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Nitrogen dynamics Alptal


This project contains research done on the site Erlenhöhe at Alptal (canton Schwyz, central Switzerland) where the impact of an increased nitrogen deposition on a subalpine forest is assessed.


A part of the infrastructure is still form the national research programm PNR 14/14+ on impacts of air pollutants on forests (1980ies). A nitrogen (N) addition experiment was set up for the European NITREX project in collaboration with the ETH Zurich (institute of terrstrial ecology), the PSI (group of stable isotopes) and the University of Zurich (group of microbiology). The experimental simulation of increased N deposition is studied in its impacts on the soil, the trees and other plants and on water quality. This experiment is ongoing, on one hand in small experimental catchments (approx. 1550 m2), on the other hand in small plots in a replicated design (approx. 10 m2). This study was used as a framework for several doctoral theses: Nathalie Muller (WSL, 1997), Hans Feyen (ETHZ, 1998), Frank Hagedorn (WSL, 1999) et Joachim Mohn (Univ. Zurich, 1999). Based on this experiment, and also in collaboration with the PSI (group of stable isotopes) and the ETH Zurich (group ecology of mountain forests), the project IRISALP was realised from 2000 till 2005 with the thesis of Isabelle Providoli financed by the Swiss National Fund for Scientific Research. The main topic of this study was to follow with the isotope 15N the fate of deposited N in the ecosystem. This project was coupled with similar experiments by the EPF Lausanne (group of soil science) at the Grandvillard site (thesis of Isabelle Morier).

From 2007 to 2011, this long-term N addition experiment was also used to study the effect of N deposition on the exchanges of greenhouse gases (CO2, CH4, N2O). This work was part of the European project NitroEurope as well as of the COST Action FP0601 Forman, and as such supported by the Swiss State Secretariat for Education and Research. This was the basis of the doctoral thesis of Mr. Kim Krause, which was carried out in collaboration with the ETH Zurich (institute of terrestrial ecosystems), with the university of Zurich (institute of evolutionary biology / environmental sciences) and with the university of Michigan (natural resources & environment).

Further, part of the trees were girdled in 2009 and felled in 2010. Stem disks from the felled trees were used to reconstruct the long-term effect of the nitrogen treatment upon tree growth. Nitrate leaching from the meanwhile nitrogen-saturated ecosystem is further studied as affected by tree felling.