Narragansett Bay Research Reserve Technical Reports Series 2004:2

Narragansett Bay Research Reserve Technical Report Habitat Classification and Inventory for the Narragansett Bay 1 National Estuarine Research Reserve 2004:2 Thomas E. Kutcher; NBNERR Kenneth B. Raposa; NBNERR Francis Golet; University of Rhode Island, Department of Natural Resources Science February 2004 Technical Report Series 2004:2 ABSTRACT A classification system was developed for natural and modified habitats in Rhode Island and employed at the Narragansett Bay National Estuarine Research Reserve (NBNERR) on Prudence, Patience, Hope, and Dyer Islands. The classification system builds on previous national and local classification schemes, is hierarchical, and was designed for use in a geographic information system (GIS). It consists of five classification levels including System, Subsystem, Class, Subclass, and Habitat, and applies to upland, wetland, and deepwater habitats. In 2003, a total of 2601 acres of the NBNERR was mapped using this classification system including 652 polygons from 4 systems,6 subsystems, 20 classes, 26 subclasses, and 72 different habitat types. The highly modified south end of Prudence Island consisted of 33 habitat types dominated by Red Maple Swamp , Coastal Shrubland , and mosaics of Oak, Maple, and Pitch Pine forests. The north end of Prudence Island and Patience Island were dominated by Coastal Shrubland and Coastal Cherry/Eastern Red Cedar Forest habitats, and Dyer Island and Hope Island were dominated by Coastal Shrubland . The classification system is already enhancing the stewardship and management functions of the NBNERR and should prove useful in other areas of Rhode Island and southern New England. 2 INTRODUCTION The Narragansett Bay National Estuarine Research Reserve (NBNERR or Reserve) is one of 22 reserves that comprise the National Estuarine Research Reserve System (NERRS). This national network is funded and administered by the National Oceanic and Atmospheric Administration in partnership with state agencies and nonprofit organizations. The goal of the NERRS is to organize and facilitate nationwide, three primary functions: estuarine research, estuarine education, and environmental stewardship. Effective stewardship requires an understanding of habitats. An inventory of habitats provides a basis for management of plants and wildlife and establishes a baseline for future monitoring and comparisons with aerial photo archives. It also facilitates contemporary ecosystem analysis and interpretation. Finally, a habitat inventory serves researchers, educators and environmental managers, as a means of communicating spatially defined ecological information. Shaughnessy (1982) inventoried the habitats of two large units of the NBNERR for the RI Department of Environmental Management in 1982. However, prior to the current study, Reserve habitats had never been completely inventoried. The initial objective of this project was to conduct an inventory of the habitats of the NBNERR and to create a useful, interactive, GIS polygon dataset. For ease of query and organization in the GIS data tables, a numerical and hierarchical classification format was needed, but no such schemes were available for local habitats. Development of a suitable classification thus became a second objective. This report describes the 3 production and the utility of the classification and inventory, provides metadata for the inventory, and outlines a protocol for future inventories. STUDY AREA The NBNERR is a 4,259-acre reserve composed of four islands and adjacent waters in the center of Narragansett Bay, Rhode Island. Narragansett Bay is an estuary comprised of three drowned glacial river valleys, with average current channel depths ranging from 30 to 50 feet and an estimated freshwater input of 2.4 billion gallons per day (Beck and Beck 1998). The salinity of the bay ranges from 13 ppt in the upper part to 31 ppt at the mouth. The largest island in the Reserve, Prudence Island, is 7.0 miles long and 1.4 miles at its widest point, covers approximately 3,500 acres, and reaches 180 feet in elevation. NBNERR contains seven parcels, which cover over 65% of the Prudence Island land surface. The Reserve also includes Patience Island (214 acres), Hope Island (94 acres), and Dyer Island (36 acres) in their entireties. Each of the four islands is composed of sedimentary rock covered by a discontinuous, thin layer of dark till. Glacial fluvial deposits cover much of the narrow north end of Prudence Island (Hermes et al. 1994). The soils of the Reserve are very diverse, predominantly falling in the US Soil Conservation Service’s hydrologic group C, with some large areas of sandy group A soils in the North Prudence Unit (Rector 1981). The topography and soils of the Reserve have been modified by a long