Fanny Dommanget, André Evette and Vincent Breton
Univ. Grenoble Alpes, Irstea, LESSEM, 2 rue de la papeterie, FR-38402 Saint-Martin d’Hères, France
Asian knotweeds are considered among the 100 worst invasive plant species in the world. Introduced from South-Eastern Asia at the end of the 19th they are now widespread throughout the Northern hemisphere, and have been reported in Chile, Australia and New-Zealand. These bamboo-like geophyte species develop in monoclonous stands and spread rapidly along rivers and roadsides due to the high repsrouting efficiency of their rhizomes. They affect plant and animal biodiversity and substantially modify soil functioning. However their true impacts are questioned (Lavoie 2017) and some studies also report positive effects on pollinating insects (Davis et al. 2018). Indeed knotweeds are nectariferous species that can provide non negligible resources for pollinators.
Management of these species is problematic as most classical technics are fastidious and/or expensive. Therefore, managers try to develop alternative methods such as bioengineering. Habitually used for riverbank protection against erosion, bioengineering also promotes the rapid recovery of plant communities through plantation or seeding. Novel ecosystems arise from these interventions, mixing residual knotweed individuals (which are rarely eradicated) with the reintroduced native species. But how do such restored ecosystems function, regarding plant recruitment and pollinator communities?
The aim of this study which will start in spring 2020 is to compare knotweed-invaded sites to bioengineering-restored sites on the basis of plant and bee communities in order to evaluate the effect of such management actions. Reference sites will also be studied and should help to apprehend the effects of knotweeds on these major components of biodiversity functioning.
Davis E. S., Kelly R., Maggs C. A. & Stout J. C. (2018) Contrasting impacts of highly invasive plant species on flower-visiting insect communities. Biodiv. Conserv. 27: 2069–2085.
Lavoie C. (2017) The impact of invasive knotweed species (Reynoutria spp.) on the environment: review and research perspectives. Biol. Invas. 19: 2319–2337.