Northwestern Italian Alps Research Articles

Hydrogeological characterization throughout deep geophysical investigations in the Verrès plain (Aosta Valley, north-western Italian Alps)

Although fresh water availability in the Aosta Valley (north-western Italian Alps) is generally granted by glaciers and snow seasonal melting at high altitudes, hydrogeological conditions are not favorable everywhere. Most part of the territory is typically mountainous, with prevailing metamorphic rocks and, secondarily, glacial deposits. Relevant ground water bodies can be found only in the main bottom valley, where glacial excavation, fluvio-glacial and lacustrine sedimentation had maximum intensity, allowing the deposition of important thickness of porous materials. Nevertheless, the geological knowledge of the subsurface is here still poor. These groundwater bodies are monitored by the Environmental Protection Agency of the Aosta Valley Region (ARPA Valle d’Aosta), according to the Italian law (D.Lgs.30/09). This study deals with geophysical investigations in the Verrès plain aquifer (southern Aosta Valley). The main goal of the study has been the first evaluation of groundwater research in potential deep aquifers. Different geophysical methodologies were applied (ERT, TDEM, HVSR, and Re.Mi.), in order to identify the deep aquifer geometry and the rock basement depth.

Primary vegetation succession and the serpentine syndrome: the proglacial area of the Verra Grande glacier, North-Western Italian Alps

Initial stages of pedogenesis are particularly slow on serpentinite. This implies a slow accumulation of available nutrients and leaching of phytotoxic elements. Thus, a particularly slow plant primary succession should be observed on serpentinitic proglacial areas. The observation of soil-vegetation relationships in such environments should give important information on the development of the “serpentine syndrome”. Plant-soil relationships have been statistically analysed, comparing morainic environments on pure serpentinite and serpentinite with small sialic inclusions in the North-western Italian Alps. Pure serpentinite supported strikingly different plant communities in comparison with the sites where the serpentinitic till was enriched by small quantities of sialic rocks. While on the former materials almost no change in plant species composition was observed in 190 years, 4 different species associations were developed with time on the other. Plant cover and biodiversity were much lower on pure serpentinite as well. Extremely low P and high Ni contents in soil were strongly related with these differences, but none of them could be interpreted as the actual limiting factor for plant development on pure serpentinite. Other nutrients or bases were not related with the different primary succession speed and species composition.

A new vertebrate for Europe: the discovery of a range-restricted relict viper in the western Italian Alps

We describe Vipera walser, a new viper species from the north-western Italian Alps. Despite an overall morphological resemblance with Vipera berus, the new species is remarkably distinct genetically from both V. berus and other vipers occurring in western Europe and shows closer affinities to species occurring only in the Caucasus. Morphologically, the new species appear to be more similar to V. berus than to its closest relatives occurring in the Caucasus, but can be readily distinguished in most cases by a combination of meristic features as confirmed by discriminant analysis. The extant population shows a very low genetic variability measured with mitochondrial markers, suggesting that the taxon has suffered a serious population reduction/bottleneck in the past. The species is extremely range-restricted (less than 500 km2) and occurs only in two disjunct sites within the high rainfall valleys of the Alps north of Biella. This new species should be classified as globally ‘endangered’ due to its small and fragmented range, and an inferred population decline. The main near-future threats to the species are habitat changes associated with reduced grazing, along with persecution and collecting.

Hummocks affect soil properties and soil-vegetation relationships in a subalpine grassland (North-Western Italian Alps)

