Table 1—Constancy of ubiquitous and restricted woody species on forty .10-ha plots located in the Balsam Mountains

of western North Carolina
Ecological type
Rich Northern High-elevation Red spruce- Fraser
Principal cove hardwood red oak Fraser fir fir
species Od o)) (10) (12) 8)
lalallala tata taetatatalatabatetatate Percent --~------------0+-----------
Ubiquitous
Red spruce 80 90 80 100 100
Yellow birch 100 100 30 1 100
Serviceberry 60 80 80 100 33
Beech 60 80 40 64 0
Restricted
Northern red oak 20 10 100 36 0
Fire cherry 25 50 0 36 100
Yellow birch snag 40 50 10 55 33
Fraser fir 0 30 0 55 100
Mountain ash 0 10 0 27 100
Hemlock 80 10 40 0 0
Silverbell 80 0 50 0 0
Sugar maple 60 50 10 9 0
Black cherry 20 30 20 18 0
Mountain maple 0 30 0 9 33
Yellow buckeye 0 50 0 18 0

Numbers in parentheses are the number of plots for each ecological type.

tulipifera L.) and basswood. This type probably represents
a transitional community between true cove forests at lower
elevations and montane boreal forests on the higher slopes
(Schafale and Weakley 1990).

Many species occurred throughout the study area but
varied in their importance among ecological types. Red
spruce AIV declined from 37.7 in the spruce-fir type to 3.2 in
rich cove forests, but maintained its presence in both the
overstory and understory at lower elevations. Yellow birch
had ATV of approximately 13 across spruce-fir, northern
hardwood, and rich cove types but was almost entirely
absent (AIV 1.8) from most plots dominated by northem red
oak. In contrast, northem red oak was present in 4 of the 5
ecological types but importance ranged from an AIV of 19.8
in the red oak type to 8.9, 4.3, and 1.5 in spruce-fir, northern
hardwood, and rich cove types, respectively. American
beech was important in both northern red oak (ATV 19.5) and
northern hardwood (AIV 16.3) types.

Table 2 shows the mean topographic conditions for the five
ecological types. Elevation was the most important
discriminating variable among ecological types. Fraser fir
forests were correlated with high elevation (> 1800 m),
exposed landscapes which are very restricted in the Balsam.
Mountains. Slopes were generally moderate and sites tended

to be somewhat convex. Red spruce-Fraser fir forests were
associated with slightly lower landscapes between 1650 and
1800 m but still on relatively exposed ridges and upper
slopes. Landscape position, aspect, and slope steepness
were highly variable within this type and at least two
subtypes appeared to occur. In general, yellow birch, Fraser
fir, and serviceberry were more important components of red
spruce-Fraser fir forests on more sheltered or north-facing
slopes, while northern red oak and beech were more
important on exposed convex ridges and south-facing
slopes. Many of the dome-shaped knobs that dot the crest
of the Balsam Mountain range are covered by well-
developed, mature stands of red spruce with many large-
diameter (60 to 75 cm d.b.h.) stems. The age of several trees
in these stands was more than 120 years (determined by
increment core analysis), and understories were generally
open with little ground cover.

Xeric landscape positions, such as steep, south-facing
slopes and ridges below 1650 m with no higher landforms
nearby, were correlated with the high-elevation red oak type.
Seventy percent of plots dominated by northern red oak
occurred on sites with S-SW-W aspects. At approximately
1650 m, northern red oak communities blended with beech
and red spruce to form mixed stands. On sites that appeared
to be more disturbed, American beech was codominant with



Table 4—Comparison of mean terrain attributes associated with ecological types in the Balsam Mountains and Wine

Spring Creek study areas, western North Carolina

Terrain attribute
Ecological
type Elevation Aspect Gradient LF TSI
Meters Degrees Percent
Balsam Mountains
Rich cove 1301 64 32 0.25 0.08
Northern hardwood 1644 137 43 24 0S
High-elevation red oak 1500 161 28 12 -01
Wine Spring Creek
Rich cove 1051 216 35 34 07
Northern hardwood 1415 157 33 22 05
High-elevation red oak 1472 188 24 09 -04
LFI = landform index, TSI = terrain shape index. -
Ecological Restoration Acknowledgments

In addition to predicting potential wildlife habitat based on
current vegetation-site relationships, our approach to
landscape modeling may be useful in targeting areas for
ecological or habitat restoration projects. As mentioned, the
Balsam Mountains study area included the Shining Rock-
Graveyard Fields area, which was severely impacted by
logging, fire, and erosion in the early part of the 20 century.
This area was predicted by the Balsam Mountain
classification model to be covered primarily by Fraser fir, red
spruce-Fraser fir, and northern hardwood types (fig. 3) and
represents approximately 30 percent of the landscape in the
study area above 1 500-m elevation.

While recolonization rates by tree species have not been
documented, much of the area remains in open grass-forb-
shrub communities or forested stands that do not appear to
contain the species diversity and structure of surrounding,
less disturbed forests. Nevertheless, CNFS have been
caught in nest boxes in wooded habitats along the margins
of open areas and in riparian zones (see footnote 2). Areas in
this landscape that may be more conducive to
reestablishment of northern hardwood-red spruce
communities due to soil depth, soil moisture, or organic
matter build-up, e.g., concave or north-facing sites, could be
targeted for habitat restoration work. Selection of the most
favorable parts of the Shining Rock-Graveyard Fields area
for restoration of northern hardwood-red spruce
communities would appear to be a cost-effective way of
focusing limited resources for habitat restoration in areas
where the likelihood of success is greater.

