**Characterization of Plant Community**

**Structure and Abiotic Conditions on**

**Climbed and Unclimbed Cliff Faces in the**

**Obed River Gorge**

**Gary Walker, Ph.D., Department of Biology, Appalachian State
University**

**Emily Parisher, M.S. Candidate, Department of Biology, Appalachian
State University**

**Peter Smith, M.S., Department of Biology, Appalachian State
University, North Carolina Natural Heritage Program**

**David Whitlock, B.S., Department of Geography and Planning,
Appalachian State University, Earth Satellite Corporation**

**David Kramar, B.S., Department of Geography and Planning, Appalachian
State University; M.S., Department of Geography, Virginia Tech**

**Uta Matthes, Ph.D., Department of Botany, University of Guelph**

**Leslie Morefield, B.S. Candidate, Department of Biology, Appalachian
State University**

**Technical support provided by:**

**Keith Bowman**

**William Farrell**

**Lara Souza**

**Josh Bixley**

**Karen Ritchie**

**Justin Wynns**

**Abstract:**

Many rare or endemic species have been found on cliff faces around the
world, but most of the world's cliff ecosystems remain unexplored by
biologists and little is known about ecosystem processes on cliffs.
There is a growing concern however, that biodiversity on cliffs may be
threatened by impacts from recreational rock climbing. Several recent
studies have validated this concern. The Obed River Gorge in Tennessee
boasts one of the richest floras in the southeastern United States and
is also a popular rock climbing destination. Vascular plants,
bryophytes, and lichens were sampled on cliff faces, cliff edges and on
talus slopes along sixteen climbed and sixteen unclimbed transects in
six different cliff areas of the Obed River Gorge and its tributary,
Clear Creek. Cliff-face flora was sampled from pairs of 1m^2^ plots
located at three-meter intervals along the transect. Unclimbed transects
were paired with and adjacent to climbed transects. Abiotic factors
including aspect, slope, surface heterogeneity, and light were measured
for each pair of plots. Canonical Correspondence Analysis (CCA) was
performed to determine the relative importance of each of these abiotic
factors, as well as the impact of rock climbing, in shaping the
cliff-face plant communities of the Obed River cliffs. Results indicate
some impacts of foot traffic in the talus slopes of climbed areas on
vascular and non-vascular species. Habitat and site were the most
important variables accounting for variation in the vegetation. In
addition, preliminary sectioning of a *Juniperus virginiana* snag in the
talus slopes yielded eight-hundred annual rings.

**Statement of Problem**:

Recent research done by the Cliff Face Ecology Research Group at the
University of Guelph, Canada and at Appalachian State University (ASU),
North Carolina, has demonstrated that cliff-face plant communities
represent ancient forests, with trees dated in excess of 1000 years of
age (Larson et al. 1999) (Larson et al. 2000). New species of lichens
have been discovered on cliff faces in Canada and North Carolina and the
plants on cliff-faces in the Southern Appalachians have been found to
represent glacial relict species from the last ice age (Walker 1987).
Additionally, these relict plants have also been determined to contain
levels of genetic variation far in excess of those in their main range,
potentially representing a genetic reservoir in interglacial periods
(Walker 1987).

Horizontal rock outcrop plant communities have been the subject of
investigation for many decades, and have been found to contain a wealth
of rare, endemic plant species. While ecologists have devoted much
attention to these communities, vertical cliff faces have been largely
ignored due to their inaccessibility and the idea that cliff faces
represent geological features, not biological habitats (Larson 2000).

With rock climbing as an increasingly popular sport, vegetational
surveys for areas heavily impacted by rock climbing, such as the Obed
River Gorge, are crucial for sound management practices. As we discover
new species on cliff faces, realize that cliff-face forests may
represent the remnants of old-growth forests undisturbed by fire and
humans for thousands of years, and see cliff-face communities as genetic
and species refugia since the last ice age, their study and protection
becomes of immediate concern to both scientists, land managers, and
environmentally concerned members of the rock-climbing community.
Collaborative research by cliff-face researchers at the University of
Guelph, Department of Botany, and Appalachian State University,
Department of Biology, have developed consistent techniques to answer
questions regarding community composition and to measure the impact of
human disturbance in cliff-face systems (Larson et al. 2000) (Smith
1999). By working with local rock-climbing groups and management
agencies, cliff-face ecologists have been able to develop strategies
that serve both public access to climbing areas as well as protecting
the fragile and rare cliff-face ecological communities.

**Background Information:**

Recognized for its free-flowing condition, rugged terrain, and pristine
waters, the Obed River was included into the Wild and Scenic Rivers
System in 1976 and established as a unit of the National Park Service.
The Obed is one of only nine Wild and Scenic Rivers authorized in the
Southeastern United States. The Obed River flows over 45 miles through
some of the most rugged, and undeveloped terrain in eastern Tennessee.
It offers a vast array of both cultural and natural resources. A complex
network of streams drain park and adjacent lands supporting diverse
flora and fauna as well as providing numerous recreational
opportunities.

Limited studies of the vegetative communities in the Obed have been
completed. In 1982, Paul Schmalzer completed the Final Report -
Vegetation, Endangered and Threatened Plants, Critical Plant Habitats
and Vascular Flora of the Obed Wild and Scenic River (Schmalzer et al.
1985), (Schmalzer. 1988), Schmalzer. 1989). This study covered the
entire park and did not specifically address cliff-face ecology.
Recently a short study of the cliff face and cliff base area was
completed. This study revealed that numerous bryophytes are found along
the cliff face and cliff base. A large number of these have not been
reported in other areas of the Cumberland Plateau (Risk, 1998). A new
species of lichen, *Canoparmelia amablilis* was discovered in 1999.
*Canoparmelia amablilis* was discovered within the climbing area and at
this time due to its recent discovery it is the only known location of
this lichen (Heiman 1999).

Several old growth trees have been discovered within the climbing area.
In 1999, four red cedars (*Juniperus virginiana*) were cored to
determine age. These trees ranged in age from 287 years to 381 years.
Several other trees that had been cut at the base of several climbs were
studied, their ages ranged from 150 to 200 years old (Heiman 1999). In
light of this information, the National Park Service determined that an
in-depth study of the vegetation on the cliff face, cliff base and cliff
edges was necessary to assist in managing climbing within Obed Wild and
Scenic River.

**Cliff-face ecological investigations:**

Research on cliff-face plant and lichen communities in Linville Gorge
Wilderness Area in Western North Carolina, conducted by researchers from
ASU, demonstrated that cliff-face vegetational communities are
significantly different in species composition from those on rock
outcrops (Smith 1999). Further, a significant difference in species
composition between the upper and lower reaches of cliff faces, with
shifts in community composition along this gradient was shown to occur.
The implications of these findings are that cliff-face vegetation
represent a community type previously undescribed quantitatively in the
plant ecological literature. They also represent very complex spatial
associations that have been suggested in British literature but
previously undescribed in North America.

Lichens are symbiotic organisms with components consisting of fungi
associated with algae or cyanobacteria. They are important colonizers of
bare rock and often the initiators of primary succession in such
habitats. Since lichens are an important component of cliff-face and
rock-outcrop vegetational assemblages it is crucial that they are
included in such surveys. In a comparison of climbed and unclimbed cliff
faces in Linville Gorge, as expected, there was a significant difference
between disturbed and undisturbed cliff faces in lichen and plant
community composition. Unexpected was the finding that as disturbance
from climbing apparently removes some groups of lichens and plants, one
group, the crustose lichens, actually increase in abundance following
such disturbances, likely resulting from competitive release from
species that would otherwise shade them out. A new species of lichen was
discovered and is being described in this same study (Smith 1999).
Similar results have been reported from the Niagra Escarpment cliff
faces in Ontario, Canada, (Larson 2000).

