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Braun S.,Institute For Angewandte Pflanzenbiologie Ch | Rihm B.,Meteotest CH
Schweizerische Zeitschrift fur Forstwesen | Year: 2012

Ozone (O3) is highly phytotoxic. Basing on dose-effect relationships resulting from fumigation experiments, the United Nations Economic Commission for Europe (UNECE) has set critical levels for protection of the vegetation. The present article compares the AOT40 (accumulated ozone over a threshold of 40 ppb) summing up hourly ozone concentrations with a flux-based risk assessment taking into account stomatal ozone uptake. Both ozone quantifications were calculated for rural monitoring stations in Switzerland, mapped and compared to the corresponding critical levels.The data suggest that the ozone load in Switzerland is high enough to provoke clear reductions in forest growth. Source


Remund J.,Meteotest CH | Augustin S.,Bundesamt fur Umwelt CH
Schweizerische Zeitschrift fur Forstwesen | Year: 2015

Climate scenarios for the 21st century for Switzerland show increasing temperatures and more frequent weather extremes and the risk of drought will become more important. The objective of the study was the calculation of indicators which allow the estimation and evaluation of drought risks on a regional scale. The site water balance and the ratio between actual and potential evapotranspiration (ETa/ETp) were used as indicators. They are closely related to vitality parameters of trees. For projections in the future were used the A1B climate scenario, which assumes a warming of 2.7 to 4.1°C in Switzerland, and three regional climate models (CLM, RCA, REGCM3), which predict different developments regarding precipitation and temperature. Historical time series between 1951 and 2012 and scenarios up to 2100 for different climatic regions were calculated. The indicators reproduce well the measured trends and the regional differences. In all regions there was in the past a trend to increased drought. The Geneva/ Vaud region as well as the western midlands and north Switzerland show the most pronounced changes. Projections with the CLM model (which reproduced best the historic trend 1981-2010 for Switzerland) show increasing drought and, in general, an increasing variability of the climate for the mid-century. Source


Braun S.,Institute For Angewandte Pfl Nzenbiologie Ch | Remund J.,Meteotest CH | Rihm B.,Meteotest CH
Schweizerische Zeitschrift fur Forstwesen | Year: 2015

The application of climate models to forecast future forest development asks for quantitative drought-response relationships, with the term "drought" first needing a definition. The long-term data series of an intercantonal forest observation program allowed to test various drought indicators, to compare them and to derive quantitative relationships for beech and Norway spruce. For basal area increment of both tree species indicators of the site water balance (SWB) performed best. For beech mortality site water balance and several indicators basing on the ratio between actual and potential evapotranspiration (ETa/ETp) were equivalent, whereas for spruce mortality ETa/ETp during the first 80 days of the season was the best indicator. With these indicators the average drought related growth reduction after 2003 - a year with extreme drought - was estimated to amount to 32% for beech and 37% for Norway spruce. Mortality of Norway spruce increased by 130%, whereas the estimates for the increase of beech mortality vary between 54 and 110%, depending on the indicator. The observed quantitative relationships for growth were applied to map drought responses of growth for Switzerland. The maps clearly show the dry regions of Switzerland (northern Switzerland, southern Jura foothills, Lemanic region, Valais and Rhine valley around Chur), where basal area increment of beech and Norway spruce was reduced by more than 40%. Source


Braun S.,Institute For Angewandte Pflanzenbiologie Ch | Rihm B.,Meteotest CH | Fluckiger W.,Institute For Angewandte Pflanzenbiologie Ch
Schweizerische Zeitschrift fur Forstwesen | Year: 2012

Because of their rough surface forests are an efficient sink for nitrogen compounds emitted by industry, traffic and agriculture. Deposition maps reveal that nitrogen deposition in Swiss forests exceed 30 kg N/(ha × yr) in various regions, which is clearly higher than the critical loads set by the United Nations Economic Commission for Europe (UNECE). The calculated deposition data base on emission inventories, dispersion models, measurements of various deposition components (gaseous, aerosols, wet) as well as on balance calculations. The evaluation of the effects on forests bases on two summary reports: the workshop report of a UNECE meeting on critical loads for nitrogen held in 2010 and a summary of own nitrogen addition experiments published in 2011. The presented data suggest that in Switzerland nitrogen inputs are high enough to cause changes of forest ecosystems. Source

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