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Vertical Distribution of Lichen Growth Forms in Tree Canopies of Great Smoky Mountains National Park
Erin Fanning, Joseph S. Ely, H. Thorsten Lumbsch, and Harold W. Keller

Southeastern Naturalist, Volume 6, Special Issue 1 (2007): 83–88

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1Department of Biology, University of Central Missouri, Warrensburg, MO 64093. 2Botanical Research Institute of Texas, Fort Worth, TX 76102. 3The Field Museum, Chicago, IL 60605. *Corresponding author - Vertical Distribution of Lichen Growth Forms in Tree Canopies of Great Smoky Mountains National Park Erin Fanning1, Joseph S. Ely1,2,*, H. Thorsten Lumbsch3, and Harold W. Keller1,2 Abstract - Great Smoky Mountains National Park is an area known for its incredible species diversity. This study was conducted in order to determine the vertical distribution of lichen growth forms and overall lichen species richness on selected host-tree species in the Park. Specifically, lichens were collected from Tilia americana var. heterophylla (basswood), Abies fraseri (Fraser fir), Liquidambar styracifl ua (sweet gum), and Fraxinus americana (white ash) at different canopy heights. A total of eight trees (two for each species) were sampled using the double-rope climbing technique. Overall, our results indicate that both host-tree species and canopy height infl uence lichen species richness and distribution of growth forms. Three lichen species are reported as candidates for new records in the Park: Gyalecta fl otowii Korber, Lecanora miculata Ach., and Pyrenula pseudobufonia (Rehm) R.C. Harris. Introduction Lichens are an important component of many ecoregions (Brodo et al. 2001, Nash et al. 2002) and often comprise a large proportion of species diversity. There are over 7700 species reported from North America, excluding Mexico (Esslinger 2006). Some species of lichen have wide and disjunct distributions, often showing the classical Asa Gray distribution (Kurokawa 1972, Lumbsch 2004, Yoshimura 1968). There were 194 species of corticolous lichens reported for Great Smoky Mountains National Park (GSMNP) (Ciegler et al. 2003). Species of lichen form a vital part of the canopy ecosystem and biodiversity in the Park. The aim of this study was to explore corticolous lichen species richness and vertical distribution of lichen growth forms (crustose, foliose, and fruticose) in the canopy strata on selected host-tree species in GSMNP. Methods A safe and environmentally friendly method for accessing the tree canopy involves the use of a double-rope climbing technique (Keller 2004). A climbing saddle, system of knots, and a double rope were used to ascend the tree, enabling the climber to advance and reach heights of more than 30 m to sample lichens. Samples were collected from all sides 83 The Great Smoky Mountains National Park All Taxa Biodiversity Inventory: A Search for Species in Our Own Backyard 2007 Southeastern Naturalist Special Issue 1:83–88 84 Southeastern Naturalist Special Issue 1 of the tree (at 3 m elevational increments) on four different host species. The minimum size of host trees was 42 cm in diameter at breast height. A total of two sample bags (approximately 1000 cm3 each) were filled at each height (Snell and Keller 2003). Host-tree species were Abies fraseri (Pursh) Poiret. (Fraser fir), Fraxinus americana L. (white ash), Liquidambar styraciflua L. (sweet gum), and Tilia americana L. var. heterophylla (Vent.) Loud. (basswood). A total of eight trees were sampled from different sites in the Park. Basswood was sampled from the Gabes Mountain Trail and the West Prong Trail near the Tremont Institute. Fraser fir was sampled from Clingman’s Dome, a high-elevation site. White ash was sampled from the Cades Cove Loop Road and the Baxter Creek Trail. Sweet gum was sampled from a sweet gum swamp along Cades Cove Loop Road near the Visitor Center and a northwestern section of the Park (Tritt Cemetery near Cosby). All sites were located in Tennessee and occurred at low elevations, with the exception of Clingman’s Dome, which is on the North Carolina/Tennessee border and is the highest point in the park and Tennesse. Lichens were separated into three life-form categories (crustose, foliose, and fruticose) and three height classes corresponding to the lower (0–8.9 m), mid- (9–17.9 m), and upper (18–36 m) canopy along the main trunk or bole of the tree. For the purpose of this study, lichens surveyed include both those growing directly on bark and those growing on corticolous bryophytes. Please note that