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Master theses

(1) Plant diversity and forest regeneration after forest fire

After the forest fire of Leuk during the 2003 heat wave, plant and animal species re-colonized the 300 ha large are in short time. From 2004 to 2007, re-vegetation was observed on 150 systematically arranged permanent plots. Results showed a first peak of plant species richness only 3 to 4 years after the fire. By one or two master theses, both diversity succession and tree regeneration success may be further quantified. Hypotheses to test:

- upward/downward shifts of species in early succession

- correlation of diversity and productivity

Contact

Thomas Wohlgemuth, WSL Birmensdorf (thomas.wohlgemuth@wsl.ch, 044-739-2317)

(2) Changes in ground vegetation on Swiss long-term forest ecosystem research (LWF) sites over 15 years

Ground vegetation is a key component of forest ecosystems. It contributes to the biological diversity of the forest ecosystem, plays an important functional role in the water and nutrient cycle, and interacts strongly with other biota, as habitat or source of nutrients. In addition, ground vegetation is a powerful bio-indicator of the environment, as the species composition of a plant community reflects the ecological conditions at a given site and at a given time. Vegetation surveys are therefore core assessments in the intensive forest monitoring programme (Level II) implemented within the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests, www.icp-forests.org). In Switzerland, 17 ICP Forests Level II sites were established in the mid-1990s or later, within the framework of the Swiss long-term forest ecosystem research programme (LWF, www.lwf.ch). Ground vegetation was first surveyed on all 17 sites in 1994/1998, using two approaches: 1) classical phytosociological relevés in large plots (up to 500 m²); 2) visual assessment of the cover of each species (in %) occurring in 1 m² vegetation quadrats. In these quadrats, the height and position of all tree seedlings and saplings were also inventoried in order to assess the development of natural tree regeneration.

Vegetation surveys were repeated in 1999, 2001 and 2003. Parallel to these vegetation surveys, hemispherical photographs of the canopy and measurements with a portable light sensor system (Licor LAI-2000) were made at the sites in order to assess potential light conditions, as light is a main driver of vegetation dynamics.

Objectives/Work:

1) to re-survey the ground vegetation and to measure again light conditions on all 17 sites during the summer 2011

2) to analyse the data in order to detect whether any temporal changes in the floristic composition of the plant communities are apparent

to interpret the observed changes in vegetation using the documented changes in light conditions and other relevant information (e.g. stand history, past occurrence of storms, management, atmospheric deposition…)

Voraussetzungen: Good knowledge of the Swiss flora, high flexibility. As hemispherical photographs and Licor measurements can be made only in the absence of direct solar radiation, field work may have to be done until late in the evening.

Contact

Anne Thimonier (anne.thimonier@wsl.ch)

Thomas Wohlgemuth, WSL Birmensdorf (thomas.wohlgemuth@wsl.ch, 044-739-2317)

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