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Rising air temperatures threaten the snow reliability of ski resorts. Most resorts rely on technical snowmaking to compensate lacking natural snow. But increased water consumption for snowmaking may cause conflicts with other sectors' water uses such as hydropower production or the hotel industry. We assessed the future snow reliability (likelihood of a continuous 100-day skiing season and of operable Christmas holidays) of the Swiss resort Andermatt-Sedrun-Disentis throughout the twenty-first century, where 65% of the area is currently equipped for snowmaking. Our projections are based on the most recent climate change scenarios for Switzerland (CH2018) and the model SkiSim 2.0 including a snowmaking module. Unabated greenhouse gas emissions (scenario RCP8.5) will cause a lack of natural snow at areas below 1800–2000 m asl by the mid-twenty-first century. Initially, this can be fully compensated by snowmaking, but by the end of the century, the results become more nuanced. While snowmaking can provide a continuous 100-day season throughout the twenty-first century, the economically important Christmas holidays are increasingly at risk under the high-emission scenario in the late twenty-first century. The overall high snow reliability of the resort comes at the cost of an increased water demand. The total water consumption of the resort will rise by 79% by the end of the century (2070–2099 compared to 1981–2010; scenario RCP8.5), implying that new water sources will have to be exploited. Future water management plans at the catchment level, embracing the stakeholders, could help to solve future claims for water in the region. [ABSTRACT FROM AUTHOR]

In 2018, Central Europe experienced one of the most severe and long-lasting summer drought and heat wave ever recorded. Before 2018, the 2003 millennial drought was often invoked as the example of a "hotter drought", and was classified as the most severe event in Europe for the last 500 years. First insights now confirm that the 2018 drought event was climatically more extreme and had a greater impact on forest ecosystems of Austria, Germany and Switzerland than the 2003 drought. Across this region, mean growing season air temperature from April to October was more than 3.3°C above the long-term average, and 1.2°C warmer than in 2003. Here, we present a first impact assessment of the severe 2018 summer drought and heatwave on Central European forests. In response to the 2018 event, most ecologically and economically important tree species in temperate forests of Austria, Germany and Switzerland showed severe signs of drought stress. These symptoms included exceptionally low foliar water potentials crossing the threshold for xylem hydraulic failure in many species and observations of widespread leaf discoloration and premature leaf shedding. As a result of the extreme drought stress, the 2018 event caused unprecedented drought-induced tree mortality in many species throughout the region. Moreover, unexpectedly strong drought-legacy effects were detected in 2019. This implies that the physiological recovery of trees was impaired after the 2018 drought event, leaving them highly vulnerable to secondary drought impacts such as insect or fungal pathogen attacks. As a consequence, mortality of trees triggered by the 2018 events is likely to continue for several years. Our assessment indicates that many common temperate European forest tree species are more vulnerable to extreme summer drought and heat waves than previously thought. As drought and heat events are likely to occur more frequently with the progression of climate change, temperate European forests might approach the point for a substantial ecological and economic transition. Our assessment also highlights the urgent need for a pan-European ground-based monitoring network suited to track individual tree mortality, supported by remote sensing products with high spatial and temporal resolution to track, analyse and forecast these transitions. [ABSTRACT FROM AUTHOR]

