Professor Julia Koricheva, Royal Holloway London
“Unravelling the mechanisms of forest diversity effects on herbivores”
Insect herbivory is often reduced in plant species mixtures compared to monocultures. Although several hypotheses have been proposed to explain this pattern, empirical tests of these mechanisms are rare in forests. I will present results of studies in a long-term Satakunta forest diversity experiment in Finland which explore whether forest diversity effects on herbivores are driven by concurrent changes in environment, host tree traits and interactions with other taxonomic groups (e.g. insect and mammalian herbivores). I show that reduction in insect herbivory in mixed stands is frequently linked to changes in canopy cover around a focal tree. In addition, browsing by moose alters both the magnitude and the direction of forest diversity effects in birch insect herbivores. This work identifies novel pathways linking plant diversity and insect herbivory and highlights the role of structural and trophic complexity as mediators of forest diversity effects on insect herbivores.