Multispecies invasion reduces the negative impact of single alien plant species on native flora

Aim: In the current Anthropocene, many ecosystems are being simultaneously invaded by multiple alien species. Some of these invasive species become more dominant and have greater environmental impacts than others. If two potentially dominant species invade the same area, the combined impact has been reported to be either (1) domination by one species, i.e., the competitive dominance of one invader, or (2) invasion meltdown, where the combined impact is much greater, i.e., a synergistic effect. We studied the effects of the invasion of two alien plant species that are known to strongly decrease native plant species diversity: the Persian walnut Juglans regia and goldenrod Solidago canadensis.
Location: We examined native vegetation diversity in abandoned fields (in Poland) where neither species had invaded, only one species had invaded, and both species had invaded.
Methods: Field survey data were analysed using generalized linear mixed models and ordination techniques.
Results: When ...