Earth hummocks are small cryogenic mounds, covered by grass, closely spaced in grassland or wetlands. Hummock microtopography establishes specific microclimatic conditions, with small-scale variations in soil thermal properties and water regimes, which influence biogeochemical cycles. These properties, coupled with different litter decomposability, may cause variations on soil physical and chemical properties and pedogenesis, as well as a selective distribution of plant species.The work has been carried out at the LTER site of Tellinod (Torgnon, Aosta Valley, NW, Italy). The site is characterized by a Nardus stricta subalpine hummocky grassland located at 2100masl, which shows the dominance of Nardus on hummocks and a prevalence of dicotyledons in interhummocks (i.e. the depressions between consecutive hummocks). Such distribution indicates that earth hummock pattern was reflected in soil properties. In order to confirm this hypothesis, we analyzed and compared soil pedogenesis and topsoil characteristics between hummocks and interhummocks. In addition, litter bags were incubated in hummock and interhummock positions to investigate litter decomposition rate as related to microtopography and plant species and its effects on topsoil edaphic properties.The results confirm that hummocky topography significantly influences topsoil properties, pedogenesis and vegetation distribution, with large differences between hummocks and interhummocks. The hummocky soil can be fully classified as Podzol, based on both the morphological and chemical diagnostic properties; however, morphological and chemical evidences indicate that the degree of podzolization differs significantly under hummocks and interhummocks. In addition, the results verify a faster decomposition of dicotyledons in the nutrient-richer interhummock topsoils compared to the podzolized hummocks positions, and an overall slower decomposition rate of Nardus litter. All these factors contribute to the creation and conservation of a unique pedo-environment in this subalpine grassland.

Facies and Late Triassic fossils in the Roisan zone, Austroalpine Dent Blanche and Mt Mary-Cervino nappe system, NW Alps

The Roisan zone is a metamorphic cover unit exposed along the ductile shear zone between the Dent Blanche s.s. and Mont Mary-Cervino Upper Austroalpine outliers, Aosta Valley, north-western Italian Alps. It is characterized by the occurrence of dolostones, pure marbles, marbles with quartz, calcirudites and ophiolite-free calcschists. Locally, dolostones preserve alternances of thick massive beds and thinner levels of planar stromatolites and other sedimentary structures and textures typical of a carbonate platform. In Mt Grand Pays they contain Dasycladales and foraminifers referable to the Norian. Pure marbles and marbles with quartz grains are tentatively referred to the end of Triassic–Early Jurassic, thin-bedded marbles and calcirudites to the Early and Middle Jurassic, calcschists from Middle Jurassic to Late Cretaceous. This Roisan succession is quite similar to the one of Mt Dolin, in the Swiss part of the Dent Blanche nappe, where the same Triassic foraminifer association has been reported. There, the fossils were found only in reworked pebbles, contained in calcirudites of presumed Jurassic age. Some differences exist between the two successions: calcirudites are abundant in the Mt Dolin and sporadic in the Roisan zone, whereas calcschists are very thick in the Roisan zone. As consequence the Mt Dolin succession can be considered settled down in the proximity of the faults related to the pre-oceanic rifting of the Piedmont basin, whereas the Roisan zone could have been deposited in a more distal area.

Mature vs. Active Deep-Seated Landslides: A Comparison Through Two Case Histories in the Alps

Two case histories are presented, concerning the still poorly known alpine deep-seated gravitational slope deformations (DSD) located nearby Lanzada (central Italian Alps), and Sarre (north-western Italian Alps). The Lanzada DSD is a constantly monitored, juvenile, and active phenomenon, partly affecting an existing hydropower plant. Its well-developed landforms allow a precise field characterization of the instability-affected area. The Sarre DSD is a mature, strongly remodeled phenomenon, where the only hazard factor is represented by secondary instability processes at the base of the slope. In this case, the remodeling imposed the adoption of complementary analytical techniques to support the field work. The two presented studies had to be adapted to external factors, namely (a) available information, (b) geological and geomorphological setting, and (c) final scope of the work. The Lanzada case essentially relied upon accurate field work; the Sarre case was mostly based on digital image and DTM processing. In both cases a sound field structural analysis formed the necessary background to understand the mechanisms leading to instability. A back-analysis of the differences between the study methods adopted in the two cases is finally presented, leading to suggestions for further investigations and design.

Temperature changes in the North-Western Italian Alps from 1961 to 2010

The aim of this study was to identify any possible temperature changes within the last 50 years in the North-Western Italian Alps by examining data from 16 high-altitude weather stations in the period 1961–2010. The daily temperature time series were collected, digitized and subjected to a historical research to individuate discontinuities and retrieve metadata. We also carried out the data quality control and the homogenization which allowed the climatic indices trend detection. The analysis of the temperature values showed an increase in temperature, particularly at high-altitudes sites. In fact, the stations located above 1600 m asl revealed a rise in temperatures and a decrease in the number of cold periods. For the maximum temperatures, greater increases in spring and winter have been observed, for minimum temperatures in the summer. These trends confirm that climate change is occurring in an environment particularly sensitive to temperature changes, especially during the season of snow accumulation and vegetative growth. These results may be important for policy makers to define the best adaptation strategies in order to protect one of the most sensitive environments such as mountains.