**Physical Features:**

**Geomorphology of Cumberland Plateau:**

The Cumberland Plateau is a physiographic province of the Southern
Appalachians east of the eastern Highland Rim and west of the Ridge and
Valley Provinces. It is a broad upland that extends northeast from its
Tennessee portion across Kentucky and into West Virginia and
Pennsylvania where it is known as the Allegheny Plateau, and to the
southwest into Alabama. The Cumberland Plateau of Tennessee is the
southern extension of the Appalachian Plateaus Province (Fenneman 1938).
In Tennessee it is recognized as a true tableland, with gently sloping
uplands throughout most of its extent. It its Tennessee portion it
averages 35 to 40 miles in breadth with upland elevations from 1500 feet
near Kentucky to nearly 2000 feet in the south. The two large river
systems of the Plateau are the Clear Fork-Big South Fork and the
Obed-Emory, both with similar morphologies. Unlike many stream channels
these systems flow in shallow gorges in their upper reaches and are
increasingly entrenched downstream. At the lower ends these rivers cut
300 to 400 feet below the surface of the Plateau. Much of this vertical
depth is accounted for by bluffs, making up to 100 feet of the basin
depth. While the larger tributaries join the stream at grade, the
smaller ones often enter as waterfalls and seeps (Mayfield 1984) The
bluffs of these two river systems are attractive as rock climbing
destinations, particularly in the Obed-Emory basin.

**Geology of the Emory basin:**

Because the rock strata of the Cumberland Plateau dip northeastward
while its surface elevations are generally constant, the older
Mississippian limestone rock units are exposed in the valley walls of
entrenched streams of these areas. In the Emory basin the lithology
consists of mainly near-horizontal sedimentary strata of Pennsylvanian
age with alternate layers of sandstone, siltstone, and shale composing
the bed rock. The Rockcastle Sandstone-Conglomerate is the most commonly
exposed outcrop at the surface while older shales and sandstones are
exposed in the cliff faces of the gorges. This conglomerate has a very
low intergranular permeability that is somewhat enhanced by fractures in
the unit (Newcombe and Smith 1958). Springs are commonly formed where
sandstone layers contact shale beds (Newcombe and Smith 1958).

**Hydrology of the Obed basin:**

It has been established that the streamflow of the Obed basin is able to
move water rapidly through shallow but highly permeable soils with
runoff ocurring over a short period of time (Mayfield 1979). This
results in a streamflow regime that consists of great extremes which is
anomalous when compared to other watersheds in the Cumberland Plateau.
Although the watershed of the Obed has low drainage density, gentle to
moderate slopes, heavy forest cover, permeable soils and less intense
rainfall than other watersheds that are found in its vicinity, the
impermeable bedrock and shallow soils of the basin provide minimal
storage, thus water exits the watershed rapidly as stream flow.

**Soils of the Obed-Emory basin:**

The natural fertility of the Cumberland Plateau soils is low, ranging
from 2-4 feet deep, well-drained, loamy, and relatively acidic (Springer
and Elder 1980). Most of these soils are formed from sandstone and shale
parent material on gentle slopes and are the most favorable soils of the
Plateau for agricultural use (Springer and Elder 1980). The steeper
slopes, such as those in the Obed-Emory basin range from deep, stony
colluvium, to rocky, shallow soils. Permeability is moderately rapid to
rapid (Springer and Elder 1980). Most of the soils in the Obed basin are
Ultisols and Inceptisols (Hubbard et al 1950, USDA Soil Conservation
Service 1978).

**Climate of the Obed-Emory Basin:**

The Obed River climate is humid and mesothermal (Thornthwaite 1948).
Because of the higher elevations of the Cumberland Plateau relative to
adjacent physiographic regions in its Tennessee portion, it experiences
relatively lower temperatures and higher amounts of precipitation. This
results in a greater water surplus. For example, in Crossville, the
surplus is 25 inches of water, while in Knoxville the surplus is 17.7
inches. Most of the precipitation for the Plateau comes in winter with
the fall being quite a bit drier. Total precipitation varies from about
52 inches to 61 inches (Mayfield 1984).

**Biotic features**, **Vascular Plants**:

**Previous investigations:**

The areas within the southern extent of the Cumberland Plateau of
Tennessee has been the subject of several floristic studies including
Fall Creek Falls State Park (Caplenor 1955, Shaw 2002, Bowman 2003),
Fiery Gizzard gorge (Clark 1966), Savage Gulf Natural Area (Wofford et
al, 1979), Frozen Head State Natural Area (Holtzclaw 1977), and several
areas in the Upper Cumberland River Basin (Patrick 1979). Within the
Obed River gorge Schmalzer (1985), reported 734 taxa within 393 genera
and 122 families. 102 of these taxa were within the largest represented
family, the Asteraceae, with 82 taxa in the Poaceae, the next best
represented family. Schmalzer (1985) also reported fifty-nine introduced
taxa that made up 8 percent of his total species list. Sixteen of
Schmaltzer's (1985) taxa were listed on the Tennessee list of rare
plants (Tennessee Natural Heritage Program 1982) or have been proposed
for Federal listing (U.S. Dept. of the Interior 1980). One species of
grass collected, *Sporobolus junceus*, was a state record for Tennessee
(Patrick et al. 1983). Among those species listed as of special concern
or threatened in the Schmalzer study are included *Adlumia fungosa*,
Allegheny vine or climbing fumitory, from a single population in a
boulder field on a south-facing slope along the lower Obed River,
*Polymnia laevigata*, (now also known by the synonym *Smallanthus
uvedalius*), hairy leafcup, from a single population among sandstone
boulders on a south-facing slope along the lower Obed River, and
*Talinum teretifolium*, quill fame flower, from a sandstone outcrop
above Clear Creek. The relevance of the presence of these species for
the present study is that they are in areas that could potentially
impacted by rock climbing activities.

**Species of special concern or threatened:**

![](media/image1.png){width="1.6423611111111112in"
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**Community types:**

Habitat types listed by Schmaltzer (1985) that are pertinent to the
present study are Xeric upland oak or oak-pine forests, Sandstone cliffs
and rockhouses, Sandstone boulder fields, Wet sandstone or shale cliffs
and Sandstone outcrops. The community descriptions below are directly
taken or paraphrased from Schamaltzer (1985).

Xeric upland oak or oak-pine forests are dominated by *Quercus alba, Q.
prinus*, and *Pinus stobus* with *Carya* spp. and other taxa occurring
on middle to upper slopes. Typical herbs include *Geranium maculatum*,
*Solidago caesia*, *Bromus pubescens*, and *Agrostis perennans*.

Sandstone cliffs and rockhouses form unique plant habitats. Plants
restricted to these sites include *Heuchera parviflora* and *Silene
rotundifolia*.

Sandstone boulder fields in certain areas are extensive and have
developed on gorge slopes. When these are on south-facing slopes, the
canopy vegetation is composed of *Quercus prinus* and *Q. alba*.
Herbaceous plants restricted to these sites include *Adlumia fungosa*
and *Polymnia laevigata* (now known under the synonym *Smallanthus
uvedalius*).

Wet sandstone or shale cliffs are kept moist by seepage and form a
habitat distinct from the more common dry sandstone cliffs. Plants
restricted to these sites include *Thalictrum clavatum* and *Cystoperis
protrusa*.

Sandstone outcrops occur where exposed sandstone bedrock occurs near
some cliff-edges. Deeper pockets of soil on the outcrop support dwarf
*Pinus virginiana*, shrubs (e.g., *Gaylussacia baccata, Kalmia
latifolia, Sorbus arbutifollia*), grasses (e.g., *Chasmanthium laxum,
Danthonia compressa, D. sericea*), and forbs (e.g., *Liatris
microcephala*). Shallow pockets of soil support the outcrop plants,
*Arenaria glabra* and *Talinum teretifolium*. Vegetation of Cumberland
Plateau sandstone outcrops has been considered in detail by Perkins
(1981).

**Species of special interest:**

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**Cliff-face ecology**

**Definition of Cliff Faces**:

While there is no critical angle that delineates cliff faces from other
topographical features climbers often describe a face as a surface
needing at least three points of contact for a human to stabilize
themselves. Slope angles of cliffs may range from the 180^o^ surface of
an underhang to vertical 90^o^ are all considered cliff features. Slopes
less than 90^o^ are usually not considered cliffs (Larson 2000).

**Physical features**

The various units of a cliff area are referred to as the plateau, cliff
face, and talus. In this study we will refer to the plateau as cliff
edge. Soils are thin to absent. Rooting space for plants in limited.
Cliff faces are buffered from direct insolation, talus is usually more
shaded and cliff edge may be open or under canopy.

