Final Si Management Report 10 06 10
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Sycamore Island Management Report Prepared by Applied Ecological Services Inc. 1110 East Hector Street Conshohocken PA, 19428 For Allegheny Land Trust 409 Broad Street, Suite 206A Sewickley, PA 15143 This report is made possible by the generous support from TABLE OF CONTENTS 1. OVERVIEW 2. EXECUTIVE SUMMARY 3. PROJECT PHILOSOPHY AND APPROACH 4. SITE CONTEXT ‐ p.1 4.1 Location ‐ p.1 4.1. Geology and the Shaping of the Allegheny River and Surrounding Watershed ‐ p.1 4.2. Soils, Topography, and Drainage ‐ p.2 4.3. Ecology ‐ p.2 4.4. Cultural History ‐ p.3 4.5. Impacts of a Regulated River ‐ p.5 5. NATURAL RESOURCES INVENTORY, ECOLOGICAL ASSESSMENT AND MANAGEMENT RECOMMENDATIONS 5.1. Natural Community Mapping, Vegetation and Seedbank Studies ‐ p.7 5.2. Aquatic Species Surveys ‐ Fishes, Mollusks, and Macroinvertebrates ‐ p. 33 5.3. Vertebrate Species Surveys ‐ Reptiles, Amphibians, and Mammals ‐ p. 42 5.4. Avian Species Surveys ‐ p.48 5.5. Threatened and Endangered Species Survey and Existing Studies Review ‐ p. 57 5.6. Invasive Vegetative Species Management ‐ p. 63 5.7. Geotechnical Investigation ‐ p.68 5.8. Bathymetry Survey ‐ p.75 5.9. Human Use and Impact Study ‐ p. 76 6. TEST AND DEMONSTRATIONN PLOT TREATMENT AND MONITORING PLAN ‐ p.78 7. RECOMMENDATIONS FOR PUBLIC EDUCATION AND VOLUNTEER STEWARDSHIP ACTIVITIES ‐ p.85 8. TRAIL AND INTERPRETIVE SIGNAGE PLANS ‐ p.92 9. MANAGEMENT AND PRIORTIZATION STRATEGY FOR CARRYING OUT RECOMMENDATIONS ‐ p.96 10. REFERENCES ‐ p.106 APPENDICES A. Maps B. Soil Series C. Quadrat Datas D. T & E Species Search E. Invasive Vegetation Cut Sheets F. Pubic Outreach Activities 1. OVERVIEW In May 2009, Applied Ecological Services, Inc. (AES) was retained by Allegheny Land Trust (ALT) to conduct an ecological assessment and to prepare a management plan for Sycamore Island, a 14.3 acre forested island in the Allegheny River near Pittsburgh, Pennsylvania. Ecological field investigations and public outreach activities began in June 2009 and continued through the end of September 2010. This report includes the results of our work and provides recommendations and plans for managing the ecological and cultural resources of Sycamore Island. The ecological and cultural significance of Sycamore Island is well known. Previous studies such as the 3 Rivers 2nd Nature Report conducted by Carnegie Mellon University that characterized riverbank vegetation in the Allegheny and Monongahela Rivers, have described the ecological resources and conservation value of Sycamore Island (3Rivers 2nd Nature, 2002). The Island’s floodplain hardwood forest is recognized as among the rarest plant communities of its type, both regionally and globally. The Pennsylvania Natural Diversity Index (PNDI) classifies floodplain forest as imperiled in the state, and Sycamore Island has a ranking of “high significance” within the Allegheny River BDA Natural Heritage Area. Today, it is valued as one of the last remaining undeveloped islands within the Lower Allegheny Watershed. Nonetheless, humans have impacted the island in the past with periodic interludes of recognition and appreciation as a natural refuge. In 1936, both Sycamore Island and Nine Mile Island were leased from the Pennsylvania Railroad by the Audubon Society of Western Pennsylvania, making these islands the first bird sanctuaries in the Pittsburgh region. Plans for the development of a marina on Sycamore Island were initiated during the late 1960’s but were later abandoned, leaving behind several significant features including a barge that remains embedded in the sand at the island’s southern tip, a partially installed swimming pool, docking platform and a series of offshore pilings in the back channel. During the last century, development and industrialization of the watershed contributed to changes in the island’s configuration and topography, due in part to dredge spoiling and increased sedimentation from development. Because of these changes and the island’s position in the river, its area has more than doubled from just over 6 acres in 1809 to over 14 acres today. More recent impacts to the Island’s ecology include the affects of invasive species and climate change. All of these stressors must be considered and addressed in long‐term management efforts. In January 2008, with funding from the Colcom Foundation, ALT purchased Sycamore Island to protect and manage the island’s dynamic riverine ecology and the critical wildlife habitat, educational, and recreational benefits it provides in an otherwise industrialized and urbanized landscape. In undertaking the current assessment and planning effort, ALT identified five principle goals it believes are key to successfully managing the resources of Sycamore Island: Understanding