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Nutrient Network NutNet

Long-term Forest Ecosystem Research Programme LWF

Nitrogen in the Alptal

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Nutrient discharges increasing pressure on ecosystems

Nitrogen and phosphorus are nutrients that are crucial to supporting life. However, an increased level of nutrient discharges is altering the equilibrium between these nutrients and exerting stress on ecosystems. The Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) is investigating nutrient cycles with a view to understanding how they affect the dynamic processes of nature.

The pressure on the world's ecosystems is rising all the time. One of the most widespread stress factors witnessed across the globe is the accumulation of nutrients such as nitrogen. The nitrogen content of the soil worldwide has virtually doubled since the start of industrialisation. Nitrogen escapes into the environment as an agricultural fertiliser, and it is also released by burning fossil fuels, spreading in the atmosphere across the world and becoming part of ecosystems even where these are far removed from any form of industry or agriculture.

Phosphorus too diffuses into agricultural land through fertiliser use. However, the level of discharge of this element into natural ecosystems is extremely low because – unlike nitrogen – phosphorus is hardly spread through the atmosphere. Observations currently being made by WSL researchers even indicate that in forests phosphorus levels are becoming increasingly depleted.

WSL researchers taking part in various projects are investigating how the changes in nutrient discharges are affecting the role of terrestrial ecosystems such as forests and grassland. How are the dynamic processes or productivity of an ecosystem changing? What influence do the nutrients have on plant diversity and therefore on the stability of the ecosystems? What implications does this have for the sustainable management of grassland and forests?

Nutrient Network: the global effect of fertilisers on grassland

NutNet

The Nutrient Network (NutNet) is an global research cooperative going on at over 70 sites around the world. Using standardised methods, the aim is to examine what impact the use of fertilisers has on grassland. The WSL Plant-Animal Interactions research group operates a research site in Val Müstair, which at 2,320 metres above sea level, is one of the highest-altitude sites in this network. Here the researchers investigate to what extent the changes in the nutrient supply hits the Alpine ecosystem. NutNet has found that the biodiversity of grassland is decreasing dramatically and destabilising the relevant ecosystems – not only in Switzerland, but also worldwide.

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Long-term Forest Ecosystem Research Programme (LWF): Nutrient Cycles of Forest Ecosystems

Regensammler

The WSL Long-term Forest Ecosystem Research Programme (LWF) has been recording the flows of substances in the nutrient cycles of selected forest sites in Switzerland since 1996. This programme is part of the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests), a work programme operating under the Geneva Convention on Long-range Transboundary Air Pollution that has around 500 research sites in Europe. The researchers are investigating such issues as the effects of nitrogen discharges on the forest ecosystem (e.g. the health and growth of trees, and seed production) so as to, for example, assess the repercussions for the sustainable management of forests and lay the foundations for the negotiations on emissions of air pollutants relating to the Convention on Long-range Transboundary Air Pollution.

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Nitrogen in the subalpine Alptal valley

Alptal

Since back in 1994, the WSL Biogeochemistry research group has been studying the effects of increased nitrogen deposition in a subalpine forest at the Erlenhöhe site in the Alptal valley. How do the soil, the growth of trees and other vegetation, the water quality and nitrate leaching respond to nutrient accumulation? Since 1976, discharges and leaching of nutrients have also been studied in three small catchment areas in this valley.

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