**Flora**

Cliff face vegetation has been insulated from human impact and natural
and anthropogenic fires through the course of most of human history. The
vegetation may often be composed of elements of surrounding plant
communities but may also consist of glacial relicts and species
otherwise impacted by humans and domesticated animals on the rest of the
landscape. Certain species reoccur on cliff faces throughout the
temperate zone, regardless of hemisphere, especially ferns, lichens and
mosses. For example several species of *Asplenium* are found on cliff
faces both in North America and in Europe. Likewise *Pellaea* and
*Polypodium* ferns are frequently found on cliffs. Oaks and a variety of
conifers such as *Juniperus, Thuja, Taxus* and *Pinus* reoccur on
temperate cliff faces.

**Ancient trees**

What have been described as old-growth forests or ancient stands of
trees have been found on cliff faces throughout the temperate region
(Larson and Kelly 1991, Larson et al. 2000). Trees in excess of a
thousand years in age have been found in several cliff faces throughout
the world.

**Fauna**

Cliff faces serve as roosts for many species of birds. There have been
relatively few studies done on fauna, other than birds, on cliff faces.
Microarthropods were examined in leaf litter on the ledges of cliff
faces in Linville Gorge, N.C. (Plezewski, 2003).

**Human Impacts on Cliff Faces:**

Until recently cliff faces have been relatively unimpacted by humans
other than for mining operations. But in the past few decades rock
climbing has become a popular sport throughout the western world. A few
studies have been conducted on the impacts of cliff-face vegetation by
climbers (McMillan, 2000, Smith P. 1998, Camp, R.J. and Knight, R.L.
1998, Larson, D.W. and Kelly, P.E. 1997, Nuzzo, V.A. 1995). In each
study climbing has been described as having a detrimental effect on
cliff-face vegetation to varying extents. Disturbance has included a
reduction of vegetational cover, shifts in lichen community composition,
the local extirpation of species sensitive to disturbance and skewed
size and age distributions of some vascular plants. Few of these studies
has considered the impact of the physical environment on species
composition. Nuzzo, V.A. (1995) was criticized for not considering the
impact of overhangs on cliff face vegetation with regard to rock
climbing disturbance (Larson, D.W. 2000).

**Methods and Materials**

**Site Descriptions**

Within the Obed National Wild and Scenic River, six major climbing areas
were sampled. These include the Lilly Bluffs, the Lilly Boulders, North
Clear Creek, South Clear Creek, the Obed Wall, and the Y12 Wall. These
areas are located along the Obed River and Clear Creek.

The Lilly Bluffs climbing area, located on the south side of Clear Creek
opposite the Lilly Bridge parking area, is a north-east facing cliff
band approximately twenty to thirty meters in height. There are
forty-two bolted sport climbing routes on this cliff band (Watford
1999). The base of the cliff is surrounded by hemlock forest that
includes *Betula lenta*, *Liriodendron tulipifera*, *Rhododendron
maximum*, and others. The plateau above the cliff line is characterized
by hemlock and subxeric oak forests (*Tsuga canadensis, Quercus alba, Q.
prinus, Carya spp.*)

The Lilly Boulders area is situated uphill from the Lilly Bridge, past
the Lilly Bluffs, on the right side of the road. It consists of a long
low band of rock surrounded by numerous boulders, which are scattered
among mesic deciduous and hemlock forest. The tops of these boulders are
covered in thick mats of soil, bryophytes, lichens, and vascular plants.
A network of trails provides access to the boulders.

The North and South Clear Creek climbing areas are located on the
north-east side of Clear Creek, which is accessed via a privately owned
parking area and trailhead off Doc Howard Road. The portion of the cliff
band that is designated North Clear Creek lies north of an obvious oxbow
in the creek, and the portion below the oxbow is designated South Clear.
These cliffs are south or south-west facing and are an average of thirty
meters high. The surrounding forest may be described as xeric upland oak
forest or oak-pine forest, including *Quercus alba*, *Quercus coccinea*,
and *Pinus virginiana* (Schmalzer et al. 1985).

The Y12 Wall is located on the south-west side of Clear Creek, directly
across the creek from the point between the North and South Clear Creek
climbing areas. The Y12 is accessed from the Lilly Bluff overlook
parking area via the Point Trail and rope ladders leading from the
plateau down to the talus. This steep, north-facing section of
cliff-band is perennially shady and moist. This area is characterized by
mesic deciduous forest and hemlock forest.

The Obed Wall climbing area is located in the Obed River gorge on the
north side of the river, just above the confluence of the Obed River and
Clear Creek. It is the most remote of all the areas in the study. This
south-facing cliff-line, which is approximately twenty to thirty meters
tall, is surrounded by xeric oak and oak-pine forests.

**Transect and Quadrat Construction**

A climbing guidebook (Watford 1999) was used to assign numbers to all
the routes in each of the six climbing areas described above, and a
random number table was used to choose three climbing routes from each
site. For each climbed transect chosen, an unclimbed transect was
designated directly adjacent to it and marked with biodegradable lawn
paint. Therefore, three climbed and three unclimbed transects were
chosen for each area, for a total of 36 transects. Due to time
constraints in the fall, we combined North and South Clear Creek, only
sampling four transects (two climbed, two unclimbed) at North Clear and
two (one climbed and one unclimbed) at South Clear. In addition, we were
only able to complete four transects at the Y12 Wall (two climbed and
two unclimbed).

Using the rappel rope as the center line, we sampled from a 1 m² quadrat
on each side of the rope (one plot to the left of the rope and one to
the right of the rope, labeled A and B, respectively), at three meter
intervals along the face of the cliff. Therefore, the number of face
plots sampled per transect varied with the height of the cliffs. The
quadrat was constructed of one-half inch PVC pipe and nylon twine. The
nylon twine was threaded through holes drilled in the pipe so that it
formed a five-by-five grid of subplots within the quadrat, each of which
represented four percent of the area of the quadrat. The talus was
always sampled using two pairs of plots; one pair was located directly
adjacent to the cliff face at the base of the cliff and the second pair
was located between four and five meters away from the cliff base. The
plateau (edge) was sampled in a similar manner, with a pair of plots
located on the edge of the plateau, directly adjacent to the top of the
cliff face, and another pair between four and five meters straight back
from the edge. Each of these were labeled A (left of transect) and B
(right of transect).

**Climbing Equipment**

Sixty meter rock climbing ropes were used in conjunction with climbing
harnesses, grigris, webbing, carabiners, quickdraws, 'frogs', and
helmets to access the cliff faces. In some cases the system was secured
to an anchor on the plateau, such as a large tree, and the cliff face
was accessed by rappelling down from the top. In areas where access to
the plateau was difficult, the system was set up from the talus area. In
these instances an experienced climber climbed the cliff face and either
placed the rope along the climbing route using quickdraws, which were
clipped to the bolts in the rock, or, in the case of an unclimbed
transect, placed traditional climbing protection pieces called cams,
along with quickdraws, as they ascended the cliff. A grigri was used as
a braking system when rappelling down from the tops of the cliffs, and
an ascender (also called a Jumar) was used to move up the rope from the
bases of the cliffs. 'Frogs', a relatively new type of protection used
in traditional climbing, were attached to a two meter pole and used in
areas where the cliff face was overhung in order to pull the researcher
closer in to the face. In addition, an extra rope was secured to an
anchor and attached to the researcher as a safety line. All sampling
equipment was attached to the researcher's climbing harness with
carabiners.

**Sampling Technique**

In each plot, each species present was described and the percent of the
plot that it covered was recorded. Species that covered less than one
percent of the plot were recorded as less than one percent. In addition,
environmental data including aspect, slope, surface heterogeneity of the
rock face, presence or absence of temporary or perennial seeps, presence
or absence of overhanging roofs, relative amount of visibly evident
disturbance (chalk, soil compaction, etc.) and cliff area (edge, face,
or talus) were recorded for each plot.

**Processing of Plant Samples**

All vascular plant, bryophyte, and lichen species that occurred in plots
were collected in the field and placed in a plant press (vascular) or a
paper bag (bryophytes and lichens) in the field. All specimens were
dried in a drying cabinet for at least one week. Plants were identified
using the nomenclature of Wofford (1989) and Radford (1968) and by
consulting specimens in the vascular plant herbarium at Appalachian
State University. Moss and liverwort identification was performed by
Keith Bowman according to the nomenclature of Stotler and
Crandall-Stotler (1977) and Anderson et al. (1990) . Lichen specimens
were identified by Karen Ritchie according to the nomenclature of Kirk
et al. (2004).

