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Keywords:

  • belowground herbivory;
  • C sink;
  • C source;
  • ecosystem respiration;
  • goose grubbing;
  • high arctic;
  • land-use change;
  • net ecosystem exchange;
  • Spitsbergen

Abstract

Tundra ecosystems are widely recognized as precious areas and globally important carbon (C) sinks, yet our understanding of potential threats to these habitats and their large soil C store is limited. Land-use changes and conservation measures in temperate regions have led to a dramatic expansion of arctic-breeding geese, making them important herbivores of high-latitude systems. In field experiments conducted in high-Arctic Spitsbergen, Svalbard, we demonstrate that a brief period of early season belowground foraging by pink-footed geese is sufficient to strongly reduce C sink strength and soil C stocks of arctic tundra. Mechanisms are suggested whereby vegetation disruption due to repeated use of grubbed areas opens the soil organic layer to erosion and will thus lead to progressive C loss. Our study shows, for the first time, that increases in goose abundance through land-use change and conservation measures in temperate climes can dramatically affect the C balance of arctic tundra.