The large scale project CLIMAITE, led by Risø DTU, has published its first synthesis paper in the journal Global Change Biology, and the conclusion is perhaps a little surprising that the predicted increase in plant growth, due to more CO2 in the atmosphere is noticeably limited when combined with higher temperatures -- and especially summer droughts. "When you've previously seen a significantly higher plant growth at elevated CO2 concentrations, it is typically because it has been controlled studies, where only the CO2 concentration was changed. We fundamentally had the theory that you have to look at the combination of the different climate variables, since the plants in the future will be exposed to multiple changes simultaneously," explains Klaus Steenberg Larsen, who is a researcher in the Biosystems Division at Risø DTU and lead author on the scientific paper.
The large scale project CLIMAITE, led by Risø DTU, has published its first synthesis paper in the journal Global Change Biology, and the conclusion is perhaps a little surprising that the predicted increase in plant growth, due to more CO2 in the atmosphere is noticeably limited when combined with higher temperatures -- and especially summer droughts. "When you've previously seen a significantly higher plant growth at elevated CO2 concentrations, it is typically because it has been controlled studies, where only the CO2 concentration was changed. We fundamentally had the theory that you have to look at the combination of the different climate variables, since the plants in the future will be exposed to multiple changes simultaneously," explains Klaus Steenberg Larsen, who is a researcher in the Biosystems Division at Risø DTU and lead author on the scientific paper.
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CLIMAITE is a Danish research center that investigates how climate change, as they probably appear in 2075, affects biological processes and ecosystems in nature. The CLIMAITE center is based on the climate change scenario that climate scientists have predicted for Denmark in 2075. The idea is simply to turn the clock forward 70 years and artificially create the future climate in a study area in the countryside and explore the effects.
Data from the first two years are underlying the scientific paper, and results clearly indicate that we will not get the predicted increase in plant growth in our latitudes in the future.
The core of CLIMAITE's activities is a common field scale experiment, in contrast to many other experiments conducted in laboratories under controlled conditions. Climate manipulations are still conducted with both CO2, temperature and rainfall by for example using CO2 jets and curtains that keep the rain away.
The research area is located in the military training area near Jægerspris. Here CLIMAITE has built a facility where they can make experiments at field scale with elevated CO2 using the Free Air Carbon Enrichment (FACE) technique. The elevated temperature in the ground at approx. 1 degree is achieved by passive nighttime warming and altered rainfall or drought are obtained by means of roller blinds in periods of 4-6 weeks over the summer.
In total this gives 8 different set-ups in the total 48 plots. And thus CLIMAITE is one of the largest facilities of its kind.
"We measure things such as nitrogen in precipitation, plants, soil fauna, microbes and soil water. Nitrogen is often a limiting factor for plant growth, and absolutely essential for how ecosystems respond to climate change, "says Klaus Steenberg Larsen, and continues:
"The results in the paper cover the years 2006-2007, and the experiment will run until 2014. But it takes time to gather the results from the 20-30 people who interpret and analyze the results from the many types of equipment that are set up. However, we can clearly see that especially the drying of the soil has a significant negative effect on nitrogen production - and thus on the possible plant growth - even in those areas that are exposed to increased CO2 and warming.
For further information: http://www.risoe.dtu.dk/News_archives/News/2011/0817_CLIMAITE_report.aspx or http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2486.2010.02351.x/abstract
Photo: http://gallery.usgs.gov/images/06_18_2009/i41Pht6GFa_06_18_2009/large/rought_wetland.jpg