fully the natural processes, functions and values of the Island from the treetops to river bottom and its impact on the ecology and hydrology of the Allegheny River. As well as on a broader scale, understanding the historic and present day anthropogenic stressors impacting the natural processes, functions, and values and how these factors will influence long‐term management and preservation of the island’s natural resources. Managing properly the natural processes, functions and values of the Island based upon the findings of the field assessment and inventory, and literature review of previous studies and articles. Preserving the natural processes, functions and values of the Island to protect its habitat value, and its rare floodplain hardwood forest plant community within the Allegheny River BDA Natural Heritage Area. Enhancing and restoring, where possible, the natural processes, functions and values of the Island to increase the habitat potential for aquatic, terrestrial and resident and migrating avian species. Ensuring that public use and enjoyment will not compromise the health and integrity of the Island’s natural processes, functions and values, nor interfere with ALT’s commitment to protect these unique ecological attributes. Sycamore Island approached from up river, June 2009 2. EXECUTIVE SUMMARY Roughly nine miles upstream from the point in Pittsburgh, nestled in a westerly bend of the Allegheny River, sits a valuable natural resource known as Sycamore Island. From ancient days of fielding the natural forces of a faster, freely flowing, wild river to modern times sitting somewhat buffered off to the side of a continually deepened channel in a controlled, tamed, channelized, urban waterway, the Island has always been largely a reflection of its surrounding mainland. For essentially its entire existence, the Island’s interactions were exclusively with various facets of nature: the river’s hydrology, the flow of sediment, local plant life and wildlife, and climate. Then, some time around the start of the twentieth century, a new interaction confronted the Island: human interaction. Along with urbanization of the surrounding area came river damming, boating traffic, clear‐cutting, dredge material dumping, and various levels of development. From 1967 to 1972, the Island was transformed to a recreational destination. The in 1972, Hurricane Agnes brought all development to a sudden halt. From 1972 to the present, the Island has sat largely untouched by humans and has consequently been experiencing an era of passive restoration. In 2008, Allegheny Land Trust purchased Sycamore Island with the goal of preserving the Island’s natural features, while simultaneously making it safe, accessible, and exciting to the public. In 2009, ALT engaged Applied Ecological Services, Inc. to study the Island, help lead a public process, and compile a comprehensive management report containing detailed scientific findings, compiled feedback from the public process, and a full set of recommendations and strategies. In its present state, Sycamore Island hosts a significant level of biodiversity. Relatively rare floodplain forest plant communities cover most of the Island. Species richness of fish and pearly mussels inhabiting surrounding waters has been increasing in recent decades. Many species of birds reside on, visit, or migrate past the Island. Spiny soft shell turtles inhabit the Island. Insect activity is robust. Herpetofaunal diversity is low. Mammal diversity is moderate. Impacts caused by disturbance are also clearly visible on the Island. Japanese knotweed and, to a lesser extent, other invasive plants cover parts of the Island. Invasive zebra mussels and Asian clams are common in the surrounding river. A massive barge pierces the entire lower portion of the Island. A graded roadbed and asphalt remains span an edge of the Island. Creosote‐ containing utility poles, transformers, and wires remain in varying states of disrepair. An old metal structure used as a pool, a rusting commercial oven, various containers, and piles of debris lie upon the Island. Much, if not most, of the land form is artificial, the result of years of dumping dredge materials. The Island contains a great deal of human allure. Natural beauty abounds and changes with the seasons. Inspiring outdoor spaces are framed by the arching canopy of silver maples, American sycamores, and eastern cottonwoods. Trodden paths make penetrating the forest interior feasible. An intact picnic table and fire pit invite respite. Resilient, character‐filled black willows anchor the southern tip of the Island. River‐smoothed stones and cobbles comprise the eastern shore. The derelict barge has been overtaken by beautiful native vegetation. From its supposed bow sprouts, in fitting fashion, an American sycamore.