ECOMONT: a combined approach of field measurements and process-based modelling for assessing effects of land-use changes in mountain landscapes

As a contribution to the terrestrial ecosystem research initiative (TERI) within Framework IV of the EU, ECOMONT aims at investigating ecological effects of land-use changes in European terrestrial mountain ecosystems. The project is carried out by nine European partners in six composite landscapes in the Eastern Alps, the Swiss Alps, the Spanish Pyrenees and the Scottish Highlands. An analysis of structures and processes in the context of land-use changes is performed, scaling from the leaf to the landscape level. The following research topics are being investigated: spatial distribution of vegetation and soil in the composite experimental sites; physical and chemical soil properties, soil organic matter (SOM) status and turnover; canopy structure; water relations of ecosystems and hydrology of catchment areas; micro-climate and energy budget of ecosystems; gas exchange of single plants, ecosystems and gas exchange between the composite experimental sites and the atmosphere; potential risks through land-use changes. In order to link biodiversity with ecosystem functioning and to ensure a profound analysis of the ecosystem processes at the level of composite landscapes, a specific up-scaling approach is applied in ECOMONT combining empirical field studies and mathematical modelling. At each level of integration the results of the modelling approach are validated by direct field measurements. This will be shown on the example of the bottom up approach for the gas exchange processes. The experimental up-scaling starts from measurements of the gas exchange of single leaves using fully climatised CO2/H2O porometers, proceeds to the canopy level using Bowen-ratio and Eddy-correlation techniques, and finally to the gas exchange of composite landscapes using a scintillation anemometer system/differential optical absorption spectroscopy system (SCIDAR/DOAS) equipment in combination with a instrumented aircraft flying at a constant height above the landscape. A hierarchy of process-based models is used to link the gas exchange processes at the different scales: a single leaf model based on a biochemical model of photosynthesis, a newly developed multi-species canopy model taking into account multiple light scattering and non-uniform distribution of leaves, and a landscape model providing a pixel by pixel integration.