The Lateral Spread of Tree Root Systems in Boreal Forests: Estimates Based on super(15)N Uptake and Distribution of Sporocarps of Ectomycorrhizal Fungi

The lateral spread of tree root systems in boreal forests, was analyzed. Estimates were based on super(15)N uptake and distribution of sporocarps of ectomycorrhizal fungi. The ECM sporocarp distribution on tree-girdled plots and adjacent plots were analysed and uptake of stable isotopes were studied. The average root spread of trees was c. 4-5 m. super(15)N uptake indicated a considerable potential for belowground competition because several trees took up N from each m super(2) plot. Single tree root system occupied only c. 8 and 9 m sub(2) if tree root systems were mutually exclusive. super(15)N enriched leaves of dwarf shrubs were found up to a distance of 2.5 m from the centre of the injection area.