[en] Native to North America, Acer negundo was introduced in Europe during the
seventeenth century (in France around 1749, Lair 1827, Williams 2008). Largely used as an
urban tree, its ongoing invasion mainly takes place in riparian habitats; its current distribution
now extends all through Europe (Medrzycki 2007). It forms mono-specific stands
outcompeting riparian native trees (Lamarque et al. 2012), and leading to deterioration of
river banks. By ratifying the Rio Convention, France has engaged in controlling such invasive
species.
Although the most efficient control methods would consist in the use of chemicals, we
decided against these techniques as most chemical are not allowed in wetland areas. An
experimental design was settled to test ecological-friendly methods to control boxelder in
South-West France: stem-base cut, 1 m height cut, girdling and stem cut with juglone
insertion. During two years, tree mortality was assessed. Girdling resulted in the highest
mortality rates, varying from 32% to 100% according to the site, suggesting that this method
could require a longer application to reach full success in the field.
Boxelder is capable of a high plasticity in response to increased light or nitrogen
availability that promotes its growth compared to native species (Porté et al. 2011); thus it is
desirable to implement this treatment a few years before any cutting (ex. wood harvesting) or
after a natural disturbance (ex. opening due to wind storm or flooding). This could help
controlling Boxelder and preventing the development of mono-specific maple riparian forests.
