Western Italian Alps Research Articles

Heavy Metals and Biological Properties of Subalpine Soils on Ophiolites in the Italian Western Alps

Abstract Soils on ultramafic rocks are usually colonized by plant species and communities adapted to high heavy-metal content and low Ca/Mg ratio. However, the effects of metal speciation on microbial activity and arthropodal communities have scarcely been studied, especially under coniferous forests in boreal or subalpine areas. Six typical subalpine soils, in the ophiolitic area of Mont Avic Natural Park, located in the Western Italian Alps, were studied in order to verify the chemical speciation of Ni, Co, Mn, and Cr and their effects on soil biological properties and microbial activity. Five soils, developed from till composed of mafic and ultramafic materials, showed strong signs of podzolization, while the sixth was polluted by mine spoil. All the samples had high metal content, high acidity, and high metal mobility and bioavailability. These edaphic properties deeply influenced both arthropodal communities and microbial activity, all of which were strictly correlated with parent material and bioava...

Plastic deformations in kyanites by tectonometamorphic processes: a single-crystal X-ray diffraction study

AbstractThe crystalch emistry and crystal structure of naturalky anite crystals from the Eclogitic Micaschists Complex of the Sesia-Lanzo Zone, Western Italian Alps, have been investigated by means of optical microscopy, wavelength dispersive X-ray microanalysis, and single-crystal X-ray diffraction. The association of kyanite + garnet + phengitic-mica + chloritoid suggests that the eclogite-facies stages occurred at P ≤ 2.1 GPa and T ≤ 650ºC. Kyanite grains are large (cm-sized) porphyroblasts grown dynamically during one of the deformational events related to the subduction of the Austroalpine continentalcr ust. Under the polarizing microscope, kyanite grains show almost homogeneous cores, whereas rims are sometimes symplectitic aggregates of quartz and kyanite, confirming at least two stages of growth most likely related to the multistage deformational history of these rocks. Chemical analysis shows that Fe3+ is the major substituting cation for Al3+, ranging between 0.038 and 0.067 a.p.f.u.The single-crystal X-ray diffraction investigation of the kyanites shows severely textured patterns on the (h0l)*-plane. Such evidence is not observed in the unwarped diffraction patterns on (0kl)* and (hk0)*. The most significant difference between the structuralp arameters refined in this study, with respect to those of previously published unstrained gem-quality crystals, concerns the displacement parameters. The anisotropic displacement ellipsoids of all the atomic sites are significantly larger than those previously described, and systematically oriented with the largest elliptical section almost perpendicular to [010]. The larger ellipsoids in the kyanite crystal investigated here reflect the displacement of the centre of gravity of the electron distribution, rather than an anomalous atomic thermal motion. The magnitude and orientation of the displacement parameters and the textured/strained diffraction pattern may be the result of two combined effects: (1) that the kyanite crystals are actually composed of several blocks; (2) the crystals are affected by a pervasive residual strain, as a result of tectonometamorphic plastic deformations and re-crystallization.

Influence of the elevation accuracy in the updating of large scale geo-databases in mountain urban areas using IKONOS images

Map production and revision in mountain areas by means of high resolution satellite images showed to be a difficult task. This paper investigates the influence of the elevation accuracy in the updating of large scale geo-databases (geo-DBs) in a mountain urban area of the Italian Western Alps using high resolution panchromatic IKONOS images. A simulation of 1:10,000 scale geo-DB update was performed for the city of Sauze d'Oulx (Susa Valley, Italy) and tested with respect to the Regional technical specifications recently adopted in northern Italy. Finally, results were compared to the official geo-DB available for the test site. Results show that, depending on the digital elevation model's accuracy used, it is possible to satisfy the requirements for the residual's tolerance but not those for residual's mean and standard deviation, thus high resolution DEMs may be needed for updating large scale geo-BDs in mountain areas.

