Southeastern Naturalist 443 I.M. Rossell and H. Eggleston 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 Southeastern Naturalist I.M. Rossell and H. Eggleston 2017 Vol. 16, No. 3 444 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, Southeastern Naturalist 445 I.M. Rossell and H. Eggleston 2017 Vol. 16, No. 3 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. Southeastern Naturalist I.M. Rossell and H. Eggleston 2017 Vol. 16, No. 3 446 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. Southeastern Naturalist 447 I.M. Rossell and H. Eggleston 2017 Vol. 16, No. 3 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. Southeastern Naturalist I.M. Rossell and H. Eggleston 2017 Vol. 16, No. 3 448 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. 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