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Dossier: drought in Switzerland

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Drought periods have serious consequences for agriculture, the water supply, energy generation and natural ecosystems. We create the informational basis that allows critical drought to be identified at an early stage and its consequences both on society and the natural environment to be evaluated and mitigated.

  

Comparison of the precipitation and temperature anomalies of the years 2003, 2015 und 2018 (© by MeteoSchweiz)

 

 
In an experiment, young Scots pines and black pines were subjected to different precipitation and CO2 conditions. After two months of drought the 2-year-old Scots pines are beginning to show symptoms of drought stress. Image: Christoph Bachofen, WSL
In an experiment, young Scots pines and black pines were subjected to different precipitation and CO2 conditions. After two months of drought the 2-year-old Scots pines are beginning to show symptoms of drought stress. Image: Christoph Bachofen, WSL

The risk of drought  will increase in Switzerland as a result of climate change. Switzerland is already experiencing more very warm days and fewer very cold nights. We research the conditions under which water deficits occur in soils, groundwater and surface water, and how this affects natural ecosystems and society. For example, in the dry autumn of 2015, less hydroelectric power could be generated due to a shortage of water.

On the basis of long-term observational data, we develop computer models that can be used to simulate future developments in terms of water availability. This allows us to draw lessons from the present for the future. This dossier provides an overview of our research activities on the phenomenon of drought.

 

WSL Drought Initiative 2018

 

WSL Drought Initiative 2018

The aim of this extraordinary WSL initiative is to quickly answer specific questions arising from the extreme drought of summer 2018.

  

Our projects about drought

 

DROUGHT CH

Droughts and heat waves are expected to become more frequent in Switzerland due to climate change. Droughts have major impacts on water resources, public health, ecosystems and consequently the economy. However, information about relevant economic and societal impacts and knowledge about adequate coping strategies are still lacking.

Prediction of hydrological drought

SREP-drought will evaluate how summer low flows and droughts are affected by winter snowpack in three catchments (Prealps, central Switzerland; Jizera Mountains, northern Czech Republic; Little Caucasus, central Georgia).

DROUGHT-R&SPI

There is an urgent need to improve drought preparedness through increased knowledge, drought management plans and an improved science-policy interfacing that will reduce vulnerability to future drought and the risks they pose for Europe. The EU FP7 research project DROUGHT-R&SPI will address this pressing need.

Drought 2018 - TreeNet meets Sentinel2

TreeNet permanently measures growth and tree water deficit (TWD) of about 250 tree individuals in forests all over Switzerland with so-called point dendrometers. TWD has shown to be a reasonable biological indicator for drought stress and quantifies the amount of missing water a tree needs to reach full saturation. In combination with spectral anomalies of satellite-based indices (e.g., NDWI from Sentinel2ab) between 2018 and a reference period we test whether we can find a close link between the two drought stress indicators.

Forests under stress

In this project we will assess the physiological processes by which trees adjust and interact among each other under a changing climate, determine the consequences of these processes on forest responses to climatic stresses and improve our understanding of these effects on forests functioning at a large comprehensive scale.

Soils and water regime of Swiss forests

For the whole forest area of Switzerland, we will map soil properties that are relevant for the water regime of forest stands. Based on this data we will run a water balance model for the 6000 plots of the National Forest Inventory (NFI) from 1980 to 2100 in order to detect regions that likely will suffer under increased drought in the near future.

Soil solution in LWF plots

The chemistry of soil solution and the soil water availability for plants have been monitored since 1997 in seven forest plots in Switzerland. This project, linked to the Swiss Long-term Forest Ecosystem Research project (LWF), aims to assess the soil response to atmospheric pollution (acidifying substances and nitrogen) and to climate change.

Nadelbäume und Trockenheit

Sehr starke waldbauliche Eingriffe im Gebirgswald können kurzfristig ökonomisch vorteilhaft sein. Langfristig könnten sie aber die Waldverjüngung verzögern und den Holzuwachs vermindern. Ob solche nachteiligen Auswirkungen auftreten und wie gross sie allenfalls sind, wird mit retrospektiven ertragskundlichen und dendroökologischen Erhebungen in Gebirgswäldern abgeschätzt.

Trockenheit als limitierender Faktor für An- und Aufwuchs von Hauptbaumarten

Für die Anpassung unserer Wälder an ein wärmeres Klima sind verschiedene Strategien denkbar. In diesem Projekt wird die Plastizität verschiedener Provenienzen von Waldföhre und Fichte bezüglich Trockenheit in der Jugendphase untersucht.

