MIREN T-trail survey
A third dataset was obtained from the Mountain Invasion Research Network (MIREN), comprising vegetation survey data from along elevational gradients of the Björkliden and Låktatjåkka mountain trails that are leading from the Rallarvägen into the mountains (Wedegärtner et al. 2022). For further description on both trails, we refer to the supplementary methods. Along both mountain trails, presence of all plant species was documented in 20 T-shaped transects (T-transects) at fixed distance intervals, each consisting of three plots of 2 x 10 m; one parallel and two perpendicular to the hiking trail into the vegetation (supplementary Fig. 1). For every plant species we calculated the 95th percentile of its highest elevational occurrence (elevational maximum) using the quantile function in R (R core Team, 2021).