Sampling design
Twenty transects were set up along each road at approximately equal
elevational steps following the MIREN protocol (see Haider et al. 2022
for the published version of the protocol). Each of these transect was
then divided in three 2 m x 50 m plots organized in a T-shape. The first
plot was laid out parallel to the road, encompassing the vegetation
directly impacted by the road-associated disturbance, and both the
second and third plots were set up perpendicular to the road,
respectively from 2 to 52 m and from 52 m to 102 m, covering the less
disturbed vegetation communities adjacent to the road. Henceforth, we
will refer to these plots as “roadside plots” and “adjacent plots”.
While anthropogenic disturbance was almost always higher in the roadside
plot, some of the adjacent plots were also subject to anthropogenic
disturbances, especially so at lower elevations. The presence and total
cover of all vascular plant species present in each plot were then
visually estimated and classified using the following semi-continuous
scale: 1 = <1%; 2 = 1 to 5%; 3 = 5 to 25%; 4 = 25 to 50%;
5 = 50 to 75%; 6 = 75 to 95%; and 7 = 95–100%. Plant species were
also categorized as either native or non-native following local and
regional floras, with species introduced in the country or mountain
region after AD 1500 considered to be non-native (Haider et al., 2022).
Additionally, average yearly soil temperature was extracted from the
SoilTemp global maps of soil temperature at a 1 km resolution
(Lembrechts et al. 2022). In total, our dataset included 894 plots
spread out across 62 separate mountain roads and 11 regions.