Fine-scale diversity models reveal impacts of invasive Gaillardia pulchella on regenerating vegetation in a sand dune grassland.

Abstract

Premise: Gaillardia pulchella is native to North America but invasive in Central Europe, including Hungary, and can significantly alter vegetation dynamics, thereby affecting biodiversity and community structure. This study explored the fine-scale effects of G. pulchella invasion on the regeneration of old sandy fields in open dune grasslands in Kiskunság National Park, Hungary, within the Pannonian biogeographic region. The impact of invasion on vegetation association structures was estimated by investigating the early stages of the effects of invasion on plant communities.

Methods: Diversity models were used to assess compositional diversity (CD) and the number of realized species combinations (NRC) in invaded versus noninvaded stands. Plexus graphs were used to analyze the spatial relationships between G. pulchella and neighboring species at a fine scale (5 × 15 cm).

Results: Invasion-free stands had higher species richness and greater structural complexity at fine spatial scales, as indicated by CD and NRC functions. Significantly higher CD values in invasion-free stands compared to invaded stands emphasize the negative impact of G. pulchella on coexistence among native species. Plexus graphs illustrated both negative and positive associations between G. pulchella and native species, suggesting a nuanced competitive role in invaded stands.

Conclusions: Gaillardia pulchella invasion, though not strongly characterized, has negatively impacted vegetation structure at fine spatial scales, which may potentially intensify over time. The study underscores the importance of early detection and long-term monitoring for a comprehensive understanding of invasive processes and their effects on plant communities in sandy habitats.