Professor Bernd Marschner with project members Michael Herre and Dr. Julian Heitkötter (from the left) at a soil profile © Damian Gorczany

Geosciences What sleeps under the forest

Large amounts of carbon thousands of years old are stored under the forest floor. And it is better to keep it there.

A largely unknown terrain begins not so far below the surface of the forest floor. While the processes in the top 30 centimetres of the soil are well known, deeper areas of the soil are the focus of a research group led by Professor Bernd Marschner from the Institute of Geography at the Faculty of Geosciences at Ruhr-Universität Bochum (RUB). Twice as much carbon is stored here as in the atmosphere and vegetation together. How old it is, where it comes from and why nobody metabolises it is the subject of the investigations.

Tests on representative soils

More than half of the carbon in the soil is located deeper than 30 centimetres below the surface – how long has it been there? Is there life there? Does an exchange take place with carbon in the atmosphere? To answer these questions, the researchers are conducting comprehensive tests on representative soils in the Hannover and Göttingen areas.

Almost nothing comes from the leaves

With extreme care, they dug shafts in the forest floor, from which they continuously take samples and analyse them. With great effort, they investigated how much carbon from the leaves of the trees penetrates deep into the forest floor. In autumn, they exchanged all the fallen beech leaves from some of the trees for leaves that had previously been marked. “To our surprise, we discovered that less than one percent of the carbon from the leaves had reached the deeper soil layers,” says Bernd Marschner.

There is life – but it does not touch the carbon

The carbon deep down is therefore very old, often over 1,000 years old below 50 centimetres. Where does it come from and above all: Why does it remain so untouched? Why don’t these creatures metabolise it? The researchers in the group were able to show that there is life deep in the soil. They treated samples from deep soil layers with sugar solution and suddenly discovered considerable metabolic activity.

How to prevent carbon from entering the atmosphere

Now they are examining the effects of other substances on the microorganisms in the soil in order to determine whether these can also wake them up. “This question is particularly interesting because we should try as far as possible to avoid the old carbon stored in the soil being metabolised and released into the atmosphere as CO2,” says Bernd Marschner. “Otherwise, the additional CO2 as a greenhouse gas would significantly promote climate change.”

Funding

The Subsom research group has been funded by the German Research Foundation since 2013.

Detailed article in Rubin

A detailed article on the topic can be found in the scientific magazine Rubin. Texts on the website and images from the download area may be used free of charge for editorial purposes if the copyright is cited.

Press contact

Prof. Dr. Bernd Marschner
Department of Soil Science and Soil Ecology
Faculty of Geosciences
Ruhr-Universität Bochum
Germany
Phone: +49 234 32 22108
Email: bernd.marschner@rub.de

Published

Monday
15 October 2018
1:18 pm

By

Meike Drießen

Translated by

Lund Languages

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