Calderwood Fuel Classes
Figure 9. A portion of the fuel class database in Great
Smoky Mountains National Park corresponding to the USGS
7.5-minute Calderwood topographic quadrangle.
The fire fuel class maps and GIS data sets for Great Smoky
Mountains National Park are being used for fire management
decisions and long-term planning for the protection of park
resources. As a demonstration of the use of the fuel maps for
further fire analysis, Dukes (2001) assigned risk factors
based on fuel classes, topography (isolating relatively dry
slopes, aspects and elevations) and ignition sources (e.g.
distance to roads, campsites and areas of potential lightning
strikes). Since ignition risks were found to be important
predic ors of 24 previous forest fires located in the
Calderwood quad area, this risk data layer was given a
weight of 2x in the model. A combination of all risk factors
resulted in an overall map of fire ignition risk ranked as high
medium and low (Fig. 10). An overlay of six withheld fire
locations indicted all previous fires corresponded with
designations of medium and high risk.
4. LANDSCAPE METRICS RELATED TO
VEGETATION PATTERNS
Landscape metrics comparing vegetation patterns due to
interpreter differences and human influence were derived
using the Patch Analyst, an ArcView extension that
interfaces grids and shapefiles with Fragstats Spatial Pattern
Analysis program (McGarigal and Maraks, 1995; Elkie et al.,
1999). An area corresponding to four 7.5-minute USGS
topographic quadrangles was selected to examine differences
in landscape metrics. Overstory vegetation in the Wear Cove
(WECO) and Thunderhead Mountain (THMO) quadrangles
was mapped by Interpreter #1, while the vegetation in the
Gatlinburg (GATL) and Silers Bald (SIBA) quadrangles was
mapped by Interpreter #2 (Fig. 11). (Also indicted by "b",
c". *d" and "e", respectively, in Fig. l). In addition to
interpreter differences, WECO and GATL quadrangles are
located on the outside boundary of the park and the
vegetation in these quads is subject to greater human
influence than the interior quads, THMO and SIBA (Fig. 12).
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
1290
These four quads, therefore, provide a good test for whether
interpreter differences or human influence is having a greater
impact on vegetation patterns as measured by landscape
metrics (Madden 2003).
| Fuel Risk
Topography Risk
+
2X | Ignition Sources Risk
—— m
Fire Ignition Risk Map
|
|
L
Figure 10. A schematic diagram of the GIS data layers
combined in a cartographic model to assess the risk of forest
fire and a map of fire ignition risk in the Calderwood area of
Great Smoky Mountains National Park (Dukes, 2001).
Landscape metrics, such as Shannon’s Diversity Index,
computed at the landscape level (i.e. considering all pixels in
the grid) indicate that there is very little difference that can
be attributed to the two interpreters (Fig. 13). Exterior
quads (WECO and GATL) showed a slight decrease in
diversity compared to interior quads: SIBA and THMO.
Groups of adjacent pixels with the same overstory vegetation
class were then identified using an 8N-diagonals clumping
method of the Patch Analyst (Fig. 14). Since resource
managers in Great Smoky Mountains National Park are
extremely interested in preventing wide-spread destruction of
old growth forests due to an infestation of an exotic insect
known as the hemlock wooly adelgid (Adelges Isugae),
patches representing areas containing Eastern hemlock were
isolated from the overstory vegetation database and analyzed
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