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Alpine ecosystems in a changing climate: experimental CO2 enrichment and warming

English title Alpine ecosystems in a changing climate: experimental CO2 enrichment and warming
Applicant Rixen Christian
Number 116861
Funding scheme Project funding (Div. I-III)
Research institution WSL - Institut für Schnee- und Lawinenforschung SLF
Institution of higher education Swiss Federal Institute for Forest, Snow and Landscape Research - WSL
Main discipline Ecology
Start/End 01.09.2007 - 31.03.2011
Approved amount 185'223.00
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Keywords (6)

alpine; biodiversity; carbon cycling; climate change; ecosystem functioning; treeline

Lay Summary (English)

Lead
Lay summary
Within the next decades, a two-fold increase in CO2 concentrations and a rise in temperatures by 1.4 to 5.8°C can be expected (IPCC 2001). Temperature changes in the past decades have been more pronounced in alpine and high-latitude ecosystems than in most other regions of the world (IPCC 2001). Alpine ecosystems are particularly sensitive to environmental changes because they represent a boundary ecosystem that is subjected to extreme climatic conditions. Since temperature and CO2 are key factors that regulate many ecosystem processes, the changing climate will have large effects on vegetation and soils. In this proposal, we intend to analyze effects of manipulated temperature and CO2 in alpine ecosystems at treeline. Our major aim is to study potential feedbacks between climate change, plant growth and ecosystem processes. Although the European Alps are certainly the most studied of all high mountain ranges in the world, predictions of potential impacts of climate change on ecosystems are mainly based on modeling studies or on observations of inter-annual and spatial variability. There are only a few attempts to manipulate climatic conditions in situ. A combination of an experimental increase in CO2 and temperatures in the Alps has not been carried out before. In the proposed project, we enrich experimental plots with CO2 using a FACE approach and increase temperatures with heating cables at the soil surface. The experiment has already been set up at a treeline site near Davos. The CO2 enrichment was started in 2001 and increased CO2 concentration to 550 ppm. During the 6th year of operation, as part of a co-operation with a French team, a parallel soil warming treatment was installed on half of the test plots in a crossed design with the CO2 treatment, which successfully increases soil and air temperatures by 3K. We aim at investigating the interactive effects of elevated CO2 and warming on plant growth, biodiversity and ecosystem responses. Our proposed study addresses the following key questions: Will effects of elevated CO2 persist in the longer term and will these effects change under increased temperatures? How does biodiversity and the dominant vegetation, i.e. dwarf shrubs vs. trees, react to elevated CO2 and warming? How does elevated CO2 and warming affect key ecosystem functions such as nutrient uptake and decomposition? The focus will be on the two major tree species European larch and Mountain pine and on the dominant dwarf shrub species, especially Vaccinium myrtillus and V. uliginosum. Measurements of plant growth will include length increment, productivity, phenology and reproduction. Changes in biodiversity will be monitored with repeated vegetation surveys. Nutrient uptake and carbon cycling will be determined with nutrient and isotope analyses and litter decomposition experiments. In our manipulation experiment, we will make use of a long-term study at Stillberg in the timberline zone near Davos where larch and pine trees were planted 30 years ago and where tree growth, climatic and soil conditions have been monitored since the 1960s. This alpine study site provides a unique possibility for ecological studies. The continuation of the CO2 experiment is crucial to understand long-term effects and answer remaining scientific questions. The combination of ongoing CO2 enhancement with experimental warming will give new insights into the interactions of limiting factors in alpine ecosystems. Using the existing experimental set-up will optimize the scientific outcome of the long-term experiment at minimal costs and enhance collaborations at national and international level.
Direct link to Lay Summary Last update: 21.02.2013

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