Growth, nutrient content, fruit production and herbivory in bilberry Vaccinium myrtillus L. along an altitudinal gradient

Abstract

Growth, fruit production and herbivory by ungulates in bilberry were investigated in 29 localities from three temperate habitats (oak forest, birch forest and heath) distributed along an altitudinal gradient from 750 to 2000 m a.s.l. Plant height, current year growth and damage by herbivores were influenced by altitude. The herbivory by ungulates increased with altitude inside the woodlands, but had moderate effect in the heaths despite their higher altitude. Furthermore, when only oak forest sites were considered, nitrogen content in both twigs and leaves significantly increased with altitude, and nitrogen content in twigs was significantly related to the percentage of shoots affected by ungulate herbivory. Contrarily, the herbivory was reduced in sites exhibiting higher content of acid detergent fibre in leaves. Patterns of fruit production per habitat and altitude were not consistent between years; however, fruit set within the oak forests decreased with increases in the percentage of shoots affected by herbivory. Possible effects of ungulate herbivores on nitrogen concentration of bilberry and its quality as food for herbivorous and frugivorous animals are discussed.