Michele Freppaz

Mountain ecosystems are highly vulnerable to flash flood phenomena, which can result in sudden soil water saturation and surface erosion. Saturated soils are vulnerable to solifluction and liquefaction, depending on soil plastic properties. Surface erosion and mass movements create serious hazards for the population and the infrastructures: the recognition and mapping of areas characterized by different vulnerability to erosion processes are of primary importance in order to properly manage the land use and the hydro-geological hazards. The study area is the whole Val d’Aosta region, characterized by a wide range of geological substrates, vegetation types, altitude variations and pedoclimates (from perudic in south-east and at high altitude to xeric-ustic in the intra-alpine central valley). All genetic horizons from 150 soil profiles have been described and analyzed (standard chemical analysis and Atterberg limits), in order to understand how pedogenic processes influence soil plas...

Among the potential effects of climate change in the Alpine environment during the winter, of particular interest are the shift of the snowline toward higher altitude and the increase in frequency of rain events on the snowpack. Here, we present the implementation of a new, mid-to-long term study site to simulate these changes in precipitation regimes and determine their influences

Tourism has many potential benefits for rural areas, being an important source of jobs for nonmetro communities, especially for those that are economically underdeveloped. The traditional use of lands in mountain regions is combined nowadays with surfaces devoted to recreational activities because of increasing tourist demand for winter sports. Winter-based ski tourism is a major human use of many mountain

Most of the patterned ground phenomena occur in permafrost areas, whose distribution in alpine environments at middle latitudes, is strongly controlled by local climatic conditions, and specifically by snow cover. There are problems in determining the amount of precipitation at a given site in mountain permafrost areas, because snow can be redistributed by wind or avalanches. Surface soil conditions also affect permafrost distribution. Dry blocky surfaces, peaty soils and soils with a thick organic horizon tend to favour permafrost development. The dimensions of patterned ground show significant spatial variability, depending on microclimate and soil conditions. The field study was undertaken in the Gran Paradiso National Park, at an elevation of 3028 m ASL, on a gentle slope plateau, exposed to wind. The dimension and distribution of stone circles was determined through field survey (October 2008). The soil temperature (10 cm depth) during the winter season 2007-2008 was measured b...

Climate changes have huge impacts on alpine ecosystems. One of the most visible effects is glacial retreat since the end of the Little Ice Age (LIA: 190-190 years ago), which caused the exposure of previously glaciated surfaces. These surfaces are open-air laboratories, verifying theories regarding ecosystem and soil development. In order to increase our knowledge on the effect of time and vegetation primary succession on soil development in proglacial areas, we sampled soils and surveyed plant communities on stable points on the proglacial areas of the Lys and Verra Grande glaciers, in the Italian north-western Alps (Valle d'Aosta). Sampling sites were located on dated sites (6-260 years), on the basis of literature or historical photographs). Glacial till is attacked by weathering processes immediately after deposition and stabilization, such as loss of soluble compounds, acidification, primary mineral weathering. The speed of these processes are largely increased after the es...

The presence of a thick snowpack could interfere on forest stability especially on steep slopes: potential consequences include superficial soil erosion and damage of young and old stands, due to snow pressure and movements. The aim of this work is to determine the pressure of the snowpack on stems in forest with different tree composition. The study site is located

Due to their physico-chemical properties, POPs and PAHs are subjected to long-range atmospheric transport (LRAT) and may be deposited in remote areas. In this study, the contamination with DDx, PCBs, PBDEs, and PAHs was investigated in sediments and soils collected on the southern slopes of Mt. Everest (Himalaya, Nepal) in two different sampling campaigns (2008 and 2012). The results showed a limited contamination with POPs and PAHs in both soil and sediment samples. Therefore, the southern slopes of Mt. Everest can be considered a remote area in almost pristine condition. The LRAT mechanism confirmed its primary role in the transfer of contaminants to remote regions, while the gradual melting of glaciers, due to global warming, and the subsequent release of contaminants was suggested to be a secondary source of pollution of the lake sediments. In addition, the increase of tourism in this area during the last decades might have influenced the present concentrations of PAHs in the se...

