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The following article was first published in Wild
Earth, Vol. 7, #2, pp 62-66, 1997. Some corrections and additional
information, usually in brackets, have been introduced into the text. by R. F. Mueller and Gus Mueller A strong relation exists between bedrock
geology, forest type, and land use on Warm Springs Mountain in Virginia and by
extension in other parts of the folded Appalachians. These relations have
important implications in the design of wildland reserves in the region. Most de
facto wildlands that are potential reserves are public land, which is a
consequence of low biologic productivity associated with refractory bedrock. However,
more productive rocks, such as carbonates (limestones, dolomites, and some
sandstones and shales), frequently occur on adjacent private lands or as
enclaves within public lands. The tracts on which these productive rocks occur
should be targeted for protection and restoration as vital complementary parts
of the reserves. Geology has an important role in the identification and
characterization of this diverse terrain and should be an integral part of
reserve planning. The
establishment of wildlands reserves in the Appalachian Mountains requires an
appreciation of the ecological functions of the array of forest types and other
biologic communities of the region. The varied forest types and plant
communities result in part from and interact with enveloping physical systems:
rock type and structure, topography, climate, soils, etc. They are an example
of the functional landscape mosaic listed by Noss (1995/96) as necessary to
reserve viability. Soils are usually regarded as the most
fundamental interface between biologic systems and the physical environment.
While this is in a sense true, soils are difficult to work with in the field
and represent on maps because they show so much small-scale variation in response
to local topography and even recent history of human disturbance. Geologic rock
units have an advantage over soil units in that their boundaries may be more
easily projected and interpolated. This is especially true of the folded
Appalachians where many rock unit boundaries tend to be linear along fixed
trends. Also, in colluvial deposits detached rocks may be more easily
identified than soils and traced to their points of origin. This relative ease
of identification extends to mineral specimens, using no more than a hand lens
(for texture), a knife blade (for hardness), and an acid bottle (to test
for carbonate). By contrast, soil characterization usually requires lab work.
These advantages are particularly important to activists who have little time
and few resources. For these reasons we deem bedrock geology a more practical
indicator of major regional variations in forest type, and one of our
objectives here is to demonstrate the value of geology in regional ecological
mapping. Nothing in the foregoing, however, should be seen as diminishing the
role of soils. The characteristic of variation in response to local conditions
that makes it difficult to map soils is at the same time useful in the
interpretation of microhabitats that determine precise locations of species.
For example, soil depth and type over limestone governs where alkali or
acid-favored species occur. Thus, over limestone bedrock, Chinquapin Oak (
Quercus muehlenbergii), which demands high pH, is favored by shallow
soils, while Red Maple (Acer rubrum ), an acid-lover, requires deep and
leached soils. Of course, forests also vary in response to such factors as
elevation, slope and aspect, which may be independent of geology or show their
effects within geologic formations; and indeed these factors have received
attention in the region in the past (e.g. Stephenson and Adams 1991).
Although the writers know of few specific studies of the relation between
forests and geology in the Central Appalachians, this relation is referred to
frequently in a general way by Braun (1950) and is implicit in recent works on
certain plant distributions. Thus Ogle (1989) discussed the distribution of
rare and disjunct plants which occur on certain Ordovician dolomites. Also, the
relation is well recognized by the Virginia Natural Heritage Program (Ludwig et
al 1994), which has used it in inventories of rare species and unusual
communities. Many of the ranges of the folded Appalachians
have an asymmetry with respect to rock type exposure.1 Frequently
one side of a range and the summit consists of erosion-resistant and
nutrient-poor sandstone or quartzite, while the other side is dominated by
limestone, dolomite shale or siltstone in various proportions. Usually
carbonate and/or shale also form the floors of the narrow valleys that separate
the ranges. The northeast-southwest linear extension of the ranges form fairly
extensive de facto wildland corridors in this direction. However habitat
continuity in the cross-range direction is frequently interrupted by
agricultural development not only in the valleys but also on mid-slopes. Forest
types developed on the refractory sandstones and quartzite have important
functions as remote habitat, excellent cover (e.g. laurel thickets), and
sources of certain important forage such as acorns. However, they are also
limited by lack of forage and habitat diversity and productivity. Far different
were the original forests that occupied the mid-slope and valley bottoms on the
highly productive soils associated with carbonate rocks. These forests
consisted not only of a high, complexly structured and diverse mesic canopy,
