Résumé des résultats (Abstract)
(Anglais)
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E C O M O N T: Ecological Effects of Land Use Changes on European Terrestrial Mountain Ecosystems. Research on Ecosystemic Processes in the Alpine Area, the Spanish Pyrenees and the Scottish Highlands
· Objectives (PSI):
- Episodic measurement campaigns on the test site Monte Bondone and Passeier Valley by scintillation anemometers, absorption spectrometers and aircraft measurements for H2O- and CO2-fluxes.
- Sonic measurements (eddy correlation): three campaigns on Monte Bondone and one campaign in Passeier Valley.
- Meteorological measurements according to WMO standards during the vegetation period on sites Mt. Bondone, Passeier and Stubai Valley.
- Deposition measurements (10 throughfalls, 1 dry deposition, 1 wet deposition) during the vegetation periods on sites Mt. Bondone, Passeier and Stubai Valley.
- Interpretation of the measurements for total budgets of water vapour and CO2 fluxes betweeen vegetation and atmosphere.
- Analysis of stable isotopes (d13C, d15N and deuterium) on plant material of trees on Monte Bondone and samples from the three sites for all four experimental plots.
- Vertical profiles and aircraft air sample analysis for CO2 (d13C, d18O) and water vapour (d18O).
- Statistical analysis of stable isotope measurements.
- Micrometeorological measurements in the forest stands during vegetation periods May - October 97 and 98 on Mt. Bondone and Passeier Valley sites.
- Sap flux measurements in and above the forest on Mt. Bondone and Passeier Valley sites (see package 7).
· Results and discussion:
The turbulent fluxes from the aircraft data of the field campaigns on Monte Bondone were calculated. The budget of the fluxes from the aircraft data is evaluated and compared to the scintillation mass fluxes. The flux calculations distinguish betweeen the different influences contributing to the budget of CO2 and H2O within the air layer above ground. Following this approach, a deep insite into the exchange processes between the vegetation and the atmosphere is exposed.
The scidar data from Monte Bondone were used to calculate the volume flux of the triangle formed by the light paths. Assuming a triangular slice of 1 m thickness and 1.23 km2 area, the volume flux reached values of the order of 150000 m3/s, corresponding to an airmass flux of 15 t/s. This result in turn corresponds to a vertical velocity of 1 cm/s, a resonable value for subsidence. In Passeier Valley, the predominant wind direction on sunny days is along the slope.
The analysis of stable isotopes in plant physiological and ecological research has shown that, as a result of physical, chemical and metabolic processes (depletion or enrichment of the heavier element), the isotope fractionation in plant tissue is strongly influenced by environmental impacts. In our studies we analyzed the isotope ratio of all three elements, of carbon, nitrogen and oxygen in plant organic matter, in water vapor, meteoric and leaf water and atmospheric CO2. Each of the element proved to be a specific indicator for various plant / environment interactions. The fact that we can process such a large number of samples with a high precision made the application of isotope analysis in the ECOMONT project very valuable , particularly with respect to the temporal and spatial scaling.
· Conclusions:
The measurements on the landscape level is an ideal tool to realise the scaling up procedure from the numerious experimental and model based approaches described in the other workpackages. By combining the aircraft, the ground based sonic and scintillation measurements with a numerical weather prediction model and satellite data it is posible to explain the water cycle of the individual ecosystems with the larger area and the atmosphere. The importance of ECOMONT is not restricted to a few numbers of small test areas. The knowledge of the test areas can be upscaled to the regional level to judge the Alpine ecosystem under the constraint of changing landuse.
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