history of human land use. Prudence, Patience, and Hope Islands were cleared and used as pasture and cropland from the mid 1600’s until the mid 1800’s. The Islands were taken over by 4 the U.S. Navy in 1940 for use as a munitions base and Hope and Prudence were heavily disturbed by clearing, and the construction of roads and bunkers (Beck and Beck 1998). Following World War II, the Navy returned the properties to the State of Rhode Island, and they have become vegetated. METHODS NBNERR Classification- This project focused on producing a lasting and comprehensive classification scheme to fit the needs of the Reserve. Foremost, the scheme needed to separate the Reserve into useful units. Natural communities (Enser and Lundgren 2003) or habitats (Cowardin et al. 1979), as used in this context, are areas of the landscape that are typically characterized by certain life forms or species, water regimes, substrates, and animal associations. Habitat classifications are especially useful to environmental managers because they provide information about the physical environment, flora, and fauna, which facilitates interpretation of ecological function. A classification of habitats (NBNERR classification, Appendix 1) was produced for the Reserve by inserting common habitat names into a hierarchical structure based on Classification of Wetlands and Deepwater Habitats of the United States (Cowardin et al. 1979). The five levels of the resulting hierarchy are System , Subsystem , Class , Subclass , and Habitat . In order to facilitate organization and statistical query of the habitats in GIS, text, and spreadsheet software programs, the NBNERR habitat types were organized using a strictly numerical format, with System , Subsystem , Class , and Subclass each being 5 represented by a descending order of magnitude respectively, and Habitat falling at the first and second decimal places. If desired, habitats can be subdivided by adding decimal places; thus the classification is open ended. The overall hierarchical structure and nearly all of the categories within the System , Subsystem , Class , and Subclass levels were adopted directly from Cowardin et al. (1979), while many of the habitat types used in the Habitat level were adopted from the Natural Community Classification of Rhode Island (NCCRI ) (Enser and Lundgren 2003) and other sources. The Habitat level was added below the Subclass level to facilitate communication by identifying the habitat type with a descriptive, well accepted, and defined common name. Definitions of classification levels and habitat types are appended to this report (Appendix 2). A recent draft of the NCCRI is also appended to this report (Appendix 3). The Cowardin system is the national standard for wetland and deepwater habitat classification. It classifies habitats through five levels as well as a series of modifiers describing water regime, water chemistry, and soil. A habitat is described by stringing the names (or abbreviations) of its components together. For example, a salt meadow would be described as: an estuarine, intertidal, persistent emergent wetland, dominated by Spartina patens and Distichlis spicata, with an irregularly flooded water regime, and mixohaline, hemic soil, or E2EM1nP3h (Golet 2003). The advantage of the Cowardin et al system is that any wetland can be accurately identified and described regardless of regional differences in common names. The NBNERR scheme trades off complete national standardization for ease of use. 6 The Cowardin hierarchical approach was extended to include Upland and Modified habitats, so that all Reserve habitats could be classified in a consistent fashion. With assistance from Dr Frank Golet of the University of Rhode Island, the Upland System was divided into subsystems, classes and subclasses. The Modified System was added to permit the classification of habitats that have been modified mechanically or chemically more than once per growing season (i.e., lawns or gardens), that are regularly grazed by livestock (i.e., pastures), or that have been modified to a condition that prohibits natural succession (i.e., barns, houses, and parking lots). Modified habitats were adopted from the RIGIS Anderson (1976) level 4, land-use/land-cover classification. 2003 NBNERR Inventory An inventory of Reserve habitats was conducted between June and October of 2003. Due to time constraints, deepwater habitats were not inventoried unless they were entirely or mostly enclosed by land. The GIS polygon dataset, Community_class.shp (a shapefile), was created with ArcView 3.2 software, against the RIGIS 1997 1:5000 Digital Orthophotograph Quadrat (DOQ) dataset (RIGIS 2003). Polygons were heads-up digitized at 1:3000. Accuracy of the DOQ was field-tested against a Trimble survey-

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