10

We thank Allen Boynton, Wildlife Biologist, Virginia
Department of Game and Inland Fisheries; Chris McGrath,
Wildlife Biologist, North Carolina Wildlife Resources
Commission; Nora Murdock, Wildlife Biologist, U.S.
Department of Interior, Fish and Wildlife Service; and Mark
Ford, Research Wildlife Biologist, U.S. Department of
Agriculture, Forest Service, Northeastern Research Station,
for sharing insights on the application of our work to CNFS
habitat modeling and for commenting on an early draft of
this paper. Partial funding for this study was provided by the
North Carolina Wildlife Resources Commission, North
Carolina Non-game Small Grants I—contract
#94SGO09, and grant OM-43-4568-4-1096 from the U.S.
Department of Agriculture, Forest Service, Southern
Research Station.

Literature Cited

Barden, L.S.; Woods, F.W. 1976. Effects of fire on pine and pine-
hardwood forests in the Southem Appalachians. Forest Science. 22:
399-403.

Barnes, B.V.; Pregitzer, K.S.; Spies, T.A.; Spooner, V.H. 1982.
Ecological forest site classification. Journal of Forestry. 80: 493-
498.

Blaszezynski, J.S, 1997. Landform characterization with
geographic information systems. Photogrammetric Engineering &
Remote Sensing. 63(2): 183-191.

Braun, E.L. 1950, Deciduous forests of Eastern North America.
Philadelphia: The Blakiston Company. 596 p.

Cantrell, G. 1997. Highway threatens rare squirrel. Asheville [NC]
Citizen-Times, March 23; Sect. B: 1(col. 1), 8(col. 5).



Table 3—Classification summary of observed and predicted ecological types for the analysis and validation data
sets, Balsam Mountains of western North Carolina
Predicted ecological type
Observed Fraser Red spruce- _— Northern Northern Rich
ecological type fir Fraser fir hardwood red oak cove Total
Analysis data
Fraser fir 3 - _ _ _ 3
Red spruce-Fraser fir _ +8] 1 _ _ 12
Northern hardwood _ 1 9 1 — 11
Northern red oak _ 1 1 7 1 10
Rich cove — = =— = 4 4
Total 3 13 11 8 5 40
Validation data
Fraser fir 1 _ _ _— _ 1
Red spruce-Fraser fir _ 14 — _ _ 14
Northern hardwood _ 4 1 _ _ 5
Northern red oak _ _ — 7 — 7
Rich cove = = _ _ 2 2
Total 1 18 1 7 29

— = no plots classified as a combination of predicted and observed ecological types.

equal probabilities of occurrence for two or more of the five
possible ecological types on half of the misclassified plots.

In general, the association of ecological types with
topographic conditions in this study area compare favorably
with those identified by Whittaker (1956) and others for the
Southern Appalachian Mountains. Plot elevation and
protection relationships displayed in figure 2 were compared
with Whittaker’s mosaic charts for several species common
to both areas. The distributions with regard to elevation and
landform were strikingly similar. Whittaker did not identify
northern hardwood as a type, but seems to have included
stands dominated by mixtures of beech, yellow birch,
buckeye, or sugar maple as part of the spruce-fir, beech gap,
or cove hardwood types. Separating northem hardwoods as
a type was difficult in this study; this type may occur in the
Balsam Mountains landscape only as a narrow transitional
element between more clearly identifiable forest
associations.

Validation of Ecological Types

Almost half of the observed validation plots were situated in
the red spruce-Fraser fir ecological type (table 3) because the
Parkway follows the main crest of the Pisgah Ridge through
the Balsam Mountains, with elevations ranging from 1 600 to
1700 m. An average 86 percent of the validation plots were
classified correctly (table 3), which is consistent with
classification results achieved using the analysis plots.

The log-likelihood test indicated no significant difference

(p= 0.05) between the observed and predicted ratios of
ecological types. All of the misclassifications occurred in the
northern hardwoods type, which occurred in the validation
area as a complex mosaic of small patches interspersed with
red spruce. Apparently, lack of sensitivity of the discriminant
function for northern hardwoods combined with
inaccuracies of the DEM resulted in inability to accurately
model the mosaic of these two species. Results were best
(100 percent correct) for the northern red oak type, where the
canopy was usually dominated by this single species.
Although results were good for the Fraser fir and rich cove
types, these types were insufficiently represented in the
validation area and did not provide a statistically valid test.

The final map depicting the predicted distributions of the
five ecological types in the Balsam Mountains (fig. 3) was
subjectively evaluated by the authors and by biologists from
the North Carolina Wildlife Resources Commission who are
familiar with the Balsam Mountains landscape. The
consensus was that the map portrayed the distribution of
ecological types in a manner consistent with our sense of
where these communities should occur on the landscape.’ In
addition, given the preliminary nature of this study and the
very limited field data collected, achieving an 86 percent
correct classification rate for validation plots leads us to
believe that this approach deserves more attention and a
more rigorous evaluation.

