BELOW-GROUND RESPONSES OF SCOTS PINE (Pinus sylvestris L.) SEEDLINGS TO EXPERIMENTAL WARMING, MODERATE NITROGEN ADDITION AND BARK HERBIVORY

The aim of this chamber experiment was to study the single and interaction effects of warming (+2 ○C increase), moderate N addition (30 kg N ha-1 y-1) and bark herbivory by large pine weevil (Hylobius abietis L.) on fine root morphology, mycorrhizas, root phenolics and biogenic organic volatile compounds (BVOCs) from the rhizosphere area of young Scots pines (Pinus sylvestris L.) Warming increased soil exploration by increasing specific root length (SRL) and the relative proportion of 0.2-0.3 mm roots in fine root systems, while N addition and herbivory without warming both caused an increase in the relative proportions of thicker roots in the fine root systems. Warming decreased total phenolic concentrations in the roots without N addition, while some flavonoid compounds showed complex responses to warming, N addition and herbivory. N addition in combination with warming reduced total other BVOC emissions from the rhizosphere area at the end of the experiment. Herbivory increased mycorrhizal colonisation...