Impact of Gaura parviflora invasion on urban wildness biodiversity: a campus green patch case study.

Urban wilderness has gradually emerged as a hot spot for urban ecological research due to its crucial role in maintaining urban ecosystem services and protecting biodiversity. Compared to natural areas, urban wildnesss are more susceptible to invasions by alien species, which pose a threat to the functionality of the urban ecosystem. Currently, our understanding of biodiversity within various types of urban wilderness is not comprehensive, and the laws governing biodiversity changes due to alien species invasions remain unclear. This study focuses on an abandoned grassland community on a campus in northern China, which has been invaded by the alien weed Gaura parviflora. The study measured the characteristics of the aboveground community and the soil seed bank, comparing and analyzing species composition, plant/seed density, species diversity, and similarity at different levels of invasion (uninvaded, moderately invaded, severely invaded). The findings indicate that the uninvaded abandoned grassland community is rich in species (with 32 species) and has significant recovery potential (with an average seed density of 11,671 seeds per square meter). The community harbors multiple alien invasive species both aboveground and within the soil seed bank, and its succession process is influenced by biological invasions and human disturbances. The invasion by G. parviflora alters the species composition of both the aboveground community and the soil seed bank, resulting in a significant increase in plant density within the aboveground community. Its impact on the soil seed bank varies with soil depth, leading to a notable decrease in seed density in the 0-5 cm layer compared to the 5-10 cm and 10-15 cm layers; while the Shannon-Wiener biodiversity index for the 0-5 cm and 10-15 cm layers is lower than that of the uninvaded and severely invaded plots. This study reveals that the campus abandoned grassland community faces a high risk of biological invasion, and the invasion by G. parviflora has a more significant impact on the soil seed bank than on the aboveground community, which could lead to substantial changes in community species composition and a loss of biodiversity in the soil seed bank. It is therefore strongly recommended that greater attention be given to the impact of biological invasions on seed banks within the management of campus wild ecosystems.