Rock glaciers are the most prominent geomorphic features related to the presence of permafrost in mountain areas. Climate warming is likely to have strong impacts on permafrost status, making cold areas at high altitudes especially vulnerable. Therefore, climate evolution and its impact on abiotic and biotic components of permafrost environments is a research topic of increasing importance. In this work the active Col d’Olen rock glacier, located in the Istituto Mosso LTER (Long Term Ecological Research) site, in the Aosta Valley Region (NW-Italian Alps), is the object of an interdisciplinary investigation. Instrumentation and techniques are described below. Climatic data from automatic weather stations have been collected in the study area and they will be updated and analysed. Moreover, a network of portable instruments will be established (during the summer 2014) on the rock glacier for collecting meteorological data, after a dedicated calibration procedures to assess the uncerta...

ABSTRACT Studies concerning CO2 emission from soil to the atmosphere are essential to quantify and understand the carbon source or sink strength of ecosystems and to develop a global carbon balance. Seasonally snow-covered subalpine soils have been shown to be a non-negligible source of CO2 even during the winter season. These relatively high wintertime CO2 fluxes are due to the accumulation of the seasonal snowpack, which provides thermal insulation for subnivean soils and therefore allows biological activity during the winter. In high elevation sites in Colorado, such as the one we studied, the snow-covered season can last six months or more and therefore under-snow CO2 production can have a significant contribution to the annual ecosystem respiration. Moreover, at these sites, snowmelt is the main process providing water and solutes to soils, that usually dry out from June to September. In order to compare winter and summer fluxes, we measured CO2 fluxes continuously through the snow at a subalpine meadow in the Rocky Mountains, Colorado, during the winter 2006-2007 and made bi-weekly soil chamber flux measurements during the summer 2007. Ancillary measurements include soil temperature and soil moisture. During the winter, air samples were collected through the snowpack at different depths and fluxes were calculated using Fick's law. In the summer, measurements were done using an open chamber design. While the summer measurements currently are still underway, our first, preliminary data indicate a decreasing trend in CO2 fluxes during the drying-out period from July to September.

Nitrogen transformations in soil will depend mainly on the vegetation cover, that controls the organic matter quality, and on environmental factors such as precipitation and temperature. In high latitude areas, during winter, a consistent snow cover can insulate the soil from extreme air temperatures providing therefore a favorable environment for microbially-related processes. This work aims to describe seasonal patterns of

ABSTRACT N dynamics in minerotrophic peatlands are closely tied to soil moisture, soil temperature and the organic matter (OM) quality. During winter, subalpine minerotrophic peatlands are covered by snow, that insulates the soil from harsh environmental conditions and determines therefore a favorable ambient for biological processes. Moreover, in winter the water supply is much lower than in the snow free period, resulting in an oxidative environment at the peat surface. At the snowmelt, environmental conditions in the peatland change completely in a very short time, with potential effects on N dynamics. However, biological processes occurring in peatland soils under the snow cover are little studied. This work aims to identify the main processes involving N in a subalpine minerotrophic peatland during the snow-covered period. Three intact soil cores were sampled from a 63-ha minerotrophic peatland in the NW italian Alps (1650 m ASL, Val Ferret). One core was sampled prior to the snowmelt, one during the snowmelt and one at the end of the snowmelt. Ammonium, nitrate, dissolved organic nitrogen and microbial N were determined every 5 cm along the peat profiles. Ammonium and nitrate contents were quantified in the snowpack and in the surface incoming and outflowing water during the snowmelt. The results show that the over-winter biological activity was maximum at the surface oxidative layer and resulted in a significant production of ammonium and DON within the peatland. In turn, DON and ammonium were largely lost through surface waters during the snowmelt period. In contrast, the peatland was an effective sink for the nitrate released during the snowmelt, that undergoes fast trasformations in the soil. Our results suggest that relevant biological activity occurs in peatland soils during winter, and such activity may result in large N loss through leaching.

