26.01.2022 | Gottardo Pestalozzi | News WSL
How much biomass do Swiss forests contain, and how much carbon do they store? A team from the Swiss Federal Research Institute WSL is developing a method to calculate this simply and accurately. We accompanied the researchers and filmed them.
Marina Beck and Esther Thürig trudge through the basellandschaft forest in a snowstorm. The air smells of needles and diesel. In the distance, power saws howl.
"We'll take these trees today," says Esther, pointing to a group of beech and pine trees marked with red spray.With her forest gauge Marina records the diameter of the first tree "41.7 centimeters" she calls out to Esther, who enters it on her weatherproof tablet. The procedure is repeated with the fin-clip at 7 meters, followed by the electronic height measurement. Before that, the NFI Scientific Service had recorded the crown diameters by means of terrestrial laser scanning.
It takes timber to test the calculation methods
"We want to find out how it is possible to get an accurate picture of the biomass of a forest, and then of all forests in Switzerland, with these few measurements on the standing tree. In our project, we refine the already known measurement and estimation methods. For this, we need accurate data from a number of felled trees," says Esther Thürig.
Today, Urs Schaub and his team from the "Violental forestry district" are harvesting beech, pine and ash trees in a patch of forest near Arisdorf (Basel region). The researchers have equipped the gripper arm of the forwarder with a scale. Marina can record the weight of every tree or tree part that is towed in. Colleagues then saw off slices and weigh them before transporting them to the WSL carpentry workshop. There, other project members cut out representative wedges, whose mass they measure first fresh and then dry. Finally, the pieces of wood are ground into fine powder so that a laboratory employee can determine the carbon and nitrogen content. The entire process is shown in a short film.
The project is called Swiss Biomass. Together with the Federal Office for the Environment FOEN, WSL is developing in it a conversion method that is as accurate as possible to inform forestry practitioners about two important quantities in the Swiss forest:
- How much biomass is available? This information can be used, for example, to determine the extent to which wood and bioenergy can be used sustainably.
- How much carbon does the forest retain? In the context of climate change, this is important for achieving net zero and for the greenhouse gas inventory that Switzerland compiles annually under the Kyoto Protocol.
Following the initial surveys in Zurich and Arisdorf and their evaluation, the project team plans to conduct research at six additional sites in 2022-23. It has found the first two forest sites for the next project phase this spring in Villigen (AG) and Apples (VD).
In addition to the surveys described above, further analyses are planned. For example, WSL's Soil Functions and Protection group is sampling and analyzing leaves and needles for their constituents, and the Dendrosciences group is examining increment on tree discs. Furthermore, employees of the Remote Sensing group determine the tree positions with a very accurate GPS device and take drone images.
The goal is to apply the methodology tested in the pilot phase at other sites and subsequently to provide a meaningful and simple way of calculating the biomass and carbon content of trees and forest stands for larger regions.
WSL expects to publish the results in 2024.