Invasive plants, such as Phragmites australis, can profoundly affect channel environments of large rivers by stabilizing sediments and altering water flows. Invasive plant removal is considered necessary where restoration of dynamic channels is needed to provide critical habitat for species of conservation concern. However, these programs are widely reported to be inefficient. Post-control reinvasion is frequent, suggesting increased attention is needed to prevent seed regeneration. To develop more effective responses to this invader in the Central Platte River (Nebraska, USA), we investigated several aspects of Phragmites seed ecology potentially linked to post-control reinvasion, in comparison to other common species: extent of viable seed production, importance of water transport, and regeneration responses to hydrology. We observed that although Phragmites seed does not mature until very late in the ice-free season, populations produce significant amounts of viable seed (>50 % of filled seed). Most seed transported via water in the Platte River are invasive perennial species, although Phragmites abundances are much lower than species such as Lythrum salicaria, Cyperus esculentus and Phalaris arundinacea. Seed regeneration of Phragmites varies greatly depending on hydrology, especially timing of water level changes. Flood events coinciding with the beginning of seedling emergence reduced establishment by as much as 59 % compared to flood events that occurred a few weeks later. Results of these investigations suggest that prevention of seed set (i.e., by removal of flowering culms) should be a priority in vegetation stands not being treated annually. After seeds are in the seedbank, preventing reinvasion using prescribed flooding has a low chance of success given that Phragmites can regenerate in a wide variety of hydrologic microsites.
Bibliographical noteFunding Information:
The authors thank Paul Kinzel (U.S. Geological Survey) and Jeff Runge (U.S. Fish and Wildlife Service) for orienting us to the history of ecological and social changes on the central Platte River and providing logistical guidance. We are grateful for the efforts of many technicians who assisted in the field and lab, but especially Ashlee Hartmann, who served as crew leader. Funding was provided by the U.S. Geological Survey Priority Ecosystems Studies and Northern Prairie Wildlife Research Center. Any use of trade, firm or product names does not imply endorsement by the U.S. Government.
© 2016, Springer International Publishing Switzerland.
- Common reed
- Prescribed flooding
- River restoration
- Vegetation management