A neural network method for analysis of hyperspectral imagery with application to the Cassas landslide (Susa Valley, NW-Italy)

Geomorphological analysis is an essential element of many landslide monitoring and hazard assessment studies. Remote sensing techniques have long been an effective tool for such analyses. This paper presents results regarding a geomorphological investigation performed exploiting information derived from high resolution hyper-spectral airborne sensor MIVIS ( Multi-spectral Infrared and Visible Imaging Spectrometer) images. The authors propose a workflow based on neural network algorithms used both for image geometric correction and classification. The case study area is the Middle Susa Valley (Italian Western-Alps). It includes the Cassas landslide, a well-known complex landslide affecting slopes on the southern side of the valley, near the town of Salbertrand. At this location several “lifelines” (railway, main roads, hydroelectric tunnels, etc.) are concentrated, and they suffer from a constant threat of landslide activity. Traditional geomorphological characterization of the landslide slope was improved by comparing field campaigns with further information extracted from remote-sensed datasets. Presented results include the identification and characterization of major elements of the present-day active unstable slope (debris-covered areas, fractured/disjointed rock walls, landslide accumulation borders), as well as of individual structural features and landforms (major faults and fractures, trenches, elongated depressions, counterslope scarps), related to long-term deep-seated gravitational slope deformation.

Hydromorphology and land use at different spatial scales: expectations in a changing climate scenario for medium-sized rivers of the Western Italian Alps

The study presents an investigation of the relationships between hydromorphological features and land use in two medium-sized Italian Alpine catchments. The South European River Habitat Survey (SE_RHS) method was applied in the collection of hydromorphological data. Five different spatial scales ranging from catchment to site scale were considered for the quantification of land use. Separate Principal Component Analyses for grouped data sets were run on hydromorphological variables related to different spatial scales and the type of information provided. The analyses demonstrated that the most important gradients are related to channel stability. Unstable river reaches, characterized by a significant presence of unvegetated bars, were predominantly related to natural land use. On the contrary, more stable river reaches, characterized by the presence of vegetated bars, were found to be related to anthropogenic land use. High turbulence flow types appeared to be associated with urban and industrial land use. The climate scenario predicts a general increase in temperature, a slight decrease in precipitation, a more dynamic discharge regime and an increase in extreme events, all of which may produce considerable modifications to present agricultural and river management practices. A conceptual model based on the situation observed in the studied catchments is presented, that can be used to infer possible land use changes, during climate variation, in areas adjacent to rivers.

The Effect of Weathering on Ecopersistence, Reactivity, and Potential Toxicity of Naturally Occurring Asbestos and Asbestiform Minerals

The mechanisms underlying asbestos toxicity mainly rely on experiments performed on “laboratory” fibers, but little data is available on naturally occurring asbestos (NOA). Human exposure to NOA is subject to their ecopersistence and the modulation of their potential toxicity following weathering. The effect of weathering on three fibrous minerals from the Italian Western Alps, chrysotile, tremolite, and balangeroite—a Fe-rich asbestiform mineral—was investigated by mimicking more than 100 yr of physical (freezing–thawing/wetting–drying cycles in a climatic chamber) and biochemical forces (incubation with oxalic acid). Ion release, evaluated by means of inductively coupled plasma–atomic emission spectroscopy (ICP-AES), and variation in chemical composition, evaluated by scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS), indicated that weathering modified the fibers in the series: chrysotile > balangeroite > tremolite. Kinetics of ion release from the fibers (Mg, Fe, and Si) revealed different ion removal pathways. Tremolite was poorly affected. Chrysotile preferentially released cations up to a plateau, with physical and biochemical forces acting competitively. Conversely, for balangeroite, upon which weathering forces acted synergistically, the initial loss of ions facilitated further dissolution and more Si than Mg was released, suggesting an ongoing collapse of the crystal structure. Depletion of redox-reactive ions produced a significant reduction in fiber-derived •OH radicals (EPR, spin-trapping technique), but the fibrous nature was always retained. Despite weathered fibers appearing less toxic than “stored/laboratory” ones, NOA is to be considered far from safe because of fibrous nature and residual surface reactivity. Risk assessment needs to consider the effect of weathering on exposures. Both tremolite and balangeroite may contaminate, in some areas, chrysotile asbestos. However, in contrast to tremolite, balangeroite exhibits a low ecopersistence, similar to chrysotile behavior. Any contribution of balangeroite to chrysotile toxicity will thus be related to its quantitative occurrence and not to higher structural stability.