During the past century atmospheric nitrogen deposition increased dramatically due to human activities worldwide. Currently, it exceeds the critical load for nitrogen (CLN) in over 90% of the Swiss forest area and raised bogs, in 80% of all fens and in 30% of species-rich grassland areas in Switzerland. Indirect gaseous nitrogen losses (HNO 2 , NO, N 2 O, N 2 ) from these soils induced by atmospheric nitrogen deposition are likely to be substantial. However, the approaches to estimate these indirect N emissions provided by the international organisations (UNFCCC, IPCC; UNECE, EMEP/EEA) are based on agricultural data only. They may not be suitable to estimate the indirect emissions from (semi-)natural ecosystems such as forests, extensively used grassland, and wetlands. The present study aims at calculating ecosystem-specific annual indirect N 2 O and NO emissions of (semi-)natural ecosystems in Switzerland for the years 1990, 2000, 2007 and 2010 using a simple linear model similar to the international guidelines. The approach here is based on empirical data for (semi-)natural ecosystems, derived from a literature survey, is driven by atmospheric nitrogen deposition and is ecosystem-specific with a high spatial resolution of 100 m × 100 m. Our results show that such ecosystems represent a strong source of indirect N emissions induced by atmospheric nitrogen deposition and emitted 1.61 ± 0.32 Gg N 2 O–N and 2.51 ± 0.53 Gg NO–N into the atmosphere in Switzerland in the year 2010, corresponding to 21% of the total Swiss N 2 O emissions and 10% of the NO x emissions. Thanks to the reduction of N emissions and thereby reduced atmospheric N deposition, the indirect N 2 O and NO emissions from (semi-)natural ecosystems are estimated to have been both reduced by c. 20% from 1990 to 2010. We conclude that the source strength for N 2 O and NO emissions of (semi-)natural ecosystems have been underestimated by the current approaches of IPCC and EMEP/EEA by a factor of 4.4 and 17, respectively. In regions and countries with a high fraction of (semi-)natural ecosystems, the approach offered here has the potential to improve the estimate of indirect N emissions substantially. [ABSTRACT FROM AUTHOR]

Large areas of alpine pastures and meadows currently face declining land use or abandonment, which leads to tall-grass transition ecosystems with higher leaf area index ( LAI), potentially increased evapotranspiration ( ET) and thus, reduced water yield. Elevated atmospheric CO2, on the other hand, is known to reduce stomata opening and hence, leaf-level transpiration, which may translate into higher soil moisture and enhanced total runoff. Here, we quantify these opposing effects of global change on the water balance of alpine grassland in a field experiment in the Swiss Alps (2440 m a.s.l.)., Rates of ET and deep seepage (percolation water) of four alpine grassland types (dominated by Agrostis, Nardus, Carex or forbs) were measured using intact monoliths in 51 weighing lysimeters. A part of the monoliths was clipped to simulate sheep grazing during three seasons (2008-2010). Another set was exposed to elevated CO2 (580 ppm) using free-air CO2 enrichment ( FACE) during the 2009 growing season., Simulated grazing reduced bright day ET by on average −12% across all years, with the most pronounced effects in the high-stature swards. Correspondingly, the higher biomass and LAI in unclipped grassland lowered the seasonal sum of deep seepage by −13% in a drier summer (2009) and by −5% in a rather wet summer (2010) compared to clipped swards., CO2 enrichment reduced ET in all grassland types by −3 to −7%, increased δ18 O in foliage and enhanced soil moisture, but not deep seepage. Hence, future CO2 slightly counteracts the land use effects at canopy level, however, not in terms of water yield., Synthesis. Our results indicate that both grazing and elevated CO2 are mitigating the effects of dry spells on alpine vegetation. The net effect of the continuous decline in the land use and of elevated CO2 is negative for catchment water yield and thus, for potential hydroelectric power production. Although these economic 'costs' are rather moderate per hectare of alpine grassland, sums are substantial when scaled to the vast areas potentially affected in the Alps. These calculated 'costs' attribute economic value to the eco-hydrological benefits of land care at these high elevations. [ABSTRACT FROM AUTHOR]

Abstract: In the alpine regions, more than half of the year''s precipitation is conserved as snow. We investigated inorganic ion storage in snow pack at 2500m (a.s.l.) in the Central Alps, Switzerland. Chemical composition of snow was dominated by nitrogenous and sulphate ions. Ion pools showed high local and inter-annual variability (2002, 2003), but differences in ion pools were not simply due to varying snow depth. The highest soluble nitrogen (N) pools were found in March (1.1–1.7kgNha−1). Later, in spring (April and May), N pools in snow were significantly lower (0.5–0.8kgNha−1). Ion storage in snow was compared with N fluxes in rain, which ranged between 2.0kg and 3.3kgNha−1 summer−1. Both forms of wet precipitation yielded a total wet N input into alpine grasslands of maximal 5.0kgNha−1 a−1. Atmospheric N deposition data for alpine ecosystems in the European Alps are rare and the monitored data here deviate by a factor of 2 from modelled N deposition. Nitrogen deposition in the alpine zone of the Central Alps is much smaller than previously assumed, but N pools stored in snow correspond to, at the most, 34% of N released by N mineralisation in alpine soils. Net N mineralisation accounts for only a fraction of the annual N uptake of alpine plant; thus, the additional N source by melting snow contributes substantially to alpine plants N uptake, particularly during periods when N demands are highest. [Copyright &y& Elsevier]

