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22001177 SOUTHEASTERN NATURALIST 1V6o(3l.) :1464,3 N–4o5. 03
Elevational Distribution of Temperate Lianas Along Trails in
Pisgah National Forest
Irene M. Rossell1,* and Heather Eggleston1
Abstract - In several regions of the world, the species richness of lianas (woody vines) has
been shown to decrease as elevation increases. Little is known about the relationship between
elevation and lianas in temperate forests of eastern North America. We documented the elevational
distribution of 4 high-climbing, native lianas in Pisgah National Forest (western
North Carolina) by recording the elevations of 427 vine occurrences along 53 km of trails.
All 4 taxa occurred at the lowest elevations. Mean elevations of Toxicodendron radicans
(Poison Ivy; 873 ± 71 m) Parthenocissus quinquefolia (Virginia Creeper; 895 ± 103 m) and
Vitis spp. (wild grape; 962 ±103 m) were similar. Isotrema macrophyllum (Pipevine) had a
mean elevation of 1193 ± 194 m and was the only liana occurring >1300 m. Further study
is needed in the forest interior and to determine how factors such as soil moisture, forest
structure, stem anatomy, spatial relationships with pollinators and seed dispersers, or other
factors may influence the elevational distribution of lianas in the mountains.
Introduction
Climbing vines with woody stems (lianas) are common elements of temperate
hardwood forests, thriving in early successional habitats along forest edges, in
treefall gaps, and other disturbed areas (Allen 2015, Ladwig and Meiners 2009,
Londre and Schnitzer 2006, Teramura et al. 1991). Once lianas locate and ascend
suitable hosts, they can live for decades and so are also represented in mid- to late
successional forests. Lianas contribute up to 10% of the species richness of woody
plants in temperate forests (Gentry 1991, Schnitzer and Bongers 2002), compared
with up to 35% in tropical forests (Dewalt et al. 2015).
Only a few studies have documented the effects of elevation on lianas. Specifically,
liana species richness has been shown to decrease as elevation increases
in Chile and New Zealand (Jimenez-Castillo et al. 2007), Mexico (Vazquez and
Givnish 1998), and Nepal (Bhattarai and Vetaas 2003), but no published studies
have investigated this relationship in temperate forests of eastern North America.
Our own casual observations (as well as anecdotal observations by local botanists
in our area) suggested the trend of fewer species at higher elevations might hold
true in the mountains of western North Carolina.
We were able to glean only limited information on the relationship of lianas and
elevation in our region from botanical manuals (Lance 2004, Weakley 2015, Wofford
1989). Weakley (2015) indicated Toxicodendron radicans (L.) Kuntze (Poison
Ivy) is absent from the high mountains in the southern and mid-Atlantic states, but
did not mention elevation in habitat descriptions for 3 other lianas common in the
1Environmental Studies Department, University of North Carolina Asheville, Asheville, NC
28804. *Corresponding author - irossell@unca.edu.
Manuscript Editor: Brett E. Serviss
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southern Appalachian mountains: Isotrema macrophyllum (Lam.) C.F. Reed (Pipevine),
Parthenocissus quinquefolia (L.) Planch. (Virginia Creeper), and Vitis spp.
(wild grape). Wofford (1989) and Lance (1994) noted some species of wild grape
occur in lowlands, but gave no elevational information for Pipevine, Poison Ivy, or
Virginia Creeper. Our objective was to document the occurrence of high-climbing,
native lianas along an elevational gradient in Pisgah National Forest in western
North Carolina, to serve as a baseline for further studies on the distribution of temperate
lianas.
Methods and Field-site Description
We searched for high-climbing, native lianas along 14 trails in Pisgah National
Forest in western North Carolina. We searched along trails, rather than in plots, so
we could cover a wide range of elevations in the time available. Trails were located
in 5 areas of the national forest within 40 km of Asheville, NC (35°36'N, 82°33'W),
with trail selection based on accessibility and elevation gain. Distances hiked
along each trail ranged from 1.0 to 8.0 km, depending on trail length. The lowest
trail elevation was 724 m, the highest elevation was 1865 m, and individual trails
gained between 156 and 890 m of vertical elevation. Four trails included elevations
<900 m, and 7 trails covered elevations >1500 m.
The forests surrounding all trails were characterized by upland species. Liriodendron
tulipifera L. (Tulip poplar) was the most common overstory tree. Other
common overstory species included Acer rubrum L. (Red Maple), Acer saccharum
Marsh. (Sugar Maple), Cornus florida L. (Flowering Dogwood), Quercus alba L.
(White Oak), Robinia pseudoacacia L. (Black Locust), and Tsuga canadensis (L.)
Carr. (Eastern Hemlock). Betula lenta L. (Sweet Birch) was common at elevations
less than 1000 m, and Betula alleghaniensis Britt. (Yellow Birch) was common >1000 m.