the maximum height of Fraser fir surveyed was in the mid-canopy, so there is no data for the third height class. Lichen species richness (mean and standard error) for each of the growth forms was calculated among sampled host-tree species and respective heights. Voucher specimens of the new records are deposited at the Field Museum in Chicago (F). Results Our survey resulted in the recording of seven orders, 18 families, and 68 species of lichens following Brodo et al. (2001) and Nash et al. (2002, 2004). Crustose lichens comprised six orders, 10 families, and 25 species, while two orders, five families, and 12 species were fruticose. The foliose lichens were the most species-rich group, including one order, five families, and 31 species. Several orders and families included more than one growth form. The following species of lichens identified in the course of this study are candidates as new records for GSMNP: Gyalecta fl otowii Korber (ELY 5642), Lecanora miculata Ach. (ELY 5601), and Pyrenula pseudobufonia (Rehm) R.C. Harris (LUMBSCH 19273c). There were more foliose than crustose lichens at the mid-canopy on Fraser fir and sweet gum, while there were no differences observed for white ash (Figs. 1a, b). Lichen growth forms also varied by canopy height across host species. There were more crustose lichens occurring in the 2007 E. Fanning, J.S. Ely, H.T. Lumbsch, and H.W. Keller 85 upper canopy on sweet gum than other host species (Fig. 1a). Foliose lichen richness in the lower and mid-canopy was greater on Fraser fir than either basswood or white ash (Fig. 1b). Mid-canopy crustose lichen richness was higher on basswood than white ash (Fig. 1a). Foliose lichen richness was highest on sweet gum than other host-tree species surveyed (Fig. 1b). There were more fruticose lichens growing on sweet gum and Figure 1. Mean lichen species richness and ± 1 standard error bar of crustose (a), foliose (b) and fruticose (c) growth forms among hosttree species (AF = Abies fraseri [Fraser fir], TH = Tilia americana var. heterophylla [basswood], FA = Fraxinus americana [white ash], and LS = Liquidambar styracifl ua [sweet gum]) and height (solid line = 0–8.9 m, dashed line = 9–17.9 m, and dotted line = 18– 36 m). Please note that Fraser’s fir was only sampled in the first two height classes. 86 Southeastern Naturalist Special Issue 1 Fraser fir than on other host-tree species (Fig. 1c). There was only one species of fruticose lichen that occurred on white ash and none occurred on basswood (Fig. 1c). Overall, species richness was higher in crustose and foliose lichens than in fruticose lichens (Figs. 1a–c). Discussion Our results indicate that host-tree species and canopy height infl uence lichen species richness and growth forms. The foliose growth form had the greatest species richness in comparison to the other growth forms. Other studies have found similar patterns. For example, McCune et al. (2000) showed that a significant relationship existed between lichen growth forms and tree-canopy height in a forest canopy located in the state of Washington. Fruticose lichens were less diverse than crustose and foliose lichens for all height classes and tree species. A plausible explanation for this result may be that fruticose lichens are typically found more along lateral branches, where they receive more light than foliose lichens (Esseen et al. 1996). Because our sampling was only from the trunk of the tree, our surveys are probably not representative of the total fruticose species richness of the sampled trees as a whole. There are obvious moisture and light gradients from the ground to the upper canopy of forests that determine the distribution of lichen species. Our results show that differences in the canopy had a significant effect on the species richness on several species. Similar to what McCune et al. (2000) found, there seems to be a pattern of lichen growth forms and species richness to host species and canopy height. McCune et al. (2000) studied the microhabitats of a Washington State conifer forest and observed that substrates and tree canopy structure affected the distribution of lichens. In particular, they showed that characters such as canopy height, living versus nonliving trees, amount of cover, and trunk diameter were all factors that displayed significant variation in epiphyte communities (McCune et al. 2000). Species richness was most markedly infl uenced by canopy height in that forest system. Ellyson and Sillett (2003) showed similar results in that the canopy height was the dominant gradient in the distribution of epiphytic