-situ GST and MODIS LST which range from 4.8 to 19 °C with an average of 8.5 °C. They are mainly caused by the low temporal resolution of LST data with only one observation per day which is additionally limited by frequent cloud cover contamination and the low spatial resolution of the MODIS thermal channels. Modelling the damping of the LST signal in the first centimeters of soil to simulate GST in very heterogeneous areas like alpine pastures is still challenging. This is mainly due to the resolution mismatch between ground and remote sensing observations and the poor knowledge of soil and vegetation properties needed to parametrize physical models.

The presented work deals with the numerical modeling of intense bedload-transport processes at confluences of mountain rivers and steep tributaries. Steep tributaries are characterized by having high transport capacities which supply large amounts of sediments to the confluence zone, where due to the sudden change in slope and the local hydraulic conditions, intense deposition can occur. The objectives of this study are to understand the potential applications and limitations of 2D numerical simulations for modeling these processes. The calibration of the applied 2D numerical model (BASEMENT, Basic Simulation Environment, v2.8) is based on comparing high-density point clouds of the confluence morphology at the end of flume experimental runs with numerical results. The calibrated numerical model is then used to test different discharge ratios and to investigate depositional patterns and mechanisms. The results show that key morphological features such as the confluence fan, the bank-attached bar and the scour hole can be accurately reproduced, showing that 2D numerical simulations are a valuable tool for modeling the complex interactions between morphodynamics and hydraulics at river confluences. Additionally, it is shown that the confluence morphology of steep tributaries and mountain rivers is strongly influenced by the sediment concentration in the tributary channel and the discharge in the main channel.

Subglacial sediments are a large component of the sediment budget of glacierized catchments but insights into the subglacial origin of sediments (bedload, in particular) linked to proglacial runoff dynamics remain scarce. In this study, we use a tracer-based approach to quantify meltwater proportions related to sediment transport at two proglacial streams, draining glaciers (named debris-covered and clean glacier) of different size, aspect and elevation range with contrasting distribution and thickness of debris cover and lithology of the subglacial sediments (i.e., metamorphic vs. sedimentary), in the Sulden/Solda catchment (Italian Alps). Results indicate that the glacier melt component (75 to 80 %) was associated with bedload concentrations of 1 to 10 kg m(-3) at the debris-covered glacier and much lower concentrations of 0.01 to 1 kg m(-3) at the clean ice glacier. At the seasonal scale, bedload and suspended sediment concentrations at both sites strongly varied with discharge. While daily bedload concentrations varied by up to two orders of magnitude obscured the seasonal development of bedload concentrations at both sites, a clear seasonality for suspended sediment concentrations was found. At the daily scale, the relationship of discharge, bedload, and suspended sediment was more complex because discharge and sediment transport did not always follow the daily variation of air temperature, or similar daily air temperatures resulted in different discharge and sediment transport responses and vice versa. Glacier size, presence of debris cover, and substrate were identified as the main drivers of meltwater dynamics and sediment transport at both glaciers. This study adds further insights into the interplay of meltwater contributions and sediment transport, which are essential to better assess the impact of climate warming on sediment supply in glacierized catchments.

Windstorm events are the primary natural disturbances in the Italian Alps. The combined effects of climate change and windstorm-induced land cover changes are expected to significantly influence the hydrological and erosional responses of forested watersheds. This study presents preliminary results from both plot-scale monitoring and large-scale modeling conducted in the subalpine catchment of Val d'Ega (BZ). At the plot scale, runoff and erosion were monitored in 4.5m x 6m plots, which were characterized by either natural or artificial regeneration following storm events. Water and sediment yields were measured across 75 rainfall events from 2021 to 2023. Initial results reveal considerable inter-plot variability in runoff and erosion dynamics, with artificially regenerated plots exhibiting higher water and sediment transport rates. Furthermore, the pre-storm soil conditions and microtopography appear to play a significant role in these dynamics. At the larger scale, surface runoff and sediment yield were evaluated using the SWAT model, comparing pre- and post-Vaia windstorm (October 2018) conditions. Four different scenarios, varying in both spatial extent and scale of land use changes, were assessed. Results indicate a 3% to 16% increase in annual surface runoff in scenarios accounting for land cover changes, compared to the ‘no-damage’ scenario. Consequently, sediment yield increased by up to four times, with the greatest impact observed in subbasins most affected by the Vaia windstorm. These findings highlight the need for further investigation into effective management strategies in response to the evolving post-windstorm hydrological and erosional dynamics.

