The forest floor is an important carbon store and habitat for countless organisms. Experts have therefore now named it Bodes of the Year 2024. The soil of the Tharandt Forest near Dresden serves as an exemplary title holder. Since it is not suitable for agriculture, it is still relatively primitive and has the nutrient-providing humus layer made up of dead animal and plant parts that is typical of natural forest floors. But more and more forest soils are facing major problems.
The ground beneath our feet is more valuable than many may realize. For example, in a single handful of soil there are more microorganisms than there are people on earth. The soil also stores more carbon than vegetation, protects against erosion, filters pollutants and is essential in the fight against climate change. In order to draw attention to these often underestimated services of the soil, a committee of experts led by the Federal Environment Agency and the Federal Environment Ministry has chosen the Soil of the Year every year since 2004.
The base of the forest in focus
For 2024, the title of “Soil of the Year” now goes to the forest floor. “Forest soil doesn’t actually exist as a specific individual type,” explains Karl-Heinz Feger from the TU Dresden, President of the German Soil Science Society. “The subsoil in our forests is made up of a wide variety of very different soil types.” Which soil has developed at a location depends on the interaction of various factors such as the source rock, the vegetation, the climate, but also the influence of humans.
The soil of the Tharandter Forest near Dresden therefore serves as an exemplary title holder for the forest floor. It consists of so-called Pseudogley, a soil type common in Central European forests. Typical for this is a marbling of light and rusty brown spots as well as a sequence of heavily compacted, clayey soil layers that accumulate water in the ground. This makes soils of this type difficult to cultivate and therefore largely unsuitable for agriculture. The Tharandter Forest was therefore able to grow relatively undisturbed by humans.
Like other forms of natural forest soil, Pseudogley has numerous useful properties that make it indispensable for nature and humans. It and other forest floors serve as an important habitat for plants, animals, fungi and microorganisms. They use leaves and other dead plant parts to create a humus layer in the forest floor, which supplies the trees with nutrients and at the same time stores large amounts of carbon. The forest floor even stabilizes the climate. At the same time, it prevents erosion and holds back heavy rain, thereby providing natural flood protection.
Forest floors have a hard time
But many forests managed by humans can no longer fulfill all of these useful functions. For example, by planting tree species that are not suitable for the soil or by regularly driving heavy forestry machines over the forest floor, the soil is compacted, the humus layer is destroyed and with it an important component of natural forest soils. At the same time, many forests around the world are threatened by deforestation. It is estimated that up to 5,000 years ago, 90 percent of the country's area was covered with forests. Today it is only about a third due to agriculture. In addition, the remaining forests usually grow on nutrient-poor and stony soils that are not suitable for agriculture, which makes them particularly vulnerable to disruptive factors.
But forest floors are exposed to a number of other man-made stressors. For example, industrialization has led to the topsoil being damaged by widespread acidification, the entry of heavy metals and nutrient depletion. Due to climate change, forests and forest floors are increasingly affected by drought, fires and storms, which, combined with pest infestation, lead to the widespread death of trees. These bare areas in turn release CO2 and continue to lose nutrients through erosion. The decision to choose the forest floor as soil of the year is also intended to draw attention to this.
Source: Johann Heinrich von Thünen Institute, Federal Research Institute for Rural Areas, Forests and Fisheries, Technical University of Dresden