Climate variability and Alpine glaciers evolution in Northwestern Italy from the Little Ice Age to the 2010s

In this work, we analyze climate variability and glacier evolution for a study area in the Northwestern Italian Alps from the Little Ice Age (LIA) to the 2010s. In this area, glacier retreat has been almost continuous since the end of the LIA, and many glaciers are now extinct. We compared glaciological and climatic data in order to evaluate the sensitivity of glaciers to temperature and precipitation trends. We found that temperatures show significant warming trends, while precipitation shows no clear signal. After the 1980s, the total number of positive trends in temperature increased, particularly minimum temperature. The latter does not seem to be the only cause of glacier shrinkage but rather on acceleration of an ongoing trend documented since the end of the LIA. In some rare cases, the effects of warming trends on glacier dynamics have been accentuated by a concomitant decrease in precipitation. We hope that this study will contribute to increase the knowledge of the relationships between climate variation and glacier evolution in the Greater Alpine Region.

Quality assessment in the Italian mountain huts

Because of its intangibility, the evaluation of the quality in the lodging services is extremely complicated. In the last 30 years several studies have focused on the measurement of the quality in the tourist organisations, in order to define a methodology able to evaluate their performances. The paper contribution to the debate is focused on the quality of service in a specific kind of accommodation, the mountain hut, which operates in a fragile habitat. The study presents the results of an empirical analysis on the perception of quality in the mountain huts conducted by interviewing 372 guests in the Piedmont Region in the north-western Italian Alps. The analysis highlights the importance, on the one hand, of a correct communication of the activities conducted by managers of the mountain huts and, on the other hand, the substance of avoiding a short-contact experience between guest and structure. Finally, the paper underlines how this experience was also useful in order to reason about the definition of a quality label specifically thought for mountain huts.

Snow Pressure on a Semiflexible Retaining Structure

AbstractSnow avalanche hazard is one of the most critical aspects in the urbanization of mountainous areas. The risk from these natural phenomena can be reduced if proper countermeasures for reducing the danger or preventing avalanche triggering are taken. For instance, in the avalanche initiation zone, devices able to withstand snowpack gliding and prevent crack propagation can be installed. These can be classified as rigid (snow bridges) or flexible (snow net) structures, depending on the mechanisms involved under snow loading. In recent years, a new kind of structure called a snow umbrella, based on a net panel supported by rigid beams, has been designed and installed in the northwestern Italian Alps. As the real behavior of these structures is far from being simple to understand because of the complex interaction with snowpack movements, an umbrella was instrumented and monitored during the winter season of 2010–2011. The recorded data are used for testing two possible pressure distributions and evalu...

Assessment of the Gastrointestinal Helminth Fauna of Mountain Hares (Lepus timidus varronis) from the Northwestern Italian Alps, with New Records of Parasite Occurrence

We describe the gastrointestinal parasite community of Lepus timidus varronis, a subspecies of the mountain hare (L. timidus) living in the Alps. Two nematode species are reported for the first time in L. timidus.

Pastoral Practices to Reverse Shrub Encroachment of Sub-Alpine Grasslands: Dung Beetles (Coleoptera, Scarabaeoidea) Respond More Quickly Than Vegetation

