Simulated moose (Alces alces L.) browsing increases accumulation of secondary metabolites in bilberry (Vaccinium myrtillus L.) along gradients of habitat productivity and solar radiation.

We have addressed the impact of moose (Alces alces L.) on accumulation of secondary metabolites, lignin, and nitrogen in bilberry (Vaccinium myrtillus L.) along gradients of habitat productivity and solar radiation. The study was conducted within a long-term research project on direct and indirect impacts of moose on the ecosystem. In the experiment, browsing, defecation, and urination corresponding to four different moose densities were simulated for eight years before bilberry tissue was collected and analyzed. Some quantitatively dominant flavonoids were affected by the simulated moose browsing and by habitat productivity and light. The content of flavonoids increased with increasing moose density and light, and decreased with increasing habitat productivity. The higher concentration of secondary metabolites in bilberry from nutrient-poor sites may have resulted from the increased photosynthesis relative to growth, which facilitated secondary metabolism. The higher concentration of secondary metabolites in plants subjected to simulated moose- herbivory might have been caused in part by loss of biomass. In addition, in areas with high biomass loss, i.e., high moose density, a more open canopy was created and more solar radiation could have induced secondary metabolism.