Pasture dynamics of Alpine areas are linked to the complex cryospheric hydrology of Alpine catchment and to the interspecies competition, which are in turn expected to change remarkably under ...prospective global warming scenarios.
This study aimed at assessing the impact of climate change on the productivity of mountain pastures in the Gran Paradiso National Park (Italy).
The hydrological model Poli-Hydro was used, coupled with the Poli-Pasture model, able to simulate pasture growth, which was further integrated with CoSMo model to consider interspecific competition. Two (competing) species were chosen for low altitude LowAlt areas (below 1800 m asl), Trifolium alpinum and Dactylis glomerata, and two for high altitude HighAlt areas (above 1800 m asl), Festuca rubra and Nardus stricta. Model tuning and evaluation were performed against estimates of leaf area index (LAI), derived from satellite imagery during 2005–2019. Then, climate change impacts were projected until 2100 by considering four IPCC AR6 scenarios and six GCMs. Target variables included a set of agroclimatic indices, LAI and pasture yield.
Due to the projected increase in temperatures during the XXI century, a measurable potential increase in productivity would be expected, especially in the highest areas (up to +97% by 2050, and + 123% by 2100 for the SSP5–8.5 scenario). The relative abundance of pasture species appears to remain mostly stable; at most, the species with higher fodder value even increases slightly. This suggests that a loss in the overall quality of biomass should not occur. These results provide preliminary evidence for the potential development of livestock farming, and thus of a relevant part of the economy in the valleys, at higher altitudes than now. However, to a certain extent pasture performance could be threatened by the projected reduction in summer rainfall, and possibly spreading of pests with increasing temperature.
The results obtained here could be useful for policy makers, and scientists in the field of pasture/grasslands management, to depict scenarios of future productivity, and to support redefinition of periods, and areas designated for grazing activities in the mountains.
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•Agro-climatic indices provide a tool for future management of alpine pasture areas.•Pasture productivity is simulated considering the interspecific competition.•Pasture productivity is simulated for the total area of Gran Paradiso National Park.•Rising temperatures lead pasture yields to increase, if enough water is available.•An increase of productivity of high fodder value species is expected at high altitude.
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•Alpine forests and grasslands provide regulating services but the contribution is unkown;•We estimated soil organic carbon (SOC) stock in different mountain habitats;•We found higher ...SOC in meadows and deciduous forests compared to coniferous forests;•We investigated relationships between SOC, organic layers, forest structure and biodiversity.•Diversity of staphylinids, ants and orthoptera correlated with characteristics of organic layers;•Diversity of carabids, birds, spiders and butterflies correlated with vegetation parameters.
Ecosystem services (ES) evaluation is included in the environmental programs and policy strategies of protected natural areas in many countries. Alpine forests and grasslands play an important role in climate regulation but their contribution is still unknown. In this study, we estimated soil organic carbon (SOC) stocks for forest and grassland habitats by collecting samples from 87 plots in Gran Paradiso National Park (western Italian Alps). Results of the LMM show that habitat type affects SOC stock; grasslands and mixed broadleaf forests store higher SOC than mixed coniferous forests, spruce forests and larch forests. We investigate the relationships between biodiversity, SOC stock, OC stock in organic layers, soil types, forests structure and other environmental features using a canonical component analysis and a Pearson correlation matrix. The results show that biodiversity is mainly influenced by the altitude, OC stock in organic layers OH and habitats of coniferous forests. Biodiversity positively correlates to organic layers (Staphylinidae, Formicidae, Orthoptera), forests’ Shannon and evenness indices (Carabidae, Formicidae, Orthoptera, Aranea, Lepidoptera) and forests’ basal areas and stem density (Staphylinidae, Formicidae, Aranea). Further studies are needed to better investigate the relation between biodiversity and habitat features on ecosystem functions and thus on the provision of ES.
Quantitative phase petrology analysis of two samples showing variable strain record and different peak pressure (P) conditions show that H2O is a key parameter in the development of contrasting ...high-pressure (HP) peak conditions in adjacent polymetamorphic rocks. A shear zone in a paragneiss from the Gran Paradiso nappe, Western Alps, shows an Alpine foliation and records a peak P of 1.9 GPa, for a temperature of 500 to 520 °C. A few tens of meters away from the shear zone, a paragneiss showing no apparent Alpine age deformation records a peak P of maximum 1.4 GPa for the temperature range of 500 to 520 °C. The H2O content of the latter has potentially been reduced to low contents following the pre-Alpine, Variscan amphibolite facies, and the absence of re-hydration prior to Alpine orogeny could have inhibited the formation of HP mineral assemblages. The validity of this interpretation is questioned here by considering the mechanical effect of H2O undersaturated rocks on deformation and P during deformation. Based on a thermo-mechanical numerical modelling study, we show that heterogeneities in fluid saturation conditions between rocks lead to strength contrasts that are sufficient to trigger a dynamic P in the range of several hundreds of MPa. In particular, the models successfully reproduce the measured peak P between the two paragneiss studied. This model could be applied to other H2O deficient rocks from HP tectonic units to further explore the role of H2O on the rheology and hence assess its potential impact in the preservation of low P bodies in otherwise HP units from continental collision settings.
