Results of likelihood-ratio model comparisons of nested linear mixed-effects models to test whether B. nigra (presence vs. absence), B. nigra range (invasive vs. native; fitted sequentially after B. nigra), Achillea presence (presence vs. absence of Achillea millefolium), and all possible interactions had a significant effect on the community aboveground biomass.

^aRemoval of effect compared to: random part + B.nigra + A. millefolium.

^bRemoval of effect compared to: random part + A. millefolium + B. nigra + B. nigra range.

^cRemoval of effect compared to: random part + A. millefolium + B. nigra + B. nigra range + A. millefolium x B. nigra.

^dRemoval of effect compared to: random part + A. millefolium + B. nigra + B. nigra range + A. millefolium x B. nigra + A. millefolium x B. nigra Range.

Significant factors are marked in bold.