Generalized additive modelling (GAM) results for total earthworm abundances and the observed earthworm species with PSS as predictors.

GAMs were computed with log-link function and quasi-Poisson error distribution with the observed sums at the measurement plots and averaged afterwards. The spatial coordinates of the measurement plots f(x,y) were included as a bivariate function smoothed with thin plate regression splines. Model validation was performed using leave-one-out cross validation.