Increased growth and phenolic compounds in bilberry (Vaccinium myrtillus L.) following forest clear-cutting

Abstract

Bilberry (Vaccinium myrtillus L.) is a keystone species in boreal forests, but the few studies available concerning influence of forestry on bilberry growth, reproduction and chemical composition reveal conflicting results. We compared bilberry from mature stands and clear-cuts in a spruce forest landscape in south-central Norway, and applied the following experimental treatments: fertilisation, root cutting and flower removal to evaluate the effect of resource availability. During the second growing season we estimated bilberry shoot biomass as well as flowering and berry production, while bilberry shoots and leaves were collected in early summer and autumn for analysis of nitrogen, carbon and phenolic compound concentrations. The biomass of bilberry shoots was highest on clear-cuts and after fertilisation. All groups of phenolic compounds were also highest on clear-cuts, and phenolic acids and flavonols were highest in non-fertilised plots. Catechins and condensed tannins were highest in autumn, while phenolic acids and flavonols were highest in summer. Removal of flowers and root cutting had no effects. Nitrogen concentrations in shoots were highest in summer, after fertilisation, and when flowers were removed. The amount of flowers was highest in non-fertilised, mature forest sites, while the berry production was not significantly affected by any of the treatments or the site type. Our results indicate that in the studied area, the performance of bilberry is not negatively affected by clear-cutting, it rather seems that the environment on the clear-cuts give the plants abundant resources for enhancements both in growth, reproduction and defence compared with the mature forest sites. In the eyes of a herbivore, however, the quality of bilberry shoots as a feed-plant may be reduced on a clear-cut because of the higher phenolic concentration.