2 Personal communication. 1998. Chris McGrath, Wildlife Biologist,
North Carolina Wildlife Resources Commission, 315 Morgan Branch
Road, Leicester, NC 28748.



Table 2—Mean terrain attributes associated with ecological types in the Balsam Mountains of western North
Carolina

Terrain attribute

Ecological

type Elevation Aspect Gradient LF TSI

Meters Degrees Percent

Rich cove 1301 64 32 0.25 0.08
Northern hardwood 1644 137 43 2A 05
High-elevation red oak 1500 161 28 12 01
Red spruce-Fraser fir 1706 190 36 14 -01
Fraser fir 1858 262 18 09 -.03

LFI = landform index, TSI = terrain shape index.

red oak in the overstory and often formed pure beech
thickets in the understory. Some of these sites occurred on
relatively flat knobs or ridge tops close to the Parkway and
may have received concentrated use during construction of
the roadway. The sedge C. pensylvanica was the
predominant ground cover in these areas.

Both northern hardwood and rich cove types occupied
relatively sheltered landscape positions or were associated
with northerly aspects or concave microsites when they
occurred on more upper slope positions of ridges. Plots
classified as rich cove ecological type occurred at lower
elevations and on more moderate slopes than those
classified as northern hardwood. As noted by Schafale and

Weakley (1990, pp. 28-29), these two communities are
difficult to separate at moderately high elevations where
cove landforms are not pronounced and true cove species
are not abundant.

Elevation and LFI were the most important discriminating
factors in the classification of study plots (fig. 2), although
all terrain variables seemed to play a role in defining land
types associated with the five ecological types.
Approximately 85 percent of the 40 analysis plots were
correctly classified by the discriminant functions (table 3).
No pattern of errors was evident among the six misclassified
plots, although most occurred in the northern red oak
ecological type. The discriminant functions predicted nearly

1950 ®@ Rich cove
a a Red spruce-Fraser fir
1850 5 . a eo hasdecod
° ‘ & Fraser fir
=> 1750 2 2 8
E 1650 a
3S Le °
§ 1550 ;
Boiasof °° .
1350 “8 + 8
Exposed = ; j ; j ; wr Sheltered
1250

0.00 0.05 0.10 0.15

0.20 0.25 0.30 0.35 0.40

Landform index

Figure 2—Distribution of study plots coded by ecological type along elevation and landform index gradients in the Balsam

Mountains of western North Carolina.



Potential users of these models in geographic areas other
than the Balsam Mountains should conduct on-site analyses
of relationships between vegetation and topography before
relying on our model predictions for management decisions.
For example, similar vegetative communities of the Balsam
Mountains occur also in the Black Mountains, about 80 km
northeast of our study area (Braun 1950, Davis 1930, Dull
and others1988, McLeod, 1988). However, similar climatic,
geologic, and edaphic conditions with different disturbance
regimes in the Black Mountains could combine to produce
significantly different environmental relationships for some
ecological types, especially red spruce (Sullivan and others
1980). Additional study would determine the area over which
our discriminant functions are applicable.

Potential Applications

Predicting Potential Habitat for the Carolina Northern
Flying Squirrel

A current study of Carolina northern flying squirrel (CNFS)
populations in the Southern Appalachians offers an
opportunity to test the utility of our approach in predicting
the extent of potential habitat for this species. The CNFS, a
federally listed endangered species, occupies high-elevation
northern hardwood and mixed conifer-hardwood forests in
the Southern Appalachian Mountains (Weig! 1990, Weigl
and others 1999) and is known to occur at several sites in the
study area (see footnote 2) and region (Cantrell 1997). The
CNFS appears to be restricted to relict islands of high-
elevation forest that were more widely distributed during the
Pleistocene. The Recovery Plan for the CNFS outlines a
number of research questions and management issues
regarding conservation of the species that need to be
addressed (U.S. Department of the Interior, Fish and Wildlife
Service 1990). These questions and issues include the lack
of good information about the spatial distribution of
potential habitat.

Squirrels have been found most often in forests above 1500
m with an overstory of northern hardwoods, red spruce, and
Fraser fir. However, they have also been captured in mixed
hardwood-hemlock forests on northerly aspects or in coves.
This species does not commonly occur in forests dominated
by mast-bearing species, such as northern red oak, or in pure
stands of spruce-fir. Weigl and others (1999, pp. 52-53) point
out that while the composition and structure of the
vegetation among CNFS sites can be variable, these sites are
usually characterized by cool, moist conditions and high soil
organic matter. Can these conditions be defined by
topographic variables and delineated using terrain-based
modeling?

Results from the Balsam Mountains ecological classification
study were used to assess potential CNFS habitat in the
Balsam Mountain study area and at a site in the Nantahala

Mountains where similar classification work has been done
(McNab and Browning 1993). In the Balsams, the map of
predicted ecological types was used to select 22 locations
for placement of 330 CNFS nest boxes in 1995. Half of the
sites were in areas predicted to be suitable (i.e., northern
hardwood-spruce ecotone). The boxes were monitored for
squirrel activity for 4 years. Complete results have not been
published, but preliminary indications are that CNFS were
found more often in areas predicted as northern hardwoods
by the Balsam Mountain model (see footnote 2).

