TECHNICAL UNIVERSITY OF MUNICH

PRESS RELEASE

Global warming leads to declining humus

Climate change threatens Mountain Meadows

• Climate change has a negative impact on humus content, soil structure and nitrogen storage
• Organic fertilization with liquid manure can partially compensate for the effect
• Size of soil clods can be an early warning sign of soil degradation

Mountain meadows are unique ecosystems. A research team led by the Technical University of Munich (TUM) has now discovered that climate change reduces the humus content as well as the nitrogen stores in the grassland soils of the Alps and disturbs the soil structure. Organic fertilization, for example with liquid manure, can compensate this loss of soil organic matter to some extent.

To recreate the effects of climate change under realistic conditions, the researchers used soil-plant mesocosms. These miniature ecosystems consist of units containing soil samples. By moving the mesocosms along an elevation gradient from higher, cooler locations to lower, warmer locations, the scientists simulated climate change. Thereby, they simulated a warming of up to 3 degrees Celsius, depending on the difference in altitude between the original and the new locations. " Studying soil responses to climate change in detail helps us to better understand the long-term effects on alpine grassland ecosystems," says soil researcher Dr. Noelia Garcia-Franco. The study was carried out on various areas in the Bavarian districts of Weilheim-Schongau and Garmisch-Partenkirchen. Half of the mesocosms were cultivated intensively and the other half extensively, i.e. they were mowed at different frequencies and fertilized with liquid manure, for example. Soil samples were taken after four years.

Humus content, soil structure and nutrient stores decline dramatically

The results show: As a result of 2 and 3 degree temperature increases, the humus content declined rapidly and sharply, with the decline being even more pronounced under extensive management. With extensive management, the soil lost 22 % of humus at a temperature increase of 3 degrees and 14 % at 2 degrees. Under intensive management, soil humus loss amounted to 11 % under these conditions. The more intensive organic fertilization was able to partially compensate for the loss of organic matter. Overall, increased temperature significantly impairs the soil structure. The clods of earth that make up the soil are destabilized and, as a result, soil organic matter is degraded increasingly. "The size of the soil clods could be an early warning signal for the impending loss of humus and soil structure," says Garcia-Franco. The researchers also observed that the soil stock of the important plant nutrient nitrogen declined.

Important carbon reservoirs under threat

Climate change is progressing faster in central and northern European mountain regions in particular than in other areas. For example, the average annual temperature in the European Alps has risen by two degrees since the 1980s. The special combination of high precipitation and low average temperature means that the soils there store a particularly large amount of carbon as humus. Grassland in the Alps and Alpine foothills is one of the largest reservoirs of soil-bound organic carbon in Central Europe. However, higher temperatures increase the activity of microorganisms in the soil, especially in the winter months. As a result, humus is broken down more quickly and released as CO2. Mountain meadows fulfill important economic and ecological functions: They produce large quantities of high-quality animal feed and play an essential role in storing water and nutrients as well as maintaining a high diversity of plants and soil organisms. Climate change could impair these functions in the long term.

Publication:

Garcia-Franco, Noelia; Wiesmeier, Martin; Buness, Vincent; Berauer, Bernd J.; Schuchardt, Max A.; Jentsch, Anke; Schlingmann, Marcus; Andrade-Linares, Diana; Wolf, Benjamin; Kiese, Ralf; Dannenmann, Michael; Kögel-Knabner, Ingrid. (2024). Rapid loss of organic carbon and soil structure in mountainous grassland topsoils induced by simulated climate change. Geoderma, 442, Art.-Nr.: 116807. DOI: 10.1016/j.geoderma.2024.116807.

Further information:

• The Federal Ministry of Education and Research (BMBF) funded the project "Sustainable use of alpine and pre-alpine grassland soils in a changing climate" (SUSALPS) as part of the "Soil as a sustainable resource" (BonaRes) program.
• The study was carried out jointly by TUM, the Bavarian State Institute of Agriculture, the Swedish University of Agricultural Sciences, the University of Hohenheim, the University of Bayreuth, the Baden-Württemberg Agricultural Center in Aulendorf, the Helmholtz Zentrum München and the Karlsruhe Institute of Technology.

Additional information for editors:

Photos for download: https://mediatum.ub.tum.de/1741442

Scientific contact:

Dr. Noelia Garcia-Franco

Technical University of Munich

Chair of Soil Science

noelia.garcia-franco@tum.de

www.lss.ls.tum.de/en/boku

Contact in the TUM Corporate Communications Center:

Magdalena Eisenmann

Media Relations

Tel. +49 8161 71-6127

presse@tum.de

www.tum.de/en

Die Technische Universität München (TUM) ist mit rund 650 Professuren, 52.000 Studierenden und 12.000 Mitarbeitenden eine der weltweit stärksten Universitäten in Forschung, Lehre und Innovation. Ihr Fächerspektrum umfasst Informatik, Ingenieur-, Natur- und Lebenswissenschaften, Medizin, Mathematik sowie Wirtschafts- und Sozialwissenschaften. Sie handelt als unternehmerische Universität und sieht sich als Tauschplatz des Wissens, offen für die Gesellschaft. An der TUM werden jährlich mehr als 70 Start-ups gegründet, im Hightech-Ökosystem München ist sie eine zentrale Akteurin. Weltweit ist sie mit dem Campus TUM Asia in Singapur sowie Büros in Brüssel, Mumbai, Peking, San Francisco und São Paulo vertreten. An der TUM haben Nobelpreisträger und Erfinder:innen wie Rudolf Diesel, Carl von Linde und Rudolf Mößbauer geforscht. 2006, 2012 und 2019 wurde sie als Exzellenzuniversität ausgezeichnet. In internationalen Rankings wird sie regelmäßig als beste Universität in der Europäischen Union genannt.