This thesis focuses on the so-called spruce mires of the Pokljuka plateau, which like true-raised bogs can also be classified as peat bogs. The characteristics of these mires come mainly from the presence of spruce trees (Picea abies (L.) Karst). The features of the mires include a distinctively mosaic structure and mixed character. By using cluster analysis of the phytosociological relevés, we have classified the mires and their edges into several groups that belong to different syntaxa: Pino mugi-Sphagnetum, Sphagno-Caricetum rostratae, Sphagno girgensohnii-Piceetum var. geogr. Carex brizoides, Rhytidiadelpho lorei-Piceetum. Individual vegetation groups also mark the transitions between clearly defined syntaxa. Apart from a similar vegetation structure, the defined groups also have specific pedologic, hydrologic, nutritional and growth conditions of the spruce, which emphasises the indicative value of the vegetation. We found the greatest diversity of plant species on the mires covered predominantly with sedge fen vegetation andat their transitions into the spruce-forest margins on the automorphic soil. The characteristics of the investigated mires and their margins are the heterogenic soil conditions which are represented by a larger number of defined soil types and lower pedosystematic units. Because of significant differences, the vegetation groups are classified mainly according to the levels of soil humidity, the pH of the soil, the amount of total carbon and the C/N ratio of the soil. The groups are, apparently, also different according to their average quantities of Ca2+, H+ and Al3+ exchangeable cations as well as the base saturation degree and the cation exchange capacityof the soil (CEC). In addition, the amount of N and Ca in one-year-oldspruce needles indicates the completely different nutritional conditions of particular vegetation groups. The selected spruce trees from themires and areas around them are not essentially different in terms of theirage, however, we have discovered characteristic differences in terms of height, diameter and the average tree-ring width. For most of the mires, dendrochronological analyses have shown unstable growth of the spruce during their juvenile phase, which indicates the intensive competition for space and mineral nutrients. Because of a variety of their floristic, vegetational and growth conditions, the spruce mires contribute significantly to the biodiversity of the forested area on Pokljuka.