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The purpose of the present study was to determine the link between planktivorous little auks (Alle alle) and their soil fertilization, the concentration of total, and different forms of phosphorus in the surface layer of the High Arctic soils and the vascular plant composition of the tundra vegetation. Samples of the surface soil layer (0–10 cm) were collected along three pairs of transects (affected and unaffected by little auks) at different locations in Spitsbergen (Svalbard). The surface layer of soils affected by little auks was characterized by a significantly higher mean concentration of Ptot (1.02–1.44 g kg−1) compared to those not affected by seabirds (0.58–0.77 g kg−1). The mean concentration of different forms of P was also generally higher in soils affected by seabirds (i.e., labile P: 0.13–0.34 g kg−1, moderately labile P: 0.31–0.90 g kg−1, stable P: 0.27–0.39 g kg−1) than in unaffected soils (labile P: 0.04–0.18 g kg−1, moderately labile P: 0.30–0.37 g kg−1, stable P: 0.12–0.24 g kg−1); however, the differences were not always significant, most likely due to the high heterogeneity of specific environmental conditions at the local scale such as soil type, soil chemical composition, and vegetation type. Vascular plant cover was significantly and positively related to the concentration of the P forms studied in the soil. The phosphorus gradient significantly altered the composition of the vascular plants and explained 58.4% of its variation. Little auks are an important source of soil phosphorus in terrestrial ecosystems in the High Arctic that significantly affect the cover and composition of vascular plants. [ABSTRACT FROM AUTHOR]