Brandbjerg (CLIMAITE), DK

Site location and background

The experimental site of Brandbjerg (CLIMAITE), Denmark (55°53'N 11°58'E) is situated on a hilly nutrient-poor sandy deposit in a semi-natural terrestrial ecosystem with dry heath/grassland vegetation dominated by the grass Deschampsia flexuosa, the evergreen dwarf shrub Calluna vulgaris and various moss species. The mean annual temperature is 8.0 °C and the mean annual precipitation is approximately 620 mm.

CLIMAITE I - climate change manipulations

The original CLIMAITE experiment was operated from October 2005 until May 2014. It included treatments of elevated CO2 concentration, increased temperature, drought in late spring/summer, and all their combinations in a full-factorial design. Each octagon spans 6.8 m and the individual treatment plots are 9.1 m2 in area.
The CO2 concentration in the original experiment was enhanced by a Free Air Carbon Enrichment (FACE) system with a target concentration of 510 ppm – a value which is expected to be reached in 2075 – depending on future human emission rates. The temperature enhancement was achieved by passive night-time warming, where a light scaffolding (0.5 m height) carrying a curtain reflects the outgoing infrared radiation.The curtains were automatically pulled over the vegetation at sunset and retracted at sunrise.
The drought treatment was applied with water proof curtains which automatically pulled over the vegetation during rain events. The figure below shows aerial photos of curtains (panels c and d). The treatments were applied singly and in all possible combinations (A, T, D, CO2, TD, TCO2, DCO2, TDCO2). Each experimental treatment was replicated six times, (total of 48 plots) in a split plot design with six octagons at ambient CO2 and six receiving elevated CO2. 

CLIMAITE II – climate change manipulations

From summer 2014 until the summer of 2016 the experimental treatments were inactive but since June 2016 new and permanent rainout shelters have been installed at the site on the ‘old’ drought plots. The new treatments are more severe and at three different levels instead of one shifting the experiment from a traditional ‘ANOVA’ design towards a gradient/regression design.
From Jan 2018, CLIMAITE became part of AnaEE Denmark – a national Danish research infrastructure for experimentation and analysis on ecosystems (anaee.dk).

Research activities and research ideas

At Brandbjerg the ongoing research focuses particularly on two issues:

• Ecosystem responses to combined changes of all three climate change factors: atmospheric CO2 concentrations, temperature and water availability.
• Changes in temporal variation patterns including extension of the growing season, increased frequency of freeze/thaw cycles, number of frost free days, frequency of extreme weather events etc.

The effects of the treatments on individual species, ecosystem structure and ecosystem functioning are investigated through targeted studies on the soil, plants, meso- and microfauna and microorganisms. The studies include changes in carbon and nutrient balances and circulation, stress tolerance and adaptation, species competition and composition and plant tissue chemistry and herbivory. The research takes advantage of novel research tools, including field scale ecosystem manipulations, stable isotope techniques, controlled herbivory and DNA techniques.

Funding

The Brandbjerg/CLIMAITE experiment was originally built and run in the period 2005-2014 by a large donation from the Villum Kann Rasmussen Foundation as a joint venture between six research groups from the Technical University of Denmark, Aarhus University and the University of Copenhagen. Since 2015, the site has been maintained by the University of Copenhagen and since 2018 is part of the national Danish research infrastructure AnaEE Denmark (anaee.dk)