We examined manganese uptake and translocation in 30-year-old silver fir trees (Abies alba Mill.) showing severe symptoms of needle chlorosis by analyzing both xylem and phloem sap of shoots and an extract of root sap originating from both xylem and phloem elements. Manganese concentrations in shoot xylem and phloem sap were significantly lower in chlorotic trees than in neighboring healthy trees. The Mn concentration of root sap was also lower in these Mn-deficient trees than in healthy trees, indicating reduced Mn uptake by Mn-deficient trees. Although Mn deficiency had no effect on the Mn concentration of whole roots, separation of root tissue into root cortex and stele (wood) suggested impaired translocation of Mn from the cortex to the stele in Mn-deficient trees. Triphenyltetrazolium chloride (TTC) tests indicated that there was no decrease in reducing capacity of the fine roots (< 1 mm in diameter) of Mn-deficient trees. Fine roots of Mn-deficient trees contained significantly more organic acids than fine roots of healthy trees, including increased concentrations of malic, quinic, trans-acontic and formic acid; however, concentrations of pyruvic and acetic acid were lower than in fine roots of healthy trees. The total amounts of organic acids in the rhizospheric soil were similar for healthy and Mn-deficient trees. Pyruvic acid concentration was significantly increased in the rhizospheric soil of Mn-deficient trees, and concentrations of simple aliphatic acids like formic and acetic acid also tended to be higher in the rhizospheric soil of Mn-deficient trees. Both pH and water content were higher in bulk soil and rhizospheric soil around Mn-deficient trees compared with soil around healthy trees. Although lower concentrations of exchangeable Mn were found in the soil around Mn-deficient trees, the active Mn concentration (sum of exchangeable and reducible Mn) did not differ between healthy and Mn-deficient trees. A considerable proportion of manganese was in an oxidized form in the soil around Mn-deficient trees. [ABSTRACT FROM PUBLISHER]

Increased atmospheric nitrogen (N) deposition is driving nutrient imbalances, soil acidification, biodiversity losses and the long-term reduction in stability of sensitive ecosystems which previously had limited N. In this study, we analysed the concentrations of seven different N compounds in precipitation and in the air at 34 sites across Switzerland. We calculated the N deposition by precipitation (bulk deposition) and applied the inferential method to derive dry deposition (gases, aerosols) from air concentrations. We then quantified the total inorganic N deposition by adding together the bulk and dry deposition. Finally, the total inorganic N input into the sensitive ecosystems of the 34 sites was compared to the critical loads of these ecosystems. N deposition by precipitation was the main contributor to the total N load in 16 out of 34 sites, especially into open ecosystems such as alpine/subalpine grassland, mountain hay meadows, and raised bogs. Dry deposition of ammonia (NH 3) was the second most important pathway, in particular for forests close to agricultural activities, due to high NH 3 concentrations and the higher deposition velocity. The N deposition exceeded the lower limit of the Critical Load of Nitrogen (CLN) range at most sites, and at many sites even surpassed the upper limit of the CLN range. No, or minor, exceedances of the critical loads for N were found only at remote sites at higher elevation in the Central Alps. Annual inorganic N deposition between 2000 and 2017 revealed a significant decline in oxidised N compounds at four of five sites (−1.6–1.8% per year), but reduced compounds only decreased at two sites (−1% and −1.4% per year) and even increased at one site (+1.2% per year), despite adopted abatement strategies for agricultural practices. This emphasises that most sensitive ecosystems in Switzerland continue to be exposed to excessive N loads through atmospheric deposition, with detrimental consequences for the biodiversity and stability of these ecosystems. • Current inorganic nitrogen (N) input to sensitive Swiss ecosystems exceeds the critical loads. • N deposition by precipitation is the main contributor to N loading in non-forested ecosystems. • Dry deposition of NH 3 from agricultural activities adds substantially to the N load in forests. [ABSTRACT FROM AUTHOR]