VEGETATION CLASSIFICATION AND MAPPING
AT ALLEGHENY PORTAGE RAILROAD
NATIONAL HISTORIC SITE

Technical Report NPS/NER/NRTR--2006/079

Stephanie J. Perles¹, Gregory S. Podniesinski¹,
Ephraim A. Zimmerman¹, Elizabeth Eastman ²,
and Lesley A.Sneddons<sup>3

1</sup> Pennsylvania Natural Heritage Program
Western Pennsylvania Conservancy
208 Airport Drive
Middletown, PA 17057

² Center for Earth Observation
North Carolina State University
5112 Jordan Hall, Box 7106
Raleigh, NC 27695

³ NatureServe
11 Avenue de Lafayette, 5th Floor
Boston, MA 02111

March 2007

U.S. Department of the Interior
National Park Service
Northeast Region
Philadelphia, Pennsylvania
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Executive Summary

Vegetation classification and mapping was conducted at Allegheny Portage Railroad National Historic Site, creating a current digital geospatial vegetation database for the park. Sixteen vegetation associations, Alder Riverine Shrubland, Allegheny Hardwood Forest, Conifer Plantation, Dry Eastern Hemlock - Oak Forest, Eastern Hemlock - Northern Hardwood Forest, Eastern Hemlock - Tuliptree - Birch Forest, Japanese or Giant Knotweed Herbaceous Vegetation, Modified Successional Forest, Northern Hardwood Forest, Northern Red Oak - Northern Hardwood Forest, Reed Canarygrass Riverine Grassland, Sparsely Vegetated Cliff, Successional Old Field, Sugar Maple Floodplain Forest, Tuliptree - Beech - Maple Forest, and Wet Meadow, that occur within the park were identified and described in detail. These vegetation types are strongly influenced by the varied environmental settings and land use history of the park.

The most abundant association in Allegheny Portage Railroad National Historic Site is Allegheny Hardwood Forest, covering over half (52%) of the park area. This association is the most common forest type in the Summit Level section of the Main Unit of the park and is typical in northern and western Pennsylvania on higher elevations of the Allegheny Plateau. Northern Hardwood Forest is the second most common vegetation association within the park (17% of the park area). The higher quality examples of these two forest types occur in the Main Unit to the north and west of the Hollidaysburg Reservoir.

Several other forest associations occur scattered throughout the park within these two common forest types. Three hemlock - hardwood types are differentiated from each other by their environmental setting and the species of co-dominant hardwoods. Dry Eastern Hemlock - Oak Forest occurs on dry upper slopes and is co-dominated by oaks, including chestnut oak (Quercus prinus). Eastern Hemlock - Tuliptree - Birch Forest, co-dominated by tuliptree (Liriodendron tulipifera) and birches (Betula spp.), is restricted to ravines and streamsides. Eastern Hemlock - Northern Hardwood Forest is more common (6% of the park area) than the other two hemlock types. It occurs in areas where hemlock mixes with the two common hardwood forest types, and is co-dominant with maples (Acer spp.), birches, and black cherry (Prunus serotina).

Northern Red Oak - Northern Hardwood Forest also occurs in patches throughout the park; however, this association was often misclassified during the classification analyses and reported very low errors of commission and omission during accuracy assessment. This was caused by the patchy and inconsistent distribution of northern red oak (Quercus rubra) and other oaks (Quercus spp.) within the Allegheny Hardwood Forest and Northern Hardwood Forest. The other association that reported a low error of omission was Tuliptree - Beech - Maple Forest. This association is most abundant in the Staple Bend Unit, where tuliptree colonized the mesic slopes after they were cleared. The errors were caused by difficulties with aerial photography interpretation and the great variation in the composition of the hardwood forests due to previous logging and disturbances.

The forest types in the Staple Bend Unit are generally of lower quality, compared with the forests at higher elevations in the Main Unit. Much of the Staple Bend Unit contains dense infestations of Japanese knotweed (Polygonum cuspidatum), giant knotweed (Polygonum sachalinense), or the hybrid of those two species (Polygonum x bohemica). All of the mapped occurrences of Japanese or Giant Knotweed Herbaceous Vegetation are located within the Staple Bend Unit.

Three associations are associated with riparian habitats along rivers, streams, and drainages. Alder Riverine Shrubland occurs in one small patch along the Little Conemaugh River in the Staple Bend Unit. The Main Unit contains a single occurrence of Reed Canarygrass Riverine Grassland along small drainages in the southeast corner of the unit. Wet Meadow occurs in a few locations within the Main Unit where herbaceous and graminoid vegetation surrounds small drainages. Sugar Maple Floodplain Forest covers more area than the previous two associations at the Main Unit, but is limited in extent to areas surrounding Blair Gap Run. Nine Sparsely Vegetated Cliff sites are shown in the vegetation association map; however, there may be additional cliffs in the park that were not captured by the map.

Due to previous disturbances and land use history, Modified Successional Forest, Conifer Plantations, and Successional Old Field are fairly common associations in the park, especially in the southeastern corner of the Main Unit. These vegetation types are a direct result of previous disturbances. They typically contain invasive species and often occur as mosaics with other disturbed or successional associations.

A map showing the locations of vegetation associations in the park was created, following the USGS/NPS Vegetation Mapping Program protocols (TNC and ESRI 1994a, b, c). These vegetation associations were also crosswalked to the National Vegetation Classification System in order to provide a regional and global context for the park’s vegetation. A dichotomous field key was developed for these vegetation associations to assist with field recognition and classification. This project documents the vegetation associations of Allegheny Portage Railroad National Historic Site based on 2003 aerial photography and 2005 field sampling, and completes one of 12 basic inventory data sets for the park.

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The file for this report is large, therefore it has been divided into 4 pdf files. Click on a file to open it.

pdf file 1
Front Matter through Materials and Methods

pdf file 2
Results through Northern Hardwood Forest

pdf file 3
Tuliptree-Beech-Maple Forest through Japanese or Giant Knotweed Vegetation

pdf file 4
Wet Meadow to end