Predators protect tree seedlings and forest grouse
In my doctoral thesis, I examine the interactions in boreal food webs, especially whether predators have direct or indirect cascading effects on the lower trophic levels. Overall, the results of my thesis further support the idea that there are cascading effects in the forests of Northern Europe, and that they are triggered by both direct and non-lethal effects of predation.

Based on my results, the golden eagle decreases the overall abundance of black grouse, but in contrast has a protective effect on the juvenile black and hazel grouse. Interestingly, this positive effect on the juvenile grouse is not dependent on the abundance red foxes or pine martens, predators of grouse broods. Conversely, the protection effect on grouse could arise from fear effects that are not reflected on fox or marten abundance, and it may also be mediated by other medium-sized mammalian predators (so-called mesopredators). However, it remains unclear through which smaller predators the positive effect of the golden eagle on grouse is mediated.
Owls reduce vole browsing through an intimidation effect, which is a novel result of the cascading effects of owl vocalization. My herbivory-seedling studies highlight how different groups of mammalian herbivores vary in their effects on the growth and condition of different tree seedlings. Lowered cervid abundances can improve birch regeneration, which indirectly supports the idea that the key predators of cervids could cause cascading effects also in Fennoscandian forests.
28 Jan 2016
Mari S. Lyly