Effects of Ambrosia trifida L. invasion on plant community structure and the short-term effectiveness of mechanical control

Abstract

Ambrosia trifida is an invasive annual plant species that creates dense stands, suppressing native vegetation in affected habitats. To assess its ecological impact and the short-term effectiveness of mechanical management, we conducted field removal experiments using cutting and uprooting methods. We examined plant community composition, species richness, and diversity before and after treatment. Mechanical removal significantly altered plant community structure, leading to increased emergence of native species and reduced dominance of A. trifida, while control plots showed minimal change. Treated plots also had substantially lower soil seed bank density, with most remaining seeds concentrated in the upper 0-5 cm layer, indicating that limiting annual seed input is crucial for suppressing population persistence. However, recovery responses varied by site: Mugunri experienced notable declines in A. trifida cover and a greater establishment of native species, whereas the CCZ site retained A. trifida as a sub-dominant and saw limited recruitment of native species. These differing outcomes suggest that site-specific environmental conditions, initial species pools, and residual seed bank size may affect vegetation recovery after invasive plant removal. While this study demonstrates that mechanical removal disrupts A. trifida dominance and encourages short-term vegetation recovery, its one-year duration limits our understanding of long-term successional pathways. Continued monitoring, repeated annual removal, and assessments across multiple sites are necessary to better understand the mechanisms driving post-removal recovery and to inform the development of effective restoration strategies.