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 tre e seedling survival and growth. We studied below-and above-ground comp etition and phytotoxicity of V. myrtillus on transplanted Picea abies (L.) Karat. seedlings in a 3-year full factorial field experiment. Exc lusion tubes were used to reduce and selectively test for belowground competition by V. myrtillus. Shoots of V. myrtillus were folded back t o reduce aboveground competition. Reduced belowground competition by V . myrtillus increased P. abies current-year shoot length, shoot and ro ot biomass, seedling nutrient concentration, and mycorrhizal colonizat ion. Reduced aboveground competition affected P. abies seedling root b iomass positively whereas seedling survival, shoot length, and shoot/r oot ratio were negatively affected Addition of activated carbon to the soil surface to reduce the effect of possible phytotoxic leachates fr om 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 belowg round resource competition.