Spatial and temporal patterns in seed predation as revealed by reciprocal experiments and video surveillance in neighbouring beech and spruce forests

ABSTRACT

European beech and Norway spruce are late successional and competitive species meeting each other in southern Norway. Beech is predicted to expand northwards with increased temperature, implying increased competition between the two tree species. Seed survival is a key process in this competition and here we estimate detection times and predation rates of beech and spruce seeds in adjacent beech and spruce forests by combining quantitative and qualitative approaches based on reciprocal seed predation experiments and video surveillance. These experiments were repeated over two growing seasons, and by using a video-surveillance technique, we were able to precisely reveal seed detection times and high seed predation rates, up to 15 seeds min⁻¹, with bank vole and chaffinch as main predators. Moreover, the two main predators were different in their seed preferences, that is, beech seeds were exclusively removed or predated by the vole, while the finch consumed spruce seeds only. As we show high predation rates, even small variations in seed predator population densities would impact the regeneration success of beech and spruce. Because the highest predation rates were recorded for spruce seeds, it is likely that this will alter the competitive balance between the two tree species in favour of beech.

KEYWORDS:

• Fagus sylvatica
• Picea abies
• seed detection time
• seed predation rate
• seed predators
• seed removal
• video monitoring

Acknowledgements

We thank Ronny Steen for building the surveillance equipment and for giving us fundamental advice. We also thank Geir A. Sonerud for help with seed predator identification, and Anne Sofie Bergene Strømme and Silje Skjelnes Vågen for assistance in the field.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

We thank the Research Council of Norway for financial support [project 225018].