Shrub cover in northern Nunavik: can herbivores limit shrub expansion?

Abstract

Recent climate changes have increased the primary productivity of many Arctic and subarctic regions. Erected shrub has been shown to increase in abundance over the last decades in northern regions in response to warmer climate. At the same time, caribou herds are declining throughout the circumboreal regions. Based on observation of heavy browsing on shrubs at Deception Bay (Nunavik, Canada), we hypothesized that the densification of shrubs observed in nearby locations did not occur at our study site despite of observed warming because of a recent peak of the Rivière-aux-Feuilles caribou herd. To assess shrub cover changes, we compared a 1972 mosaic of aerial photos to a 2010 satellite image over a 5 km2 area, divided into 56 grids of 100 30 m × 30 m cells. Most cells (n = 4,502) did not show any changes in the cover of shrubs but those who did were as likely to increase as to decrease. The relative cover of shrubs in cells who changed was not higher in 2010 (6.1 ± 0.2 %) than in 1972 (7.3 ± 0.4 %). More than 70 % of birch and willow had more than 50 % of their shoot browsed, suggesting that caribou may limit shrub expansion at this site. We cannot rule out that abiotic factors also contribute to the inertia in shrub cover. Increases in shrub abundance reported in Nunavik and elsewhere were located closer to the tree line or in discontinuous permafrost, whereas our site is characterized by herbaceous arctic tundra, continuous permafrost and relatively low annual precipitation.

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Acknowledgments

This project is part of the Caribou Ungava research program (http://www.caribou-ungava.ulaval.ca/en/accueil/) funded by Natural Science and Engineering Research Council of Canada, Ressources Naturelles et Faune Québec, Network of centers of excellence ArcticNet, Fonds de recherche sur la nature et les technologies du Gouvernement du Québec, Hydro Québec, Xstrata Nickel, Fédération des pourvoiries du Québec inc., Fédération Québécoise des chasseurs et pêcheurs, First Air, Makivik Corporation, CircumArctic Rangifer Monitoring and Assessment, International Polar Year, Canada Foundation for Innovation, Institute for Environmental Monitoring and Research, Fondation de la Faune du Québec, Ouranos, the Canadian Wildlife Federation, and the Northern Scientific Training Program. We are particularly indebted to Xstrata Nickel-Raglan Mine for their collaboration, logistical support and the continuous use of their infrastructures. The Quarqalik landholding corporation of Salluit welcomed our team on their land. Thanks to Raglan Mine employees, B. Doyon, V. Saucier, J. Boulanger-Pelletier for fieldwork, and to E. L’Hérault of Centre d’Études Nordiques and M. LeCorre for help with the analyses. G Daigle from the Service de consultation statistique at Université Laval provided statistical guidance.

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Correspondence to Sabrina Plante.

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Plante, S., Champagne, E., Ropars, P. et al. Shrub cover in northern Nunavik: can herbivores limit shrub expansion?. Polar Biol 37, 611–619 (2014). https://doi.org/10.1007/s00300-014-1461-6

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Keywords

  • Shrub expansion
  • Caribou
  • Plant-herbivore interactions
  • Climate change