U–Pb zircon ages for post-Variscan volcanism in the Ligurian Alps(Northern Italy)

Abstract: Ages of Permian volcanic rocks from the Ligurian Briançonnais domain (Western Italian Alps) have been determined by laser ablation inductively coupled plasma mass spectrometry U–Pb dating of zircon. Three major volcanic units yielded zircons that were dated: calc-alkaline rhyolites (285.6 ± 2.6 Ma), andesites (with inherited cores yielded ages c . 476 Ma and older) and voluminous rhyodacites–rhyolites (272.7 ± 2.2 Ma). Following an amagmatic, sediment-starved time gap of c . 14 Ma, alkaline volcanic activity is recorded, at the top of the sequence, by K-alkaline rhyolites dated at 258.5 ± 2.8 Ma. The Ligurian segment of the Southern Variscan belt records transtensional and then extensional tectonics associated with the volcanic activity. The switch from calc-alkaline to alkaline activity corresponds to the transition from a post-orogenic to an anorogenic setting in the Southern Variscides; it may represent progressive and increasing delamination of the continental lithosphere, accompanied by partial melting of the lithospheric mantle. Supplementary material: Technical and data acquisition parameters, U–Th–Pb isotope analyses and calculated ages of zircons from samples and standard, and trace element compositions of selected zircons are available at: http://www.geolsoc.org.uk/SUP18322 .

Mont Avic Natural Park – Management Supported by Scientific Research and EMS

The Mont Avic Park protects an area of the south-eastern Aosta Valley (Italy) with particular landscapes and natural features which, until the late 1980s, remained almost unexplored from a scientific point of view. In the course of its twenty years of operation, the park administration has promoted a substantial series of environmental monitoring research projects and campaigns and the protected area is now one of the best-known of the Western Italian Alps. For the last seven years, the park has also implemented an Environmental Management System which, in 2003, led to its ISO 14001 certification as well as to EMAS registration, thus becoming the first protected area in Italy and in Europe to have received this prestigious recognition by the European Community. The management policy for the protected area, developed through this innovative approach, provides for a continual improvement of the knowledge about the various environmental components through specific scientific research activities, enabling the park administration to create a framework of reference material, which is increasingly comprehensive and constantly updated, and ensuring that adequate management and planning strategies are carried out to protect the biodiversity and promote the territory, with additional positive effects on the local communities and local economy.

Food–niche relationships within a guild of alpine ungulates including an introduced species

AbstractTo assess competition for trophic resources within a guild of ungulates, we studied the food niches of sympatric ungulates in an alpine area of the Italian Western Alps and evaluated the extent of their dietary overlap, especially with regard to the presence of the introduced mouflon Ovis musimon. The roe deer Capreolus capreolus had the most diverse diet including dicotyledons, young sprouts of trees and an unusually high percentage of graminoids. The red deer Cervus elaphus and chamois Rupicapra rupricapra mainly consumed graminoids, supplemented with dicotyledonous herbs and woody plants. The mouflon was a grass feeder, with graminoids representing the majority of items ingested in all seasons. Among the native species, we recorded a high overlap of feeding choices between red deer and chamois, which frequently used the same areas and are both intermediate feeders. The mouflon showed considerable dietary overlap with the chamois and red deer in all seasons, while the similarity with roe deer was low. High food–niche overlap can imply competition but only if resources are limited and the species use the same habitats.

Structural evolution of different tectonic units across the Austroalpine–Penninic boundary in the middle Orco Valley (Western Italian Alps)

A structural study along the Orco Valley, which represents a geological section through the Alpine belt (western Italy), is reported. A Lower Tectonic Element, composed of units with eclogite facies relics (Gran Paradiso and Zermatt–Saas-like Unit) and an Upper Tectonic Element, made of greenschist facies units (Combin-like Unit and Gneiss Minuti Complex of the Sesia–Lanzo Zone) have been distinguished. These two elements show a different main Alpine tectono-metamorphic event (D 1) and are separated by a mylonitic contact (D 2) developed under greenschist facies conditions (Orco Shear Zone). This regional scale shear zone was responsible for the exhumation of the deeper eclogitic units, and has been inferred as the continuation of the Combin Fault south of the Aosta Valley. From D 3 onward, the same tectono-metamorphic evolution was recorded in all units. The following extensional crenulation cleavage (D 4) occurs mostly along a NNE–SSW deformation zone about 1 km thick at the base of the Upper Tectonic Element which leads to a further exhumation of the Lower Tectonic Element.

