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Nitrogen and ground vegetation
Nitrogen availability and ground vegetation dynamics. Role of anthropogenic and natural factors?
Anne Thimonier (Project leader)
Ground vegetation is a powerful bio-indicator of the environment. As such it has been widely used to establish forest types. More recently, it has been used to detect changes in the environment which may be ascribed to human activities (air pollution and in particular nitrogen deposition, climate change). The advantage of such vegetation studies lies in their lower cost in comparison with the measurement of the causal factors (e.g. air chemistry) or the response factors (e.g. soil chemistry). However, the results of vegetation studies are difficult to interpret. Ground vegetation often reflects a combination of ecological factors rather than a single one, or it may react identically to different factors. This is especially the case for vegetation changes indicating improved nitrogen availability.
The project aims at discriminating the various factors which may influence the spatial and temporal dynamics of ground vegetation. Emphasis is being given to the role of nitrogen.
The project uses the data from vegetation assessment carried out in the project "Biogeochemical cycling and ground vegetation".
The vegetation is surveyed at three levels of intensity:
The vegetation assessment are carried out every second year, in summer and, for sites with a distinct vernal flora, also in spring.
The data on soil, nutrient fluxes, climate, stand history collected in the other LWF projects will contribute to the interpretation of the spatial and temporal dynamics of ground vegetation. In addition to these measurements, potential light conditions are assessed with hemispherical photographs of the canopy above the permanent quadrats and the Leaf Area Index (LAI) is estimated with an LAI-2000 Plant Canopy Analyzer (Li-cor, Inc., Lincoln, NE).
1995-2001: vegetation assessment, hemispherical photographs and LAI measurements with the LAI-2000 on all LWF plots, every second year.
2002: evaluation of hemispherical photographs
Selected data will be available at a later date.
Project 6.95.943 "Disponibilité en azote et réponse de la végétation de sous-bois. Rôle des facteurs naturels et anthropiques?"
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