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Model predictions project
- An increase in global mean surface temperature of 1-3.5 oC
- more vigorous rain/drought events.
Elevated CO2 and temperatures and extended droughts will affect the functioning of natural and semi-natural environments through a series of interacting processes.
- Increased CO2 may stimulate plant growth leading to increased C sequestration in the ecosystems (negative feed back to the atmosphere).
- Elevated temperatures will stimulate a large number of processes in the ecosystem, e.g. increased mineralisation causing increased nutrient availability and loss of nutrients to surface and ground waters, increased soil respiration with increased emission of CO2 and other green house gasses to the atmosphere (positive feedback). Changes in nutrient availability may affect plant species competition and thereby species composition and ultimate biodiversity.
- Extended drought may alter species composition to favour drought tolerant species change and may hamper mineralisation processes to reduce nutrient availability and change soil/atmosphere exchange of greenhouse gasses.
Greenhouse (1200 m2) in Southern Norway covering a complete catchment facilitating experiments with increased CO2 and temperature
Many natural and semi natural ecosystems are already known to be threatened or sensitive to environmental pressures as for example heathland ecosystems where shifts from shrub to grass dominated systems have been reported as a consequence of increased N input, increased frequency of heather beetle outbreaks and drought and/or ground water lowering. Future changes in the earth climatic conditions are therefore likely to change ecosystem functioning of these ecosystems.
RISØ is involved in several projects investigating the effects of climate change on ecosystem functioning.
Experimental approaches
The impacts of changes in CO2 and the climate, can be investigated in several ways involving experimental manipulation or studies along natural gradients.
Experimental manipulation
Effects of changes in atmospheric and climatic conditions can be studied by manipulating the factors in the laboratory, in growth chambers or in the field. Studies in RERAF are conducted to highlight the effects of increased CO2 and temperature on the plant level. Experimental manipulations at the ecosystem scale in the field have been conducted in the CLIMEX project where a greenhouse to manipulate both temperature and CO2 covered a complete catchment. Presently field scale manipulation is conducted in the VULCAN project by a newly developed experimental approach to heat terrestrial ecosystems – the passive nighttime warming approach. In this approach reflective covers automatically covering the ecosystem at night cause warming of the ecosystem. The reflective covers reflect the long wave IR radiation back to the ecosystem at night thereby heating air, soils and plants. This method has the advantage over traditional field scale manipulation approaches that the artefacts or unintended effects are minimal. A corresponding method is used to study drought effects.
Experimental heating in a heathland ecosystem at Mols Bjerge – the CLIMOOR and VULCAN projects
Our flagship within field scale experiments related to climate change is the CLIMAITE experiment with a field station at Brandbjerg near Jægerspris. Here a shrubland/grassland ecosystem is manipulated with all combinations of elevated CO2 (510 ppm), increased temperature (+2 oC) and prolonged summerdroughts (5-8 weeks drought). The technique used for CO2 elevation is the FACE technique, and for warming and drought similar techniques as in the VULCAN project are used.
Natural gradients
By studying comparable terrestrial ecosystems under different natural climatic conditions, this natural difference can be used as a surrogate for time (space for time substitution). The differences in important ecosystem processes among different sites may indicate the long-term consequences of climatic changes, or it may serve as a strong tool for evaluating the sensitivity of terrestrial ecosystems under different climatic conditions. This approach is used in the EUROFLUX an CARBOEUROFLUX projects studying carbon exchange in a large number of forest ecosystems in Europe, in the upcoming NITROEUROPE (NEU) studying nitrogencycling and greenhouse gas emission from European ecosystems under various climates, environmental pressures and landuse and in the CLIMOOR and VULCAN projects studying the effects of warming and drought on ecosystem functioning at 6 European shrubland ecosystems.
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