Forest floor. Photo: Friederike Lang
In contrast to arable soils, forest soils are not mechanically mixed. As a result leaf and needle litter, brushwood and seeds accumulate on the surface and form a unique zone of transition between the fresh biomass and the mineral soil, which is called the forest floor. Forest floors can store large amounts of CO2, provide habitat for special biotic communities and have decisive influence on the vitality and stability of forests. The influence of climate change on this soil zone, which is extremely sensitive to environmental changes, raises many unanswered questions.
This is where the "Forest Floor" research unit, recently approved by the German Research Foundation (DFG) and led by Prof. Dr. Friederike Lang from the Institute of Forest Sciences at the Faculty of Environment and Natural Resources at the University of Freiburg, comes in: "We want to investigate the properties and functioning of forest floors, and thus the part of the soil that is probably most sensitive to climate change but is of central importance to forest ecosystems," Lang explains the research goal. The DFG will support the group from July 2022 for an initial four years with a total of 4.8 million euros.
Joint project of twelve international research projects
Based on the motto "Forest floor: Functioning, dynamics and vulnerability in a changing world", twelve different international research projects are joining forces to form a joint project. In addition to Friederike Lang, Prof. Dr. Jürgen Bauhus, Dr. Cornelia Herschbach, Dr. Martin Kohler, Dr. Helmer Schack-Kirchner and Prof. Dr. Christiane Werner from the Freiburg-based Institute of Forest Sciences and Prof. Dr. Markus Weiler from the Institute of Earth and Environmental Sciences are also involved. Further members of the research unit work at the Forest Research Institute Baden-Württemberg, the Technical University of Munich, the Helmholtz Centre Munich, the Johann Heinrich von Thünen Institute - the Federal Research Institute for Rural Areas, Forestry and Fisheries, the University of Göttingen, the University of Hamburg, the University of Copenhagen in Denmark, the ETH Zürich in Switzerland, the Swiss Federal Institute for Forest, Snow and Landscape Research in Birmensdorf, Switzerland, the Kew Royal Botanic Gardens and the Imperial College in London, England are participating. "The funding will allow us to continue a great interdisciplinary collaboration on forest soils, which we have already found very gratifying, stimulating and successful during the application phase," says Lang. The project will create positions for eleven PhD students, one Post-Doc and a coordinating position.
Identifying forest floor properties
The team will analyze the functioning of the forest floor at twelve sites in mixed beech forests in Germany and Switzerland through measurements in the ecosystem and joint experiments. The research unit wants to examine whether the properties of the forest floor of European forests are shaped by adaptations of the trees and associated microorganisms to the nutrient content of the soil and what influence climate warming has on it. A special focus is on the comparison between the forest floor beneath European beech, Norway spruce and Sycamore maple.
Clarifying the forest floor's importance
"The humus layer contains vital minerals and nutrients for plant growth and improves the air and heat balance of the soil," explains Lang. "Many processes that are crucial for the properties of the entire soil or even the ecosystem take place in forest floors. This is thus the hub of the forest ecosystem." The researchers' goal is to better understand the role of interacting factors in the humus layer, such as temperature or nutrient and water supply, as well as the composition of soil fauna and microorganisms. With this information, the importance of the forest floor as a habitat for soil organisms, tree growth and regeneration should also become clearer.
