Bilberry (Vaccinium myrtillus L.) in a boreal forest ecosystem : effects on tree seedling emergence and growth

• Main Author: Jäderlund, Anders
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2001
• Subjects: Forest Science; Ecology; Norway; Northern Sweden
• Online Access: https://pub.epsilon.slu.se/17737/; https://pub.epsilon.slu.se/17737/1/jaderlund_a_201006.pdf

The interference effects of bilberry ( Vaccinium myrtillus) on bee seedling emergence and growth was studied in a series of indoor bioassays and in three field experiments in a bilberry dominated clear-cut in northern Sweden. Water extracts of senescent bilberry leaves reduced aspen (Popuhts tremula) seed germination and growth in bioassays aimed to test phytotoxicity. Those inhibition effects were removed by the addition of activated carbon. When senescent leaves were used as a seedbed, Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and silver birch (Betula pendula) seed germination was significantly reduced, but water rinsing of seeds reversed the inhibition in pine and spruce. Establishment and growth of pine and spruce seedlings were negatively affected by senescent and decomposed bilberry leaves, when applied as surface litter. These results suggests that the inhibitory compounds are water soluble and are released during decomposition. Under field conditions phytotoxic effects from bilberry reduced pine seed germination, while growth and nutrient acquisition of pine and spruce seedlings were greatly unaffected. Pine and spruce seedlings were planted in exclusion tubes to study below ground competition by bilberry. Reduced below ground competition strongly increased biomass growth and nutrition of pine and spruce seedlings, also mycorrhizal colonisation was increased. Water addition had a small positive, but mostly non-significant effect on pine and spruce seedling biomass growth and nutrition. Reduction of above ground competition by folding back bilberry shoots actually reduced spruce seedling survival, shoot length and shoot to root ratio, but increased root biomass. The results clearly show that below ground nutrient competition is the main reason for reduced tree seedling growth and nutrition. I also tested the effectiveness of steam treatment in reducing bilberry competition with pine and spruce as a site preparation technique. Steam treatment effectively killed bilberry vegetation and re-colonisation was slow. Pine seed germination was enhanced in the first year after treatment, especially when activated carbon were added to steamed plots. Pine seedling growth and nutrient content were also strongly increased when grown in steam treated vegetation compared to intact vegetation. I conclude that bilberry has the capacity to influence on establishment and growth of conifer seedlings in boreal forest ecosystems.