ABSTRACT In many Alpine catchments, the development of winter tourism determined a widespread change in land use, shifting from forested and cultivated lands to ski slopes. The construction of a ski slope implies a strong impact on the landscape, with potential consequences on the soil quality. In most cases, the construction procedures include the total or partial removal of the soil body, the reallocation of the fine hearth fraction, the subsequent seeding of plants and the use of organic fertilizers. This work aims to evaluate soil physical and chemical properties and nitrogen (N) dynamics in anthropogenic soils from ski slopes of different age. Study sites were located in Champoluc (AO)- NW Italy between 2400 and 2700 m ASL. Topsoils (0-10 cm depth) were sampled in 4 ski slopes hydroseeded with commercial mixtures 4, 6, 10 and 12 years earlier, and in 4 control plots at the same exposure and altitude as the ski slopes. Soil samples were characterized, N dynamics in winter was evaluated with the buried bag technique and snowpack was analyzed for chemical and physical properties. Total nitrogen (TN) content in topsoil ranged 0.75-1.06 g kg-1 and was not correlated with the ski slope age. In all but one site, the TN content was significantly lower in the ski slope than in the control plot. A positive net ammonification and nitrification throughout the winter were found in all but one ski runs. These results suggest a high variability in the evolution degree of these anthropogenic soils. The net overwinter N mineralization that we report demonstrates that these soils are biologically active during the winter season. Such activity results in a pool of labile inorganic nitrogen potentially available for plant demand at the spring snowmelt.

ABSTRACT Among the potential effects of climate change in the Alpine environment during the winter, of particular interest are the shift of the snowline toward higher altitude and the increase in frequency of rain events on the snowpack. Here, we present the implementation of a new, mid-to-long term study site to simulate these changes in precipitation regimes and determine their influences on soil carbon and nutrient cycles in forest environment. The study site is located in a forest (Larch stand), at 2020 m a.s.l., in Piedmont (NW-Italy) and includes tree plots equipped with soil moisture and temperature sensors: in the first plot the snow is removed, during December and January, to simulate a winter with late snowfall; in the second plot the snow is drizzle, in January, with liquid water chemically comparable to rain; in the control plot, the snowpack is left undisturbed. Tree repetitions for each treatment are equipped, at 30 cm of depth, with two suction lysimeters in order to weekly sample the soil solution where dissolved organic matter, inorganic N, microbial biomass C and N will be determined. Additionally, tree repetitions for each snow treatment are used as snow fields, for snow chemical analyses, to quantify ionic input to the soil, and physical characterization, in order to evaluate the influence of treatment-induced changes in snow density and grain composition on soil temperature and moisture regimes. Data will be collected during the ongoing winter (2009-2010), but we also attempt to get a mid-term effect by repeating the experiments during next winter seasons. KEYWORDS: Climate changes, forest environment, lysimeters, soil solution, SOM and nutrients, snow.

Since 1994, a number of investigations have been performed in the Val Masino catchment, in the Central Italian Alps, in order to understand interactions between the atmospheric fluxes and the biological compartment. In front of a N atmospheric input of 15 kg ha-1 yr-1, several observations, notably the strong soil N retention, seem to indicate N-limitation in the forested portion.

ABSTRACT Mountain agriculture needs to face several limitations related to climate and topography. Land levelling, reshaping, and terracing are widely adopted in Europe, in order to ease mechanization and make agriculture more profitable. However, while the economic and productive benefits of these operations are well known, the effects on soil chemical and physical properties are not always assessed, and need constant monitoring over time. Intense soil rebuilding has been carried out in Aosta Valley (NW Italian Alps) to improve the accessibility and mechanization, including irrigation, of mountain grasslands. In this research we considered 3 study sites established in grasslands subject to soil rebuilding practices. The aim was to investigate the effects of land-reshaping operations on soil chemical and physical properties, by comparing changes in some selected soil properties such as organic C and soil laboratory indexes for quantifying soil structural resistance. The soil profiles generally showed a simpler morphology after rebuilding. Soil structure and consistency, that are recognized as soil physical quality indicators, after a sharp negative effect of the disturbance (i.e. decrease in liquid limit, increased soil aggregates loss) generally showed a trend towards the restoration of the characteristics of the original soils in the medium or long-term time span. Despite the limited sample size, the results represent a first attempt to assess the effects of a technique which is being more and more applied in a mountain region, such as the Aosta Valley Region, where manufactured soils are a significant part of agricultural land. The main findings of our research indicated that: (1) structure and consistency of soils (i.e. aggregate loss, LL, PL) can be used as indicators of soil quality in response of anthropogenic soil disturbance due to land-reshaping operations, as they reflect the evolution of soil properties after intense disturbance; (2) after disturbance, soil recovery was relatively quick, despite the strong deterioration of the physical quality in the immediate (�6–12 months) aftermath of the operations.