In recent decades, pastoral abandonment has produced profound ecological changes in the Alps. In particular, the reduction in grazing has led to extensive shrub encroachment of semi-natural grasslands, which may represent a threat to open habitat biodiversity. To reverse shrub encroachment, we assessed short-term effects of two different pastoral practices on vegetation and dung beetles (Coleoptera, Scarabaeoidea). Strategic placement of mineral mix supplements (MMS) and arrangement of temporary night camp areas (TNCA) for cattle were carried out during summer 2011 in the Val Troncea Natural Park, north-western Italian Alps. In 2012, one year after treatment, a reduction in shrub cover and an increase in bare ground cover around MMS sites was detected. A more intense effect was detected within TNCA through increases in forage pastoral value, and in the cover and height of the herbaceous layer. Immediately after treatment, changes in dung beetle diversity (total abundance, species richness, Shannon diversity, taxonomic and functional diversity) showed a limited disturbance effect caused by high cattle density. In contrast, dung beetle diversity significantly increased one year later both at MMS and TNCA sites, with a stronger effect within TNCA. Multivariate Regression Trees and associated Indicator Value analyses showed that some ecologically relevant dung beetle species preferred areas deprived of shrub vegetation. Our main conclusions are: i) TNCA are more effective than MMS in terms of changes to vegetation and dung beetles, ii) dung beetles respond more quickly than vegetation to pastoral practices, and iii) the main driver of the rapid response by dung beetles is the removal of shrubs. The resulting increase in dung beetle abundance and diversity, which are largely responsible for grassland ecosystem functioning, may have a positive effect on meso-eutrophic grassland restoration. Shrub encroachment in the Alps may therefore be reversed, and restoration of grassland enhanced, by using appropriate pastoral practices.

Feeding habits of the sand lizard, Lacerta agilis, from North-Western Italian Alps

The dietary habits of a population of the sand lizard Lacerta agilis were studied in the Alpine valley Stura di Demonte, Northwestern Italy. The faecal contents of 33 adults (16 females and 17 males) and 8 juveniles were analysed. There were negligible sexual differences in terms of trophic diversity and of the overall diet based on taxonomic prey categories. Juveniles had a lower prey diversity value in comparison with females but not with males. There was a positive relationship between the total number of prey items found in individual faecal contents and lizard body size, and this result may explain the more diverse diet of adults in comparison to juveniles. When the adult trophic strategy was analysed by means of the relativized electivity index, that takes into account prey availability, it was observed that the main taxonomic prey groups were eaten according to their proportion in the environment, with the only exception of ants (Formicidae) that were highly avoided by lizards.

Snow gliding and loading under two different forest stands: a case study in the north-western Italian Alps

The presence of a thick snowpack could interfere with forest stability, especially on steep slopes with potential damages for young and old stands. The study of snow gliding in forests is rather complex because this phenomenon could be influenced not only by forest features, but also by snow/soil interface characteristics, site morphology, meteorological conditions and snow physical properties. Our starting hypothesis is that different forest stands have an influence on the snowpack evolution and on the temperature and moisture at the snow/soil interface, which subsequently could affect snow gliding processes and snow forces. The aim of this work is therefore to analyse the snowpack evolution and snow gliding movements under different forest covers, in order to determine the snow forces acting on single trees. The study site is located in a subalpine forest in Aosta Valley (NW-Italy) and includes two plots at the same altitude, inclination and aspect but with different tree composition: Larch (Larix decidua) and Spruce (Picea abies). The plots were equipped with moisture and temperature sensors placed at the snow/soil interface and glide shoes for continuous monitoring of snow gliding. The recorded data were related to periodically monitored snowpack and snow/soil interface properties. Data were collected during two winter seasons (2009–10 and 2010–11). The snow forces on trees were analytically calculated either from snowpack data and site morphology or also from measured snow gliding rates. Different snow accumulations were observed under the two different forest stands, with a significant effect on temperature and moisture at the snow/soil interface. The highest snow gliding rates were observed under Larch and were related to rapid increases in moisture at the snow/soil interface. The calculated snow forces were generally lower than the threshold values reported for tree uprooting due to snow gliding, as confirmed by the absence of tree damages in the study areas.