but also a multitude of fruiting and tuber-producing plants, fungi, and
resident fauna that provided abundant foraging opportunities for animal life
with access to them. The areas once occupied by these forests, but which now
possess them only in degraded form if at all, are thus priority targets for ecosystem
recovery. Warm Springs
Mountain extends 28 miles (45 km) northeast from Covington, Virginia. Like a
number of similar ranges in this part of the folded Appalachians, it averages
about three miles (5 km) in width and is capped by erosion-resistant Silurian
sandstone and quartzite. It attains 4000 feet (1220 meters) elevation in
several places, with Bald Knob at 4225 ft (1288 meters) being the highest. In
terms of geologic structure it is part of an anticlinal fold (folded layers
form an upward pointing crest), but this anticline has been breached by erosion
over much of its length, exposing older Ordovician rocks that form its core (
Figure 1). The central and oldest of these rocks are limestones and dolomites
of the Beekmantown Group and the Moccasin Formation, which underlie the Warm
Springs Valley just northwest of the range. Slightly younger carbonate-bearing
shales of the Martinsburg Formation form the northwest slope, and these are
overlain by shales, siltstones and sandstones of the Juniata Formation. The
Juniata is in turn overlain by the Silurian Clinch quartzite of the summit. A feature of Figure 1 that needs to be clarified
is the apparent absence of Silurian rock on the northwest limb of the
anticline. This is a consequence of a failure to distinguish the Silurian from
lower Devonian in this area as well as the relative thinness of the Silurian (
Rader and Evans 1993). If the pattern of land ownership (Figure 2) is
compared with the distribution of rock types, it appears that correspondence is
quite good. Public land, and particularly National Forest, is largely confined
to areas underlain by Silurian rocks of low productivity, while limestone and
carbonate areas are predominantly in private hands. Where the areas of Silurian
age are expanded southwest and northeast of the Ordovician belt (points A and
B of Figure 2), the anticline is not breached and the forest cover is similar
to that which occurs on the southeast limb (points C, D and E of Figure 2).
It should also be noted that in the vicinity of point B the Silurian rocks of
the anticline plunge beneath the Devonian as a result of cross deformation.
Everywhere on the uplands this forest is dry and ericaceous, consisting
dominantly of Chestnut Oak (Quercus prinus ) with lesser amounts of
White (Q. alba ), Northern Red (Q. rubra), Black (Q.
velutina ) and Scarlet Oak (Q. coccinea), Red Maple (Acer
rubrum) and Black Gum (Nyssa sylvatica ). The shrub layer consists
largely of Mountain Laurel (Kalmia latifolia), Upland Low Blueberry (Vaccinium
pallidum) and Black Huckleberry ( Gaylussacia baccata ). The leaf
mat is heavy and ground cover is usually confined to scattered small heaths
such as Teaberry (Gaultheria procumbens) and Trailing Arbutus (Epigaea
repens ) and herbs such as Wood Tickseed (Coreopsis major). Leucobryum
cusion moss and Cladina lichen are common at tree bases and on patches
of open ground. Examples of [at] least one other forest type
occur at lower elevations on the silica-rich Silurian rocks. These are the
mesic forests along streams and in well-watered coves. Like those of the upland
forests, soils are acid, as reflected in both woody vegetation and herbs. The
most imposing example is Dolly Ann Hollow (point E, Figure 2). The canopy
here is dominated by large old-growth Canada (or Eastern) Hemlock (Tsuga
canadensis ), White Pine (Pinus strobus ), White and Chestnut Oaks
and Pignut Hickory (Carya glabra ), with smaller sized Black Gum,
Northern red Oak, Tuliptree (Liriodendron tulipifera), American
Basswood (Tilia americana ) and Shagbark Hickory (Carya ovata). Witch Hazel (Hamamelis viginiana), and especially Great
Rhododendron (Rhododendron maximum), form thickets along the stream. The
acid and nutrient-poor near-surface soil layers result in sparse herbaceous
ground cover and its limitation to a few species such as Partridge Berry (Mitchella
repens ). Similar "acid-mesic" forests also occur in coves near
location A (Figure 2), but here contain such species as Striped Maple (Acer
pensylvanicum ), Canada Mayflower (Maianthemum canadense ) and
Starflower [Trientalis borealis ] in response to somewhat higher
elevations than at Dolly Ann Hollow. Our point here is that despite abundant
moisture in the acid-mesic forests, they differ greatly from the mesic forests
on rich or circumneutral soils. If we now consider the forests developed on
carbonate rocks of the Ordovician formations, we see stark differences delineated
by geologic boundaries. The richest soils and those most utilized for
agriculture, occur on the limestone and dolomite rocks of the Warm Springs
Valley along US Route 220 (Figures 1 and 3). Forests here are diverse, with
many mesic species such as maples, elms, ashes and Tuliptree: yet they also
contain many oaks, due to the ready subsurface drainage of limestone bedrock
and the consequent drying of soils during periods of drought. Indeed, this
valley is a notable karst area with many sinkholes and caves (Hubbard 1988). Of greater interest to us than the valley
limestones is the Martinsburg Formation because it underlies areas nearer the
Silurian rocks and public lands. This formation consists of predominantly
"yellow to brown weathering limy shale" with a thickness of about