The'Wine Spring Creek (WSC) watershed is located
apptoximately 70 km west of the Balsam Mountains study
site (fig. 1), and although elevations are somewhat lower,
topographic conditions and ecological types in the WSC
area were found to be similar to those in the Balsam
Mountains.’ Fraser fir and red spruce-Fraser fir ecological
types do not occur in the WSC area; however, northern
hardwood-hemlock, high-elevation red oak, and cove types
do occur in areas with topographic conditions similar to
those in the Balsam Mountains (table 4). Northern hardwood
forests occurred on steep, somewhat concave, and north-
facing slopes in both areas; and the presence of hemlock
was confirmed in the WSC drainage by examination of color-
infrared aerial photos and field observations. Although
CNFS have not been found in the WSC watershed (extensive
surveys have not been done), the distribution of ecological
types in the WSC area appears to represent a disjunct
continuum of those in the Balsam Mountains and may
represent potential habitat for CNFS. The Unicoi Mountains,
40 kn west of WSC, are a similar area of disjunct habitat
(without the red spruce-Fraser fir type) where the CNFS has
been found recently (Cantrell 1997).

Predicting the distribution of ecological types known to
support CNFS populations may or may not provide
important insights into what habitat components are critical
to their survival. For example, a large part of the diet of CNFS
includes lichens and sporocarps of mycorrhizal fungi (Weigl
and others 1999), which may be associated with the spruce-
fir ecological type (Maser and others 1978). However, if the
species composition and topographic setting of forest
communities that support squirrel populations do reflect
other important habitat conditions such as food abundance,
then an ecological type classification based on easily
derived topographic data may be a good starting point for
delineating potential habitat for this and other endangered
species,

3 Odom, R.H. 1996. Application of an ecological landscape
classification model for the identification of Carolina northern flying
squirrel (Glaucomys sabrinus coloratus) habitat in the Wine Spring
Creek watershed, Nantahala National Forest, North Carolina, U.S.A.
6 p. Unpublished final report on file with: Southern Research Station,
Bent Creek Experimental Forest, 1577 Brevard Road, Asheville, NC
28806.



United States

Department of
Agriculture

Forest Service

Using Digital Terrain Modeling
to Predict Ecological Types in the

Balsam Mountains of Western
North Carolina

Southern
Research Station

Research Note
SRS-8

Richard H. Odom, Jr., and W. Henry McNab!

July 2000

Abstract

Relationships between overstory composition and topographic
conditions were studied in high-elevation (> 1300 meters) forests in
the Balsam Mountains of western North Carolina to determine
whether models could be developed to predict the occurrence of
vegetative communities in relation to topographic factors. Size and
number of woody species and topographic variables (elevation,
landscape position, surface geometry, slope gradient, aspect) were
measured on 0.10-hectare plots located across a range of mountainous
landforms. Analysis of species density and dominance using
multivariate classification and ordination techniques identified five
ecological types. Multivariate discriminant analysis indicated that
elevation and landscape position were the most important
environmental variables associated with presence of ecological types.
Landscapes in the study area > 1300 meters were classified into
predicted ecological types by applying discriminant functions to
digital terrain models, using a desktop computer-based Geographic
Information System. Accuracy of the classification, evaluated with an
independent data set, indicated 86 percent agreement with model
predictions. This approach may offer a relatively quick method for
analyzing and predicting with limited data the distribution of
important ecological conditions over large areas. To explore potential
applications of this approach, results were applied in the Balsam
Mountains and nearby Nantahala Mountains to predict occurrence of
potential habitat for the endangered Carolina northern flying squirrel
(Glaucomys sabrinus coloratus) and to aid in making decisions about
recovery efforts and field surveys for the species.

Keywords: Carolina northern flying squirrel, discriminant analysis,
Glaucomys sabrinus coloratus, northern hardwoods, potential habitat,
spruce-fir.

Introduction

Forest ecosystems in the Southern Appalachian Mountains
of Eastern North America have long been recognized as
some of the most diverse on the continent (Braun 1950). The

" Odom is a Landscape Ecologist and Manager of Ecological Services,
The Forest Technology Group, 125 Crosscreck Drive, Summerville,
SC 29485; and McNab is a Research Forester, U.S. Department of
Agriculture, Southern Research Station, 1577 Brevard Road, Asheville,
NC 28806.

variable geologic parent materials, complex topography, high

rainfall, and diverse biotic communities of this bioregion
create an array of ecological conditions that have posed

substantial challenges for resource managers since the days

of Schenck and Pinchot. Over the last 50 years, a number of
studies have documented both local- (Day and Monk 1974,
McLeod 1988, Mowbray and Oosting 1968) and landscape-
level (Braun 1950, Davis 1930, Whittaker 1956) relationships
between plant communities and various environmental
gradients that are primarily controlled by topography. In

addition to influencing environmental gradients, such as soil

moisture and atmospheric temperature regimes, topography
has also played a major role in determining the extent and

severity of disturbances, such as drought (Hursh and Haasis

1931) and lightning-caused forest fires (Barden and Woods
1976), in these landscapes. These studies have provided a
basis for understanding the ecological relationships among
vegetation, landform, and soils in the Southern
Appalachians. Using this knowledge, land managers can
apply forest management activities in appropriate ecological
contexts (Barnes and others 1982).