Much of the surface area in mountain regions has been converted to recreational activities in recent decades due to the increasing demand of tourists for winter sports. In general, ski-run construction and management have a great influence on the chemical and physical properties of underlying soils. To create ski-runs the natural landform is often changed to level the surface, thus exposing unweathered parent material or deep soil horizons. Thus the original soil thickness can be reduced often resulting in a “turbated” topsoil. The result is that soils in ski-runs have an almost complete lack of structure, with subsequent problems of soil compaction and reduction of water and air permeability. Erosion on ski-runs is thus enhanced. One control that is often pursued is artificial seeding. However, depletion of soil organic matter, reduction in soil aggregate stability, and nutrient imbalance may affect plant development. In ski-run restoration the improvement of soil organic matter an...

Abstract An automated approach is presented, with the purpose of computing snow cover duration from satellite imagery and to, validate them with in-situ measured data. In the present study the employed MODIS dataset has a spatial domain covering the entire study ...

After the maximum expansion phase of the Little Ice Age, soils located in proglacial areas in the Italian Alps evolved over a time span of about 190 years. In the future, as a consequence of climate change, additional areas will become ice-free and therefore subject to pedogenesis. In such conditions, ice retreat time and topography are expected to play a major role among soil formation factors. Due to extreme environmental characteristics, soil evolution will be rather slow, and heavily influenced by severe soil loss phenomena (e.g. water erosion due to extreme rainfall event and snowmelt, avalanche erosion). We investigated the soil formation along a glacial chronosequence of an Alpine glacier foreland. The Pré de Bar glacier is located in North West Italy (Aosta Valley Region), in the Mont Blanc massif, between 3750 and 2150 m a.s.l. and it covers an area of 340 ha. The glacier was chosen because of the availability of old photographs documenting the glacier retreat phases starti...

The development of winter sports determines an increasing impact on the high altitude ecosystems, as a consequence of increased participation and an increasing demand of high quality standards for skiable areas. The construction of a ski slope is ...

ABSTRACT Purpose Climate change is driving strong variations in mountain habitats, such as glacier retreat, which is releasing large surfaces soon colonized by vegetation and attacked by weathering and pedogenesis. Many proglacial soil chronosequences have been studied in different parts of the world, but no study is available on early soil development and pedogenesis on serpentinite. Materials and methods We analysed the development of the main chemical (pH, organic matter, nutrients and exchangeable cations) and morphological properties in three soil chronosequences in the Verra Grande Glacier forefield (Italian side of the Monte Rosa Group, Western Alps), characterized by slightly different parent materials (pure serpentinite or serpentinite with small gneiss inclusions) and topography (steep lateral moraines or flat basal till). Results and discussion Organic matter accumulation, acidification and base and metal leaching are the most important pedogenetic processes active during early stages of soil formation on serpentinite in the upper subalpine altitudinal belt. These processes are associated with minor changes in color and structure showing weak mineral weathering. Biocycling of nutrients is limited on pure serpentinite because of weak primary productivity of the plant community. Pedogenesis is quite slow throughout the forefield, and it is slowest on pure serpentinite. On flat surfaces, where slow erosion permits a fast colonization by Ericaceae, the podzolization process begins after few centuries since moraine deposition, while on steep slopes more time is required. Conclusions Pedogenesis on serpentinite is extremely slow. The fast colonization by grassland species increases the speed of pedogenetic trends where serpentinitic till is enriched by small quantities of P-rich gneiss. The encroachment of forest-shrub species increases the speed of pedogenetic trends thanks to a strong nutrient biocycling.

Abstract The effect of a lack of snow cover in winter was investigated in two soils, beneath larch and meadow, in NW Italy (Vallée d'Aoste Region). During the late 1980s and early 1990s and 2000s, this region experienced extreme climatic conditions including a low ...

