Riparian Vegetation, Natural Succession, and the Challenge of Maintaining Bare Sandbar Nesting Habitat for Least Terns and Piping Plovers.

摘要

This technical note provides a framework for effective (and cost- effective) management of pioneering vegetation on bare riverine sandbars that may provide nesting habitat for federally listed Interior Least Terns (ILT) (Sternula antillarum) or Great Plains Piping Plovers (GPPP) (Charadrius melodus). The authors acknowledge that significant costs (and potential consequences) can be associated with vegetation management; the decision to actively manage vegetation on any one river will be made in full consideration of a range of management alternatives in the framework of meeting multiple objectives, many of which may have nothing to do with endangered species (Schultz et al. 2010). This technical note assumes that vegetation removal is at least being considered for an area and provides the basic principles necessary for a vegetation removal program to be successful. It is also acknowledged that habitat-forming flows are less frequent than they were prior to dam placement on many rivers (Galat and Lipkin 2000; U.S. Fish and Wildlife Service (USFWS) 2003, 2005a; Parham 2007). When sandbar nesting habitat becomes degraded due to advanced vegetation succession (e.g., Johnson 2000) the only alternative to provide regional nesting habitat for the two listed bird species mentioned above may be mechanical sandbar restoration, which is extremely costly and may have undesirable ecological consequences (U.S. Department of Interior (USDOI) 2006, U.S. Army Corps of Engineers (USACE) 2011). Consequently, managers within systems where habitat renewal via flooding is infrequent may want to consider an approach of maximizing the number of years that new bare sandbars remain suitable for nesting. They may also want to consider managing vegetation early in the successional sequence to forestall the loss of depositional areas (which may be in short supply regionally) to late- successional forests that could provide future sandbar nesting habitat after future high-release events.