DOI: 10.5061/dryad.t1g1jwt15
title: Terrestrial lichen data for Northwest Territories, Canada

description: Increased fire activity due to climate change may impact the successional
 dynamics of boreal forests, with important consequences for caribou
 habitat. Early successional forests have been shown to support lower
 quantities of caribou forage lichens, but geographic variation in, and
 controls on, the rates of lichen recovery have been largely unexplored. In
 this study, we sampled across a broad region in northwestern Canada to
 compare lichen biomass accumulation in ecoprovinces, including the
 Saskatchewan Boreal Shield, the Northwest Territories Taiga Shield and
 Northwest Territories Taiga Plains, divided into North and South. We
 focused on the most valuable Cladonia species for boreal and barren ground
 caribou: Cladonia mitis and C. arbuscula, C. rangiferina and C. stygia, C.
 stellaris and C. uncialis. We developed new allometric equations to
 estimate lichen biomass from field measurements of lichen cover and
 height; allometries were consistent among ecoprovinces, suggesting
 generalizability. We then used estimates of lichen biomass to quantify
 patterns of lichen recovery in different stand types, ecoprovinces, and
 with time following stand-replacing fire. We used a hurdle model to
 account both for the heterogeneous nature of lichen presence
 (zero-inflation), and the range of abundance in stands where lichen was
 present. The first component of the hurdle model, a generalized linear
 model (GLM), identified stand age, stand type and ecoprovince as
 significant predictors of lichen presence. With a logistic growth model, a
 measure of lichen recovery (time to 50% asymptotic value) varied from 28
 to 73 years, dependent on stand type and ecoprovince. The combined
 predictions of the hurdle model suggest the most rapid recovery of lichen
 biomass across our study region occurred in jack pine in the Boreal Shield
 (30 years), while stands located in the Taiga Plains (North and South)
 required a longer recovery period (approximately 75 years). These results
 provide a basis for estimating future caribou habitat that encompasses
 some of the large variation in fire effects on lichen abundance and
 vegetation types across the range of boreal and barren ground caribou in
 North America.
description: 346 plots were established
 with 5, 1 by 1 m quadrats within predetermined burn age classes (37-38 and
 46-49 years post-fire) and areas with no recorded burn history or
 'control' (&gt;70 years). Destructive samples of caribou
 forage (i.e. <i>Cladonia mitis</i> and <i>C.
 arbuscula</i>, <i>C. rangiferina</i> and <i>C.
 stygia</i>, <i>C. stellaris</i> and <i>C.
 uncialis, Flavocetraria </i>spp.,<i> Cetraria </i>spp.,
 <i>Stereocaulon </i>spp., <i>Cladonia </i>spp.
 (cup lichen only)) and were collected in 20 x 20 cm quadrat at one third
 of the sites in each ecoprovince to sample the full range of variation in
 lichen thallus height and cover present within the study area. Lichen
 biomass samples were processed in the lab to obtain measurements of lichen
 dry weight per unit area. Plant parts, non-target species, dirt, plant
 litter and decaying basal regions of lichens were separated from lichen
 samples with tweezers and deionized water, then lichens were placed in
 paper bags and stored at room temperature. After sorting, all samples were
 oven-dried at 30°C for 24 hours and weighed with a digital scale (minimum
 precision ± 0.001 g).
description: Each data file has a metadata sheet.  Site
 description of mature stands (&gt; 70 years post-fire) are available
 from the Dryad Digital Repository: &lt; https://doi.org/10.5061/dryad.76hdr7sth &gt; (Baltzer et al. 2020).