Forest communities we traversed included Northern Hardwood Forest, Rich Cove
Forest, Acidic Cove Forest, and Montane Oak–Hickory Forest (Schafale 2012).
We walked each trail once between 4 June and 5 August 2012, recorded all vine
occurrences within 10 m of the trail (5 m on either side), and determined the elevation
of each occurrence with a handheld global positioning dystem (GPS) unit (Garmin
eTrex Vista H, Kansas City, KS). Vine occurrences were defined as a stem growing
along the ground, on a rock, or on a host plant. Because most of the wild grape had
reached the canopy, we were unable to differentiate individual species and grouped
observations as Vitis spp. Common species in the region include V. aestivalis Michx.
(Summer Grape) and V. labrusca L. (Fox Grape). Due to the nature of our surveys,
our results are summarized with descriptive (not inferential) statistics.
Results and Discussion
We hiked 53 km of trails and recorded 427 occurrences of high-climbing, native
lianas (8 per km). Overall, Virginia Creeper (38.2%) and Pipevine (37.9%) were
most abundant, and wild grape (16.4%) and Poison Ivy (7.5%) were least abundant
(Table 1). In a floristic survey of the Balsam Mountains of North Carolina,
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Pittillo and Smathers (1979) also encountered very little Poison Ivy. The nearly
equal abundance of Pipevine and Virginia Creeper in our study accounted for
three-fourths of liana occurrences. Interestingly, our relative abundance results
were similar to those reported by Leicht-Young et al. (2010) in Michigan (where
Pipevine is out of range). Of the 3 taxa occurring in both studies, Virginia Creeper
was noted most often, followed by wild grape, then Poison Ivy. In our study, Pipevine
was distributed the most widely, occurring along 10 of the 14 trails we walked
(Table 1). Wild grape and Virginia Creeper each occurred along half of the trails,
and Poison Ivy occurred along about one-third of trails.
All 4 lianas were present at the lowest elevations in our study (≤780 m). The
mean elevations of Poison Ivy (873 ± 71 m) and Virginia Creeper (895 ± 103 m)
were similar (Fig. 1), and neither species occurred >1200 m. The mean elevation
of wild grape was 962 ± 103 m, with an overall distribution skewed by outliers to
Table 1. Occurrences and elevations of 4 high-climbing, native lianas along 14 trails in Pisgah National
Forest (total distance = 53 km). Occurrences were defined as a stem growing along the ground,
on a rock, or on a host plant. Trail elevations ranged from 724 to 1865 m.
Pipevine Poison Ivy Virginia Creeper Wild grape
Total number of occurrences 162 32 163 70
Lowest elevation occurrence (m) 780 752 724 774
Highest elevation occurrence (m) 1531 1100 1188 1292
Vertical elevation span (m) 751 348 464 518
Number of trails 10 5 7 7
Figure 1. Elevations of 4 taxa of
high-climbing, native lianas along
53 km of trails in Pisgah National
Forest. Each box plot includes
mean elevation (X), median elevation
(horizontal line), first quartile
(bottom of box), third quartile (top
of box), 1.5 times the interquartile
range (whiskers), and outliers
(circles). Note that the median
elevation for Poison Ivy is so close
to the third quartile that it does not
appear as a distinct horizontal line
within the box in this figure.
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somewhat higher elevations than Poison Ivy and Virginia Creeper (Fig. 2). This
would be an interesting trend to explore further with a larger sample size. Pipevine
(mean elevation 1193 ± 194 m) was the only liana occurring >1300 m. Pittillo and
Smathers (1979) also reported Pipevine as the only liana in high-elevation (1300–
1500 m) boulder fields in the Balsam Mountains of North Carolina. Although we
observed Pipevine at the highest elevations in our study, its native range extends
only as far north as Pennsylvania, while the 3 other taxa extend into New England
and Canada (Kartesz 2015, Weakley 2015). The fact that the 2 species restricted to
the lowest elevations in our study (Poison Ivy and Virginia Creeper) extend well
into the cold climes of the northeastern United States makes their absence from
high elevations of the western North Carolina mountains even more intriguing. Of
the 4 taxa, Poison Ivy had the most restricted distribution, spanning only 348 m of
vertical elevation (Table 1, Fig. 2), whereas Pipevine spanned the greatest range in
vertical elevation (751 m).
The reasons for these distribution patterns are likely complex and influenced
by specific microhabitat variables at each elevation and location. In addition,
the unique physiology of lianas may affect their distribution differently when
compared to other plant types (Schnitzer 2005). Dewalt et al. (2015) concluded
that beyond disturbance, little is known about what governs the distribution of
lianas in temperate forests. Many factors could have affected liana distribution
in Pisgah National Forest; here we discuss a few possible factors (soil moisture,
forest structure, xylem structure, and spatial relationships with pollinators and/
or seed dispersers).