**Statistical Analysis**

All data were entered into an excel spreadsheet. Detrended
Correspondence Analysis (DCA) was performed, followed by Canonical
Correspondence Analysis (CCA), by Dr. Uta Matthes, Ph.D., using CANOCO©
statistical software. Analyses were performed on the entire data set as
a whole (referred to as the large data set), on each of the face, edge,
and talus data sets alone, and on each of the six sites separately.

**Ancient Tree Analysis**

Two stands of ancient Eastern red cedar trees (*Juniperus virginiana*
L.) were found in the talus areas of both the North Clear Creek climbing
area and the Obed Wall climbing area. Preliminary sampling of the North
Clear Creek stand consisted of the removal of a section of a large snag
using a small pruning saw. The section was sanded and then the rings
were counted in the field using a 10x hand lens, yielding approximately
eight-hundred annual rings. The snag section was then brought to the
dendrochronology lab at Appalachian State University, Department of
Geography and Planning, and was found to have eight-hundred sixty-three
annual rings. That finding prompted subsequent increment coring of five
different living trees, two from the Obed Wall talus and three from the
North Clear Creek talus. The extracted cores were placed in drinking
straws and brought to the dendrochronology lab at Appalachian State
University, Department of Geography and Planning.

Dendrochronological analysis was performed by Ms. Leslie Morefield. Each
core was mounted in a core tray with wood glue, which was then placed in
a vice for sanding. Cores were sanded down using at least three grades
of sand paper: coarse (320), fine (P400), and extra fine (15µ). Core
samples were then rubbed with natural wool, which leaves a film of
lanolin on the wood, which in turn renders the annual growth rings more
easily distinguishable. Next, the rings were counted by hand using a
National® brand biocular dissecting microscope. Years for each core were
placed in a spreadsheet and especially wide or narrow ring years were
noted. During manual counting, dots were placed on the wood using a
pencil to indicate decade, fifty year, and one-hundred year increments
of annual growth rings. After manual counting, the cores were
cross-dated and their annual growth-rings measured using a dissecting
microscope connected to a computer equipped with Measure J2X © software.
This process involves centering the microscope crosshairs on the edge of
an annual growth ring, pushing a button, and then moving to the next
ring edge and pushing the button again. This allows the computer to
record width, to cross-reference the different trees, and to calculate
the variance between years.

**Results**

**CCA of Large Data Set**

Climbing and disturbance were statistically significant factors
influencing the vegetation in the large data set. However, they were the
second and third least significant variables of those measured.
Disturbance was highest in talus plots, regardless of climbing status.
Habitat, site, and the presence of a roof were also significant
variables organizing the vegetation (Table 1). The presence of a seep
was insignificant. Habitat was the most important variable accounting
for variation in the vegetation, with the edge habitat having the most
unique community assemblage. Site was the next most important variable,
indicating that the vegetation varies between the six sites sampled.

  ------------------------------------- ------------------ --------------
  **Table 1. CCA of Large Data Set**                       

  Variable                              P                  F

  Edge                                  0.002              7.81

  SCC                                   0.002              5.08

  OBE                                   0.002              5.01

  Roof                                  0.002              4.94

  Face                                  0.002              3.80

  LBO                                   0.002              3.19

  LBL                                   0.002              3.57

  NCC                                   0.002              2.67

  Seep                                  0.130              1.40

  Climbing                              0.030              1.31

  Disturbance                           0.002              1.95
  ------------------------------------- ------------------ --------------

**CCA of Face Data Set**

Climbing and disturbance were insignificant for the cliff-face data set
(Table 2). Site, the presence of a roof, vertical position, and the
north-south component of aspect were all statistically significant
variables organizing the cliff-face vegetation. Of the six sites that
were sampled, the South Clear Creek site had the most unique community
assemblage. The east-west component of aspect, the presence of a seep,
slope, and surface heterogeneity were all insignificant for the cliff
faces. Since site differences were the most important factor accounting
for variation in the vegetation on the cliff faces, a second run of the
CCA was performed on the face data set, in which sites were defined as
covariables. This allows us to answer the question, 'Once differences
among sites are accounted for, how much of the remaining variation in
the vegetation can be accounted for by the variables measured?' For the
second run, the north-south component of aspect,

  ------------------------- ------------------------- -------------------
  **Table 2. CCA of Face                              
  Data Set (Run 1)**                                  

  Variable                  P                         F

  SCC                       0.002                     7.99

  Roof                      0.002                     6.29

  OBE                       0.002                     5.71

  Y12                       0.002                     4.39

  Position                  0.002                     4.39

  Northness                 0.002                     3.45

  LBL                       0.002                     3.45

  LBO                       0.002                     2.95
  ------------------------- ------------------------- -------------------

vertical position, the presence of a roof, the east-west component of
aspect, and slope were all significant (Table 3). The presence of a
seep, climbing, disturbance, and surface heterogeneity were all
insignificant. However, it is important to note that the eigenvalues
were much lower for the second run, meaning that once variation among
sites is removed, the remaining variables have relatively less influence
on the vegetation.

**CCA of Face Data Set -- Vascular Plants Only**

Climbing and disturbance were insignificant variables for cliff-face
vascular plants. The north-south and east-west components of aspect were
the most important variables influencing the distribution of vascular
plants on the cliff faces, followed by site differences (Table 4).
Several variables were omitted due to negligible variance. These include
roof, the Lilly Boulders site (LBO), and the North Clear Creek site
(NCC). This is because there were no vascular plants on the cliff faces
beneath roofs, nor on the cliff faces sampled at Lilly Boulders and
North Clear Creek.

  ------------------------------------- ------------------ --------------
  **Table 4. CCA of Face Data Set -                        
  Vascular Plants Only**                                   

  Variable                              P                  F

  Northness                             0.002              2.84

  Eastness                              0.002              2.29

  Slope                                 0.076              2.07

  SCC                                   0.028              1.85

  OBE                                   0.008              1.87

  LBL                                   0.092              1.86

  Disturbance                           0.070              1.78

  Position                              0.132              1.42

  Climbing                              0.366              1.07

  Seep                                  0.446              1.03

  Surfacehet                            0.442              1.06
  ------------------------------------- ------------------ --------------

**CCA of Face Data Set -- Bryophytes Only**

Climbing was not a significant influence on bryophyte distribution on
the cliff faces. Site, both the north-south component and the east-west
component of aspect, disturbance, slope, surface heterogeneity, the
presence of a seep, and vertical position on the face were all
statistically significant variables organizing the bryophyte communities
on the cliff faces (Table 5). The Y12 site had the most unique
assemblage of bryophyte species, followed by the Lilly Boulders site.

  ----------------- -------- ------ ------ ------------- --------- -------------
  **Table 5. CCA of                        **Table 6.              
  Face Data Set -                          CCA of Face             
  Bryophytes Only**                        Data Set -              
                                           Lichens                 
                                           Only**                  

  Variable          P        F             Variable      P         F

  Y12               0.002    6.10          SCC           0.002     15.53

  Northness         0.002    5.60          Roof          0.002     12.65

  LBO               0.002    5.77          OBE           0.002     10.36

  Disturbance       0.004    3.48          Position      0.002     9.69

  OBE               0.018    2.56          Y12           0.002     8.27

  Slope             0.008    2.12          Northness     0.002     5.72

  Surfacehet        0.016    1.96          LBL           0.002     5.53

  LBL               0.044    1.90          LBO           0.002     4.27

  Eastness          0.004    2.86          Slope         0.042     2.11

  Seep              0.002    3.32          Climbing      0.016     2.10

  Position          0.016    1.95          Seep          0.084     1.93

  Climbing          0.358    1.06          Eastness      0.136     1.72

  NCC               0.974    0.26          Disturbance   0.172     1.41

                                           Surfacehet    0.270     1.26
  ----------------- -------- ------ ------ ------------- --------- -------------

**CCA of Face Data Set -- Lichens Only**

Climbing had a statistically significant influence on cliff-face lichens
(Table 6). Disturbance was insignificant. Site, the presence of a roof,
vertical position on the face, and the north-south component of aspect
were all significant variables influencing lichen distribution on the
cliff faces. Slope was marginally significant. The presence of a seep,
the east-west component of aspect, and surface heterogeneity were all
insignificant for cliff-face lichens.

