Dynamics of ectomycorrhizal fungi and growth of Norway spruce seedlings after planting on a mounded forest clearcut

One- and two-year-old Norway spruce container seedlings (Picea abies (L.) Karst.) were planted on mounded and untreated spots in two forest clearcuts in central Finland. The effects of mounding on shoot and root growth, ectomycorrhizal (ECM) colonization and number of ECM-strains of the seedlings were assessed 1 and 2 years after outplanting. Mounding had no influence on the shoot growth of the seedlings during the first 2 years after outplanting, but increased root growth significantly. With mounding, the structure of the root systems was also better ramified. In all samples, the degree of ECM-colonization was high, but in seedlings planted on mounds it was even higher. No effects on ECM-diversity due to mounding were observed in fingerprints of denaturing gradient gel electrophoresis (DGGE) or in ECM-morphotyping. However, mounding caused changes in the structure of the ECM-community. Many of the observed fungal sequences colonizing root tips that grew out into the soil probably originated from the nursery. Both altered soil characteristics caused by mounding and the effect of ECM-inoculum on growth and branching of the roots may affect seedling performance after mounding.