Diversity of fungal flora in raw milk from the Italian Alps in relation to pasture altitude

The present paper explores the diversity of mycobiota inhabiting raw milk sampled at different altitudes (1400 m, 1800 m, 2200 m) from cows grazing Alpine pastures of Valle d’Aosta (North-Western Italian Alps). To this aim, multilocus sequencing was performed at barcodes commonly used for fungal identification (ITS1, D1/D2 domains of the 26S rRNA gene, and part of the β-tubulin gene). A total of 31 species were detected, most of them yeasts, followed by moulds and by 2 sequences of macroscopic fungi. Several yeasts and moulds were well-characterized inhabitants of the dairy environment, known to positively contribute to cheesemaking. Among these, Candida was the most represented genus with a tendency to cluster at the highest altitudes (6 over 8 observations at ≥ 1800 m), and Kluyveromyces marxianus the most abundant single species, retrieved at all altitudes. The environmental ascomycetous Atrotorquata lineata, never put in relation with food nor described outside North-America, was another species among those most frequently retrieved and was detected in 6 milks at 1400 and 1800 m. The remaining fungi, in general never reported in milk, were mostly environmental. Many of them resulted associated with plants as pathogens or symbionts. Finally, the highest sampled altitude yielded a significant fungal diversity (17 species). This work enlarges the knowledge of fungal consortia inhabiting raw milk and introduces microbial ecology among the altitude-dependent factors, in the composition of Alpine pastures, with the potential of shaping the properties of milks and cheeses, together with the already described physical, chemical and botanical variables.

The winter roosting and diet of Black Grouse Tetrao tetrix in the north-western Italian Alps

The factors influencing the selection of Black Grouse Tetrao tetrix winter roost sites and choice of roosting strategy (open-air roosts vs. snow burrows, or ‘igloos’) were assessed in the Alps, including the influence of winter diet, snow conditions and habitat at different scales. Of 337 roosts detected, 31 % were igloos and 69 % were open-air roosts. At the larger scale (30 × 30 m), ground curvature, altitude, slope, southerly aspect and mountain pine Pinus montana uncinata cover were positively correlated with roost presence. At the smaller scale (10 m radius), roost presence was positively correlated with a northerly aspect, cover of green alder Alnus viridis, and a low cover of vegetation downslope from the roost. Roosting strategy was related to temperature and snow conditions (with more igloos when snow depth was greater, but fewer igloos when a hard snow crust had formed). The winter diet of the Black Grouse mostly comprised mountain pine needles (84 % of droppings). The results suggest that a range of factors influence choice of roost site, including predator avoidance, food availability and topography. The latter showed contrasting effects at different scales, suggesting that Black Grouse select colder sites (with deeper snow) within warmer areas (energetically more favourable). Management to encourage the mountain pine, whilst maintaining scattered green alder in the understorey, is likely to improve Black Grouse winter habitat quality. Choice of roosting strategy is, however, dictated by weather conditions. If the reduction in precipitation and snow cover continues as forecast, open-air roosting might be more frequent in the future. However, open-air roosting might increase predation risk, which could be deleterious for the species’ conservation.

Differential responses of ground dwelling arthropods to ski-piste restoration by hydroseeding

The construction of ski-pistes can cause serious damage to all the components of an ecosystem and may therefore be considered as one of the main causes of human-driven environmental changes in mountain habitats. This study was aimed at assessing the responses of different ground dwelling arthropod assemblages (i.e. ground beetles, spiders and grasshoppers) to ski-piste restoration through hydroseeding with commercial seed mixtures. The soil, vegetation and arthropods of restored and un-restored ski-pistes and the adjacent grassland have been sampled at two high altitude sites in the north-western Italian Alps. The ski-piste soil was characterized by a higher skeletal content and, consequently, a lower amount of fine earth and organic matter than that of the undisturbed adjacent grassland. The plant cover of the restored ski-pistes was very low above 2,500 m a.s.l.; the vegetation cover below this threshold was higher in the study area, mainly due to the seeded species. The unrestored ski-pistes showed very large proportions of bare ground. The responses of the three ground-dwelling arthropod groups to vegetation conditions were different. GLMMs and IndVal analyses showed that all three groups avoided the unrestored ski-pistes plots, which were characterized by a very scarce vegetation cover, irrespective of the altitude. The low altitude plots of the restored ski-pistes, which were characterized by a high vegetation cover, had a significantly larger number of grasshoppers on the ski-pistes than on the adjacent grassland plots. Moreover, these restored ski-piste plots were used in equal proportion to the adjacent grassland plots by ground beetles but avoided by spiders. When ski-pistes become sufficiently revegetated by hydroseeded plants, they are colonized by grasshoppers and, to a lesser extent, by ground-beetles. Spiders, instead, do not colonize the pistes, thus demonstrating that they are the most sensitive arthropods and may therefore represent the best indicators of human-driven environmental changes in high altitude alpine habitats.

