Top predators can provide fundamental ecosystem services such as nutrient cycling, and their impact can be even greater in environments with low nutrients and productivity, such as Arctic tundra. We estimated the effects of Arctic fox (Vulpes lagopus) denning on soil nutrient dynamics and vegetation production near Churchill, Manitoba in June and August 2014. Soils from fox dens contained higher nutrient levels in June (71% more inorganic nitrogen, 1195% more extractable phosphorous) and in August (242% more inorganic nitrogen, 191% more extractable phosphorous) than adjacent control sites. Inorganic nitrogen levels decreased from June to August on both dens and controls, whereas extractable phosphorous increased. Pup production the previous year, which should enhance nutrient deposition (from urine, feces, and decomposing prey), did not affect soil nutrient concentrations, suggesting the impact of Arctic foxes persists >1 year. Dens supported 2.8 times greater vegetation biomass in August, but δ15N values in sea lyme grass (Leymus mollis) were unaffected by denning. By concentrating nutrients on dens Arctic foxes enhance nutrient cycling as an ecosystem service and thus engineer Arctic ecosystems on local scales. The enhanced productivity in patches on the landscape could subsequently affect plant diversity and the dispersion of herbivores on the tundra.

QuestionsIn most ecosystems, some organisms can be considered ecosystem engineers because they modify their physical environment in a way that can affect many other organisms. Nutrient deposition may be extremely important as an ecosystem engineering activity in nutrient‐limited environments, but this mechanism remains understudied. In low‐Arctic tundra, a region characterized by continuous permafrost, low‐nutrient soils, and slow nutrient turnover, Arctic foxes (Vulpes lagopus) concentrate nutrients on their dens through faecal deposition and feeding their young. This nutrient concentration enhances productivity in patches on the landscape, likely creating a unique habitat for a variety of plants, and could have cascading effects on the distribution and diversity of vegetation on the tundra.LocationLow‐Arctic tundra in Wapusk National Park, Manitoba, Canada.MethodsWe quantified differences in vegetation composition between 20 fox dens and adjacent control sites.ResultsPlant growth form differed greatly between dens, which were dominated by deciduous grasses near the coast and erect shrubs farther from the coast, and control sites, which were dominated by evergreen prostrate shrubs. Dens also had more forb cover and less cover of lichens, mosses, and sedges. Species composition also varied greatly between control and den areas, with 17 of the 20 species found in at least 10% of the sampled sites being indicator species for dens or control sites.ConclusionsBy providing habitat for plants reliant on higher nutrient availability not typical of tundra heath, Arctic foxes enhance the biodiversity of the region. These erect plants may also help create new habitat by retaining snow on normally windswept beach ridges. Overall, this study illustrates the broader impacts of predators on diversity and community composition through mechanisms other than predation.