Interference of Vaccinium myrtillus on establishment, growth, and nutrition of Picea abies seedlings in a northern boreal site

Vaccinium myrtillus L. ground vegetation in boreal forests reduces tree seedling survival and growth. We studied below-and above-ground competition and phytotoxicity of V. myrtillus on transplanted Picea abies (L.) Karat. seedlings in a 3-year full factorial field experiment. Exclusion tubes were used to reduce and selectively test for belowground competition by V. myrtillus. Shoots of V. myrtillus were folded back to reduce aboveground competition. Reduced belowground competition by V. myrtillus increased P. abies current-year shoot length, shoot and root biomass, seedling nutrient concentration, and mycorrhizal colonization. Reduced aboveground competition affected P. abies seedling root biomass positively whereas seedling survival, shoot length, and shoot/root ratio were negatively affected Addition of activated carbon to the soil surface to reduce the effect of possible phytotoxic leachates from V. myrtillus leaves and litter had no effects on P. abies seedling survival and growth. No significant interactions among treatments were found. We conclude that suppressed growth of P. abies seedlings in V. myrtillus sites of northern boreal forests is caused mainly by belowground resource competition.