ABSTRACT Among the potential effects of climate change on subalpine forest ecosystems during the winter season, the shift in snowline towards higher altitudes and the increase in frequency of rain events on the snowpack are of particular interest. Here, we present the results of a 2-year field experiment conducted in a forest stand (Larix decidua) in NW Italy at 2020 m a.s.l. From 2009 to 2011, we monitored soil physical characteristics (temperature and moisture), and soil and soil solution chemistry, in particular carbon (C) and nitrogen (N) forms and their change in time, as affected by simulated late snowpack accumulation and rain on snow events. Late snowpack accumulation determined a stronger effect on soil thermal and moisture regimes than rain on snow events. Also soil chemistry was significantly affected by late snowfall simulation. Although microbial biomass C and N were not reduced by soil freezing, soil contents of the more labile dissolved organic carbon and inorganic N increased when the soil was affected by mild/hard freezing. Variations in the soil solution were shifted with respect to those observed in soil, with an increase in N-NO3− concentrations occurring during spring and summer. This study highlights the potential N loss in subalpine soils under changing environmental conditions driven by a changing climate. Copyright © 2013 John Wiley & Sons, Ltd.

ABSTRACT Snow avalanches are among the most important disturbances that affect mountain ecosystems, influencing forest dynamics, establishment and mortality processes. At the same time, forests can affect the likelihood of avalanche release and can, in some cases, protect human settlements and infrastructure. Yet, since the ability of a forest to protect settlements is largely a function of its stand structure and composition, snow characteristics and topography, under particular conditions, avalanches can be triggered in forested areas. The aim of this work is to identify forested areas in the Aosta Valley (NW Italy) where at least an avalanche release occurred and to determine, through case studies, the main forest features that may prevent an avalanche release. Based on analysis of the regional avalanches cadastre, 5.4% of all the recorded avalanches released from a forested area. A sample of 15 avalanche sites with a release zone within a forested area was chosen, to compare the structural characteristics with neighboring forested areas located at the same altitude, aspect and slope, where no avalanches occurred. Most of the avalanches released at the end of winter and in the early spring, during periods when the danger level was equal or higher than 3-considerable. In our case studies, stem density (stems/ha) was the most important factor for snowpack stabilization, while the shrub canopy cover increased the probability of avalanche release.By enlarging the current database, it might be possible to relate forest structural characteristics to the snowpack structure, and consequently to avalanche release. In some cases, it might be preferable to use sustainable practices, such as suitable silvicultural approach, instead of permanent defense structures (less ecologic and often more onerous) in order to achieve a satisfactory avalanche protection.

... Luisella Celi*{ Fulvia Rosso* Michele Freppaz* Alberto Agnelli{ and Ermanno Zanini* ... Mikan et al., 2002; Weintraub and Schimel, 2003; Shaver et al., 2006; Uhlırová et al., 2007), and could yield promptly available nutrient forms for plants and microorganisms (Schmidt et al ...

ABSTRACT Snowpack evolution and glacier ice surface temperatures were studied oil the Indren glacier (Northwestern Alps, Italy) under different meteorological conditions: ill winter 2002-2003, rich in snow from the beginning of the season, and in winter 20052006, poor in snow until February. Periodical snow profiles were made to measure the physical properties of snow. while data loggers measured the snow/ice interface temperature. Furthermore, in winter 2002-2003, the influence oil the snowpack evolution of ail artificial increase ill the snow density was evaluated. During the season rich in snow there was it prevalence of rounded crystals originated by melt-freeze metamorphism, while in the season poor in snow depth hoar and faceted crystals prevailed. due to the higher temperature gradient. From these two winter seasons, it appeared that a deep snow, cover of at least 100 cm was able to maintain the snow/ice temperature at around -5 degrees C until the snow cover reached isothermal conditions, whereas, during the winter of 2005-2006. the shallow depth of snow did not allow basal temperature to reach ail equilibrium value and the snow/ice interface temperature oscillated between -2 and -8 degrees C. The altered snow density had no effect oil the snow/ice interface temperature, whereas it Caused a delay in the time of reaching isothermal conditions, thus allowing snow cover on the glacier to persist longer.

Snow avalanches can exert considerable erosive forces on soils. If a snow avalanche flows directly over bare ground, basal shear forces may scrape away and entrain soil. Soil material entrained by the avalanche is transported to the deposition zone, changing the ...