The effect of soil preparation (no soil preparation (control), mounding, and removal of the humus layer) on the parameters of root systems of Picea abies seedlings was analyzed. The soil preparation methods have not influenced the total root biomass.
Seedlings growing on mounds demonstrated both extensive and intensive mechanisms of utilizing soil resources (increasing the length of conducting roots and the average length of last-order roots, enlarging the surface area of last-order roots by increasing the diameter of ectendomycorrhiza (EEM) and its share among last-order roots). Many parameters had similar values in the control plots and in the plots with the removed humus layer (length of conducting roots, average length of last-order roots, surface area of one ectomycorrhiza (EM), total surface area of tips (TSA), percentages of EM, EEM, and roots with disturbed structure among last-order roots, the ratio of EM and EEM surface areas in the TSA). The differences between the root systems of P. abies seedlings in the plots with removed humus and those in the control are manifest in the intensification of the use of soil resources (by increasing the EEM diameter and the density of last-order roots). The soil preparation methods have not influenced the formation of EM. The surface area of EM in plots with mounding and humus removed did not change versus the control, but the intensity of EM mycorrhization among last-order roots was different. The diameter and the intensity of mycorrhization of EEM were the parameters the most significantly altered by soil preparation. All the examined cross-sections of last-order roots had endotrophic features.