Data from: Topographic and vegetation drivers of thermal heterogeneity along the boreal–grassland transition zone in western Canada: implications for climate change refugia

Climate-change refugia are areas that are relatively buffered from
contemporary climate change and may be important safe havens for wildlife
and plants under anthropogenic climate change. Topographic variation is an
important driver of thermal heterogeneity, but it is limited in relatively
flat landscapes, such as the boreal plain and prairie regions of western
Canada. Topographic variation within this region is mostly restricted to
river valleys and hill systems, and their effects on local climates are
not well documented. We sought to quantify thermal heterogeneity as a
function of topography and vegetation cover within major valleys and hill
systems across the boreal–grassland transition zone. Using iButton data
loggers, we monitored local temperature at four hill and 12 river valley
systems that comprised a wide range of habitats and ecosystems in Alberta,
Canada (N = 240) between 2014 and 2020. We then modelled monthly
temperature by season as a function of topography and different vegetation
cover types using general linear mixed effect models. Summer maximum
temperatures (Tmax) varied nearly 6 oC across the elevation gradient
sampled. Local summer mean (Tmean) and maximum (Tmax) temperatures on
steep, north-facing slopes (i.e., low levels of potential solar radiation)
were up to 0.70 oC and 2.90 oC cooler than highly exposed areas,
respectively. Tmax in incised valleys was between 0.26 and 0.28 oC cooler
than other landforms, while areas with greater terrain roughness
experienced maximum temperatures that were up to 1.62 oC cooler. We also
found that forest cover buffered temperatures locally, with coniferous and
mixedwood forests decreasing summer Tmean from 0.23 to 0.72 oC, and
increasing winter Tmin by up to 2 oC, relative to non-forested areas.
      Spatial predictions of
temperatures from iButton data loggers were similar to a gridded climate
product (ClimateNA), but the difference between them increased with
potential solar radiation, vegetation cover and terrain roughness. Species
that can track their climate niche may be able to compensate for regional
climate warming through local migrations to cooler microsites. Topographic
and vegetation characteristics that are related to cooler local climates
should be considered in the evaluation of future climate-change impacts
and to identify potential refugia from climate change.