Geochemistry of apatite-rich layers in the Finero phlogopite–peridotite massif (Italian Western Alps) and ion microprobe dating of apatite

Highly metasomatized apatite-rich peridotite layers (AP-layer) occur in the Finero phlogopite–peridotite massif (western Italian Alps). The AP-layer and the host peridotite are characterized by higher concentration of REE (total REE > 80ppm), especially LILE, and lower HFSE, than those of the other rocks in the Finero massif. The AP-layers and their host peridotites have bulk silicate Earth-like Sr and Nd-isotope compositions except for one sample containing rare carbonate aggregates. The carbonate aggregates occur in a late serpentine-talc veinlet and show relatively high d 13C and d 18O, high 87Sr/ 86Sr and lower ɛNd than the other samples. These results, combined with the previous data, indicate that the carbonates formed late at relatively low temperatures. The petrochemical results along with the literature suggest that the AP-layer was locally formed from a metasomatic agent geochemically distinct from that formerly producing phlogopite-bearing harzburgite widely distributed throughout the massif. We propose that the metasomatic agent for the AP-layer was an orthopyroxene-saturated, CO 2-bearing hydrous fluid/melt that evolved through the crystallization of metasomatic minerals upon reactions with peridotites. Sensitive high-resolution ion microprobe (SHRIMP) analyses of apatite grains yielded a Tera-Wasserburg concordia three-dimensional isochron age of 215 ± 35Ma in the 238U/ 206Pb– 207Pb/ 206Pb– 204Pb/ 207Pb diagram. The age is similar to intrusions in the Finero area, suggesting that the carbonate- and apatite-metasomatism was synchronous with Triassic magmatic activity.

A density management diagram for Scots pine ( Pinus sylvestris L.): A tool for assessing the forest's protective effect

Density management diagrams (DMD) are graphical tools used in the design of silvicultural regimes in even-aged forests. They depict the relationship between stand density, average tree size, stand yield and dominant height, based upon relevant ecological and allometric relationships such as the self-thinning rule, the yield-density effect, and site index curves. DMD effectively summarize stand structural descriptors, and are therefore helpful in determining stand characteristics needed to achieve a range of management goals. We constructed a DMD for Scots pine ( Pinus sylvestris L.) forests in the western Italian Alps. We used 210 sample plots from a region-wide forest inventory to determine the maximum density line and volume and top height isolines. Site index curves were used to assess the time taken by stands to progress along their development trajectories. The protection provided by Scots pine stands is most effective against rockfall, due to the frequent occurrence of such forests in active source or transition areas. We used the DMD to identify combinations of size and density representing optimal and sub-optimal protection from rockfall. An actual pine stand was used as a case study to illustrate how the diagram can be used to assess current functionality of the forest, forecast its likely development and compare alternative management strategies.

Geomorphological hazards related to deep dissolution phenomena in the Western Italian Alps: Distribution, assessment and interaction with human activities

Deep dissolution affects great part of soluble rocks (e.g. gypsum and anhydrite) of the Western Italian Alps. The related superficial phenomena (sinkholes, gravity-induced processes and a local worsening of geomechanical rock properties) are not limited to typical karsts landscape and cause slope instability also affecting populated sites and infrastructures. The paper aims to describe general characteristic of dissolution phenomena, to interpret their conditioning factors and evolutionary stages and to assess possible hazards due to their superficial effects. The search for evidences of deep dissolution leads to the selection of representative sites in the central part of the Western Italian Alps (Piemonte and Valle d'Aosta Region). Detailed geological and geomorphological studies have been used to classify the selected sites by type, size and variable state of activity. Very different evolutionary stages of dissolution phenomena have been interpreted by comparison of case-studies: some are early “embryonic”; others are more evolved, up to typical sinkholes, or even remodelled by other phenomena. Some cases show an extreme complexity in the interactions between corrosion phenomena and other geomorphic processes: slope deformations, from one side, and karst, fluvial and glacial phenomena, to the other. A wide range of movement rates on slope instabilities induced by deep dissolution have been estimated by topographic and geomorphic data. Geochemical data on removed rocks by dissolution indicate 0.4 mm/year values for local subsidence. Historical and technical data indicate low frequency of major dissolution-induced collapses, but highlight widespread damages to tunnels, roads and buildings, especially along slopes.