**CCA of Edge Data Set**

Climbing was statistically insignificant for the top edges of the cliffs
sampled (Table 7). Disturbance, however, was a significant factor
accounting for variation in edge vegetation distribution. Site was the
most important variable accounting for differences in edge vegetation,
with the Obed Wall (OBE) site having the most unique species
composition. The presence of a seep was insignificant. Eigenvalues for
this analysis were slightly lower than those for the other data sets,
meaning that less of the variation in edge vegetation can be explained
by the variables measured. A second run of the CCA of edge data was
conducted, with sites defined as covariables. Once variation among sites
was accounted for, disturbance and the presence of a seep were the most
important variables (Table 8). However, since the eigenvalues for the
second run of the CCA were very low, these variables actually have a
minimal influence on the vegetation. Climbing remained insignificant.

  ---------------- ------- ------ --------- --------------- ------- --------
  **Table 7. CCA                            **Table 8. CCA          
  of Edge Data                              of Edge Data            
  Set**                                     Set (Run 2)**           

  Variable         P       F                Variable        P       F

  OBE              0.002   3.08             Disturbance     0.018   1.70

  NCC              0.002   2.85             Seep            0.014   1.31

  LBL              0.002   2.34             Climbing        0.120   1.13

  LBO              0.006   2.32                                     

  Disturbance      0.004   1.70                                     

  Seep             0.144   1.31                                     

  Climbing         0.240   1.13                                     
  ---------------- ------- ------ --------- --------------- ------- --------

**CCA of Talus Data Set**

Disturbance was the second most important variable influencing talus
vegetation (Table 9). Climbing was also significant for the talus,
though it was the least important significant variable measured. Site
was the most important significant variable for the talus. The presence
of a seep was also significant. A second run of the CCA for the talus
was conducted to account for site variation. Once sites were defined as
covariables, the presence of a seep and disturbance were the most
important variables accounting for variation in the talus vegetation
(Table 10). Climbing remained an insignificant influence on talus
vegetation.

  -------------- ------- ------ -------- --------------- ---------- ------ --
  **Table 9. CCA                         **Table 10. CCA                   
  of Talus Data                          of Talus Data                     
  Set**                                  Set (Run 2)**                     

  Variable       P       F               Variable        P          F      

  LBO            0.016   1.98            Seep            0.002      1.67   

  Y12            0.006   1.97            Disturbance     0.010      1.38   

  Disturbance    0.002   1.95            Climbing        0.086      1.31   

  OBE            0.002   1.94                                              

  Seep           0.002   1.91                                              

  LBL            0.002   1.87                                              

  Climbing       0.006   1.59                                              
  -------------- ------- ------ -------- --------------- ---------- ------ --

**CCA of Individual Sites**

Since the vegetation of the Obed cliffs is fairly site specific, we ran
CCA analyses on each of the six sites individually. These analyses were
conducted on the cliff-face data for each site (edge and talus data were
excluded). Both the north-south and east-west components of aspect, as
well as the presence of seeps were excluded from individual site
analyses because they have high variance inflation factors.

**Lilly Bluffs**

Climbing and disturbance were insignificant for the Lilly Bluffs face
data set (Table 11). Slope, the only significant variable for Lilly
Bluffs, was only marginally significant. Vertical position on the cliff
face and surface heterogeneity were both insignificant.

**Lilly Boulders**

Climbing was statistically insignificant for the Lilly Boulders site
(Table 12). Disturbance was the most important significant variable
measured, although the eigenvalues for this analysis were very low. This
is primarily due to low sample size, since there were only a total of
twenty-five face samples for the Lilly Boulders site. Slope was
marginally significant. Vertical position and surface heterogeneity were
insignificant for the Lilly Boulders.

  ---------------- -------- ------ --------- --------------- ------- -------
  **Table 11. CCA                            **Table 12. CCA         
  of LBL Face Data                           of LBO Face             
  Set**                                      Data Set**              

  Variable         P        F                Variable        P       F

  Slope            0.03     2.04             Disturbance     0.036   2.15

  Position         0.144    1.34             Slope           0.048   1.93

  Surfacehet       0.73     0.66             Position        0.506   0.91

  Climbing         0.588    0.84             Surfacehet      0.694   0.70

  Disturbance      0.174    1.43             Climbing        0.786   0.55
  ---------------- -------- ------ --------- --------------- ------- -------

**North Clear Creek**

Both climbing and disturbance were statistically significant for the
North Clear Creek site (Table 13). Although climbing is not included in
the forward selection table for this analysis, it has a 1.0 correlation
with disturbance, meaning these two variables are identical for this
site. Slope is the most important variable accounting for variation in
the vegetation on the cliff faces at North Clear Creek, followed by
disturbance (and climbing). The eigenvalues for the first two axes of
the CCA are high enough for these results to be considered reliable.
Vertical position on the face was also significant for North Clear
Creek. Surface heterogeneity was insignificant.

  -------------- ------- ------ -------- ----------------- -------- ------ --
  **Table 13.                            **Table 14. CCA                   
  CCA of NCC                             of SCC Face Data                  
  Face Data                              Set**                             
  Set**                                                                    

  Variable       P       F               Variable          P        F      

  Slope          0.002   4.40            Surfacehet        0.012    2.70   

  Disturbance    0.004   4.31            Disturbance       0.004    2.53   

  Position       0.002   4.09            Slope             0.03     1.91   

  Surfacehet     0.77    0.54            Postion           0.012    1.91   

                                         Climbing          0.23     1.33   
  -------------- ------- ------ -------- ----------------- -------- ------ --

**South Clear Creek**

Disturbance was the second most important significant variable

organizing the cliff-face vegetation at South Clear Creek (Table 14).
Although climbing was insignificant according to the forward selection
results, it is highly correlated with disturbance. Surface heterogeneity
was the most important significant variable for the South Clear Creek
site, followed by disturbance, slope, and vertical position on the face.
The first two axes of the CCA have acceptable eigenvalues.

**Obed Wall**

Climbing was significant for the Obed Wall site, and was the second most
important variable influencing the distribution of cliff-face vegetation
there (Table 15). Vertical position on the face was the most important
variable. Disturbance was marginally significant. Surface heterogeneity
and slope were both insignificant. The first axis eigenvalue is fairly
high and the second axis eigenvalue is still respectable.

  ---------------- -------- ------ --------- --------------- ------- ------
  **Table 15. CCA                            **Table 16. CCA         
  of OBE Face Data                           of Y12 Face             
  Set**                                      Data Set**              

  Variable         P        F                Variable        P       F

  Position         0.002    2.54             Disturbance     0.002   4.82

  Climbing         0.008    2.33             Climbing        0.002   4.43

  Disturbance      0.048    2.03             Slope           0.044   1.88

  Surfacehet       0.788    0.66             Position        0.354   1.12

  Slope            0.746    0.52             Surfacehet      0.654   0.72
  ---------------- -------- ------ --------- --------------- ------- ------

**Y12**

Disturbance and climbing were the two most important variables
accounting for variation in the cliff-face vegetation at the Y12 site
(Table 16). Slope was marginally significant. Vertical position on the
face and surface heterogeneity were insignificant for the Y12 site. The
first axis eigenvalue is fairly high but the other three are quite low.

**Discussion**

Habitat (edge, face, or talus) and site were by far the most important
variables accounting for variation in the vegetation in the large data
set, indicating that the vegetative communities in each habitat are
distinct, and that the communities differ between the six sites. The
variation in species composition between habitats is illustrated by the
ordination attribute plots for habitat (Fig. 1, 2, and 3). The
clustering of points within each habitat demonstrates the relative
similarity of species composition within a particular habitat, as well
as the dissimilarity between habitats. By comparing figure 1 with
figures 2 and 3, it is evident that the plots separate out across the
first axis based on habitat type, and that edge habitats are the most
unique with respect to species composition, since the edge cluster is
further away from the other two clusters (face and talus plots). This is
also supported by the forward selection results, in which the edge
habitat had the highest F-value (Table 1).

