Long term monitoring of a rare riparian community in the Delaware Water Gap National Recreation Area: Eastern Rivers and Mountains Network

Perles, Stephanie; Callahan, Kristina; Marshall, Matthew

The Eastern Rivers and Mountains Network (ERMN) contains diverse, unique, and globally significant plant communities associated with the floodplains and other geomorphic and hydrologic features of large rivers. Due to the significance of these resources, long-term monitoring of these rare riparian communities was identified among the highest priority vital signs during the ERMN prioritization process. A study was conducted in 2010 at the Dingmans Ferry Calcareous Riverside Outcrop and Calcareous Riverside Seep site in the Delaware Water Gap National Recreation Area (DEWA) in order to: 1) Measure changes in the distribution, abundance, and composition of plant species within the Dingmans Ferry Site since 1998; and 2) Compare the effectiveness and efficiency of a plot-based sampling methodology utilized in 1998 to a point intercept sampling methodology. This study documented changes in the distribution, abundance, and composition of plant species within the co-occurring Calcareous Riverside Outcrop and Calcareous Riverside Seep at the Dingmans Ferry site since 1998. Important findings include: The appearance of three new invasive exotic plant species and the spread of eight other previously observed invasive exotic species were documented. Although the percent cover of purple loosestrife (Lythrum salicaria) did not measurably change between 1998 and 2010, the number of L. salicaria stems decreased significantly. Changes in abundance for many individual species were documented. The cover of woody species increased significantly between 1998 and 2010, This study also compared the original plot-based sampling methodology to a point-intercept sampling methodology. Though both methods yielded similar results, the plot method was clearly better at capturing more species and was more efficient per sampling unit. Given these findings and recommendations from other similar studies, the original plot method should be retained for future monitoring at the Dingmans Ferry site and the two other Calcareous Riverside Outcrop and Calcareous Riverside Seep sites in DEWA so that direct comparisons can be made with the 1998 data. Although the point-intercept method could be appropriate for other rare riparian communities in the ERMN that do not exhibit strong environmental or species gradients from woodland to river, the plot method will likely be more cost-effective given that each sampling unit requires less time, and that more species are captured by the plot method.

Long term monitoring of a rare riparian community in the Delaware Water Gap National Recreation Area: Eastern Rivers and Mountains Network

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