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.