Channel incision and narrowing have occurred in the 20th century in most Alpine rivers. However, the causal links between sediment-related human engineering and exploitation and morphological changes in rivers are mostly unclear. This study presents an analysis of the evolutionary trajectories of the main active channels in the upper Etsch/Adige River basin (Eastern European Alps) coupled with their modifications in terms of coarse sediment transport. Channel planform variations were quantified in 15 rivers (total length of 630 km) using multi-temporal analysis of historical maps and orthophotos. Sediment volumes excavated from river channels or trapped by hydraulic structures (dams and retention basins) were retrieved from historical records, along with geospatial information regarding the presence of lateral and longitudinal consolidation works and land use variations. Results indicate that most rivers underwent slight narrowing and some of them experienced widening, from the mid-19th century to the 1950s. From the 1950s to the late 1990s, severe variations in terms of narrowing and morphological simplification took place in all rivers. The analysis of channel changes in relation to human activities shows that gravel mining carried out in the period 1970s-1990s appears to have been the main cause of sediment imbalance in the rivers which narrowed the most. Since the 2000s, when gravel mining was banned by law, channel adjustments have become negligible throughout study area. Nevertheless, the trapping of a large share of coarse sediment fluxes-at the river basin scale-by retention check dams and hydropower dams has impeded rivers from recovering to their original conditions. Sketch illustrating how rivers have generally changed in South Tyrol since the 19th century in response to anthropic alterations.dagger image

Confluences are dynamic morphological nodes that are found in all river networks. In mountain regions, they are influenced by hydraulic and sedimentary processes that occur in steep channels during extreme events in small watersheds. Sediment transport in the tributary channel and aggradation in the confluence can be massive, potentially causing overbank flooding and sedimentation into adjacent settlement areas. Previous works dealing with confluences have mainly focused on lowland regions, and those that have focused on mountain areas have used sediment concentrations and channel gradients that are largely under-representative of mountain river conditions. The presented work contributes to filling this research gap with 45 experiments that use a large-scale physical model. Geometric model parameters, the applied grain size distribution, and the considered discharges represent the conditions at 135 confluences in South Tyrol (Italy) and Tyrol (Austria). The experimental program allowed for a comprehensive analysis of the effects of (i) the confluence angle, (ii) the tributary gradient, (iii) the channel discharges, and (iv) the tributary sediment concentration. In contrast to most research dealing with confluences, results indicate that, in the presence of an intense tributary sediment supply and a small tributary-to-main-channel discharge ratio (0.1), the confluence angle does not have a decisive effect on confluence morphology. Adjustments to the tributary channel gradient yielded the same results. A reoccurring range of depositional geomorphic units was observed in which a deposition cone transitioned to a bank-attached bar. The confluence morphology and tributary channel gradient rapidly adjusted, tending towards an equilibrium state to accommodate both water discharges and the sediment load from the tributary. Statistical analyses demonstrated that the confluence morphology was controlled by the combined channel discharge and the depositional or erosional extent was controlled by the sediment concentration. Applying conclusions drawn from lowland confluence dynamics could misrepresent depositional and erosional patterns and the related flood hazard at mountain river confluences.

With climate change intensifying, forests globally are becoming more susceptible to extreme weather events, such as windstorms, which account for a significant share of Europe's economic losses. The Vaia windstorm of late autumn 2018, striking Italy's North-East alpine ecosystem, highlighted this vulnerability, toppling over 8.5 million cubic meters of timber and sparking debates on forest management's role in mitigating such disasters. This study aims to evaluate the impact of structural and topographical characteristics on the damage caused by Vaia, using Airborne Light Detection And Ranging (LiDAR) data collected before the storm, in four heavily affected forest areas in the Italian Alps (Carezza in the Province of Bolzano-Bozen, Predazzo, Manghen, and Primiero in the Province of Trento). We analyzed structural metrics like forest height heterogeneity (HH), forest mean height, and density, alongside topographical features such as aspect, slope, and altitude, to discern their influence on the storm's severity. Our results revealed that the most significant difference between affected and unaffected areas is forest mean height that was found higher in areas hit by the storm. Forest density played a lesser but important role, with denser areas experiencing more severe damage, though this was only significant in certain areas. Contrary to common assumptions, our analysis revealed that forest height heterogeneity (HH) did not have a significant effect on damage levels. The findings, consistent with previous research, revealed a significant association between specific aspects, particularly the South-East orientation, which aligned with the predominant wind direction during the Vaia storm, and an increased likelihood of damage. Both structural and topographical factors interact in complex ways to influence the outcome of such extreme events. The study emphasizes the dominant impact of the Vaia windstorm, noting that while managing forest height and density may help, the diverse topography complicates these efforts. Our study explicitly tested the effectiveness of using Airborne LiDAR data to explore forest structural and topographical factors that influenced Vaia storm damage. The achieved results demonstrate that LiDAR serves as a useful tool to field data, offering valuable insights for broader applications in this domain.

