Figure 4. Effects of Mean Summer Soil Temperature (MSST, in °C) and distance of the Rallarvägen trail to the railroad (x-axis, in m) on the total number of ruderal species (top) and the number of non-native ruderal species (bottom) per 1-km transect along the Rallarvägen. To make interpretation easier we centered the covariate MSST at its sample mean (see methods). Graphs are prediction plots with the estimated marginal effects. Lines show the model means (blue) with standard deviation (green and red); shading indicates at which chi-squared value a significant p-value is reached. Raw data points are not shown for clarity. Model coefficients and p-values are shown in supplementary Tables 7-8.
Importantly, transects with lower ruderal species richness had a higherZ -score (Fig. 5, supplementary Table 9), indicating that the few species present in these transects were common throughout the region. Transects with higher ruderal species richness – especially those nearest to the railway stations – hosted more and on average rarer ruderal species that only occurred in these few transects.