Uprooting is a promising tool to control invasive giant ragweed and recover native diversity

Abstract

Ambrosia trifida (giant ragweed) is an invasive species that causes habitat destruction and competitively excludes native plants in many parts of Europe and Asia. In this study, we evaluated the effects of selective cutting and uprooting on A. trifida and native plant diversity, as well as the effects of sowing the seeds of native annual, perennial and woody species after eradication. We hypothesised that: (i) selective uprooting will be more effective than cutting in controlling invasion by A. trifida because fewer propagules would be left behind, with no increase in the number of existing invasive propagules and (ii) sowing native seeds will increase invasion resistance and accelerate the recovery of native plant diversity. The eradication methods were applied in July 2022, seeds were sown in March 2023 and the response variables (i.e. importance values (%) of A. trifida and diversity index (H') of native species) were measured in September 2023. The importance values of A. trifida were lowest and diversity index of native species was highest in the uprooting treatment, supporting the first hypothesis. Sowing native seeds following invasion removal did not exert significant additional suppressive effects on invasion or increase native species diversity. These results reveal that selective uprooting is a promising tool to control A. trifida and to support the recovery of native diversity, while sowing native seeds does not improve the quality of restoration.