Research projects make forest areas fit for the future

Test plantings of eight tree species will be carried out In Unterägeri this autumn in order to test their climate tolerance over the long term. In Menzingen, meanwhile, the improvement of soil quality using limestone is being researched. A look over the shoulder of the expert.

Research will be carried out In the Hinterwidenwald in Unterägeri over the next few decades, as part of a national project. "We will plant and cultivate eight tree species here in the coming autumn or in the spring of 2022," announces Sabrina Maurer of the Zug Office for Forests and Game (Amt für Wald und Wild). This is one of the locations for a long-term national test planting series for the study of the climate tolerance of a total of 18 tree species carried out by the Federal Research Institute for Forests, Snow and Landscape (WSL), the Federal Office for the Environment (Bafu), 20 cantonal forest offices and various forestry operations.

Many regional tree species are coming increasingly under dry stress due to climate change. "The project is about helping to secure the future performance of forests," explains Peter Brang of the WSL. "Under the climatic conditions that are expected towards the end of the 21st century, other tree species will grow better in many forest locations than those that are thriving there today."

The experts want to accelerate this necessary change of species. "To do this, we need to better understand which conditions are suitable for each tree species, and which are not." With this in mind, 18 tree species will now be planted at 57 experimental sites throughout Switzerland with very different climatic conditions, and their development will be monitored over 30 to 50 years.

Photo 1: Sabrina Maurer coordinates the work at the two project sites in Unterägeri and Menzingen
Photo 2: Measuring station for the removal of water from the ground
Photo 3:Foliage and needles accumulate in fishing nets, which, like the soil, are regularly examined.
Photos: Stefan Kaiser (Unterägeri, 22 December 2020)

"Tree species that cannot adapt to the climate cannot create a healthy forest," emphasises Brang. "If you do nothing, less wood will be produced, and less carbon dioxide will be bound in the future. In addition, gaps will arise in the forest, and protection against avalanches and rockfalls will no longer be guaranteed." This scenario could be reduced by choosing well-suited tree species.

Seeds with adapted genetic material
"Climate, soil construction and water balance promote the emergence of certain plant species. Under similar conditions, similar groups of species develop, and are distributed in forest societies," says Sabrina Maurer of the Zug Office for Forests and Game. As the climate is a decisive location factor, changes in the climate will inevitably lead to other groupings of species. This process, which in itself is natural, is being accelerated by climate change.

Trees and plants are adaptable. "There are individuals and populations that live in locations that already have the conditions we expect in our region in a few decades time." A beech tree in the Jura, for example, is accustomed to low rainfall and stronger heat.

"So you take seeds from these trees, which already contain genetic information that is adapted to the harsher climate, plant them in experimental areas where beech is already native today, and observe whether and how they thrive."

In this way, the existing forest society will be made fit for the future. Not only 18 tree species are being tested throughout Switzerland, but also seeds from seven different origins.

Various locations have been selected
"We wanted to expose the trees to as many different climatic conditions as possible," continues Brang. "This is referred to as a large climate gradient. Test areas were therefore selected ranging from the warmest to cold locations." What this actually means is a range from low altitudes in Ticino to almost up to the upper tree line in the Alps. "We also wanted different conditions for soil, such as shallow soils that store little water, and deep soils. The conditions also have to be as uniform as possible within each test area." The total of about 55,000 trees were grown in tree nurseries, who delivered them to the WSL, where their height and trunk thickness are measured and they are prepared for the respective planting area. Forestry workers then plant the trees under the guidance of WSL experts. "We planted ten areas in the autumn of 2020, and we will plant another ten next spring, and so on until the last area is planted in the spring of 2023," says Brang.

De-acidifying the soil by means of lime
In a second, much smaller national research project resulting from a political initiative, an investigation is being carried out to investigate whether acidic forest soils could be rehabilitated by means of the application of limestone. "Many forest sites in Switzerland are affected by acidification due to excessive nitrogen, which has an impact on the stability of forests," says the official project description. This nitrogen is the result of human activities. The Federal Council has identified the main objective of the experimental research as the improvement of the nutrient status of forests.

"Three research sites throughout Switzerland were selected for this purpose," says Sabrina Maurer. One of them is in Menzingen. "Limestone has now been spread on the forest floor." Dolomite has been used for this, a natural limestone. It is extracted from calcareous rock formations and crushed so that it can be evenly distributed. Due to the lime, the supply of calcium and magnesium in the soil increases and the pH value rises. This makes the chemical environment for plants and soil organisms more favourable again.

"According to the Swiss Fertilizer Book Ordinance, however, limestone is a soil improver product," says Maurer. Since it is in principle prohibited to fertilise the forest floor, this pilot project is subject to authorisation by the Federal Government.