•H2O saturation conditions impact not only the metamorphic evolution, but also the stress state and deformation.•Heterogeneous stress conditions develop during deformation of similar rocks with contrasting H2O saturation conditions.•Metamorphic pressure variations can be recorded due to local variability in H2O (under)saturation conditions•The history of polymetamorphic units constitutes a geological heritage controlling future metamorphism and deformation style.
The Late Pleistocene to Holocene transition in the Northern Hemisphere was characterized by abrupt millennial-scale climatic changes testified in the Alpine Chain by proxy records derived from ...glacial landforms and deposits. A detailed reconstruction of the paleo-glaciers during the deposition of the pre-Little Ice Age (LIA) moraines and newly obtained 10Be exposure ages provide information on the timing of a glacier advance in the Gran Paradiso Group (Western Alps, Italy) related to the regional Egesen stadial as a response to the climatic deterioration at around 12.9–11.7 ka (corresponding to the Younger Dryas in northern Europe and to the Greenland stadial 1 in the INTIMATE event stratigraphy). The study area represents a key site to define the behaviour of the Egesen paleo-glaciers, since they are located in a significant climatic area between the moister Maritime Alps and the Northern Alps. The ELA reconstructions and the comparison with other Alpine sectors provide evidence that current relatively drier conditions in the area postdate the LGM and were already present during the Egesen stadial. Our results support a strong positive YD Arctic Oscillation index, which led to drier conditions in southern Europe and caused negative winter precipitation anomalies.
•First chronological constraint of the Egesen stadial in the Gran Paradiso.•ELAs during the Egesen stadial among the highest values recorded in the entire Alps.•Seasonal paleoclimatic information at the ELA reconstructed for the Egesen stadial.•Current relatively dry conditions were established at least since the Egesen stadial.
Garnet–chloritoid‐bearing micaschists from the Gran Paradiso massif (Western Alps) contain evidence of a polymetamorphic evolution. Detailed textural observations reveal that two stages of garnet ...growth are present in the micaschists, interpreted as: (i) relics of an early metamorphism of pre‐Alpine age and (ii) newly grown Alpine garnet, respectively. Both generations of garnet preserve growth zoning. From thermocalc‐based numerical modelling of mineral assemblages in pressure–temperature (P–T) pseudosections, we infer that garnet 1 grew at increasing temperature and slightly increasing pressure, whereas garnet 2 grew at decreasing pressure and slightly increasing temperature. Estimated P–T conditions are ∼620 °C, 6 kbar for the peak of the pre‐Alpine event, and of 490 °C, 18–20 kbar for the pressure peak of the Alpine event. Modelling of the modal proportion and chemical composition of garnet (i) shows that the subsequent decompression (to 14–15 kbar at 550 °C) must have been accompanied by moderate heating and (ii) does not support a stage of final temperature increase following decompressional cooling. This argues against a late thermal pulse associated with mantle delamination. Preservation of growth zoning in both generations of garnet and the limited amount of diffusive re‐equilibration at the boundary between the two garnets suggests that the rocks were subjected to fast burial and exhumation rates, consistent with data obtained from other internal Alpine units.
In the Western Alps, the Money Complex of the Gran Paradiso Massif, metamorphosed under blueschist facies during the Alpine cycle, is considered to be Permo-Carboniferous in age, but no ...palaeontological or radiometric data constrain this interpretation. A revision of the lithostratigraphy of the Money Complex allows recognizing a polygenic (graphite-rich) and a monogenic (graphite-poor) meta-sedimentary formation. Detrital zircon U–Pb geochronology in both meta-sedimentary formations shows that (i) the main population is Cambrian and Ordovician in age, (ii) the youngest grains are Silurian and Lower Devonian, and (iii) Carboniferous zircon grains are lacking. A careful study of the age distributions in the Alps suggests that potential source for the detrital material in the Money Complex is the Briançonnais basement. Late Carboniferous magmatism is widespread in the Helvetic Zone of the Alps. Permian magmatism is dominant in the Briançonnais, the Austroalpine and the Southalpine basements. The lack of Carboniferous zircons in the Money Complex suggests that the detritus was not shed from the Helvetic zone, which was separated from the Money basin by the Zone Houillère basin, where the main drainage pattern was developed from south to north and where the depocenters migrated northwards from the Upper Missisippian to Upper Pennsylvanian. We suggest that the Money Complex may had been located to the east of the main river drainage inside the Zone Houillère basin or alternatively may represent a small basin, located on the east of the Zone Houillère.