Habitat use and movement patterns in the endangered ground beetle species, Carabus olympiae (Coleoptera: Carabidae)

One of the most compelling challenges for conservation biologists is the preservation of species with restricted ranges. Carabus olympiae Sella, 1855, a ground beetle species inhabiting two small areas in the western Italian Alps, is an example of a steno-endemic and endangered insect species. Despite the fact that this species is historically well known to professional and ama- teur entomologists, its autecology is virtually unknown. In the present study we used pitfall traps to study habitat selection and phe- nology, and radiotelemetry to measure differences in movement parameters between sexes, habitats and periods. Data from pitfall trapping suggested that C. olympiae actively selects both shrubberies (alpen rose Rhododendron ferrugineum and bilberry Vaccinium myrtillus) and beech forests and avoids pastures, and that population size peaks in July. All radio-tagged individuals (n = 21) moved without a preferred direction, and were more active at night than by day. Males covered greater distances and had more tortuous tra- jectories than females. Distances covered in forests and alpen rose shrubberies were not significantly different, but paths in beech forests were more convoluted than in shrubberies. The movement pattern observed fits the requirements of a typical olfactory- tactile insect predator that looks for prey by systematically exploring its territory. Movement parameters suggested that both beech forests and alpen rose shrubberies are suitable for this species and indicated that the spatial distribution of shrubs in shrubberies can constrain trajectories. The implications for conservation are: (i) any human intervention which results in enlargement of the present coverage of pastures should be controlled; (ii) forest management may be tolerated, with the condition that alpen rose shrubberies remain or develop after tree-cutting; (iii) once a shrubbery has established, it should be preserved through appropriate managem ent.

AN ECLOGITISED OCEANIC PALAEO-HYDROTHERMAL FIELD FROM THE ST. MARCEL VALLEY (ITALIAN WESTERN ALPS)

The eclogite-facies Servette metaophiolites (St. Marcel Valley, Italian Western Alps) belong to the Piedmont Nappe. They are glaucophanite, chloriteschists, talcschists and associated mineralised quartzite derived from different types of hydrated Tethyan oceanic crust affected by sea-floor and sub-sea floor hydrothermal alteration. We first describe the geology and lithology of the Servette metaophiolites and their chemical signature, and then we focus on the estimation of the Alpine subduction-related peak P-T metamorphic conditions and associated microstructures. Estimation of the peak P-T conditions was performed via calculations of pseudosections representing the equilibrium assemblages in the studied rocks using THERMOCALC. These calculations yielded relatively uniform values for the high-pressure metamorphic equilibration, with temperatures of 550 ± 60°C and pressures of 2.1 ± 0.3 Gpa, higher than the previously estimated P-T in the St. Marcel Valley (T max = 500°C and P max = 1.4 GPa), but lower than those obtained in other localities of the Zermatt-Saas zone (T up to 550-600° C and P up to 2.5-3.0 GPa). Comparison with similar rocks from the Zermatt-Saas zone helps to constrain the peculiar conditions at the P peak of these hydrated rocks within the Alpine subduction slab.

Quantitative basin characterisation to refine debris-flow triggering criteria and processes: an example from the Italian Western Alps

This paper investigates rapid channelized debris flow related to rainfalls in small alpine basins. Its goal is to evaluate and correlate different geological and technical aspects with predisposing and triggering factors that can control these phenomena. The study area is the upper part of the Susa Valley where 12 small basins were selected. For each of them, lithological, geomorphological, climatic and technical information were mapped and analysed. Debris-flow triggering conditions, flow and depositional processes were related to physical characteristics of the basin that can be easily measured and quantified. At least three different groups of basins were found: G1) basins with one event each 4–6 years, characterised by massive or blocky calcareous rocks, G2) basins with more than one event per year that show an abundance of layered or sheared fine-grained rocks and G3) basins with recurrence levels exceeding 10 years, activated only by heavy and prolonged rainfalls, marked by massive or blocky coarse-grained igneous rocks. Furthermore, important morphometric differences were found. These considerations are useful in terms of hazard zonation and risk mitigation.

