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).