Can we restore natural habitats after plant invasion? Lessons from years of management

Negative impacts of invasive plants on natural habitats have been widely demonstrated. Hence, the management of invasive plants, aiming at eradicating, or at least controlling their spread, is being more and more developed. For this purpose, we need to identify the most efficient management techniques which could lead to the restoration of invaded ecosystems. Up to now, management methods mentioned in literature were pragmatic tools and often lacked scientific assessment. For several years, we have tested similar mechanical and chemical management techniques in the field on highly invasive plant species, representative of different life forms and invaded habitats: herbaceous rhizomatous perennial Fallopia japonica, ligneous rhizomatous Spiraea spp., ligneous root suckering Acer rufinerve and ligneous stoloniferous Cotoneaster horizontalis. We investigated the efficiency, cost and feasibility of these techniques, and their effects on the restoration of invaded ecosystems. The best performing management technique was found to be highly species specific and was also influenced by the invaded habitat type. For these perennial species, long-term management must be considered, to reduce their competitive capacities with repeated mechanical or chemical techniques (cutting or pulling out several times a year, injection combined with mechanical methods, etc.). For species with sexual reproduction, like Acer rufinerve and Cotoneaster horizontalis, seed bank and seed dispersal must also be taken into account to avoid dissemination when managing. We can conclude invasion plant management is usually expensive and hard to implement but some results are encouraging and show the importance to carry on research on invasive plant management methods.