New study in cooperation between the University of Rostock and the German Research Center for Geosciences in Potsdam shows unexpected effects of the drought on rewetted moors. Temporary drying out can accelerate the long-term development of the target vegetation. In addition, the rapid increase in biomass can offset the drought-related increase in carbon dioxide emissions.

Climate change also poses new challenges for nature conservation. When moors are rewetted, the goals of habitat and species protection are combined with climate protection goals. Adequate water supply is considered crucial in order to stop further degradation of the peat and the associated CO₂ emissions. As part of WETSCAPES, a project of the state excellence initiative Mecklenburg-West Pomerania, scientists are investigating the development and climate impact of rewetted fens. Based on long-term observations at two study sites, researchers from the University of Rostock and the GFZ German Research Center for Geosciences have now been able to draw a detailed picture of the effects of drought events. The study on the impact of the 2018 Europe-wide drought has now been published in a special issue of the journal Philosophical Transactions of the Royal Society B.

As expected, increased CO_² outgassing occurred during the dry period due to peat degradation. However, the temporary sinking of the moor water level has also rapidly accelerated the spread of vegetation. After the vegetation development in both bogs had stagnated for years, areas that were previously bare of vegetation were now colonized with new plants within a few weeks of drying out. Since the new vegetation fixes additional CO_^2,a significant part of the increased CO_² outgassing caused by the drought could be compensated.

In addition, the drought reduced emissions of the greenhouse gas methane, which is produced in bogs in the absence of oxygen. Surprisingly, the highest reduction effects occurred in the year following the drought, 2019. A delay effect that shows that the drought has a lasting effect on the microbiological conversion processes in the bog body.

In one of the locations, the researchers were now able to observe how the newly formed vegetation became permanently established. "It sounds a bit paradoxical, because we naturally want to protect bogs from drying out, but apparently the brief drying out of rewetted sites makes it easier for new vegetation to settle. In some cases, climate protection goals could be achieved more quickly in this way," notes Franziska Koebsch from the University of Rostock. "However," the scientist emphasizes, "we always have to keep an eye on the condition of the peat. Intermittent drought events can be helpful in accelerating vegetation development, but for peatlands to help mitigate climate change, they need to be permanently wet.”

Link to the study: https://royalsocietypublishing.org/doi/10.1098/rstb.2019.0685

Contact:

Dr. Franziska Koebsch

• University of Rostock
• Landscape Ecology and Site Evaluation
• Faculty of Agricultural and Environmental Science
• Tel.: +49 381 498-3234
• E-Mail: franziska.koebschuni-rostockde

Prof. Dr. Torsten Sachs

• Remote Sensing and Geoinformatics
• Helmholtz Center Potsdam German Geo Research Center
• Fernerkundung und Geoinformatik
• Telegrafenberg
• Gebäude A 70, Raum 303
• 14473 Potsdam
• Tel.: +49 331 288-1423
• E-Mail: torsten.sachs@gfz-potsdam.de