Coarse sediment transported by steep mountain tributaries during channelized flash flood events with intense bed load transport poses a significant threat to life, property, and infrastructure. Intense bedload transport occurring in tributary channels and insufficient transport capacity of the main channel flow can provoke flooding at the confluence. Deposition in the confluence can lead to overbank flooding and sedimentation into adjacent settlement areas. Extensive research has been carried out investigating lowland river confluences, where it has been determined that the confluence angle and discharge ratio have the most significant influence on channel morphology and hydraulics. However, there is a lack of information concerning confluences with low width and discharge ratios, high sediment concentrations, and gradients, typically found in steep mountain channels. This study presents results from large‐scale laboratory experiments coupled with numerical modelling with a standardized river confluence geometry. Bedload transport capacities, the shape, and volume of the deposition zone in the confluence, bedload dispersion characteristics, hydraulic and morphological dynamics, and spatial boundaries were analysed for various discharges and sediment concentrations. The confluence angle was 90°, sediment concentration was 5%, 7.5%, and 10%, and the discharge ratio was 0.1. The model was designed to accommodate scale factors of 20–40. With this configuration, a set of experiments based on steady‐state hydraulic conditions was accomplished. Results show that when the discharge ratio and confluence angle are constant, different morphologies occur, indicating that in addition to the confluence angle and the discharge ratio, the sediment concentration, flow velocity, and unit stream power significantly impact both hydraulic and morphologic zones in the confluences of mountain rivers. Additionally, backwater effects upstream of the confluence, and sedimentation in the tributary channel increases with increasing sediment concentration, which not only influences confluence morphodynamics and hydraulics but also the potential for overbanking of both channels.

In mountain rivers, long‐term observations of water and sediment fluxes are crucial for understanding the dynamics of bedload fluctuations. We analyze 7 years of continuous data gathered from eight geophone plates at a monitoring station in the glacier‐fed Sulden/Solda River (South Tyrol, Italy) to estimate the bedload flux at 1‐min scale. Sixty‐five bedload samples were used to derive the calibration equations adopted to quantify the transported bedload mass. The signal power is proposed as a more effective metric than threshold‐based impulses for calculating bedload masses. Results show (a) a remarkable variability of bedload rates for the same value of flow discharge, (b) the joint effect of storm‐driven flood events and seasonal changes in sediment supply on bedload rates, and (c) the strong impact of climatic factors (i.e., temperature and snow cover) on bedload fluxes. Moderate bedload rates occurring in late spring/early summer are likely related to the mobilization of riverbed sediments, while sustained bedload transport during melt flows in July–August—corresponding to the effective bedload discharge range—is associated with the activation of glacial and proglacial sediment sources. The data set shows a complex climatic control on bedload transport at the basin scale, where precipitation, air temperature, and snow cover determine flow and glacier melting dynamics. These findings suggest how the effects of climate change in the Alps likely will lead to an increase in peak bedload rates in a context of declining annual bedload yields as melt flows will progressively reduce in the next decades.

Alpine rivers and their floodplains have been highly modified by human activities during the last decades. River restoration projects aim to counteract these negative impacts and to restore ecosystem services provided by riparian habitats. We studied two recently restored river sites in the Ahr/Aurino and Mareit/Mareta Rivers (Italian Alps) to investigate how geomorphic conditions, soil moisture, and groundwater level affect the source of water used by grey alder ( Alnus incana (L.) Moench). We compared the isotopic composition (δ 2 H) of tree sap at different locations (low terraces formed during bed incision and recent floodplains formed after restoration) with that of potential water sources, that is, groundwater, soil water, and rainfall. The monthly variation in the isotopic composition of rainfall was reflected in both shallow and deeper soil water, as well as in the isotopic composition of sap. The redistribution of precipitation and groundwater in the soil differed between the post‐restoration floodplain sites and the post‐incision terraces, leading to a different relation between the sap water, soil water, and groundwater isotopic composition. The results show that transpiration of A. incana trees growing on recent floodplains is mostly supported by stream‐fed soil water, whereas trees growing on terraces mainly use precipitation‐fed soil water. These marked, morphology‐related differences in the source of transpiration water of grey alder highlight how channel degradation still affects the ecohydrological processes in Alpine fluvial corridors. Nonetheless, large restoration interventions—in terms of channel widening—can enable the self‐formation of new floodplain areas characterized by stream water‐fed riparian ecosystems.

