The harsh polar environment results in the dominance of mosses and liverworts in tundra communities. To date, very little research has been devoted to the diversity and ecology of these groups in the High Arctic. The aim of this research was to investigate the diversity and community composition of mosses and liverworts in various stages of the ecogenesis of Svalbard ecosystems, and to identify environmental factors affecting species distribution. In 2017, 270 plots were established in a grid in eight glacier forelands and the mature tundra surrounding them. Within these plots, the percentage cover of mosses and liverworts was investigated. In 201 plots, soil samples were taken and environmental data (aspect, bare ground cover, biological soil crust cover, distance from the glacier forehead, rock cover, slope, time elapsed since the glacier’s retreat, Topographic Wetness Index, and total insolation) were obtained. In total, 105 species were recorded. Species number and composition depended on effects of both habitat type (foreland and mature tundra) and the geographical locations of glaciers, while species cover was also associated with the interaction between those factors. The following factors affected species distribution: cover of bare ground and vascular plants, distance from the glacier forehead, soil conductivity, contents of total organic carbon and total nitrogen in soil, K+ content, silt and sand contents, soil pH, time elapsed since the glacier’s retreat, and total insolation. In the glacier forelands, mosses and liverworts are less exposed to competition from other species. Therefore, in the future, if global warming progresses at its current rate, forelands may serve as important species refugia.

Assessment of photosynthetic activity is one of the quick and simple methods of verification whether the studied environmental factors have a stressful effect on photosynthetically active organisms. High-intensity light can be a stress factor that could have a potential impact on the maximum productivity of photosystem II. The purpose of the conducted research was to observe changes in photosynthetic activity of the lichen Cladonia mitis and the bryophyte Pleurozium schreberi exposed to artificial high-energy lighting under laboratory culture conditions. The obtained results showed variability of photosynthetic activity over time, depending on the amount of light energy supplied. C. mitis and P. schreberi at full exposure (light energy: 52.03 W m ^-2 and photosynthetically active radiation 167.24 μmol m ^-2) showed a slow downward trend in photosynthetic activity, while at half the light intensity periodic fluctuations were observed without changes in the controls. Long-term and high-light intensity exposure of photosynthetically active organisms may cause gradual degradation of the photosynthetic apparatus, which in turn leads to cell death. Low values of photosynthetic activity may indicate a situation in which, due to excess light, the rate of photosystem II damage exceeds the rate of its repair. This leads to irreversible damage to the photosynthetic apparatus.