DOI: 10.5061/dryad.w3r2280nf
title: Data from: Microgeography, not just latitude, drives climate overlap on mountains from tropical to polar ecosystems

description: An extension of the climate variability hypothesis is that relatively
 stable climate, such as that of the tropics, induces distinct thermal
 bands across elevation that render dispersal over tropical mountains
 difficult compared to temperate mountains. Yet, ecosystems are not
 thermally static in space-time, especially at small scales, which might
 render some mountains greater thermal isolators than others. Here, we
 provide an extensive investigation of temperature drivers from fine to
 coarse scales, and demonstrate that the degree of overlap in temperatures
 at high and low elevations on mountains is driven by more than just
 absolute mountain height and latitude. We compiled a database of 29
 mountains spanning 6 continents to characterize “thermal overlap” by
 vertically stratified microhabitats, biomes, and owing to seasonal changes
 in foliage, demonstrating via mixed-effects modeling that micro- and
 mesogeography more strongly influence thermal overlap than macrogeography.
 Impressively, an increase of one meter of vertical microhabitat height
 generates an increase in overlap equivalent to a 5.26° change in latitude.
 In addition, forested mountains have reduced overlap – 149% lower –
 relative to non-forested mountains. We provide evidence in support of a
 climate hypothesis that emphasizes microgeography as a determinant of
 dispersal, demographics, and behavior, thereby refining classical theory
 of macroclimate variability as a prominent driver of biogeography.
  
description: We compiled published and unpublished
 temperature data from a combination of author field collection, personal
 communications, and public data repositories (see data citations) for a
 total of 29 mountains on six continents representing gradients of
 vegetation, environmental degradation, and climate (table A1, fig. A1).
 Temperatures at low and high elevation sites were recorded on each
 mountain, as was the difference in elevation between low and high sites
 (yet of note is that not every low site was at the “bottom” of the
 mountain, nor the high site always at the mountain peak; in addition slope
 or aspect both varied between sites). Difference in elevation between low
 and high sites (henceforth “Δ elevation”) was a parameter of interest (see
 <i>Mixed-Effects Models</i>), therefore a broad range of
 elevation gradients from 122 to 3080 meters were represented. Time series
 length varied from 74 days to 64 years; although sampling of 13 of the 29
 mountains did not include every day of the year, seasonal coverage did not
 vary systematically (see “Mixed-Effects Modeling” for how variation in
 time series length was accounted for). At each elevation band (low and
 high), at least one of three vertically stratified microhabitats was
 monitored: soil, surface, and (in forests only) canopy. Of the 29
 mountains, 6 sites had all three vertical strata represented, and 14 had
 at least two vertical strata represented. Soil temperature sensors varied
 in depth from 2 to 12 cm into topsoil (although most were between 7-10 cm
 in depth), surface-level sensors were 1-3 meters above the ground, and
 canopy sensors were typically between 19-25 m high, placed within canopy
 foliage. When available, temperatures from multiple plots at the same
 approximate elevation on a mountain– that is, less than 5% of Δ elevation
 apart– were averaged. All thermal sensors included in our study were
 shielded from direct radiation (table A1), which is common in ecological
 research. While shielding reduces irregular sensor performance due to high
 solar radiation, it also dampens variation depending on shielding methods
 (Terando et al. 2017). As a result our estimates of microclimate variation
 may be conservative, but the majority of sites (17 out of 29) followed
 best practices as recommended by global micrometeorological networks
 (Beeck et al. 2018; Rebmann et al. 2018).<b> </b>Both
 microhabitat category (soil, surface, canopy, henceforth “vertical
 microhabitat”) and depth belowground or height aboveground of sensor
 (henceforth “microhabitat height”) were used in analyses. See methods section of manuscript for more
 details. Additional details will be provided here upon
 publication.