DOI: 10.5061/dryad.50t9d
title: Data from: Simulated caribou browsing limits the effect of nutrient addition on the growth of Betula glandulosa, an expanding shrub species in Eastern Canada

description: 1.Warmer summer temperatures and enhanced soil fertility increase shrub
 growth in tundra ecosystems, and these factors have likely contributed to
 shrub expansion at the circumpolar scale over the last decades.
 Conversely, large herbivores have the potential to counteract the positive
 impacts of climate change on shrub growth. Indeed, by stripping the
 leaves, herbivores have the potential to control the growth of shrub
 species and, consequently, limit their expansion. 2.To disentangle the
 impacts of climate change and herbivory on Betula glandulosa Michx., we
 conducted a 5-yr factorial experiment near Deception Bay, Nunavik, Canada,
 in which we simulated warmer temperatures, increased nitrogen availability
 and three caribou browsing intensities during the growing season. At the
 end of the experiment, we harvested the aboveground biomass of B.
 glandulosa and conducted dendrochronological analyses on stems.
 3.Fertilized plots under ambient temperature had 34% greater shrub biomass
 than plots assigned to the combined treatment of nitrogen addition and
 warmer temperatures. Browsing intensity had no effect on final biomass.
 Nitrogen addition increased radial growth (18-33%; 3 years out of 5).
 Overall, browsing had a cumulative negative impact on B. glandulosa radial
 growth during the 5-yr experiment. While browsing had no effect in the
 first year of the experiment, moderate browsing (leaves stripped on 25% of
 available shoots) decreased radial growth by 27% at year 2, 32% at year 4
 and 27% at year 5. Heavy browsing (leaves stripped on 75% of available
 shoots annually) decreased radial growth by approximately 27% at year 2,
 37% at year 3, 50% at year 4 and 48% at year 5. We did not observe
 significant interactions between browsing, temperature and nitrogen
 availability. 4.Synthesis. Our results clearly showed that caribou
 browsing may limit the growth of B. glandulosa, and thus can potentially
 limit its expansion. Herbivory should thus be considered when predicting
 tundra vegetation changes in the Arctic, at least in areas with high
 herbivore densities.
description: Radial growth of Betula
 glandulosa after 5 years of simulated warming and
 browsingData used for to fit
 linear mixed-effect models (package lme4, R v. 3.2.3) to assess the effect
 of nitrogen addition, warmer temperatures and browsing intensity on radial
 growth of Betula glandulosa (Table 3, figure 3)gr_experiment.csvAboveground biomass of Betula glandulosa after 5 years of simulated warming and browsingData used for to fit linear mixed-effect models (package lme4, R v. 3.2.3) to assess the effect of nitrogen addition, warmer temperatures and browsing intensity on total aboveground biomass of Betula glandulosa (Table 2 and Figure 2)inside_productivity.csvBiomass of Betula glandulosa leaves after 5 years of simulated warming and browsingData used for to fit linear mixed-effect models (package lme4, R v. 3.2.3) to assess the effect of nitrogen addition, warmer temperatures and browsing intensity on Betula glandulosa leaves biomass (Table 2)leaves.csv