Nitrogen dynamics Alptal

Girdling a spruce tree: it will dry out as if attacked by bark beetles. What will be the impact on the carbon and nitrogen cycles?

This framework 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 major 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 2006 to 2010, the N addition experiment is also used to study the effect of N deposition on the exchanges of greenhouse gases (CO₂, CH₄, N₂O) within the European project NitroEurope. These studies are done in collaboration with the ETH Zurich (institute of plant sciences).
Since 2008, we study the impact of tree girdling, mainly on nitrate leaching and on exchanges of greenhouse gases, this in interaction with the achieved enrichment of the ecosystem in N. This project is part of the COST Action FP0601 Forman and is supported by the State Secretariat for Education and Research, which finances the thesis of Kim Krause.
Results: see the publication list of this framework project.