The edge habitat also had the highest species richness, which can be
seen by comparing figure 1 with figure 4. In the species richness
diagram (fig. 4), each point represents a sample plot and the size of
the point corresponds to the number of species in

![](media/image10.png){width="2.1458333333333335in"
height="2.3854166666666665in"}![](media/image11.png){width="1.8479166666666667in"
height="2.3979166666666667in"}![](media/image12.png){width="1.9534722222222223in"
height="2.4090277777777778in"}

![](media/image13.png){width="1.9270833333333333in"
height="2.1666666666666665in"}

that plot. Most of the plots with the highest species richness are
clustered together in the lower right quadrant of the diagram in figure
4, which corresponds to the edge plots shown in figure 1.

According to the forward selection results for the large data set, site
was the second most important variable organizing the vegetation. This
means that the Obed cliff vegetation is fairly site-specific. This trend
can be seen in the attribute plots for the individual sites, in which
the plots from each site seem to separate out on the second axis. (Fig.
5-10). Plots within each site are clustered closely together and away
from the plots from other sites. The separation of plots from different
habitats across axis 1 can also be seen in the site diagrams.

Although climbing and disturbance were statistically significant
variables according to the forward selection results (Table 1), they
were the least influential of the significant variables, and examination
of the ordination attribute plots for these variables

reveals no clear pattern (Fig. 11 and 12). This can be interpreted to
mean that, for the

large data set at least, variation in the vegetation among sample plots
is not correlated to the climbing status (climbed or unclimbed) or the
observed level of disturbance in those plots.

![](media/image14.png){width="1.7430555555555556in"
height="1.9881944444444444in"}
![](media/image15.png){width="1.8701388888888888in" height="2.125in"}

![](media/image16.png){width="1.7in" height="2.040277777777778in"}
![](media/image17.png){width="1.6506944444444445in"
height="1.9930555555555556in"}

![](media/image18.png){width="1.5666666666666667in"
height="1.7979166666666666in"}
![](media/image19.png){width="1.5576388888888888in"
height="1.7979166666666666in"}

![](media/image20.png){width="1.84375in" height="2.0833333333333335in"}
![](media/image21.png){width="1.8645833333333333in"
height="2.1145833333333335in"}

Since habitat was the most important variable accounting for variation
in the vegetation in the large data set, we conducted CCA analysis on
each habitat type individually, beginning with the cliff-face plots only
(face data set). Site was the most important significant variable for
the face data set, meaning that most of the variation in cliff-face
vegetation can be attributed to differences between the six sites (Table
2). The South Clear Creek (SCC) site had the most unique community
assemblage, as indicated by its F-value relative to the other
significant variables. The variability between sites is reiterated by
the attribute plots for individual sites in the face data set (Fig.
13-18), in which the plots within any particular site are tightly
clustered together.

![](media/image22.png){width="1.8722222222222222in"
height="1.4243055555555555in"} ![](media/image23.png){width="1.86875in"
height="1.382638888888889in"}

![](media/image24.png){width="1.8708333333333333in"
height="1.3284722222222223in"}
![](media/image25.png){width="1.917361111111111in"
height="1.4215277777777777in"}

![](media/image26.png){width="1.86875in" height="1.3416666666666666in"}
![](media/image27.png){width="1.91875in" height="1.4326388888888888in"}

The presence of an overhang (roof) was the second most important
significant variable accounting for variation in the cliff-face
vegetation. By comparing the attribute plots for roofs (fig. 19) and for
species richness (fig. 20), it is clear that the plots occurring beneath
an overhang have the lowest species richness.

![](media/image28.png){width="2.11875in" height="1.5020833333333334in"}
![](media/image29.png){width="2.120138888888889in"
height="1.5298611111111111in"}

The second run of the face data set CCA allowed us to ask the question,
'once variation among sites is accounted for, how much of the remaining
variation in the vegetation is due to the other variables measured?'
Since the eigenvalues are notably lower for the second run, we may
conclude that a large portion of the variation in the cliff-face
vegetation is due to variation among sites. However, these eigenvalues
are still considered respectable by statisticians, and the next two most
important variables influencing the cliff-face vegetation are the
north-south component of aspect (called northness) and the vertical
position on the face. This indicates that species composition on the
cliff faces differs between north- and south-facing areas and from the
bottom to the top of the faces. This is further supported by the
ordination diagram of environmental variables (fig. 21), in which
northness seems to be correlated with axis 1 (the most important
gradient) and vertical position with axis 2 (the second most important
gradient).

![](media/image30.png){width="2.28125in" height="2.627083333333333in"}

Based on the forward selection results and ordination diagrams for the
face data set, it is quite clear that climbing and disturbance are among
the least important factors influencing species composition in the
vertical cliff-face habitat. The attribute plots for climbing (fig. 22)
and disturbance (fig. 23) on the cliff faces show no discernible
pattern, indicating that changes in species composition are not
correlated with climbing or disturbance.

![](media/image31.png){width="2.3229166666666665in"
height="1.7395833333333333in"}
![](media/image32.png){width="2.2604166666666665in"
height="1.7395833333333333in"}

CCA was also conducted on the face data set for individual vegetation
types (vascular plants, bryophytes, and lichens). Climbing and
disturbance were insignificant for cliff-face vascular plants,
suggesting that there is no difference in vascular plant species
composition or species richness between climbed and unclimbed cliff
faces.

Aspect is the most important variable influencing the distribution of
vascular plants on cliffs, even more important than variation among
sites, and both the north-south and east-west components are
significant. This result differs from the analysis for the large data
set, indicating that aspect is more important in determining vascular
plant community composition than it is in determining the composition of
the vegetation as a whole, and that vascular plants are relatively more
similar among sites than the vegetation as a whole. Comparison of the
attribute plot for cliff-face vascular plant species richness (fig. 24)
and the environmental variables diagram (fig. 25) appear to indicate
that vascular plant species richness is higher in the south-facing
plots.

![](media/image33.png){width="2.6041666666666665in"
height="2.1458333333333335in"}
![](media/image34.png){width="2.7444444444444445in"
height="1.8215277777777779in"}

Climbing was not a significant influence on bryophyte communities on the
cliff faces, but the level of disturbance was significant in this
analysis. Since the amount of climber traffic is highly variable between
routes, a categorical value of anthropogenic disturbance was assigned to
each plot, in an attempt to assess the intensity of climbing (this also
allowed us to assess impacts in the talus where disturbance is not
restricted to areas directly beneath a climbed route). The attribute
plots for bryophyte species richness on the faces (fig. 26) and for
disturbance on the faces (fig. 27) seem to indicate fewer bryophyte
species in the most disturbed plots. However, it remains unclear if
these differences in species richness are actually correlated with
disturbance level or if the pattern is merely an artifact of variation
among sites.

![](media/image35.png){width="2.21875in" height="1.7395833333333333in"}
![](media/image36.png){width="2.186111111111111in"
height="1.7006944444444445in"}

Site was the most important variable for cliff-face bryophytes, and the
site attribute plots for bryophytes indicate that they are the most
site-specific type of vegetation there, since plots within sites are
clustered very tightly and far apart from those from other sites (fig.
28-33). The Y12 site had the most unique bryophyte community assemblage,
as indicated by the forward selection results. Northness was the second
most important variable influencing bryophyte distribution on the cliff
faces, indicating that bryophyte community composition is also driven by
aspect.

![](media/image37.png){width="1.9479166666666667in"
height="1.5729166666666667in"} ![](media/image38.png){width="2.09375in"
height="1.6041666666666667in"}

![](media/image39.png){width="2.0416666666666665in"
height="1.5520833333333333in"}
![](media/image40.png){width="2.0729166666666665in" height="1.59375in"}

![](media/image41.png){width="2.1194444444444445in"
height="1.6229166666666666in"} ![](media/image42.png){width="2.125in"
height="1.6354166666666667in"}

Climbing was a statistically significant variable influencing the
cliff-face lichen communities of the Obed. However, it was the fifth
most important significant variable for lichens, suggesting that its
influence on lichen distribution and species composition is low relative
to the other variables (Table 9). The cliff-face lichen attribute plots
for climbing reveal no obvious pattern, with the exception that the
unclimbed plots/transects (the small points on the diagrams) seem to lie
above the climbed plots/transects (large circles) (fig. 34 and 35). This
is suggestive of a *slight* shift in lichen species composition in
response to climbing.