Figure 2. Percent occurrences of 4 taxa of high-climbing, native lianas with increasing
elevation along 53 km of trails in Pisgah National Forest.
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Soil moisture
High elevation soils are often drier than soils on lower slopes (Black 1996), yet
the lianas we encountered have not demonstrated consistent relationships with soil
moisture in other studies. Poison Ivy, Virginia Creeper, and wild grape have been
reported in dry as well as mesic soils (Bell et al. 1988, Brush et al. 1980, Collins
and Wein 1993, Lance 2004, Morano and Walker 1995, Weakley 2015, Wofford
1989). Pipevine (which is endemic to the south-central Appalachians) is generally
associated with mesic forests and rich woods (Lance 2004, Weakley 2015, Wofford
1989). However, we observed it at the highest elevations in our study, and Pittillo
and Smathers (1979) reported it in boulder fields, suggesting soil moisture may not
limit its distribution. These findings may support the work of Schnitzer (2005), who
suggested the deep and extensive root systems of lianas allow access to water, even
during drought conditions.
Forest structure
Another factor that could influence liana distribution in the mountains is the
structure of the forest at different elevations. For example, Poison Ivy and Virginia
Creeper climb via adventitious roots and adhesive disks, respectively, so can
ascend large-diameter trees (Carter and Teramura 1988, Talley et al. 1996). Wild
grape climbs via tendrils that are adapted to trellises of small-diameter understory
plants, as well as small branches within tree canopies. In contrast, the twining
stems of Pipevine restrict it to small-diameter hosts. Bolstad et al. (1998) reported
a higher density of small-diameter trees at higher elevations in a southern Appalachian
watershed, which they attributed to slower tree growth and past disturbances
on ridges. This association of small-diameter trees with higher elevations could
support our observations of Pipevine at those locations.
Xylem structure
Internal morphology might play a major role in liana distribution. Jimenez-Castillo
et al. (2007) concluded the most likely reason for liana elevational differences
in the southern hemisphere is the structure of their vascular systems. These authors
suggested lianas capable of growing at the highest elevations may have the narrowest
vessels. In our study, that would be Pipevine, but we were unable to find
published information on the size or structure of Pipevine vessels.The poorly insulated
stems of lianas are susceptible to freezing (Schnitzer and Bongers 2002), and
their wide xylem vessels are vulnerable to winter air embolisms (Angyalossy et al.
2015, Zimmerman and Brown 1971). Schnitzer (2005) suggested lianas growing
in moderately cold temperatures may have smaller than average vessel elements.
Virginia Creeper has wide vessels (Bell et al. 1988) and was limited to the lowest
elevations in our study, which would be least affected by cold temperatures. Wild
grape also has wide vessels (Sperry et al. 1987); its elevation distribution was similar
to that of Virginia Creeper in our study. However, both of these species currently
occur in northern areas with cold climates where they experience frequent freezing
temperatures in the winter. Thus, it would not seem likely that an intolerance to
cold and freezing due to morphology or other factors limits their elevational range.
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Perhaps some other implication of xylem vessel structure or different morphological
characteristics might explain the distribution we observed.
Spatial relationships
A final factor worth considering is the spatial relationship of lianas with pollinators
and/or seed dispersers. Pipevine was the only liana we observed at high
elevations, and differs from the others in its flower and seed characteristics. All 4
taxa are insect-pollinated, but only Pipevine has solitary flowers, which could make
it attractive to a different suite of pollinators. In addition, Pipevine is the only species
with wind-dispersed seeds. The others rely on frugivores for dispersal, so their
elevational distributions may be limited by bird movement.
Conclusions
In summary, Pipevine was the only high-climbing liana occurring at the highest
elevations in our study, suggesting the distribution of lianas may be influenced in
part by elevation in the southern Appalachians. The reasons for this relationship
are unknown but could include liana responses to soil moisture or forest structure,
pollination or dispersal modes, limitations imposed by xylem structure or other
morphologcial characteristics, or other factors. We collected elevational data along
trails, which represent a disturbance in the forest community at some point in the
past. Further research is needed in the forest interior, and throughout the range of
each species .
Acknowledgments
We thank former University of North Carolina Asheville undergraduate students S. Henry,
M. McCafferty, and A. Case for sharing their earlier work on woody vines; C. Toth, C. Delorenzo,
and G. Casebeer for field assistance; Dr. J.W. Miller for technical assistance; and Dr.
B. Collins at Western Carolina University for interesting conversation and insights regarding
woody vines. C. Reed Rossell, Jr. provided valuable comments on an earlier draft of the
manuscript. Financial support was provided by 2 grants from the Undergraduate Research
Program at the University of North Carolina Asheville to H. Eggleston. We also thank 2 anonymous
reviewers for helpful comments and suggestions regarding this manuscript.
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