Combined effects of simulated browsing, warming and nutrient addition on forage availability for migratory caribou in Nunavik, Canada
At high population size, migratory caribou (Rangifer tarandus) are regulated by forage abundance in their summer range. Climate warming likely affects forage availability by increasing productivity and advancing phenology of vegetation. Our objective was to investigate the combined effects of browsing and climate warming on the availability of dwarf birch (Betula glandulosa). We simulated direct (warming, with open-top chambers) and indirect (increased nutrient cycling) effects of climate warming in interaction with simulated browsing (leaf stripping) from 2009 to 2013 in Nunavik, Canada. We measured the effect of treatments on dwarf birch biomass and phenology. Moderate and heavy browsing reduced the estimated biomass of birch leaves by 14% and 34%, respectively. Fertilization did not increase the biomass of birch leaves, but increased the biomass of another forage, Poaceae. The warming treatment advanced the opening of birch leaves by 4 days (95% CI: [3, 6]) in 2011 and 7 [5, 8] days in 2013, the two years colder than average. The absence of significant phenological shifts in warmed plots during warmer springs suggests that established dwarf birches may have reached a threshold in a limiting resource, likely soil moisture, under which they cannot respond to further warming. Our results demonstrate that browsing can reduce forage biomass, but the variability in caribou populations could provide windows of opportunity for shrub growth.
KeywordsBetula glandulosa Climate change Herbaceous arctic tundra Phenology Rangifer tarandus
V. Saucier received scholarships from Caribou Ungava, EnviroNord, Association of Canadian Universities for Northern Studies and the Beverly and Qamarniqjuak management board. This project is part of the Caribou Ungava research program (https://www.caribou-ungava.ulaval.ca/en/accueil/) funded by Natural Sciences and Engineering Research Council (NSERC Grant no. CRDPJ 369122-08) of Canada, Ministère des Forêts, de la Faune et des Parcs du Québec, ArcticNet, Fonds de recherche du Québec nature et technologies, Hydro Québec, Xstrata Nickel (now Glencore), Fédération des pourvoiries du Québec inc., Fédération québécoise des chasseurs et pêcheurs, First Air, Makivik Corporation, CircumArctic Rangifer Monitoring and Assessment (CARMA), International Polar Year, Canada Foundation for Innovation, Institute for Environmental Monitoring and Research, Fondation de la Faune du Québec, Ouranos, and the Canadian Wildlife Federation. We are particularly indebted to Glencore—Raglan Mine for their collaboration, logistic 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, S. Lavoie, M. LeCorre, A.-A. Simard, A. Drolet, M. Bonin, G. Daigle, M.-C. Martin, A. Brousseau, B. A. Campeau, and especially J. Boulanger-Pelletier, D. Côté-Vaillancourt and F. Dulude-de-Blouin for their help with field work. We are grateful to C. Hins and S. De Bellefeuille for logistical help, to M. LeCorre for help with the NARR data and to A. Drolet, M. Bonin, and S. Lavoie for reviewing an earlier version of this manuscript.
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Conflict of interest
The authors declare that they have no conflict of interest.
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