Wetlands are highly prone to invasions but even after extensive management, they often experience re-invasions and secondary invasions. What are the best approaches to manage invasions, re-invasions, and secondary invasions? We address these questions in Great Salt Lake wetlands, the most important wetlands in the Intermountain West of the U.S., which have been invaded by the non-native grass Phragmites australis. In a field experiment at two Phragmites patch scales (0.2 and 1.2 ha), we investigated the response of Phragmites, secondary invaders, and native plants to various herbicide treatments. We found that Phragmites cover was greatly reduced overall with herbicide, but there was some Phragmites reinvasion, particularly at the large patch scale, relative to the lowest Phragmites covers reached in the first two years post-herbicide application. At both patch scales over the five years, as the cover of native emergent plants increased, the cover of Phragmites decreased substantially. We saw a similar relationship with Phragmites cover declining over time as a secondary invader, Typha, increased in cover. These findings highlight the importance of native plant communities for minimizing reinvasions. Thus, in two outdoor mesocosm experiments, we looked at competitive dynamics between Phragmites and native emergent plants. We identified which species (Schoenoplectus acutus) and which native seeding rates (2, 3, and 5x the standard restoration seeding rate in the region) were most effective at limiting Phragmites invasion. Taken together, these studies highlight how invasions, re-invasions, and secondary invasions can be managed more effectively in wetlands through native plant biotic resistance.
Audio/Video, Conference Presentation, SER2019
Pre-approved for CECs under SER's CERP program
Society for Ecological Restoration