communities in a Sequoia sempervirens (Lamb. ex D. Don) Endl. (redwood) old-growth forest. In a midwestern Quercus-Carya (oak-hickory) forest, Peck et al. (2002) showed that there was a limited number of lichen species (26%) that were generalists across host-tree species and habitats, and the remaining species were more specific with respect to substrate, habitat, and host-tree species. Furthermore, they found that the majority of species encountered in the lower and mid-canopy were crustose and foliose lichens. Results shown here have certain limitations. First, there is a limited number of host-tree species sampled (n = 4) and also a limited number of individual trees sampled per host species (n = 2). In addition, there were no microenvironmental attributes (e.g., soil, slope, light) measured or recorded. 2007 E. Fanning, J.S. Ely, H.T. Lumbsch, and H.W. Keller 87 This preliminary study suggests that interesting patterns of lichen stratification exist in the canopies of living trees. More data is needed from additional individuals of each tree species to confirm trends noted here. In addition, micro-environmental (light, moisture, temperature) and habitat (aspect, slope, elevation) data need to be further investigated in order to understand the processes associated with the patterns of lichen stratification within GSMNP. Acknowledgments This study was financially supported in part by the National Science Foundation DEB Award #0343447, Discover Life in America Award #2004-6, National Geographic Society Committee for Research and Exploration Award #7272-02 to H.W. Keller, Sigma Xi Grant-in-Aid of Research Award #3040094, and the University of Central Missouri (UCM) McNair Scholars program to Erin Fanning. Special thanks go to the UCM student climbers for their assistance in data collection (Cheryl Dunham, Tommy Fayette, Amber Ferguson, and Ashley Willard). Charly Potorff and Kenneth Snell were instructors for the rope-climbing techniques. Literature Cited Brodo, I.M., S.D. Sharnoff, and S. Sharnoff. 2001. Lichens of North America. Yale University Press, New Haven, CT. Ciegler, A., U.H. Eliasson, and H.W. Keller. 2003. Tree-canopy lichens of the Great Smoky Mountains National Park. Evansia 20:114–131. Ellyson, J.T., and S.C. Sillett. 2003. Epiphyte communities on Sitka spruce in an old-growth redwood forest. The Bryologist 106(2):197–211. Esseen, P.A., E.K. Renhorn, and R.B. Pettersson. 1996. Epiphytic lichen biomass in managed and old-growth forests: Effect of branch quality. Ecological Applications 6(1):228–238. Esslinger, T.L. 2006. A cumulative checklist for the lichen-forming, lichenicolous, and allied fungi of the continental United States and Canada. Available online at First posted 1 December 1997; most recent update 2007. North Dakota State University, Fargo, ND. Keller, H.W. 2004. Tree canopy biodiversity: Student research experiences in Great Smoky Mountains National Park. Systematics and Geography of Plants 74: 47–65. Kurokawa, S. 1972. Probable mode of differentiation of lichens in Japan and eastern North America. Pp. 139–146, In A. Graham (Ed.): Floristics and Paleofl oristics of Asia and Eastern North America. Elsevier, Amsterdam, The Netherlands. Lumbsch, H.T. 2004. Lichen-forming fungi in the tree canopies in the Great Smoky Mountains National Park. Inoculum 55(4):24–25. McCune, B., R. Rosentreter, J.M. Ponzetti, and D.C. Shaw. 2000. Epiphyte habitats in an old conifer forest in western Washington, USA. The Bryologist 103:417– 427. Nash III, T.H., B.D. Ryan, C. Gries, and F. Bungartz (Eds.). 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol. 1. Lichens Unlimited, Arizona State University, Tempe, AR. 532 pp. 88 Southeastern Naturalist Special Issue 1 Nash III, T.H., B.D. Ryan, C. Gries and F. Bungartz. 2004. (Eds.). Lichen Flora of the Greater Sonoran Desert Region. Vol. 2. Lichens Unlimited, Arizona State University, Tempe, AR. 742 pp. Peck, J., J. Grabner, and D. Ladd. 2002. The lichen communities of the southeastern Missouri Ozarks: Lessons in species associations, habitat partitioning, and distribution from the MOFEP study. A report to the Missouri Department of Conservation-Missouri Ozark Forest Ecosystem Project, Jefferson City Missouri. 41 pp. Snell, K.L., and H.W. Keller. 2003. Vertical distribution and assemblages of corticolous myxomycetes on five tree species in the Great Smoky Mountains National Park. Mycologia 95:565–576. Yoshimura, I. 1968. The phytogeographical relationships between the Japanese and North American species of Cladonia. Journal of the Hattori Botanical Laboratory 31:227–246.