Ecological land classification provides a framework through
which ecological knowledge, such as plant-site
relationships, can be applied at various scales to support
land use planning and forest resource management (Barnes
and others 1982, Driscoll and others 1984, McNab 1996).
However, information needed on soils and vegetation
communities to adequately define and map ecological units
at appropriate scales (e.g,, >1:50,000) isnot available for
many areas in the Southern Appalachians, especially

ecosystems at high elevations. It is at these scales that most

forest management activities occur and where patterns of
biodiversity are often most apparent, e.g., the contrast
between riparian, cove hardwood, and upland communities
along a landform gradient from stream to ridge top.

This paper describes preliminary results of a study that
predicted ecological types (a predictable forest community
with a typical species composition inhabiting sites with a



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Davis, J.H., Jr. 1930. Vegetation of the Black Mountains of North
Carolina: an ecological study. Journal of the Mitchell Society. 45:
291-318.

Day, F.P.; Monk, C.D. 1974. Vegetation pattems on a Southern
Appalachian watershed. Ecology. 55: 1064-1074.

Driscoll, R.S.; Merkel, D.L.; Radloff, D.L. [and others]. 1984.
An ecological land classification framework for the United States.
Misc, Publ. 1439. Washington, DC: U.S. Department of
Agriculture, Forest Service. 36 p.

Dull, C.W.; Ward, J.D.; Brown, H.D. [and others]. 1988.
Evaluation of spruce and fir mortality in the Southern Appalachian
Mountains. Protection Rep. R8-PR. Atlanta, GA: U.S. Department
of Agriculture, Forest Service, Southem Region. 92 p.

Eastman, J.R. 1992. IDRISI 4.0 user’s guide. Worcester, MA: Clark
University, Graduate School of Geography. 178 p.

Ford, W.M.; Odom, R.H.; Hale, P.E.; Chapman, B.R. 2000. Stand
age, stand characteristics and landform effects on understory
herbaceous communities in Southern Appalachian cove-hardwoods.
Biological Conservation. 93: 237-246.

Hill, M.O. 1979a. TWINSPAN: a FORTRAN program for arranging
multivariate data in an ordered two-way table by classification of
individuals and attributes. Ithaca, NY: Cornell University,
Department of Ecology and Systematics. 90 p.

Hill, M.O. 1979b. DECORANA: a FORTRAN program for detrended
correspondence analysis and reciprocal averaging. Ithaca, NY:
Cornell University, Department of Ecology and Systematics. 52 p.

Harsh, C.R.; Haasis, F.W. 1931. Effects of 1925 summer drought
on Southern Appalachian hardwoods. Ecology. 12: 380-386.

Iverson, L.R.; Dale, M.E.; Scott, C.T.; Prasad, A. 1997. A GIS-
derived integrated moisture index to predict forest composition and
productivity of Ohio forests (U.S.A.). Landscape Ecology. 12:
331-348,

Maser, C.; Trappe, J.M.; Nussbaum, R.A. 1978. Fungal-small
mammal interrelationships with emphasis on Oregon coniferous
forests. Ecology. 59: 799-809.

McLeod, D.E. 1988. Vegetation patterns, floristics and
environmental relationships in the Black and Craggy Mountains of
North Carolina. Chapel Hill, NC: University of North Carolina.
222 p. Ph.D. dissertation.

McNab, W.H. 1989. Terrain shape index: quantifying effect of minor
landforms on tree height. Forest Science. 35(1); 91-104.

MeNab, W.B. 1991. Predicting forest type in Bent Creek
Experimental Forest from topographic variables. In: Coleman, $.S.;
Neary, D.G., eds. Proceedings of the sixth biennial southem
silvicultural research conference; 1990 October 30-November 1;
Memphis, TN, Gen. Tech. Rep. SE-70. Asheville, NC: U.S.
Department of Agriculture, Forest Service, Souther Forest
Experiment Station: 496-504. Vol. 1.

MeNab, W.H, 1993. A topographic index to quantify the effect of
mesoscale landform on site productivity. Canadian Journal of
Forest Research, 23: 1100-1107.

MeNab, W.H. 1996, Classification of local- and landscape-scale
ecological types in the Southern Appalachian Mountains.
Environmental Monitoring and Assessment. 39: 215-229.

ee

McNab, W.H.; Browning, S.A. 1993. Preliminary ecological
classification of arborescent communities on the Wine Spring
Creek watershed, Nantahala National Forest. In: Brissette, J.C., ed.
Proceedings of the seventh biennial southern silvicultural research
conference; 1992 November 17-19; Mobile, AL. Gen. Tech. Rep.
SO-93. New Orleans, LA: U.S. Department of Agriculture, Forest
Service, Southern Forest Experiment Station: 213-221.

Mowbray, T.B.; Oosting, H.J. 1968. Vegetation gradients in relation
to enivironment and phenology in a southem Blue Ridge gorge.
Ecological Monographs. 38: 309-344.

