Vegetation Mapping for San Juan Island National Historical Park, Washington
Robert A. Norheim, David L. Peterson
Abstract: We are developing geodatabases of vegetation and fuels
for San Juan Island Historical Park using field-based classification and
data collection.This will provide
park managers with a valuable database relevant to scientific and managerial
applications.We outlined patches
on color DOQs, using color and texture clues in the imagery.We
then conducted sampling in the field, touring all of each patch and revising
boundaries as necessary.Because
the park is only 715 hectares, we are able to achieve essentially 100%
coverage.Allocation of heterogeneous
patches to combinations of fuel models and community types led to some
interesting cartographic results.
San Juan Island National Historical Park (Figure 1) was founded in 1966
to commemorate the peaceful mid-1800s dispute between Britain and America
over the alignment of the USA/Canada border between the Strait of Juan
de Fuca and the mainland.The park
is in two units, English Camp and American Camp, at opposite ends of San
Juan Island, where each side stationed troops during the dispute.We
developed geospatial datasets of the vegetation and fuels of the park to
assist in park management. This is the first georeferenced description
of the vegetation of the park and is intended to provide park managers
and others with a valuable database relevant to scientific and managerial
applications.The fuels component
of the database will provide better understanding of fuels distribution
and facilitate calculations of predicted fire behavior.
Although the focus of park management is to interpret and preserve historical
sites on the island, there are significant natural resource management
objectives as well.Specifically,
the park is to be managed such that the historic landscape (ca. 1850-1870)
is maintained in perptuity.Variation
in the visual and vegetative landscape of the park before, during, and
after the historic period was described in some detail by Agee (1984).Ecosystem
dynamics plus human activities have had a significant effect on park resources
over the past 150 years.Managing
for specific cultural landscape characteristics in the park is proving
to be as challenging as ecosystem-based management for natural processes
in other parks.
A key to management of vegetative resources at the park is knowing their
current distribution and abundance and having a database available as a
GIS coverage.An excellent description
of the forested plant communities of the park was developed by Agee (1987),
including some description of potential vegetation (through successional
time), fuel characteristics, and limited geographic distribution.The
scientific context for further analysis of vegetation and fuels at the
park is provided by Agee (1984, 1987), National Park Service (1984), and
Rolph and Agee (1993). The
current project is to develop a geographically accurate and detailed map
of vegetation and fuels for the park.
Because the park is located on a desirable island and has many vacation
homes abutting the park boundaries, the park has a keen interest in understanding
how wildland fires might behave in the park.The
fuels component of this work will enable the park to run fire modeling
software to understand potential fire behaviour.
We used a visual examination of recent digital orthophotos as a basis for
our work.We outlined vegetation
patches based on color and texture changes and digitized the patches into
a coverage.Printed map sheets with
patch boundaries overlaid on the orthophotos, as well an ancillary information
such as trails, were taken into the field.Because
of the small size of the park (715 hectares) and the number of patches
(138), we were able to do an exhaustive sampling of the park.We
visited each patch and set up one to three plots in each forested patch
to collect vegetation and fuels data.The
boundaries determined from the orthophotos were verified in the field,
and in some cases revised with the aid of GPS.The
ability to visit many patches in a single day was a welcome change from
our work in larger national parks where only a limited sampling is possible
and many vegetation communities are far from the road.
Vegetation was classified according to Agee (1987) and FGDC (1997).Agee's
system consists of 11 plant communities relevant to the forested areas
that dominate the park.These
forest communities are based on empirical data and subsequent analysis
that confirms the robustness of the individual communities as discrete
entities.This classification provided
an accurate representation of the forest composition of the park in terms
of species dominance.
Data collected for each patch included an exhaustive species list for
both overstory and understory plants, a tree survey, forest community,
fuel model, ground fuels, and characteristics essential to calculating
Data from the field work was entered into a database.The
field data was manipulated to produce statistics for each patch. For patches
with more than one plot, data were averaged from the different plots. Stem
count and basal area for each patch were derived from the tree survey.
Number of communities per patch, number of fuel models, number of understory
and overstory species, dominant fuel model and dominant community for each
patch were determined from patch characteristics.Crown
bulk density for each patch was determined from the modal tree and tree
survey. Fuel loadings for each patch were determined from the ground fuels
data.This provides the fuel variables
necessary to run FARSITE (Finney 1998), which simulates the spatial and
temporal spread and behavior of fire. We
also developed a crosswalk from the Agee (1987) community system to the
National Vegetation Classification System (NVCS) (FGDC 1997, USGS 1997)
to meet the Department of Interior requirement that vegetation mapping
use the NVCS.
We transferred the major characteristics of each patch from the database
to a geospatial coverage, enabling mapping of those attributes.Figure
2 contains maps showing the dominant community types per Agee (1987).Because
each patch might have multiple plots, and each plot might reflect more
than one community type, a patch could potentially have a number of community
types.In the field, we recorded
community types as a percentage of the area surrounding a plot.Thus,
each patch may have several community types, expressed as a percentage.Several
plots did not have a majority community type, so the dominant community
type as mapped was the one with the greatest percentage.
Figure 2(a). English Camp
Figure 2(b). American Camp
This work was funded by the National Park Service. We thank the Cascadia
Field Crew (Sarah Schrock, Seth Kirby, Megan Wilson, Marnie Tyler, Don
McKenzie, Steve Goodman, Amy Hessl, and Carolyn Menke) for their help with
field work and Craig Dalby and Bill Gleason of the National Park Service
for their assistance.Paige Eagle
gave expert advice in MS-Access.
For more information
Please visit the San Juan Island National Historical Park web site at http://www.nps.gov/sajh/,
and USGS FRESC Cascadia Field Station's web site at http://www.cfr.washington.edu/research.usgs/cascadia/.
J.K. 1984. Historic landscapes of San Juan Island National Historical Park.
Report CPSU/UW 84-2. National Park Service, Seattle.
J.K. 1987. The forests of San Juan Island National Historical Park. Report
CPSU/UW 88-1. National Park Service, Seattle.
vegetation classification standard, FGDC-STD-005. USGS Federal Geographic
Data Committee, Reston, VA.
M.A. 1998. FARSITE: Fire Area Spread Simulator, model development and evaluation.
USDA Forest Service Research Paper RMRS-RP-4.
Park Service. 1984. Rabbits, redoubts, and royal marines. National Park
D.N. and J.K. Agee. 1993. A vegetation management plan for the San Juan
Island National Historical Park. Technical Report NPS/PNRUW/NRTR-93/02.
National Park Service, Seattle.
1997. The USGS-NPS Vegetation Mapping Program. Online document at http://biology.usgs.gov/npsveg.
Robert A. Norheim
David L. Peterson
and Rangeland Ecosystem Science Center Cascadia
University of Washington College
of Forest Resources
Seattle, WA 98195-2100
206 543-9138, 206 543-1587