Long-term consequences of goose exclusion on nutrient cycles and plant communities in the High-Arctic

Abstract

Abstract Geese can profoundly affect arctic ecosystems directly (e.g., by grazing vegetation) and indirectly (e.g. by changing nutrient cycling resulting from faces inputs and by reducing plant litter). In the Arctic, behavior and abundance of geese have changed due to climate and land-use change. While the short-term effects of increased goose populations on tundra ecosystems are known, there is a knowledge gap for long-term consequences of goose population changes on nutrient cycling and plant communities, especially in the High-Arctic. Here, we compared wetland sites where geese have been almost absent for at least 50 years (Pond Inlet), and nearby sites where geese are abundant or sites where they have been excluded experimentally by cages and where the ground has been experimentally fertilized for over 16 years (Bylot Island). Long-term goose disappearance increased inorganic nutrients in wetlands through increased plant litter decomposition and changed community composition, likely by altering competitive relationships between three dominant vascular plant species that are different in terms of nutrient acquisition and use. In experimentally fertilized sites, inorganic nutrients were similarly increased, but fertilization had contrast effects on plant community composition compared with herbivory, released plant species from the nutrient limitation and converted wetland habitats to a dryer state. Overall, our results suggest that the direct effects of goose herbivory on vegetation are more profound than their indirect effects through an alternation of nutrient cycling even in nutrient-limited wetlands of the Arctic. These findings emphasize the need to assess long-term direct impacts of herbivores on vegetation.