1,721,118 research outputs found
Changes in the seasonal snow cover of alpine regions and its effect on soil processes: A review
No full textAt its maximum annual development, snow can cover more than half the Northern Hemisphere land area with one-third experiencing seasonal snow cover. The precise conditions that develop during the annual pattern of snowpack development formation have implications for: (i) soil microbiological activity and nutrient transformations; (ii) the capacity of the accumulating snowpack to retain atmospheric derived solutes; (iii) preferential elution and rapid runoff of solutes from the snowpack during periods of thaw; and (iv) leaching of solutes. Long-term records of annual snow accumulation suggest that substantial, regional scale shifts in snowpack characteristics have been occurring. The accompanying changes in the frequency and timing of freeze-thaw episodes and the evidence of their disruptive and selective influence upon soil microbial processes, when human induced, suggests there are wider implications for nutrient cycling and functioning of mountain ecosystems. This review is focused on alpine landscape
Snow gliding and glide snow avalanches: recent outcomes from two experimental test sites in Aosta Valley (NW Italian Alps)
Full text linkWe have been continuing our research on snow gliding and glide snow avalanches in two experimental test sites in Aosta Valley Region. The sites are located in the Monterosa Ski resorts at 2100-2200 m a.s.l. and are equipped with a couple of glide-snow shoes, temperature and volumetric liquid water content (VLWC) sensors in the soil (at 5 and 15 cm depths) and in the basal snowpack layer. In the surrounding a manual snow station and an automatic weather station recorded snow and weather data. Starting from the preliminary presentation given at the ISSW 2014, we are now able to present new outcomes deriving from different analyses made on a more complete database. In the two monitoring seasons 2013-14 and 2014-15 we registered 9 glide snow avalanches: 2 cold and 7 warm-temperature events. A simple descriptive statistics of the variables registered at the moment of the glide avalanche events showed that the cold glide snow avalanche events were characterized, in average, by: i) a higher soil VLWC (26.9 % and 25.3 %) than in case of warm events (25.6 % and 24.9 %) at 5 cm and 15 cm depths, respectively; ii) a lower VLWC (0.6 %) in the snowpack basal layer than in case of warm events (2.5 %); iii) a slightly higher soil temperature at 5 and 15 cm depths (difference of 0.1 and 0.3 °C respectively) than in case of warm events. In the only warm glide snow avalanche event which presented a continuous gliding before, the daily glide rate showed a significant exponential relationship with the soil VLWC at both depths. Conversely, we did not found any relationship between the glide rate and the driving factors in the continuous cold gliding periods, as we have recently found in another experimental test site in the same region. In conclusion, this study contributes to assess the importance of soil VLWC, which seems to be one of the most important driving factor for gliding processes. Therefore, this study supports the need, already suggested by other scientists, of analysing such processes with an interdisciplinary approach which integrates snow and soil sciences
Simulating soil freeze/thaw cycles typical of winter alpine conditions: Implications for N and P availability
No full textSeasonally snow-covered alpine soils may be subjected to freeze/thaw cycles, particularly during years having little snow and during the late winter and early spring periods. Freeze/thaw cycles can stimulate soil mineralization and could therefore be one factor regulating nitrogen (N) and phosphorus (P) availability and cycling. In this study laboratory incubation experiments using four soils having contrasting properties have been used to characterize the change in N and P forms (microbial and soluble inorganic/organic) that occur after simulated freeze/thaw cycles. Soil samples were collected from locations representing extreme examples of either direct human management (grazed meadow (site M) and extensive grazing beneath larch (site L)) or those disturbed by more natural events (recent avalanche and colonisation by alder (site A)) and from beneath the expected forest climax vegetation beneath fir (site F). Topsoil from these sites, maintained at two different water contents (20 and 30%, w/w), were exposed to either a single (SF) or four sequential (4SF) freeze/thaw cycles. Each cycle consisted of 12 h at -9 °C and 12 h at +4 °C mimicking a diurnal pattern. A SF cycle reduced microbial N for soils from sites F and A and was accompanied by a significant increase in dissolved organic nitrogen (DON) at both moisture contents. In contrast, the microbial N of soils from M and L was not affected by the freeze/thaw cycles, suggesting a particular adaptation of soil microbes to these extremes in temperature. Freeze/thaw cycles resulted in a significant increase in the net ammonification in all soils. Extractable total dissolved N (TDN) and total dissolved P (TDP) increased in all soils after a SF cycle, however, the relative importance of the different N and P forms differed. At the lower soil moisture content, NO3 - concentrations remained constant or slightly decreased in all soils, except that from site M. In all other soils DON appeared to replace NO3 - as the potentially mobile N source after the freeze/thaw cycles. The relative contribution of dissolved organic P to TDP after freeze/thaw remained significant, and greater than 50% in all soils. Freeze/thaw cycles, in seasonally snow covered soils, are likely to have a selective effect on the microbial biomass. Freezing and thawing resulted in a pulse of net ammonification and DON release, which represent an important influence upon N cycling in these alpine systems
Properties, best management practices and conservation of terraced soils in Southern Europe (from Mediterranean areas to the Alps): a review.