1000 feet (300 meters). The overlying Juniata formation of 300 to 400 feet (90-120
meters) in thickness forms a narrow transitional zone between carbonate rocks
and the Silurian sandstones (Bick 1962). Both of these formations are
included under "Ordovician Shale" in Figure 1. One of the most striking-and
accessible-transformations in forest type associated with the contact between
two rock units occurs in the high gap by which State Route 39 crosses the range
just east of Warm Springs, VA. Here (point F, Figure 2), after passing
through oak forest on the southeast slope, is an abrupt change in vegetation at
the gap. At almost 3000 ft (914 meters) elevation Black Walnut (Juglans
nigra ) and other mesic species, including particularly many grape vines (Vitis
aestivalis), suddenly appear. Othe mesic species encountered on descent of
the northwest slope are Slippery Elm (Ulmus fulva ), Northern Red and
White Oaks, Black Birch (Betula lenta ), Shagbark, Bitternut and Pignut
Hickories (Carya ovata, C. cordiformis and C. glabra ),
Butternut (Juglans cinerea), Cucumber Magnolia (Magnolia acuminata), White Ash (Fraxinus americana), White Basswood (Tilia
heterophylla), Black Cherry (Prunus serotina), Black Locust (Robinia
pseudoacacia ), Red, Sugar and Black Maples (Acer rubrum, A. saccharum
and A. nigrum ) and Red Mulberry (Morus rubra). Shrubs include
Black Elderberry ( Sambucus canadensis), Witch Hazel, maple Leaf
Viburnum (Viburnum acerifolium ) and Flowering Raspberry (Rubus
odoratus ). Black Maple in particular is considered to be an indicator of
the richest (eutrophic) forest type in the state (Rawinski 1994).
Martinsburg Shales are conspicuous in road cuts on the slope. A similar transition of forest types may also be
observed in the southern part of the range along State Rout 606. This road
ascends the northwest slope obliquely toward a broad wind gap at the range
crest. The aspect here varies from west to southwest, but the forest is mesic.
Approximately 2 miles (3.2 km) southeast of Route 220 (point G, Figure 2)
typical Martinsburg Shale is exposed in a road cut beneath dark brown mull type
soil which is characteristic of mixed mesophyte forest. Although this forest is
secondary and has suffered obvious degradation, its original character is identifiable.
The canopy is dominated by White Ash with subordinate Sugar Maple, Black Locust
and a little Northern Red Oak, the most mesic of oaks. As is characteristic of
such mesic forest, there is virtually no leaf mat. It appears that the water
retaining properties and fertility of the limy shale are, despite the
unfavorable aspect, adequate to maintain mesic conditions throughout the year,
enabling the observed species to out-compete such oaks as appear on the valley
limestones. The mesic character of the forest is maintained to the mountain
crest. At this point Route 606 meets Route 703, which follows the ridge to the
northeast. The transition from mesic to dry oak forest occurs in 0.3 mile (
0.5 km) along this road, where it climbs out of he gap and encounters
resistant sandstone. The forest here, and extending along the ridge, consists
of Chestnut, White and Northern Red Oaks and considerable Red Maple. Mountain
Laurel is common in the shrub layer. Above approximately 3500 feet (1070 meters)
this oak forest itself undergoes a transition to predominantly Northern Red
Oak, as is usual for higher elevations in the region (Mueller 1996). On the
exposed culmination of the ridge at Bald Knob, the oak forest becomes stunted
and wind contorted. On the most exposed slopes it gives way to Pitch Pine (Pinus
rigida) heath with shrubby Bear Oak ( Quercus ilicifolia), Catawba
Rhododendron (Rhododendron catawbiense), Minnie-bush (Menziesia
pilosa), Black Chokeberry (Aronia melanocarpa), huckleberry and
blueberries. Accompanying these are such boreal species as American Mountain
Ash (Pyrus americana ), Canada Mayflower, and the rare Variable Sedge (
Carex polymorpha ). Close correspondence appears to exist
between the geology and forest type on Warm Springs Mountain, a fairly typical
range of the folded Appalachians. This correspondence includes not only the
obvious contrast between valley bottom and ridge top, but also the slope
formations. In at least some situations the effect of bedrock dominates that of
aspect and other slope factors and may be the primary determinant of forest
type distributions. Although the present study was confined to Warm Springs
Mountain, a perusal of geologic, land use and forest cover maps, as well as
cursory field observation, indicates that similar relations probably occur on
many ranges of the folded Appalachians. Specific examples include Peters,
Clinch and Walker Mountains in southwest Virginia and ranges to the north and
northwest of Warm Springs Mountain. To varying degrees, such relations should
occur in unglaciated terrain quite generally, and even in glaciated terrain
where bedrock is near the surface. Correlations between fluvial and glacial
deposits and forest type have also been recognized, an example being the
association of Jack Pine (Pinus banksiana) and glacial outwash (Braun
1950). Relations between fluvial deposits and forest type in the unglaciated
Appalachians should be investigated. This study indicates that geologic formation
delineation and trend lines can facilitate ecological mapping. Relations
between geologic formation, topography and forest type should also enhance the
value of aerial photographs and aid field work. The use of geology thus
provides several converging avenues to ecosystem protection and recovery.