Cellular-Automata Model for Dense-Snow Avalanches

This paper introduces a three-dimensional model for simulating dense-snow avalanches, based on the numerical method of cellular automata. This method allows one to study the complex behavior of the avalanche by dividing it into small elements, whose interaction is described by simple laws, obtaining a reduction of the computational power needed to perform a three-dimensional simulation. Similar models by several authors have been used to model rock avalanches, mud and lava flows, and debris avalanches. A peculiar aspect of avalanche dynamics, i.e., the mechanisms of erosion of the snowpack and deposition of material from the avalanche is taken into account in the model. The capability of the proposed approach has been illustrated by modeling three documented avalanches that occurred in Susa Valley (Western Italian Alps). Despite the qualitative observations used for calibration, the proposed method is able to reproduce the correct three-dimensional avalanche path, using a digital terrain model, and the order of magnitude of the avalanche deposit volume.

A Multidisciplinary Methodology for Hazard and Risk Assessment of Rock Avalanches

A quantitative procedure for hazard and risk assessment of large landslides that can develop as rock avalanches is discussed in this paper. Reference is made to the IMIRILAND project, where a multidisciplinary methodology has been developed paying particular attention to the landslide modeling process that leads to the quantification of the hazard, i.e. the prediction of the occurrence probability, the involved area and the run-out velocity. The risk assessment methodology is exemplified in the paper with reference to two cases: the Ceppo Morelli and Rosone landslides, both of which are located in the Italian Western Alps. The results of these applications show that, despite the development of sophisticated 3D numerical methods, many uncertainties still remain in the process of modeling large and complex landslides, related in particular to the definition of the probability of failure and the rheological parameters to be used for the prediction of rock mass behavior. However geo-mechanical models are found to be very valuable tools to verify, from a mechanical point of view, the assumptions introduced through the geo-structural and geo-morphological analyses concerning the volume and the kinematics of the unstable mass, and their role is fundamental for the determination of the involved area when mechanical parameters can be assumed with sufficient reliability.

The role of the wolf in shaping a multi‐species ungulate community in the Italian western Alps

The impact of predation by wolves on prey populations was analysed in a portion of the western Alps characterized by a rich wild ungulate community. The number of wolves ranged from 7 to 15 (1.7–2.9 wolves/100 km2) during the study period (2000–2001). The diet of wolves mainly consisted of wild ungulates. Red deer and roe deer were the staple prey, while chamois was consumed less despite its high density. From 2000 to 2002, wolves annually removed 20–34 red deer, 21–58 roe deer, and 7–14 chamois per 100 km2. These amounts were equivalent to 19–51% of the annual mortality of red deer, 6–28% of roe deer and 6–9% of chamois. Additionally, hunting accounted for 58–94% of the annual mortality of red deer, 18–29% of roe deer and 22–43% of chamois. Other mortality factors (i.e. traffic accidents, disease, poaching) constituted a small percentage of the annual mortality of red deer (5–6%), roe deer (6–9%) and chamois (1%). During the study period, the density of prey animals was stable. Wolf predation did not seriously affect ungulate populations. The role of wolves on wild ungulate populations in the Susa Valley seemed to be compensatory.

Influence of the Kid on Space Use and Habitat Selection of Female Alpine Ibex

Abstract: Mammalian females change their behavior during the last stages of pregnancy and during the weaning as a response to new energetic requirements and antipredator behavior. From March 2001 to December 2004, we studied the effects of parturition and weaning on home‐range sizes and habitat selection in 28 female Alpine ibex (Capra ibex) in a 1,700‐ha free area in the Gran Paradiso National Park (Western Italian Alps). We calculated Kernel home range enclosing 95% of each female's locations according to seasonal and bimonthly timescales. Pregnancy did not seem to modify spatial behavior. Lactating females showed smaller home ranges than nonlactating ones after the birth period in June‐July. Hot summers slowed kids' growth and prolonged maternal care, modifying mothers' behavior. In summer 2003, which was hotter and drier than usual, weaning females showed even smaller home ranges. Because of their use of antipredator tactics during the weaning season, lactating females showed a higher use of safer habitats, such as rocky slopes. Our results are consistent with the findings of previous cervid and bovid studies, and they suggest that ungulate mothers may move to suboptimal, but safer, habitats during weaning to reduce the predation risk for their offspring.