Fish stocking is a serious threat to originally fishless mountain lakes. We used non-chemical eradication methods (i.e. gillnetting and electrofishing) in four high mountain lakes in the Gran ...Paradiso National Park (Western Italian Alps) to eradicate alien brook trout
Salvelinus fontinalis
. Data of amphibians, macroinvertebrates, zooplankton, chlorophyll-a, nutrient concentrations, and water transparency were used as indicators of the recovery process. All treated lakes were returned to their original fishless condition in spite of their different sizes and habitat complexity, without permanent negative side-effects for native species. Several ecological indicators showed that many impacts of introduced fish can be reversed over a short time period following eradication. The present study adds to a still growing body of specialized literature on the recovery of habitats after the eradication of alien species and provides further evidence that physical eradication methods are effective and can be part of a more general strategy for the conservation of high mountain lake biota.
Exhumation rates for high-pressure metamorphic rocks need to be carefully estimated to decipher tectonic processes in subduction/collision belts. In the Gran Paradiso Massif (Western Alps), the Money ...Unit crops out as a tectonic window below the Gran Paradiso Unit. According to previous studies, the Gran Paradiso and Money Units reached peak pressure conditions at ~ 18 to 20 kbar, 480–520 °C and ~ 17 to 18 kbar, 500–550 °C, respectively. This yields a maximum difference of ~ 9 to 10 km in the subduction depth reached by these two units during the Alpine history. Thrusting of the Gran Paradiso Unit over the Money Unit led to the simultaneous development of the main foliation under the same metamorphic conditions (~ 12.5 to 14.5 kbar and 530–560 °C) in both units. The thrust contact was subsequently folded and then both units were exhumed together. The relative timing of the growth and dissolution of the accessory phases was assessed by combining thermodynamic modelling with inclusion, textural and chemical (major and trace element) data from both major and accessory phases. The age of monazite constrained the high-pressure metamorphism in both the Gran Paradiso Unit and the Money Unit at 41.5 ± 0.3 and 42.0 ± 0.6 Ma, respectively. Allanite replacing monazite in the matrix has been dated at 32.7 ± 4.2 Ma. The late growth of xenotime associated with the crystallization of biotite pseudomorphs at the expense of garnet (at about 10 kbar) was dated at 32.3 ± 1.0 Ma. Our petrochronological data indicate about 10 m.y. between the peak pressure conditions and the crystallization of xenotime leading to an exhumation rate of the order of 2.2–5 mm/year. The new ages allow to better constrain the timing of the displacement of the thrust defining the lower boundary of the extruding wedge of eclogite-facies rocks.
In the Gran Paradiso metagranodiorite (Western Alps) small scale lower amphibolite facies shear zones record the transition from a mylonite composed of polycrystalline mineral aggregates to a ...homogeneous ultramylonite with a grain scale phase mixture. Polycrystalline quartz aggregates in the mylonite deform by dislocation creep developing a crystallographic preferred orientation (CPO) and a monoclinic surface orientation distribution function (ODF). The polymineralic matrix of the mylonite and the ultramylonite deform by diffusion creep. In the ultramylonite the quartz CPO is randomized and the surface ODF becomes orthorhombic. The transition from mylonite to ultramylonite is accompanied by a grain size decrease and a disintegration of quartz aggregates, concomitant with the precipitation of K-feldspar (±biotite) between quartz grains.
In quartz, reduction from the dynamically recrystallized grain size in the aggregates (110 μm) to the size of the dispersed grains in the ultramylonite (25 μm) occurs through the following processes: K-feldspar precipitates at opening sites along grain boundaries (strain incompatibility) pinning the grain size in quartz aggregates. Coalescence of K-feldspar leads to enhanced grain boundary sliding and disintegration of the quartz aggregates. Solution precipitation reduces the size of the dispersed grains to less than subgrain size (∼45 μm).
► Quartz aggregates in the mylonite deform by dislocation creep. ► Polymineralic fine grained matrix deforms by diffusion creep. ► The ultramylonite (qtz–kfs–plg–bio) deforms by diffusion creep. ► Disintegration of quartz aggregates by nucleation and growth of kfs and bt. ► Quartz grain size decrease by combination of pinning and dissolution.
This work presents the structural evolution of a poorly studied key-area in the middle Ala Valley, Western Alps, where two tectono-metamorphic units are exposed. A geological map at the 1:10.000 ...scale, integrated with meso- and microstructural analysis, has been realised. We investigated the contact area between Gran Paradiso Massif in the footwall and Lower Piedmont Zone in the hanging wall. Both tectono-metamorphic units, with a different paleogeographic affinity, preserve similar polyphasic deformation histories, defined by four deformation phases. The Dp phase, strongly transposing previous structural relicts, is marked by a high-pressure assemblage associated with the Sp foliation. Dp controls the lithological boundary attitude. A mylonitic zone, developed during the Dp, showing kinematic indicators pointing to a top-to-the N-NW sense of shear, is responsible for the juxtaposition of the two units. Dp structural elements are deformed by Dp+1 and Dp+2 subsequent phases. A greenschist-facies overprinting was observed during the Dp+1 phase.
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