Odom, R.H. 1996. Developing a forest land classification system
from/ digital elevation models. In: Arthaud, G.J.; Hubbard, W.C., eds.
SoForGIS ’96: Proceedings of the southern forestry geographic
information systems conference; 1996 December 11-13; Athens,
GA. ‘Athens, GA: University of Georgia: 212-220.

Odom, R.H. 1998, Developing a forest land classification system
digital elevation models: methodology, evaluation and
application. In: Whiffen, H. J-H; Hubbard, W.C., eds. SoForGIS '98:
Proceedings of the second southem forestry geographic
information systems conference; 1998 October 27-29; Athens,
GA. Athens, GA: University of Georgia: 93-102.

Schafale, M.P.; Weakley, A.S. 1990. Classification of the natural
communities of North Carolina: third approximation. Raleigh, NC:
North Carolina Natural Heritage Program. 325 p.

Sullivan, J.H.; Pittillo, J.D.; Smathers, G.A. 1980. Dispersal and
establishment of red spruce and Fraser fir in three bald areas of the
Southern Appalachians. Res/Resour. Mgmt. Rep. 41. Atlanta, GA:
U.S. Department of Interior, National Park Service, Southeast
Regional Office, Natural Science and Research Division. 49 p.

U.S. Department of Agriculture, Natural Resources
Conservation Service. 1997. Soil survey of Haywood County
area, North Carolina, Washington, DC: U.S. Department of
Agriculture, Natural Resources Conservation Service. 276 p.

U.S. Department of Interior, Fish and Wildlife Service. 1990.
Appalachian northern flying squirrels (Glaucomys sabrinus
coloratus and Glaucomys sabrinus fustus) recovery plan, Newton
Comer, MA: U.S. Department of Interior, Fish and Wildlife
Service, 53 p.

Weigl, P.D. 1990. Fly by night refugees. Wildlife in North Carolina.
54: 22-27.

Weigl, P.D.; Knowles, T.W.; Boynton, A.C. 1999. The distribution
and ecology of the northern flying squirrel, Glaucomys sabrinus
coloratus, in the Southem Appalachians. Raleigh, NC: North
Carolina Wildlife Resources Commission. 93 p.

White P.S.; Buckner, E.R.; Pittillo, J.D.; Cogbill, C.V. 1993.
High-elevation forests: spruce-fir forests, northern hardwoods
forests, and associated communities. In: Martin, W.H.; Boyce, S.G.;
Echternacht, A.C., eds. Biodiversity of the Southeastern United
States: upland terrestrial communities. New York: John Wiley &
Sons: 305-337.

Whittaker, R. H. 1956. Vegetation of the Great Smoky Mountains.
Ecological Monographs. 26(1): 1-80.

Wilds, S.P, 1997. Gradient analysis of the distribution of a fungal
disease of Cornus florida in the Southern Appalachians, Tennessee.
Journal of Vegetation Science. 8: 811-818.

Zar, J.H. 1996, Biostatistical analysis. Upper Saddle River, NJ:
Prentice Hall, Inc. 662 p.

U.S. GOVERNMENT PRINTING OFFICE: 2000-565-019/00031 11



bis
ECOLOGICAL TYPE

om} UNCLASSIFIED

I FRASER FIR

RED SPRUCE-FRASER FIR
GH ELEVATION RED OAK
IM NORTHERN HARDWOOD
Wl RicH cove

(NMJ BLUE RIDGE PARKWAY,

Figure 3—Map of predicted ecological types resulting from implementation of multivariate discriminant models in a geographic
information system for the Sam Knob, NC 7.5° topographic quadrangle.



being part ofa ridge (LFI<0.15), slope (LFI 0.15 to 0.25) or
cove (LFI > 0.25) landform and can be viewed as an indicator
of exposure to solar radiation, wind, and other biological and
meteorological factors. Terrain shape index and LF] are
determined by algebraically averaging slope readings taken
from the center of a plot to the edge of the plot and to the
horizon, respectively.

Data Analysis

Vegetation and topographic data were analyzed using a
series of multivariate techniques. An average importance
value (AIV) of each species was calculated for each plot:

AIV = (relative density + relative dominance) /2,
where

relative density = (number of individuals of species / total
number of individuals) x 100 and
relative dominance = (dominance of a species / dominance of

all species) x 100,

where

dominance = mean basal area per tree x the number of trees
of the species or all species.

Individual plots were classified into groups of similar
vegetation using Two-Way Indicator Species Analysis
(TWINSPAN), a widely used computer program that
objectively forms clusters of plots based on similar species
composition and abundance (Hill 1979a). Detrended
Correspondence Analysis (DECORANA) (Hill 1979b) was
used for indirect gradient analysis of species and plots to
gain insight into their relationship with major environmental
gradients and for objective grouping into ecological types.
Ecological types, defined as recurring groups of species and
their physical environment, were identified based on the
classification and ordination analysis, and named based on
descriptions of vegetative communities (Schafale and
Weakley 1990). Multivariate discriminant analysis was then
used to develop a prediction model for each ecological type
based on the topographic variables measured at each plot
(McNab 1991).