![](media/image43.png){width="2.03125in" height="1.4583333333333333in"}
![](media/image44.png){width="2.2083333333333335in"
height="1.3541666666666667in"}

Site was again the most influential variable for cliff-face lichens,
meaning that lichen species composition varies between sites. Roof was
the second most important variable accounting for variation in lichen
distribution and species composition on the cliff faces, and the lichen
attribute plots for roof (fig. 36) and for species richness (fig. 37)
clearly show that lichen species richness is lowest in plots beneath an
overhang/roof.

![](media/image45.png){width="2.1458333333333335in"
height="1.5520833333333333in"}
![](media/image46.png){width="2.2958333333333334in"
height="1.645138888888889in"}

The insignificance of climbing for the edge data set was expected due to
the 'no top-out' policy. Disturbance, however, was statistically
significant for the edge habitat, indicating that the edge vegetative
communities, which are the most unique with respect to species
composition, are sensitive to disturbance. These areas have very thin
soils that require long periods of time to accumulate, so it is not
surprising that the vegetation there is quite intolerant of disturbance
in the form of trampling. The high levels of disturbance observed at a
few of the edge sites (e.g. North Clear Creek) can most likely be
attributed to hikers seeking a nice view rather than to climbing. The
only threatened plant species observed, *Talinum teretifolium*, a state
threatened species in Tennessee, occurs on the edge habitat above the
Lilly Bluffs climbing area, which is mostly protected from trampling
thanks to the no top-out policy and the boardwalk at the overlook area.
Site was the most important influence on edge community composition,
again indicating that the vegetation in this habitat type is
site-specific. When the analysis was conducted a second time with sites
defined as covariables, disturbance became the most important variable
accounting for variation in the edge vegetation, supporting the
conclusion that cliff-edge vegetation is quite sensitive to disturbance.
However, the eigenvalues for the second run of the edge data set CCA are
very low, indicating that most of the variation in edge species
composition is attributable to site differences.

The results for the talus are similar, since site was the most important
variable organizing the vegetation, followed by disturbance. Climbing
was insignificant for the talus, which makes sense because impacts in
the talus are not restricted to areas directly beneath a climbing route.
Climbers and non-climbing hikers alike walk along the cliff bands in the
talus areas, so many talus plots that were sampled along an 'unclimbed'
transect were actually impacted by climbers and/or hikers. This was one
of the reasons for recording the level of disturbance in addition to the
climbing status for each sample plot. Sites were defined as covariables
in the second run of the edge data set CCA, with the result that
disturbance became the most important variable influencing the
distribution of vegetation in the talus. However, it must be noted that
the eigenvalues are very low for the second run of the edge analysis,
indicating that most of the variation was due to sites and that less was
due to disturbance. Even so, disturbance remains a statistically
significant factor. Climbing remained insignificant in the second run.

Since the vegetation is so consistently site-specific, CCA was performed
on each site individually in an attempt to understand what drives
variation in the vegetation within a given site. Climbing became
significant for some of the individual site analyses, whereas it was
insignificant for the data set as a whole. There are two main reasons
for this. First, there are few sources of variation left in the data for
an individual site. Recall that only the face plots were included in
these analyses and both aspect and seep were excluded from the analysis
due to high variance inflation factors, meaning they are highly
correlated with site. In other words, differences in aspect and seep are
related to site differences, and are therefore irrelevant to the
analysis of any single site. At some sites there is little overall
variation left, as indicated by low eigenvalues (e.g. Lilly Bluffs and
Lilly Boulders). The CCA must use the variables supplied, so it extracts
whatever little pattern there is left.

The second reason climbing appears to play a more important role in the
individual sites analyses is small sample size. There are a limited
number of climbed and unclimbed transects within any given site.
Furthermore, the vegetation is fairly transect specific, i.e. the
transects usually separate out clearly in the ordination diagrams.
Therefore it is difficult to determine if any pattern with respect to
climbing can truly be attributed to climbing, or if the climbed
transects just happen to fall on one side of the graph and the unclimbed
on the other side, by chance. If there was a general effect of climbing
that applied equally at all sites, it would have shown up in the overall
(large data set or whole face data set) analysis. The effect of climbing
may in fact be site-specific, since the vegetation is so variable among
sites and because there is considerable variation in climbing traffic
among sites (e.g., less traffic at the Obed Wall, due to its
considerable distance from parking).

It is safe to say that there is definitely no effect of climbing on the
cliff faces at Lilly Bluffs (p = 0.588). The attribute plot for climbing
at Lilly Bluffs shows no pattern; climbed plots are scattered about the
diagram in no particular pattern (fig. 38). Disturbance was also
insignificant there (fig. 39).

![](media/image47.png){width="1.7666666666666666in"
height="2.1743055555555557in"}
![](media/image48.png){width="1.8131944444444446in"
height="2.2784722222222222in"}

There is a significant effect of disturbance at Lilly Boulders (faces
only), and disturbance is highly correlated with climbing in that
analysis. However, the effect of disturbance/climbing at Lilly Boulders
is not convincing simply because there are two few data points. The
small sample size, in conjunction with low eigenvalues, seems to suggest
that climbing is not an important factor there.

The eigenvalues for North Clear Creek are much higher and disturbance
and climbing, which have a correlation of 1 (meaning they are exactly
the same), are significant. However, the attribute plots for North Clear
Creek for the climbing/disturbance variable are unconvincing (fig. 40
and 41). There are two climbed transects and one unclimbed, and the
three transects are spaced equally apart. The factor that separates the
transects may be unrelated to climbing.

![](media/image49.png){width="2.1458333333333335in"
height="1.1979166666666667in"}
![](media/image50.png){width="2.7444444444444445in"
height="0.8736111111111111in"}

With three transects, there is a two in three chance that the unclimbed
one will lie on either end, rather than in the middle, resulting in
significance in the analysis. In the climbing attribute plot for axis 1
vs. axis 3, the transects still separate out clearly, but the unclimbed
transect falls in the middle instead of on one end. This renders the
significance of climbing unconvincing for the North Clear Creek site.

Although climbing was not significant for the South Clear Creek site
according to the forward selection results, it is highly correlated with
disturbance, which was the second most important variable driving
variation in the cliff-face vegetation at South Clear Creek. The
attribute plots for climbing and disturbance look nearly identical (fig.
42 and 43). However, the patterns in the attribute plot diagrams for
South Clear Creek do not indicate any clear effect of climbing on the
vegetation. The plots from each transect are lined up across the
diagrams, but the disturbed/climbed transects are spaced as far

![](media/image51.png){width="2.25in" height="1.6145833333333333in"}
![](media/image52.png){width="2.2847222222222223in"
height="1.6444444444444444in"}

apart from each other as they are from the undisturbed/unclimbed
transects. This pattern could be an effect of any other unmeasured
factor correlated with the location of the transect.

Climbing was also significant for the Obed Wall site analysis. The
attribute plots for climbing at the Obed Wall contain three groups of
sample plots (fig. 44 and 45). The groups on either end consist entirely
of climbed plots and the three unclimbed transects align in the middle.
This leaves the effect of climbing somewhat questionable. However, it
could be argued that there is a real effect of climbing, since the
climbed plots spread out all over the ordination space, but the
unclimbed plots are closer together. This indicates that the climbed
quadrats are more heterogeneous. In any case, there is no clear and
definite trend with respect to climbing at the Obed Wall.

![](media/image53.png){width="1.9944444444444445in"
height="1.8284722222222223in"} ![](media/image54.png){width="1.56875in"
height="1.9868055555555555in"}

The Y12 site is similar to the Obed Wall site with respect to the
climbing attribute plots: the largest group of plots in the ordination
diagram are unclimbed and there are two groups of climbed plots that are
spaced far apart (fig. 46 and 47). However, one of these two groups is
disturbed and the other is not (see fig. 48), indicating that there is a
significant effect of both climbing and disturbance at the Y12 site.
Among the individual site analyses, the results for Y12 present the
strongest case for arguing that climbing has an effect on the
vegetation.

