DOI: 10.5061/dryad.sbcc2fr4j
title: Data from: Influence of habitat availability and fire disturbance on the northern range boundary of eastern white cedar (Thuja occidentalis L.)

description: Aim Non-climatic constraints on species northern range boundaries are
 often overlooked in attempts to predict climate-induced range shifts.
 Here, we examined the effects of habitat availability and fire disturbance
 on the distribution of eastern white cedar (Thuja occidentalis L.) at the
 northern boundary of its range. Location North-western Quebec, Canada
 (46-51° N and 74-79° W) Methods We used forest inventory data (n=4,987) to
 characterize white-cedar habitat based on edaphic and topographic
 conditions at sampled sites along a 600-km latitudinal gradient.
 Non-metric multidimensional scaling was used to assess habitat similarity
 of sites in the south, where white-cedar stands are abundant, and sites in
 the north, where white-cedar stands are rare. We constructed ensemble
 white cedar distribution models based on habitat variables in the south
 and compared ensemble forecast projections of white cedar in the north
 with observed occurrences to determine if habitat availability was
 limiting. We independently estimated the age of white-cedar stands and
 adjacent stands without white cedar along the gradient. ANOVA was
 performed to test the age difference between white-cedar and adjacent
 stands to determine if the location of white-cedar stands was influenced
 by disturbance, primarily stand-replacing fire. Results Habitat
 availability was not limiting the distribution of eastern white cedar at
 its northern range boundary. White cedar did not occupy most sites with
 suitable habitat in the north, suggesting that other factors prevent white
 cedar from establishing more stands northward. White-cedar stands were
 older than adjacent stands without white cedar all along the gradient, but
 the difference was more pronounced in the north. This suggests that
 white-cedar stands in the north are restricted to undisturbed areas. Main
 conclusions Fire disturbance, more than habitat availability, limits the
 distribution of white cedar at its northern range boundary. Projections of
 white cedar distribution under climate change that ignore fire could
 overestimate the ability of warming temperatures to extend its northern
 range limit.
description: We created a combined dataset from three types of
 forest inventory databases in Quebec, Canada: permanent (MFFP 2016a),
 temporary (MFFP 2016b), and ecological (Gosselin & Major, 2012;
 Saucier, Berger, d’Avignon & Racine, 1994) sample plots. We
 randomly sampled the combined dataset to select approximately equal
 numbers of stands with and without eastern white cedar
 (<em>n</em>= 4,987). Sites occurred across four bioclimatic
 domains: ioclimatic domain-3 sugar maple-yellow birch (<i>Acer
 saccharum </i>Marsh. - <i>Betula alleghaniensis
 </i>Britt.); bioclimatic domain-4 balsam fir-yellow birch
 (<i>Abies balsamea </i>(L.) Mill. - <i>Betula
 alleghaniensis</i>); bioclimatic domain-5 balsam fir-white
 birch <i>Abies balsamea</i> - <i>Betula
 papyrifera</i> Marsh.); and bioclimatic domain-6 black
 spruce-feathermoss (<i>Picea mariana</i> (Mill.) Britt.,
 Sterns & Poggenb.). Climate data were obtained from the USDA
 Forest Service Rocky Mountain Research station.
  
 <strong>References:</strong>
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 Schaminée (Eds.), Vegetation databases for the 21st century.
 <i>Biodiversity and Ecology.</i> (4, 432). University of
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 Faune et des Parcs (MFFP). (2016). <i>Placettes-échantillons
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