No full textTerrace soils are distinctive features of the agricultural landscape in Europe. Due to their historical and aesthetic significance, they are a resource for agriculture and tourism: however they are also a challenge for land conservation and management. Nevertheless, the fundamental role of terrace soils for agricultural quality and natural hazard prevention has not been fully investigated.
In the past, terraced slopes became ideal sites for human settlement and agricultural activities. At present, they are often used for high quality crops that grow on soils with specific chemical and physical properties. The filling material used for building terraces is a human-reworked substrate, where pedogenesis occurs under a strong human influence. This leads to soils with a generally limited pedogenic development and coarse texture, although, often, with good productivity. When abandoned, terraces are subjected to progressive decay due to erosion processes and slope failures.
This review focuses on terrace soil properties, conservation and management in Southern Europe. In particular, it reports some examples from the northwestern Italian Alps, where terraced slopes are characterised by ancient origin and, presently, are subjected to specific practices for their preservation. The different effects of land degradation at hill slope scale may be mitigated through appropriate management practices favoring the terrace walls maintenance, drainage optimization, and the presence of a spontaneous vegetation cover. These subjects require careful planning and conservation measures that could be collected in “best practices” guidelines for farmers, landowners and decision-makers
Early stages of soil development on serpentinite: the proglacial area of the Verra Grande Glacier, Western Italian Alps
No full textPurpose 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 forestshrub species increases the speed of pedogenetic trends thanks
to a strong nutrient biocycling
Mountain dairy wastewater treatment with the use of a ‘irregularly shaped’ constructed wetland (Aosta Valley, Italy)
No full textIn mountain areas, economical activities related to milk processing represent both a key source of income
and job opportunities. One of the main characteristics of cheese production is the seasonal variability in
the volume of milk processed and wastewater production that tend to limit the capacity of ecosystems to
absorb their inputs. In alpine environment, the scarcity of plain surfaces and the climatic conditions
results in the need for high CW performances of variable nutrient inputs in different seasons. By
evaluating a CW seasonal efficiency for dairy wastewaters in a mountain region (Aosta Valley-NW Italy),
this research was aimed to understand how performances of nutrient removal could be affected by
seasonal shift in temperature and loadings. Results indicate that the “irregularly shaped” CW, designed to
fit the natural landscape, shows best organic removal efficiency in winter (93 and 96% mass removal for
BOD5 in summer and winter respectively), in presence of high organic loadings and low temperatures.
Even if nitrate removal is more variable during seasons (71 and 33% mass removal in summer and winter
respectively) and differently affected by environmental conditions, overall performance meet the need of high removal efficiency
Labile nitrogen, carbon, and phosphorus pools and nitrogen mineralization and immobilization rates at low temperatures in seasonally snow-covered soils
No full textSurface mineral horizons from four ecosystems sampled in the northwestern Italian Alps were incubated at -3 and +3°C to simulate subnivial and early thaw period temperatures for a seasonally snow-covered area. The soil profiles at these sites represent extreme examples of management, grazed meadow (site M) and extensive grazing beneath larch (site L) or naturally disturbed by avalanche and colonized by alder (site A) and the expected forest climax vegetation beneath fir (site F). Changes in labile pools of nitrogen (N) and phosphorus (P) were active at all sites at both temperatures during 14 days of laboratory incubation. Ammonium was the dominant inorganic form of total dissolved N (TDN), being equivalent to 1.8-9.8 g N m-2 within the mineral horizon. Gross rates of ammonification were similar at the two temperatures but significantly (p<0.05) greater in soil from beneath fir than in the other three. Nitrification occurred in all soils and displayed a wide range in rates, from 2 to 85 mg N m-2 day-1, and was least in the two most acid soils, A and F. Immobilization of NH4+ as microbial N was greater in the fir soil than in the other three. Also, the fir soil showed greatest gross ammonification and least accumulation of NO3- and greatest tendency to retain N. This high N retention capacity in the climax ecosystem contrasted with the managed systems characterized by higher nitrification rates and greater potential spring NO3- loss. Dissolved organic N ranged between 30 and 50% of the TDN, while dissolved organic P was greater than 70% of total dissolved P (TDP). The dissolved organic compounds were important components of the labile pool, in equilibrium with a large reserve of organic N, and may significantly contribute to the soil N availability at low temperatures
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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