| Popis: |
Reed canarygrass (Phalaris arundinacea) is invasive in temperate freshwater wetlands throughout the United States and Canada and presents challenges to restoring tidal freshwater wetlands. Methods for the prevention or elimination of reed canarygrass in palustrine wetlands are generally well established, typically involving herbicide application, mechanical treatments, prolonged inundation, or establishment of competitive plant species. These methods are often not suitable for the unique conditions in tidal wetlands and alternative strategies remain poorly understood. Prolonging inundation of tidal wetlands requires a loss of habitat forming processes, connectivity, and other functions. Treatments such as mowing, discing, or fire are not feasible in the perpetually wet conditions of tidal wetlands. Restoration practitioners aiming to design self-sustaining wetlands in the lower Columbia River estuary and the U.S. Pacific Coast have found that reed canarygrass is widespread and quick to establish post-restoration creating a management burden and impacting restoration goals. Here we report the results of a comprehensive effort to develop methods for control in tidal wetlands through systematic review of the scientific literature, interviews with experienced practitioners, and field observations at nine Pacific Northwest sites. The review framework evaluated key environmental conditions affecting reed canarygrass, control methods, and practical considerations. Findings support an integrated long-term control strategy at the largest possible scale to establish effective and self-sustaining control. Appropriate and practical strategies for tidal freshwater wetlands include implementing control pre-restoration to suppress existing populations; topographic modification such as scrape-downs and mounds to support competitiveness of desired vegetation communities; seeding or planting strong native competitors; limiting nutrient availability; and periodic, targeted control to limit reinvasion. These strategies are supported by the study, but long-term results are generally not available. Formal field experiments are recommended by the authors to better evaluate factors that influence reed canarygrass control in tidal freshwater wetlands. |