Integration of remote sensing and 2D hydraulic modelling offers the potential for broader applicability of habitat modelling at the meso-scale, extending applications to larger nonwadeable streams, and allowing to survey longer river stretches.We present an example of the application of a methodological framework for meso-scale habitat suitability modelling, on a reach of the gravel-bed Aurino River (NE Italy).The framework implements the following main steps: remote sensing-based acquisition of the topo-bathymetry and a high-resolution orthophoto; 2D hydraulic modelling coupled with an unsupervised algorithm to map hydro-morphologically defined units; semi-automated mapping of substrate and refugia; and finally, the estimation of meso-scale habitat suitabilities for a target species or community.

The current study was carried out in a wind damaged forest area and it aims to estimate the effects of management strategies after storm events on runoff and sediment yield. In order to achieve the goal, four experimental plots have been established on an area hit by two windthrows in 2003 and 2018 (Vaia storm). Each plot bound an area of 27 m 2 (4.5 m x 6 m) and is located on a 40% slope facing East, previously covered with subalpine spruce forest at about 1650 m asl. The considered forest treatments were (1) salvage logging and natural regeneration, (2) no intervention, and (3) salvage logging and artificial regeneration. We measured runoff and sediments yield from September 2020 to September 2022. Water and sediments mobilized in the experimental plots are convoyed in a 1 m 3 tank where the content is weighted by a load cell, and a pressure transducer records the water level. An in-situ radar rain gauge measures cumulative precipitation and intensity. Moreover, sediments samples were collected twice a year, dried and sieved to obtain the percentage of organic material and the texture of the eroded soil. The first results show a contrasting behaviour in terms of runoff/sediment yield between the four plots upon the occurrence of an intense precipitation event. The differences could be explained by the time passed after the windthrow, and the different forest treatments applied. These and future outcomes will be of paramount importance for adapting management strategies to an increasing frequency of subsequential extreme events (windthrow and precipitation).

In the framework of water resources planning and management, the MesoHABSIM (MesoHABitat Simulation Model) approach demonstrated high potential to assess suitable environmental conditions for freshwater fish species. In the present study, the transferability capabilities of mesohabitat suitability criteria were evaluated in nine streams across Northern Italy. In particular, the Random Forest (RF) technique was used to calibrate and validate suitability criteria for adult and juvenile life stages of brown trout (Salmo trutta), marble trout (Salmo marmoratus), bullhead (Cottus gobio) Italian barbel (Barbus plebejus), and Italian vairone (Telestes muticellus). Presence/absence binary models were calibrated at the mesohabitat scale (i.e., the geomorphic unit scale) using field data collected in reference sites, selected for their natural hydro -morphological conditions and habitat characteristics. Model transferability tests were performed in streams located in different regions within the distribution area of the fish and not included in the model calibration dataset. Predictive capacities of the models were very good in terms of accuracy (ranging from 75% to 82%) and true skill statistic (ranging from 52% to 75%). The high predictive performances can be related to (i) the use of an ecologically relevant spatial resolution (mesohabitat) to predict fish presence, (H) a robust and adequate hydro-morphological characterization of the analyzed geomorphic units, and (iii) the large number of mesohabitat descriptors provided by the MesoHABSIM approach. Results showed that mesohabitat suitability criteria based on RF can be considered transferable among streams located in different regions of Northern Italy, especially when river channels are characterized by similar hydro-morphological characteristics.

Riparian zones are the paragon of transitional ecosystems, providing critical habitat and ecosystem services that are especially threatened by global change. Following consultation with experts, 10 key challenges were identified to be addressed for riparian vegetation science and management improvement: (1) Create a distinct scientific community by establishing stronger bridges between disciplines; (2) Make riparian vegetation more visible and appreciated in society and policies; (3) Improve knowledge regarding biodiversity-ecosystem functioning links; (4) Manage spatial scale and context-based issues; (5) Improve knowledge on social dimensions of riparian vegetation; (6) Anticipate responses to emergent issues and future trajectories; (7) Enhance tools to quantify and prioritize ecosystem services; (8) Improve numerical modeling and simulation tools; (9) Calibrate methods and increase data availability for better indicators and monitoring practices and transferability; and (10) Undertake scientific validation of best management practices. These challenges are discussed and critiqued here, to guide future research into riparian vegetation. This article is categorized under: Water and Life > Nature of Freshwater Ecosystems Water and Life > Stresses and Pressures on Ecosystems Water and Life > Conservation, Management, and Awareness