Figure 4. Mean net soil biota effect of plant populations in Europe and Asia grown in ‘home soil’ and ‘away soil’ from the other region (Experiment 3).

Region, soil treatment and their interaction were not found to significantly influence mean net soil biota effect, as shown by a linear model: F _Region = 0.01, d.f. = 1,16, P = 0.912, F _{Soil treatment} = 0.11, d.f. = 1,16, P = 0.749, F _{Region×soil treatment} = 0.53, d.f. = 1,16, P = 0.475. Including plant population or the interaction of plant population with soil treatment as random effects in a linear mixed-effects model did not significantly improve the fit of the model.