Development of the frequency of browsing from 1993 to 2022 in Switzerland

The Swiss National Forest Inventory (NFI) documents the frequency of terminal shoot browsing throughout Switzerland using standardized methods. This study used logistic models to analyse the development of browsing between NFI2 (1993–1995) and the start of NFI4 (2009) and during the period from 2009 to 2022 (NFI4 and NFI5) for the most common tree genera. In addition, the presence of browsed trees per inventory was compared. In the region “Southwestern Alps + Southern Alps”, browsing on the most common tree species increased from NFI2 to the beginning of NFI4. If the overestimation of browsing using the NFI2 compared to the NFI4 recording method is considered, an increase in browsing can also be assumed in most other regions. In contrast, browsing on Acer, Fraxinus and Sorbus is likely to have remained unchanged. Since 2009, browsing on the terminal shoots of ash trees has been decreasing, particularly in western Switzerland. On the other hand, browsing on maples is increasing there since the start of NFI4. In the current NFI5 data, browsing on some species is lower in the regions “Western Plateau” and “Northwestern Alps” than in the east and south of Switzerland. Beech and spruce are browsed significantly less frequently by wild ungulates than silver fir and especially the noble hardwoods. This reduces the future silvicultural potential and complicates the development of climatically adapted species-rich mixed forests.