Friends of Ridley Creek State Park and Anne Murphy, Executive Director, Chester-Ridley-Crum Watersheds Association
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Final Report Vegetation of Ridley Creek State Park Submitted to the Pennsylvania Department of Conservation and Natural Resources By Ann F. Rhoads and Timothy A. Block Morris Arboretum of the University of Pennsylvania 100 Northwestern Ave., Philadelphia, PA 19118 215-247-5777 x 134, [email protected] July 2008 Cover: Two big white oaks along a tributary of Ridley Creek north of Gradyville Road 2 Acknowledgements Roger McChesney, Manager of Ridley Creek State Park and Anthony Mosloskie, Chief Ranger spent time orienting us to the park and facilitated access by automobile via the multiuse trail. Robert Witmer, of the Bureau of Forestry introduced us to archival maps and planting records for the Jeffords Estate. We also had helpful discussions with Tim Higgens, President, Friends of Ridley Creek State Park and Anne Murphy, Executive Director, Chester-Ridley-Crum Watersheds Association. 3 4 Executive Summary Ridley Creek State Park is a suburban park in a landscape that has a long history of human use. Most of the natural vegetation was removed by the mid to late 1800s. In the past 300 years the landscape has gone from forest to farmland to private estate to heavily used public park. Today the park is a mosaic of forest remnants, scattered wetlands, successional communities, meadows, and landscaped grounds. Relatively intact natural communities cover 37 percent of the area. Non-native, invasive plants dominate many of the successional areas. These thickets of invasive shrubs and vines interfere with natural patterns of succession and represent inferior habitat for birds and other wildlife. An overabundance of white-tailed deer compounds the ecological degradation of the park landscape. Deer feed preferentially on native vegetation leaving most non-natives to proliferate. The browsing severity in the park is such that even plants such as spicebush and beech shoots are reduced to well-chewed remnants. Regeneration of canopy trees is virtually non-existent, shrub layers are decimated, and herbaceous plant diversity is reduced. Canopy failure is occurring in areas where blow downs of older trees have occurred. Management actions to address the habitat degradation that is currently occurring must first focus on achieving a dramatic reduction in deer density. Action to address the problem of invasive plants should begin with removal of scattered invasives present in the areas of most intact natural communities, the areas coded as #1 in Figure 4. Areas coded as #2 are mostly successional forest stands with an intact canopy composed of native trees. They should be treated as buffers for the more mature forest stands and eventual additions. Continued canopy development as they mature should help to diminish the vigor of non-native invasive shrubs through shading. Management of the most highly impacted sites (coded #4 and #5 on Figure 4) should be the lowest priority to be undertaken only if time and resources permit. These sites are unlikely to degrade further. Key Recommendations • Reduce deer density throughout • Remove scattered occurrences of invasive plants in highest quality natural areas • Avoid forest fragmentation by maintaining canopy continuity and minimizing edge • Remove occurrences of non-native, invasive plant species that are not yet widely distributed in the park so they do not become bigger problems in the future (see Figure 7) 5 6 Table of Contents Acknowledgements ..........................................................................................3 Executive Summary.........................................................................................5 I. Introduction Location ................................................................................................................................9` Geology..................................................................................................................................9 Hydrology .............................................................................................................................11 Water quality........................................................................................................................11 Ecological Context ...............................................................................................................11 Special designations .............................................................................................................11 Land Use History .................................................................................................................11 Establishment of the state park ..........................................................................................11 Previous Studies of the Natural Resources of Ridley Creek State Park PNHP-listed elements .......................................................................................................12 Plant communities.............................................................................................................12 Invasive species..................................................................................................................12 Deer browse survey...........................................................................................................12 II. Goals.............................................................................................................13 III. Inventory Plant Communities...............................................................................................................15 Methods..............................................................................................................................15 Results ................................................................................................................................15 Plant Diversity......................................................................................................................19 Methods..............................................................................................................................19 Results ................................................................................................................................19 Species of concern ..........................................................................................................20 Invasive species...............................................................................................................21 IV. Discussion Status of Plant Communities ..............................................................................................25 Threats ..................................................................................................................................27 Deer overabundance .........................................................................................................27 Invasive species..................................................................................................................28 V. Conclusions and Recommendations Deer overabundance .........................................................................................................31 Invasive species..................................................................................................................31 7 References..........................................................................................................................33 Appendices Appendix A. Descriptions of Plant Communities of Ridley Creek State Park ..............35 Appendix B. Ridley Creek State Park Plant List..............................................................43 Appendix C. Fact Sheets – Species of Special Concern....................................................53 Appendix D. Species Status Codes .....................................................................................57 List of Figures Figure 1. Location of Ridley Creek State Park .................................................................9 Figure 2. Geology of Ridley Creek State Park ..................................................................10 Figure 3. Plant Communities of Ridley Creek State Park ...............................................17 Figure 4. Disturbance Levels in Ridley Creek State Park ...............................................18 Figure 5. Features of Special Interest ................................................................................21 Figure 6. 1937 Aerial Photography of Ridley Creek State Park .....................................23 Figure 7. Sites of Isolated Invasive Species Occurrences .................................................24 List of Tables Table 1. Scoring system for Invasive Species Impact on Native Vegetation ..................15 Table 2. Plant Community Types of Ridley Creek State Park........................................16 Table 3. Levels of Impact of Invasive Plants on Park Vegetation...................................18 Table 4. Plant Diversity at Ridley Creek State Park ........................................................19 Table 5. Land Cover in 1937 and 2005 ..............................................................................22 8 I. Introduction Location` Ridley Creek State Park is located in the Piedmont Uplands physiographic region of southeastern Pennsylvania (Figure 1). Containing 2,206 acres, it lies in Delaware County southwest of the village of Newtown Square and 16 miles west of the city of Philadelphia. Most of the park is in Edgemont Township