![](media/image55.png){width="2.15625in" height="1.3333333333333333in"}
![](media/image56.png){width="2.2430555555555554in" height="1.36875in"}

![](media/image57.png){width="2.3958333333333335in"
height="1.4583333333333333in"}

**Conclusions and Implications for Management**

The Obed River gorge system is known for its high level of plant
diversity. That diversity is reflected in the results of this study. One
of the most important things we discovered during the course of this
research is that cliff vegetation is highly heterogeneous and varies
greatly from site to site, even when those sites are relatively close to
one another. Due to the time-consuming nature of the field work required
to study cliff vegetation, only three climbed and three unclimbed
transects were measured at most of the six sites. Although 415 total
plots were sampled, the individual site analyses, which were conducted
because of the high level of variation in vegetative composition among
sites, would benefit from a larger sample size at each site.

Another interesting and prevalent feature of the Obed cliffs is the
presence of large overhangs or roofs. These areas are sought out by
skilled climbers due to the challenges they present. The results of this
study consistently show lower species richness for all vegetation types
on the cliff faces beneath these overhangs. The lack of vegetation there
is probably an effect of very low light and moisture levels, though
these were not measured in this study. This finding suggests that, in
terms of impact on vegetation, climbing should be of little concern in
these areas.

Disturbance was a significant factor accounting for the distribution of
vegetation in the talus area. The talus vegetation is visibly trampled
in most areas of the six sites sampled. Since talus areas were disturbed
throughout the sampling sites, regardless of the climbing status of the
transect, it may be worthwhile to conduct vegetation surveys in talus
areas elsewhere in the park, located away from climbing routes and
hiking trails, in order to observe the truly undisturbed state of talus
vegetative communities in the park.

The cliff edge habitat was found to have the most unique community
assemblages. Due to the thin soils and harsh environment, many
interesting plants, vascular and non-vascular, may be found there. Among
them is the Tennessee state threatened plant *Talinum teretifolium*, the
round-leaf fameflower, which grows on the edge at Lilly Bluffs. The edge
environment was also quite sensitive to disturbance, but it appears that
the no top-out policy is working since there was absolutely no effect of
climbing in the edge habitat, and disturbed areas were relatively
infrequent.

Although there seems to be a slight shift in lichen species composition
on the cliff faces in response to climbing, it remains unclear exactly
what that shift is. Other than that observation, we cannot confidently
conclude that there is a significant effect of rock climbing on the Obed
cliff vegetation as a whole. We believe this to be related to the fact
that, while the Obed cliffs harbor some very interesting plant species,
they are not heavily vegetated overall. However, due to the high
variability among sites within the gorge and the fairly small sample
sizes within each site, we cannot completely rule out the effects of
climbing for all sites. We suggest that the effects of climbing are
probably site-specific, since the vegetation and the amount of climbing
traffic are site-specific as well, and that larger sample sizes would
allow us to make a statistically sound conclusion about the impact of
climbing at each site. Of the individual site analyses, the Obed Wall
site and the Y12 site present the strongest evidence for an effect of
climbing on the vegetation. This is interesting since these are the most
remote sites included in the study and appeared to be less disturbed
when compared to some of the other climbing areas.

**References**

Anderson, LE, HA Crum, and WR Buck. List of mosses of North America. The
Bryologist. 448-499.

Bowman, K. 2003. A survey of Bryophytes in Fall Creek Falls State Park.
Master's thesis, Dept. of Botany, University of Tennessee, Knoxville,
TN.

Caplenor,C.D. 1955. An annotated list of the vascular plants of the
gorges of the Fall Creek Falls State Park, Tennessee, J. Tenn. Acad.
Sci. 30:93-106.

Caplenor, C.D. 1979. Woody plants of the gorges of the Cumberland
Plateau and adjacent Highland Rim. J. Tenn. Acad. Sci. 54:139-145.

Clark, R.C. 1966. The vascular flora of the Fiery Gizzard gorges in
South Central Tennessee. M.A. Thesis. University of North Carolina,
Chapel Hill. 89 p.

Fenneman, N.M. 1938. Physiography of eastern United States. McGraw-Hill
Book Co., New York. 712 p.

Heiman, 1999

Holtzclaw, F.W., Jr. 1977. Floristic survey of spring flowering herbs at
Frozen Head State Park, Morgan County, Tennessee. J. Tenn. Acad. Sci.
52: 5-9.

Hubbard, E.H., B.L. Mattzer, M.E. Austin, S.R. Bacon, and K.V. Goodman.
1950. Soil Survey of Cumberland County, Tennessee. U.S.D.A.,
Agricultural Research Administration, Washington, D.C. 107 p.

Kirk, P.M. 2003. [www.indexfungorum.org](http://www.indexfungorum.org/).
CABI Bioscience website

Larson, D.W., U. Matthes, J.A. Gerrath, N.W.K. Larson, J.M.. Gerrath,
J.C. Nekola, G.L. Walker, S. Porembski, A. Charlton. 2000. Journal of
Biogeography, 27: pp. 319-331.

Mayfield, Michael W. 1979. Runoff in the Obed-Emory river basin of
Tennessee, Southeastern Geographer 19:54-65.

Mayfield, Michael W. 1984. Variations in streamflow among watersheds of
the Cumberland Plateau, Tennessee. Ph.D. Dissertation, UT Knoxville,
Knoxville, Tennesse.

Newcombe Jr., Roy, and O. Smith Jr. 1958. Groundwater resources of the
Cumberland Plateau in Tennessee, State of Tennessee Department of
Conservation, Division of Water Resources, Nashville, TN.

Patrick, T.S. 1979. Final report: Upper Cumberland River flora project.
Processed report prepared for Tennessee Heritage Program and Ohio Basin
Commission. Botany Department, The University of Tennessee, Knoxville.
75 p.

Patrick T.S., B.E. Wofford, and D.H. Wbb. 1983. State records and other
recent noteworthy collections of Tennessee plant. IV. Castanea
48:109-116.

Plezewski, R. 2003. Microarthropod Fauna on Cliff Faces in the Linville
Gorge Wilderness Area. Master's Thesis, Dept. of Biology, Appalachian
State University.

Radford, AE, HE Ahles, CR Bell. 1968. Manual of the Vascular Flora of
the Carolinas. University of North Carolina Press, Chapel Hill, NC. 1183
pp.

Risk, A.C. 1999. Bryophytes of the Obed Wild and Scenic River,
Cumberland and Morgan Counties, Tennessee. Final Report for the Nature
Conservancy, Contract Number 057916.

Schmalzer, PA., TS Patrick, HR DeSelm. 1985. Vascular flora of the Obed
Wild and Scenic River, Tennessee. *Castanea* 50:71-88.

Springer, M.E. and J.A. Elder. 1980. Soils of Tennessee. University of
Tennessee Agricultural Experimental Station Bulletin 596. University of
Tennessee, Knoxville.

Stotler, R., and B Crandall-Stotler. 1977. A checklist of the liverworts
and hornworts of North America. The Bryologist. 405-428.

Tennessee Natural Heritage Program. 1982. The State of Tennessee's
official list of rare plants. State of Tennessee, Department of
Conservation. Nashville. 8 p.

Thornthwaite, C.W. 1948. An approach toward a rational classification of
climate. Geogr. Rev. 38:55-94.

U.S.D.A., Soil Conservation Service. 1978. General soil map, Morgan
County, Tennessee.

U.S. Dept. of the Interior. 1980. Endangered and threatened wildlife and
plants: Review of plant taxa for listing as endangered or threatened
species. Federal Register 45, No 242, 15 December1980, 82480-82569.

Walker, G.L. 1987. Ecology and Population Biology of Thuja occidentalis
L. in its Southern Disjunct Range. Ph.D. Thesis, University of
Tennessee, Knoxville, TN.

Watford, C. 1999. *The Dixie Cragger's Atlas: A Climber's Guide to
Tennessee, Alabama, and Georgia*. Market Place Press, Roswell, GA. 478
pp.

Wofford, B.E., T.S. Patrick, L.R. Phillippe, and D.H. Webb. 1979. The
vascular flora of Savage Gulf, Tennessee. Sida 8:135-151.

Wofford, B.E. 1989. Guide to the Vascular Plants of the Blue Ridge.
University of Georgia Press, Athens, GA. 384 pp.