AGIS (IDRISITM, Eastman 1992) was used to apply
topographic-vegetation relationships to produce a map of
predicted ecological types. Digital elevation models
(DEM’s), corresponding to the Sam Knob and Shining Rock,
NC7.5' U.S. Geological Survey topographic quadrangles,
were used to create digital maps of elevation, landform index,
terrain shape index, slope gradient, and aspect. These maps
hada resolution (pixel size) of 30 by 30 m or 0.09 ha. Using
algorithms in IDRISITM, the predictive relationship derived
from the discriminant analysis for each ecological type was
applied to each pixel on the two DEM’s. Pixels were
classified and assigned color values based on the highest

probability of dominance by one of the predicted ecological
types.

Classification Validation

Accuracy of the classification was evaluated by the junior
author, who was not involved in field plot location or
collection of the analysis data used for model development.
A validation data set was obtained from the Parkway, which
provided a 23-km linear transect through the study area.
Designated overlook parking areas along the Parkway were
considered as randomly situated sample points. A sample
site beyond the disturbed road right-of-way along the
Parkway was randomly located from each sample point.
Based on experience of the observer, the predominant
vegetation observed at each sample site was visually
classified into one of the ecological types identified from the
analysis data. Geographical coordinates of the validation
sample sites were determined with a global position system
receiver capable of 2- to 5-m accuracy. Coordinates of the
validation sites were entered in the GIS to determine (1) the
point (pixel) in the digital version of the classified landscape
at which the field validation site was situated, and (2) its
predicted ecological type. The G statistic was calculated for
the log-likelihood ratio goodness of fit (Zar 1996) to test the
null hypothesis of no significant differences among ratios of
observed and predicted ecological types at the p= 0.05 level
of probability.

Results and Discussion

Ecological Types

Five ecological types were identified for the Balsam.
Mountains study area: Fraser fir forest, red spruce-Fraser fir
forest, northern hardwood forest, high-elevation red oak
forest, and rich cove forest. A few species were common,
although not equal in importance, to all five ecological types.
Those species occurring on more than 45 percent of the
plots within a type were considered ubiquitous and included
red spruce, yellow birch, serviceberry, and American beech
(table 1). Species occurring on less than 45 percent of the
plots within a type were classified as restricted and were
important in separating one type from another. Species such
as Fraser fir, fire cherry, mountain ash, and mountain maple
are well-known associates of high-elevation forests in the
Southern Appalachians but were not found on sites
dominated by northern red oak or in cove forests. Northern
red oak was clearly the indicator species for drier portions of
the study area; these sites were the only ones where this
species dominated the overstory. Typical cove species, such
as eastern hemlock, sugar maple, cucumber tree, and
silverbell, defined the rich cove type, although red spruce
and yellow birch were also very common. Most rich cove
plots were located at the heads of coves or in gaps at
relatively high elevations (mean elevation 1301 m) and
lacked species such as yellow poplar (Liriodendron



by the 1930’s. Over the last 30 years, the balsam wooly

adel gid (Adelges piceae) has severely impacted all Fraser fir
[Abies fraseri (Pursh) Poir.] stands in the Balsam Mountains
(ull and others 1988). With the exception of the Shining
Rock area, specific ecological impacts of early logging,
settlement, and other disturbances are mostly
undocumented in the Balsams. Most of the area is currently
covered in closed forests from 50 to over 130 years of age.

Fraser fir forests once occupied the highest elevations in the
Balsams, generally above 1 800 m. Many of these stands are
now composed primarily of standing dead trees and snags
as the result of balsam wooly adelgid infestations. Dense
thickets of blackberry (Rubus allegheniensis Porter) or
thododendron (Rhododendron catawbiense Michx.) often
dominate the understory in heavily impacted stands; fir
regeneration and a variety of shrub species are common.
where stands are more intact. Exposed knobs and ridges
between 1 600 and 1 800 m are occupied by mixed red spruce
(Picea rubens Sarg.)-Fraser fir forests, often interspersed
with hardwood species on slightly lower or more sheltered
landforms. Older spruce stands on relatively exposed sites
have a very open understory with little vertical structure,
while those on more mesic sites contain dense spruce and fir
regeneration as well as a higher diversity of shrub and
herbaceous species. High-elevation northern red oak
(Quercus rubra L.) forests dominate exposed landforms and
south-facing slopes between 1200 and 1600 m, with
American beech (Fagus grandifolia Ehrh.) as acommon.
associate. Individual trees are often open and poorly formed
in comparison to northern red oak on cove sites at lower
elevations. Understories are generally open with relatively
low species diversity. The sedge Carex pensylvanica Lam. is
common ground cover. Northern hardwood forests
dominated by yellow birch (Betula allegheniensis Britt.),
American beech, sugar maple (Acer saccharum Marsh.), and
yellow buckeye (Aesculus octandra Marsh.) occur on
concave landforms and on north-facing slopes between
1300 and 1 600 m. Serviceberry (Amelanchier laevis Wieg.) is
very common in the midstory. Shrub and small tree diversity
on mesic sites under spruce-fir and northem hardwood
overstories is often high and characterized by a number of
ericaceous shrubs, mountain ash (Sorbus americana
Marsh.), mountain maple (Acer spicatum Lam.), fire cherry
(Prunus pensylvanica L.f.), serviceberry, yellow birch, and
American beech. Mosses and ferns are the predominant
ground covers, with herbaceous species becoming more
common on concave sites. Cove hardwood communities
occur on lower slope positions and concave landforms
below 1400 m in the Balsam Mountains. Overstories may
contain many of the species listed except Fraser fir and
usually include additional species such as Eastern hemlock
[Tsuga canadensis (L.) Carr.], Carolina silverbell (Halesia
carolina L.), black cherry (P. serotina Ehth.), cucumber

tree (Magnolia acuminata L.), and basswood (Tilia
heterophylla Vent.). Dense thickets of rosebay
thododendron (R. maximum L.) are common in some cove

forests, and herbaceous communities dominate the ground
flora (Schafale and Weakley 1990, White and others 1993).

