AN APPROACH TO QUANTIFYING DESIRED FOREST CONDITIONS AT VALLEY FORGE NATIONAL PARK

Technical Report NPS/NER/NRTR—2007/082

Ery Largay and Lesley A. Sneddon
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

This report identifies one approach to quantifying possible desired forest conditions using the National Vegetation Classification System (NVCS) and ecological integrity criteria for two matrix forest communities at Valley Forge National Historical Park (NHP), a Dry Oak Forest> type and a Successional Tuliptree Forest type. The target desired conditions were identified as historical forests that occurred on the Valley Forge landscape during the period of early European settlement of southeastern Pennsylvania prior to and during the Continental Army encampment period at Valley Forge NHP from 1777–1778. The time period for historical forest research was selected to complement the Valley Forge NHP's Draft General Management Plan Park Mission to preserve the natural and cultural resources that commemorate the encampment.

Descriptions of target communities were developed from witness tree data, historical accounts, past land use studies, and ecological studies that referenced the forests of the Valley Forge area. Research was also conducted on pre-European settlement forests to determine the historical composition of American chestnut (Castanea dentata) and to identify the disturbance regimes that maintained forests prior to European settlement. References to the landscape after encampment and through the 1900s were also reviewed to provide clues as to how early forests changed in the Valley Forge area.

The target forest types identified in this report include:

• A high-quality Dry Oak Forest community dominated by chestnut oak (Quercus prinus), black oak (Quercus velutina), and American chestnut (Castanea dentata) occurring on dry, acidic soils on steep slopes.

• Dry-Mesic Chestnut Oak Forest dominated by chestnut oak and northern red oak (Quercus rubra) occurring on moderate lower slopes with mesic soils.

• Mesophytic forest community dominated by an admixture of trees including oaks, especially white oak (Quercus alba), American beech (Fagus grandifolia), tuliptree (Liriodendron tulipifera), and hickories (Carya spp.) occurring on historically farmed, fertile, limestone-derived soils that support the existing Successional Tuliptree Forest.

Existing old growth examples of Dry Oak Forest and Mesophytic forest communities within the same ecoregion and with comparable vegetation composition, soil, and geological attributes were identified as reference sites. Target forest condition criteria, including stand-specific and landscape-level metrics, were identified from old-growth studies to provide quantitative standlevel data. These metrics can be used to guide restoration and for forest monitoring and management.

White-tailed deer (Odocoilus virginianus), exotic invasive plants, a lack of natural and anthropogenic stand-maintaining disturbance regimes, gypsy moth (Lymantria dispar) outbreaks, and abiotic factors such as surrounding land use are among some of the stressors influencing the ecological integrity of the existing Valley Forge NHP forests. Without some form of adaptive management to address the stressors or the impacts of these stressors, the existing Valley Forge NHP forests are likely to be on successional trajectories with little ecological or historical value. This report proposes a set of desired conditions and potential target stand metrics for forest communities at Valley Forge NHP.

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