2021 Rallarvägen resurvey
In 2021, we documented all vascular plant species present in 1-km
transects, within 1.5 m of the edge of the trail, along the 40-km
stretch, following the taxonomic reference ‘Den nya nordiska Floran’
(Mossberg & Stenberg, 2003) (Fig. 1). The trail was surveyed twice
during the growing season (July and early August) to reduce survey bias
due to seasonal patterns in species presence. To be able to make
comparisons with the historical data, transects were merged to represent
nearby subregions as delineated in the historical surveys: Abisko =
transect 1-5, Björkliden = transect 6-15, Kopparåsen = transect 16-25,
Låktatjåkka = transect 26-30, Vassijaure = transect 31-35, Riksgränsen =
transect 36-40.
The 2021 survey was additionally used to investigate the current spatial
distribution of ruderal species in detail. For these analyses, we
calculated a species’ abundance along the trail using the Z -score
transformation for population abundance (Clark-Carter, 2005), defined
as: Z = [X - μ ]/s, where X is the
abundance of species x (between 1 and 40 transects), μ is the
mean abundance of the entire set of ruderal species along the
Rallarvägen, and s is the standard deviation of the mean
abundance of the entire set of ruderal species along the Rallarvägen.
Rescaling to Z -scores is done with a linear transformation
whereby s and μ are constants, and the result can thus be
used in linear models. Using this transformation, it is possible to
determine how rare or common a particular ruderal species is relative to
the whole group of ruderals.
Combining all surveys (1903, 1913, 1983, 2021) resulted in a total of
401 documented species. As Sylvén focused on ruderal species only, we
filtered the species based on ruderality (see below).