Although state Natural Heritage programs give most attention to rare species
and ecosystems, integration of geology into these programs can help realize the
potential of degraded but critical areas in the regional ecologic mosaic. In
the absence of geologic information, recognition of such areas and their
ecological functions will be more difficult. Consequently, we urge that
geologic mapping and formation characterization be incorporated in evaluating
ecosystems on a scale much larger than its present incidental use as a guide to
certain rare occurrences. Geological data and concepts should be
integrated into wildland planning by activists. An additional benefit of such
planning could be the involvement of a larger segment of the scientific
community. Many geologists might be surprised to learn that they can make
significant contributions to preserving and restoring biodiversity through
their knowledge of rock distributions and mineral chemistry. Scientists are
ever on the lookout to expand their activities into new fields. Unfortunately,
to the present most geologists have been single-mindedly concerned with the
exploitation of Nature. This could be changed by revealing to them the role in
wildland research and preservation. Gus Mueller is an artist and writer with an interest in
Nature and technology. Bob Mueller, a retired [ NASA ]
scientist, is coordinator of Virginians for Wilderness (Rt.1 Box 250
[now 727 Stingy Hollow Road ], Staunton, Virginia 24401).
The writers appreciate the assistance in the
field of Steve Krichbaum and Mike Jones. We also appreciate the generous
support provided by Humani-tees and The Fund for Wild Nature. Bick, Kenneth F. (1962) Geology of the Williamsville
Quadrangle, Virginia. Report of Investigations 2. Virginia
Division of Mineral Resources, Charlottesville, Virginia. Braun, E. Lucy (1950) Deciduous Forests of Eastern
North America. Macmillan, New York. Hubbard, David A. Jr. (1988) Selected Karst Features
of the Central Valley and Ridge Province, Virginia. Virginia
Division of Mineral Resources, Publication 83. Ludwig, J. Christopher, Allen Belden and Christopher A.
Clampitt (1994) A Natural Heritage Inventory of the Clinch Ranger
District, Jefferson National Forest Technical Report # 94-2. Virginia
Department of Conservation and Recreation, Division of Natural Heritage. Mueller, Robert F. (1996) "Central Appalachian
Plant Distributions and Forest Types, or what a walk in the woods can
tell you." Wild Earth 6 (1), 37-43. Noss, Reed F. (1995/96) "What Should Endangered
Ecosystems Mean to the Wildlands Project?" Wild Earth 5 (4),
20-29. Ogle, Douglas W. (1989) "Rare Vascular Plants of
the Clinch River Gorge Area in Russell County, Virginia," Castanea
53 (2), 105-110. Rader, E. K. and N. H. Evans, editors (1993)
Geologic Map of Virginia-Expanded Explanation. Virginia
Division of Mineral Resources, 80 pp. Rawinski, Thomas J. (1994) A Classification of
Virginia's Indigenous Biotic Communities: Vegetated Terrestrial and
Estuarine Community Classes, Technical Report # 92-21. Virginia
Department of Conservation and Recreation, Division of Natural Heritage. Stephenson, Steve L. and Harold S. Adams (1991)
"Upland Oak Forests of the Ridge and Valley Province in
Southwestern Virginia." Virginia Journal of Science 42 (4),
371-380.
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Geology in Reserve Design,
An Example from the Folded
Appalachians
Abstract
INTRODUCTION
WARMS SPRINGS MOUNTAIN
CONCLUSIONS AND RECOMMENDATIONS
Figure 1. Geology of Warm Springs Mountain and vicinity.
Figure 2. National Forest lands of Warm Springs Mountain and vicinity (in gray).
Figure 3. Forest cover (in gray) and 800 and 1000 meter contours of Warm Springs Mountain and vicinity.
Acknowledgement
References