Lichens affect boreal forest ecology and plant metabolism

Abstract Lichens, symbiotic organisms consisting from mycobionts (fungi) and photobionts (algae and/or cyanobacteria), play a substantial role in boreal coniferous forests. They may form thick mat that significantly interferes with young plants, mosses and rest of understory vegetation. Lichens synthesize more than one thousand of secondary metabolites, from which usnic acid is one of the most abundant. It can negatively affects plant metabolism through allelopathy. Lichen secondary metabolites can be a source of energy for soil microorganisms and at the same time, they can inhibit growth of surrounding competitive lichens, mosses and vascular plants. Lichen metabolites were also found in bark, xylem and leaves of some trees, which serving to epiphytic lichens as substrate. Although significant results, which deepening our knowledge in this area of research, were obtained during the last decades, understanding of role of lichens in boreal forests is very complex issue and requiring further studies.