Solidago gigantea invasion homogenizes soil properties and native plant communities

Solidago gigantea, a notorious invasive species in Europe and Asia, has been shown in previous studies to impact soil properties such as nutrient availability and pH. However, the strength and direction of these alterations have varied across studies. Additionally, the species reduces species richness in invaded communities, though the susceptibility of different plant communities to invasion remains unclear. To address these inconsistencies, we investigated invasion effects on soil properties and plant communities across various soil types, nitrogen and pH levels, and plant communities. Soil samples were collected from invaded and nearby uninvaded plots, with measurements taken for extractable nitrogen, pH, and moisture content. Plant species richness, diversity, Sorensen similarity, mean Ellenberg indicator values and some community mean plant traits were compared between invaded and uninvaded plots. Lastly, S. gigantea stand density and size in invaded plots were quantified. Solidago gigantea significantly altered soil extractable-N and pH, with the extent and direction of changes depending on initial soil conditions. Alterations were most pronounced in acid, N-poor soils. Species richness and diversity consistently decreased in invaded plots. However, this decline was not due to direct competition with native species but to the replacement of specialized, local plant communities with less diverse, fast growing generalist communities adapted to fertile habitats. Solidago gigantea acts as an invasive ecosystem engineer, modifying soil conditions after introduction. This not only facilitates its spread but also leads to lasting effects that can persist even after its removal. Further studies on other invasive species are needed to establish general patterns due to their varied effects on ecosystem properties.