Annual precipitation at Haywood Gap, within the study area
at an elevation of about 1650 m, averages about 215
centimeters (cm) and is equally distributed throughout the
year. Specific temperature data are not available for the
Balsam Mountains but may be inferred from long-term
average temperatures recorded at Waynesville, NC, which is
situated 10 to 15 km north of the study site at an elevation of
790 m. Annual temperature averages 12.2 °C, ranging from an
average monthly minimum of 1.8 °C in January to an average
monthly maximum of 21.1°C in July. Orographic effects
associated with the higher elevation study site would
probably result in a similar temperature regime with lower
average values.

Elevations in the study area range from 1200 to more than
1900 m, and the topography is rugged and steep. Geologic
formations are composed primarily of pre-Cambrian acid
silicate rocks such as quartzite, biotite gneiss, and mica
schist. Major soil groups include deep (> 100 cm), mesic
Umbric Dystrochrepts in coves to very shallow (<50cm)
frigid Lithic Dystrochrepts on higher ridges and peaks. Typic
Dystrochrepts predominate on side slopes. Soils are
moderately to strongly acidic (pH 5.5 to 6.0) depending on
parent material (U.S. Department of Agriculture, Natural
Resources Conservation Service 1997).

Data Collection

Forty .10-ha circular plots were located throughout the study
area over the range of landforms above 1 300 m. Plots were
located subjectively, but without conscious bias, to sample
the major landform types (e.g., ridges and coves), slope
positions (e.g., upper, middle, and lower slopes), and
aspects. Areas that appeared to be highly or recently
disturbed were not sampled . The following information was
recorded for each plot:

© species and diameter at breast height (d.b.h.) of all
stems > 10cm d.b.h.,

basal area (m? per ha),

visual ecological type,

evidence of past disturbance, e.g., old road beds,
elevation (estimated from 1:24,000 topographic map),
aspect (degrees azimuth),

average maximum slope gradient (percent),

terrain shape index (TSI), and

landform index (LFT).

The latter two parameters have been used extensively by the
authors to characterize meso- and micro-scale landforms in
the Southern and Central Appalachians (Ford and others
2000; McNab 1989, 1993; Odom 1996, 1998). Terrain shape
index quantifies plot surface shape as a continuous variable
and generally ranges from <-0.05 (convex) to>0.05
(concave). Landform index characterizes the plot location as

eoeeevecece

3



common set of environmental conditions) from topographic
attributes derived from digital terrain data. Large-scale digital
terrain data are available for most areas of the United States
and can be used to analyze terrain conditions and
topographically delineate similar landscape units in
mountainous terrain (Blaszezynski 1997, McNab 1991, Odom
1998). Because many environmental gradients and
disturbance patterns in mountainous areas are often
correlated with topography, analysis of digital terrain data in
a Geographic Information System (GIS) may provide an
efficient means of predicting the spatial distribution of
ecological types and other important ecological attributes
(Ford and others 2000; Iverson and others 1997; McNab
1996; Wilds 1997). In this paper we (1) describe the principal
ecological types of high-elevation [> 1 300 meters (m)}
ecosystems in the Balsam Mountains, (2) develop and

test predictive models for the ecological types, and

(3) demonstrate application of the ecological types to predict
potential habitat for the Carolina northem flying squirrel
(Glaucomys sabrinus coloratus), a federally listed
endangered species.

Methods and Analysis
Study Area

The study was conducted in the Balsam Mountains of
western North Carolina approximately 50 kilometers (km)
southwest of Asheville, NC (fig. 1). This mountain range is
one of the larger massifs in western North Carolina with
approximately 28 000 hectares (ha) above 1 300-m elevation.
The Balsams contain large areas of the Pisgah and Nantahala
National Forests, two designated wilderness areas, over 75
km of the Blue Ridge Parkway (Parkway), municipal
watersheds for several communities, and both industrial and
nonindustrial private forests. Portions of the Balsams were
heavily logged in the early 1900’s and some areas, such as,
the Shining Rock-Graveyard Fields area, were severely
disturbed by logging-related fires and subsequent soil
erosion. As in other areas of the Appalachians, the
introduction and spread of chestnut blight [Endothia
(Cryphonectria) parasitica] essentially removed the
American chestnut [Castanea dentata (Marsh.) Borkh.] as a
dominant overstory species in mid- to low-elevation forests

Figure 1—Location of Balsam Mountains (BM) and Wine Spring Creek (WSC) study areas (outlined in black) in the Southern
Appalachian Mountains of western North Carolina.