Germination experiment

Recent Scots pine mortality in forests of the upper Rhone valley have been suggested to be caused by climate change. In an ongoing PhD study, effects of different climate parameters and interspecific competition on the regeneration of both Scots pine (Pinus sylvestris) and black pine (Pinus nigra) are tested.

How beeches cope with drought

The BuKlim project aims to study the responses of Swiss beech provenances to drought. The results of the project help to assess the adaptational potential of this tree species to the changing climate.

CaNuPine/MICRO

In this project, adaptive and stress responses to drought stress and varying nutrient availability are being analyzed at tissue, cell and subcellular level in foliage of Scots pine and downy oak.

Isodrought

We want to explore a stable isotope tree-ring approach for analyzing physiological drought responses of trees. The results are expected to provide a novel diagnostic tool for understanding causes of tree decline.

Mycorrhiza and forest fire

In this project, we aim to investigate 1) to what extent diversity of mycorrhizal fungi is diminished by forest fire, and 2) whether this has consequences for performance of Pinus sylvestris seedlings.

DEForScen

Current plastic response of plants to climate change may be reflected by tree health. We investigate tree health data collected on ca. 6000 plots across Europe since the 1980s to figure out whether changes and trends in defoliation permit to identify species-specific response to climate change.

 

Slide show about forests and drought

How does climate change affect the Swiss forest? We are investigating this question in the Valais dry valleys. They are among the driest regions in Switzerland and are a kind of window into the future: possible effects of climate change can already be investigated there today.

 
Vor Trockenheit braune Waldföhren stocken auf einem sonnenbeschienen Hang.
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Trockenheit. Kapitelbild aus dem Buch Wald und Klimawandel(gif, 435 KB)
Grafik mit mittleren Jahrestemperaturen in Sion von 1870 bis 2010. Das langjährige Mittel ist um mehr als 2 °C gestiegen.
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Mittlere Jahrestemperaturen in Sion von 1870 bis 2010(gif, 94 KB)
Die Grafik zeigt Niederschlagssummen in Sion zwischen 1870 und 2010. Seit 1990 ist ein Rückgang des Niederschlags sichtbar.
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Niederschlagssummen in Sion zwischen 1870 und 2010(gif, 100 KB)
Eine Holzwespe sitzt auf einer Baumrinde.
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Holzwespe(gif, 379 KB)
Eine Forscherin und ein Forscher beugen sich über Holzkisten, in denen Keimlinge von Waldföhren wachsen. Die Holzkisten stehen in Reihen im Walliser Rhonetal.
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Trockenheitsexperimente im Wallis(gif, 361 KB)
Neben einem schwarz gefärbten Baumstrunk liegt quer der abgesägte, unten ebenfalls versengte Baumstamm.
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Schutzmassnahme gegen Steinschlag nach Waldbrand(gif, 447 KB)
Auf einer Waldbrandfläche wachsen fleckenweise Teppiche rosarotblühender Pflanzen.
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Zunahme Waldbrandgefahr. Kapitelbild aus dem Buch Wald und Klimawandel(gif, 439 KB)
An einem Hang stehen und liegen die nach einem Waldbrand abgestorbenen Bäume.
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Waldbrand von Visp im Frühjahr 2011(gif, 492 KB)
In einem Hang liegen quer angeordnet abgestorbene Bäume, die nach einem Waldbrand gefällt wurden.
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Steinschlagschutz nach Waldbrand(gif, 359 KB)
Ein grosser Schutzwall verläuft quer durchs Bild, unterhalb des Walls ist die Rhonebene rund um Leuk sichtbar.
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Schutzwall gegen Steinschlag(gif, 354 KB)
Zwischen schwarz angeschwärzte, abgestorbenen Bäumen wachsen grossflächig rosablühende Wald-Weidenröschen aus.
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Zwei Jahre nach dem Waldbrand in Leuk(gif, 385 KB)
Blick über die Flanke des Rhonetals. Im Vordergrund zu einem Busch herangewachsene Stockausschläge einer Flaumeiche.
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Vegetation nach Waldbrand in Leuk(gif, 345 KB)
Ein Lärchenkeimling wächst vor einem querliegenden Baumstamm.
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Junge Lärche auf Waldbrandfläche(gif, 387 KB)
 

FURTHER INFORMATION