Annual report 2023

The seed production of forest trees in Switzerland was intensively observed in 2023, revealing interesting patterns and differences. The uneven behavior of the spruce was particularly noticeable. For the most part, the stands exhibited a partial mast, but an increased occurrence of no seed production was observed mainly in the lower elevations of the Mittelland. In contrast, a half-mast was noted in the Jura and parts of the Pre-Alps. Similar observations were made for the fir. Seed production was concentrated mainly in the South Jura, while in other regions of Switzerland, a partial mast predominated. After two years of low seed production, beech trees experienced a mast year in 2023. Interestingly, mast production was more pronounced in the lower elevations than in the higher elevations and in central Switzerland. In contrast, oaks nationwide exhibited low seed production in 2023, mostly due to a significant oak mast the previous year. Overall, the year 2023 is characterized by a lower synchronization of seed production both within individual species and between different species.

Fig. 1: Map of observed and modelled seed production of Norway spruce (Picea abies) in 2023 (left). Observations of seed production along the altitudinal gradient (right).
Fig. 2: Map of observed and modelled seed production of silver fir (Abies alba) in 2023 (left). Observations of seed production along the altitudinal gradient (right).
Fig. 3: Map of observed and modelled seed production of European beech (Fagus sylvatica) in 2023 (left). Observations of seed production along the altitudinal gradient (right).
Fig. 4: Map of observed and modelled seed production of oaks (Quercus petraea, Quercus robur, Quercus pubescens) in 2023 (left). Observations of seed production along the altitudinal gradient (right).