Swiss Biomass: calculation of biomass and carbon content in the Swiss forest

In times of climate and energy change, sequestration of carbon (C) and provision of biomass are important ecosystem services (ES) of forests. At WSL, many data are available to estimate stemwood volume, but no data are available to directly estimate total aboveground biomass on individual trees.

In the WSL internal pilot project "Swiss Biomass", measurement methods were evaluated to fill these data gaps. The goal is to be able to determine the biomass of individual trees more precisely using non-destructive measurement methods. These biomass estimates are central for the greenhouse gas inventory, the Kyoto reporting and for the estimation of wood resources and bioenergy potentials.

For the WSL project "Test Plantings", approximately 50 stands of one hectare each are felled. The Swiss Biomass project is now using these felling operations for destructive data collection for improved biomass functions. The pilot project is testing methods to determine the biomass of thick trees.  This destructive measurement method is complemented by previous non-destructive surveys of individual trees and stands.

Different measurement teams from WSL are making different surveys on the same two stands. For the pilot study in autumn 2020, two stands were selected on which a well-preserved old-growth stand is located, the Waldlabor near Zurich and Arisdorf near Basel.

The surveys of the old-growth stand at the Waldlabor were all successfully completed before harvest at the end of November 2020. This included various dendrometric measurements on 363 trees. In addition, the stand was surveyed using LIDAR from the air and ground. To learn more about the nutrient balance of the stand, samples were taken from the soil, leaves, needles, branches and bark.

During felling in the first half of December 2020, 36 selected trees were measured lying section by section, the weight was determined with a crane scale, and 5 stem slices were taken from each. The stem slices were weighed (fresh weight), taken to WSL for further processing to determine fresh volume, dry volume, and dry weight.

The data in the forest stand in Arisdorf were collected between the end of December 2020 and the end of January 2021, analogous to the field surveys in the forest laboratory.

Since the end of 2021, the project is entering its second phase, during which we will conduct field surveys in six additional forest stands. See also the WSL news release of 26.1.2022.