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LONG TERM MONITORING OF
WOODLOT PLANT COMMUNITIES
AT GETTYSBURG NATIONAL MILITARY PARK
Technical Report NPS/NERCHAL/NRTR-04/092
T. W. Bowersox, D. S. Larrick,
A. T. Niewinski,
G. L. Storm and W. M. Tzilkowski
The Pennsylvania State University
College of Agricultural Sciences
School of Forest Resources
University Park, PA 16802
March 2004
(revised June 2004)
U.S. Department of the Interior
National Park Service
Northeast Region
Philadelphia, Pennsylvania
___________________________________________________________
Summary
Long-term vegetation
monitoring at Gettysburg National Military Park (NMP) is being conducted
in the following three types of plots: Demonstration, Long Term Monitoring
and Canopy Treatment plots. Vegetation monitoring was started in 1986
with un-replicated Demonstration plots in six woodlots (Biesecker, Bushman
Hill, Cobean, Pitzer, Slyder, and Spangler). From 1990 to 1992, the
Long Term Monitoring plots were established in six woodlots (Biesecker,
Bushman Hill, Herr Ridge, Pitzer, Powers Hill, and Spangler) to determine
the status of woodlot plant communities with closed canopies and the
effects of deer foraging on understory vegetation. A set of Canopy Treatment
plots was installed in 1992 to measure understory responses to creating
openings in the canopy of three woodlots (Bushman Hill, Herr Ridge,
and Powers Hill). The 1986-87 to 1994 data from Demonstration plots,
the 1990-92 data from Long Term Monitoring plots, and the 1992 data
from Canopy Treatment plots served as the baseline for long term monitoring
of changes in woody and herbaceous vegetation. This report (1) describes
the status of woodlot plant communities in the Demonstration and Long
Term Monitoring plots in 1996, and in the Canopy Treatment plots from
1994-1996, and (2) assesses the effects of various sized openings in
the overstory canopy and foraging by white-tailed deer on understory
vegetation prior to the park’s Deer Management Program in 1995.
The Demonstration plots consist of six pairs of un-replicated fenced
and unfenced 10 x 10 m plots that were intended to provide information
on the development of vegetation with and without the presence of white-tailed
deer. Surveys of tree and shrub seedling-sized (seedling) stems were
conducted in each of the six woodlots in 1986-87, 1989, 1991, 1994,
and 1996, whereas herbaceous plants and vines were only surveyed in
Biesecker and Bushman Hill woodlots in 1992.
The Long Term Monitoring plots used a fixed plot monitoring system to
survey overstory, sapling, and seedling trees and shrubs and herbaceous,
ground, and vine coverages in each of the six woodlots. For measuring
overstory and sapling stems, thirty 20 x 20 m plots were established
in each of Biesecker and Pitzer woodlots and fifteen 20 x 20 m plots
were established in each of Herr Ridge, Spangler, Bushman Hill, and
Powers Hill woodlots. For measuring seedlings and herbaceous, ground,
and vine coverages, fifteen fenced 2 x 2 m subplots and fifteen unfenced
2 x 2 m subplots were established in each of Biesecker and Pitzer woodlots,
and fifteen unfenced 2 x 2 m subplots were established in each of Herr
Ridge, Spangler, Bushman Hill, and Powers Hill woodlots. In 1996, overstory
and sapling tree and shrub stems were surveyed in Biesecker, Pitzer,
Herr Ridge, and Spangler woodlots, while seedlings and herbaceous coverage
were surveyed in all six woodlots.
The Canopy Treatment plots consisted of three 0.20 ha circular canopy
treatments (closed, partially open, and open canopies). Each treatment
was replicated three times within each of the three woodlots. Each canopy
treatment area contained a 20 x 20 m plot and a 2 x 2 m subplot. Overstory
stems were surveyed in 1992 and 1996 in each 0.20 ha treatment area,
whereas sapling stems were surveyed in 1992, 1994, and 1996 in each
20 x 20 m plot. Seedling stems and herbaceous vegetation were surveyed
in 1992, 1994, and 1996 in each 2 x 2 m subplot.
In the Demonstration plots, general trends from 1986-87 to 1996 were
(1) the number of tree and shrub seedling species increased, (2) tree
seedling density decreased, and (3) shrub seedling density increased.
In the Long Term Monitoring plots, general trends from 1990-92 to 1996
were (1) overstory, large sapling, and small sapling tree species decreased,
(2) large and small sapling tree densities decreased, (3) overstory
and sapling densities of oak species decreased, (4) total tree seedling
and oak seedling densities decreased, and (5) seedling densities of
non-native Japanese barberry and multiflora rose increased. In summary,
the general trends over all Canopy Treatments from 1994 to 1996 for
herbaceous plants, seedlings, and saplings were (1) grass, forb, vine,
and total herbaceous coverage increased (except vine coverage decreased
in the open canopy treatments), (2) seedling tree species and density
decreased, seedling shrub species increased (except in the partially
open canopy treatments), and seedling shrub densities decreased (except
in the open canopy treatments), and (3) sapling tree species decreased
(except in the open canopy treatments), sapling shrub species decreased,
and sapling tree and shrub densities decreased.
From the collective data of Demonstration, Long Term Monitoring, and
Canopy Treatment plots, it is recommended that (1) creating openings
in the canopy, (2) controlling deer herd densities, and (3) reducing
non-native herbaceous and shrub species should be considered in order
to maintain the mixed oak woodlots with native species diversity at
Gettysburg National Military Park.
_________________________________________________________
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