Glacier response to current climate change and future scenarios in the northwestern Italian Alps

We analyze longtime series of annual snout positions of several valley glaciers in the northwestern Italian Alps, together with a high-resolution gridded dataset of temperature and precipitation available for the last 50 years. Glacier snout fluctuations are on average negative during this time span, albeit with a period of glacier advance between about 1970 and 1990. To determine which climatic variables best correlate with glacier snout fluctuations, we consider a large set of seasonal predictors, based on our climatic dataset, and determine the most significant drivers by a stepwise regression technique. This in-depth screening indicates that the average glacier snout fluctuations strongly respond to summer temperature and winter precipitation variations, with a delay of 5 and 10 year, respectively. Snout fluctuations display also a significant (albeit weak) response to concurrent (same year) spring temperature and precipitation conditions. A linear regressive model based on these four climatic variables explains up to 93 % of the variance, which becomes 89 % when only the two delayed variables are taken into account. When employed for out-of-sample projections, the empirical model displays high prediction skill, and it is thus used to estimate the average glacier response to different climate change scenarios (RCP4.5, RCP8.5, A1B), using both global and regional climate models. In all cases, glacier snout fluctuations display a negative trend, and the glaciers of this region display an accelerated retreat, leading to a further regression of the snout position. By 2050, the retreat is estimated to be between about 300 and 400 m with respect to the current position. Glacier regression is more intense for the RCP8.5 and A1B scenarios, as it could be expected from the higher severity of these emission pathways.

Patterns of biodiversity in the northwestern Italian Alps: a multi-taxa approach

The current loss of biodiversity requires long-term monitoring of the distribution of living organisms, particularly in regions, such as mountains, which are highly sensitive to climatic and environmental changes. In 2007, three alpine parks in N-W Italy started a field program to determine the factors which influence animal biodiversity and identify the most appropriate methods for periodically repeatable monitoring. Twelve altitudinal transects (from montane to alpine belt) were chosen, each composed of 4–7 sampling units, for a total of 69 monitored plots. In each station, five taxonomic groups (carabids, butterflies, spiders, staphylinids, birds) were systematically sampled and topographic, environmental and micro-climatic variables were recorded. The aim was to assess the distribution of different taxa along altitudinal gradients and the relative influence of geographical, environmental and climatic factors. The data showed that species richness and community composition of invertebrates are mainly determined by altitude and microclimatic conditions, whereas birds are more sensitive to habitat structure. For invertebrates, the strong relationship with temperature suggests their potential sensitivity to climatic variations. The analysis of biodiversity patterns across vegetation belts indicated that the alpine belt hosts few species but a high percentage of endemic and vulnerable species, highlighting its importance for conservation purposes. This work offers a representative sample of the northwestern Italian Alps and it is a first step of a monitoring effort that will be repeated every five years to highlight the response of alpine biodiversity to climate and land-use changes.

Slope stabilization in difficult conditions: the case study of a debris slide in NW Italian Alps

A case study of a debris slide (estimated volume of about 35,000 m3) is described in this paper. This slide occurred in April 2009 in the North Western Italian Alps (Aosta valley) and damaged the SR25 road along the Valgrisenche valley. Ground investigations started with severe safety and logistic issues being posed. Given the need to open as soon as possible the road, the design of the landslide stabilization works was carried out using a “design as you go” approach. The stabilization measures were conceived to be flexible in order to allow for changes and integration during construction, in line with the progressive refinement of the geological–geotechnical slope model being developed. Back analysis by means of the limit equilibrium method (LEM) and the finite element method (FEM) was used. Groundwater level rise following heavy rainfall and spring snow melting was found to be the main cause of the debris slide. The stabilization works were designed by using both the LEM and FEM methods. The stability conditions of the engineered slope were assessed based on the available performance monitoring data.