Mapping and Management of the Non-native Japanese Spiraea at Buffalo Mountain Natural Area Preserve, Virginia, USA

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1 R E S E A R C H N O T E Mapping and Management of the Non-native Japanese Spiraea at Buffalo Mountain Natural Area Preserve, Virginia, USA Jeffrey J. Feldhaus 1,3 1 Department of Forest Resources and Environmental Conservation Virginia Tech Blacksburg, VA Carolyn A. Copenheaver 1 Jacob N. Barney 2 2 Department of Plant Pathology, Physiology, and Weed Science Virginia Tech Blacksburg, VA Corresponding author: jjfeld@vt.edu; Natural Areas Journal 33: ABSTRACT: Biological invasions of non-native species are an important conservation issue because of the potential negative impacts on native plant and animal communities. One species of concern in Virginia is Japanese spiraea (Spiraea japonica L.f.). At Buffalo Mountain Natural Area Preserve (BMNAP) the spread of Japanese spiraea threatens the integrity of native high-elevation grassy balds, eastern redcedar (Juniperus virginiana L.) glades, and mafic seep communities. A prerequisite to successful management of a non-native species is knowledge about where a species has established and how it spreads. Thus, our objectives were to: (1) identify current populations of Japanese spiraea at BMNAP, and (2) characterize environmental conditions favoring the growth of Japanese spiraea. Paired-plot sampling was used to compare environmental parameters from adjacent plots with and without Japanese spiraea. Canopy cover was significantly lower in plots with Japanese spiraea compared to plots without Japanese spiraea (t = 1.76, P = 0.02), suggesting Japanese spiraea is more successful in establishing in higher light environments. At BMNAP, lower canopy cover reflected historical disturbances such as old power line cuts or roads. Although Japanese spiraea is not currently invading the grassy balds or eastern redcedar glades at the Buffalo Mountain summit, existing populations pose an immediate threat to the mafic seeps at the base of the mountain. Regular monitoring and mapping will be important to prevent Japanese spiraea from hindering conservation goals. Index terms: grassy balds, invasive shrub, mafic seep communities, Spiraea japonica INTRODUCTION Biological invasions are a substantial concern worldwide and nearly every use of the word invasion implies two things: entry and harm (Alpert 2006). The introduction of a non-native plant species to new habitat poses both ecological and economic risks (Pimentel et al. 2000; Aronson and Handel 2011). Although there is debate on terminology used in invasion ecology, a non-native species is often defined as a species surviving outside its native range (Colautti and Richardson 2009). With globalization and climate change, the introduction and invasion of non-native species is likely to become more problematic (Vila et al. 2011; Bradley et al. 2012). The non-native plant species Japanese spiraea (Spiraea japonica L.f.) is a member of the Rose family (Rosaceae) and native to China, Japan, and Korea (Remaley 2005). It was introduced to the United States in the late 1800s and has spread throughout the eastern United States, primarily along the Appalachian Mountains, where it is widely planted as an ornamental. It ranges from Ontario to Georgia and as far west as Iowa. It is found in 24 states and is reported to be invasive in Kentucky, Maryland, New Jersey, North Carolina, Pennsylvania, Tennessee, and Virginia (Remaley 2005). It grows 1.2 to 1.8 m tall and has long, slender stems with clusters of pink flowers at the ends. Its egg-shaped leaves are 2.5 to 7.6 cm long with pointed tips and toothed margins. Seeds are produced in large numbers and have high rates of germination (> 91%), which aids with reproduction and rapid spread (Wilson and Hoch 2009). In a study of Japanese spiraea s rate of spread in mature deciduous forests in Austria, cover almost doubled over a 14-year period (Essl 2005), indicating it has the potential to aggressively compete with native species following introduction. Japanese spiraea is an opportunistic shrub that grows well in disturbed areas and a wide variety of habitats (Remaley 2005; Wellman 2008). It tolerates partial shade to full sun and grows well on mesic and xeric sites. It is commonly found in old fields, at forest edges, along roadways, and along streams forming dense thickets that compete with native vegetation. Japanese spiraea s high annual seed production increases local propagule pressure, and dispersal via water or wind are common (Lockwood et al. 2005; Pysek and Richardson 2007). Viable seeds have been identified in seed bank studies even when no spiraea is currently growing at the site, implying that the seeds remain viable for several years to provide a potential for future establishment and growth (Sullivan and Ellison 2006). The Natural Area Preserve System in Virginia was created to conserve rare ecosystems and to protect organisms dependent on these habitats for survival. When non-native species threaten to invade Volume 33 (4), 2013 Natural Areas Journal 435

2 preserves, timely responses are important or we risk losing the integrity of rare and endangered communities. The first step in management of non-natives is assessment of the existing size and character of the invasion (Britton et al. 2010). Therefore, our research objectives for this project were to: (1) map current populations of Japanese spiraea at Buffalo Mountain Natural Area Preserve (BMNAP), and (2) characterize environmental parameters favoring growth of Japanese spiraea. METHODS Study area Buffalo Mountain Natural Area Preserve ( N, W) is situated in Floyd County, Virginia (Figure 1), within the Blue Ridge Physiographic Province. The 460-ha preserve is owned and managed by the Virginia Department of Conservation and Recreation s Natural Heritage Program for the protection of rare and endemic organisms that inhabit grassy balds, eastern redcedar (Juniperus virginiana L.) glades, and mafic woodland seep communities. Scattered within the closed-canopy forest near Buffalo Mountain s summit are grazing- and fire-maintained, prairie-like openings known as grassy balds (Copenheaver et al. 2004) dominated by warm-season grasses and home to 12 rare plant species, including bog bluegrass (Poa paludigena Fern. & Wieg.), Gray s lily (Lilium grayi S. Wats.), large-leaved grass-of-parnassus (Parnassia grandifolia DC.), plains frostweed (Helianthemum bicknellii Fern.), and three-toothed cinquefoil (Potentilla tridentata Sol.). Common trees surrounding the balds are northern red oak (Quercus rubra L.), black oak (Q. velutina Lam.), pignut hickory (Carya glabra (Miller) Sweet.), mockernut hickory (C. tomentosa (Poiret) Nutt.), and yellow poplar (Liriodendron tulipifera L.) (Copenheaver et al. 2004). The preserve is also home to three rare invertebrates, including the endemic Buffalo Mountain mealybug (Puto kosztarabi Miller & Miller) (Miller and Miller 1993). Buffalo Mountain has a strong cultural legacy among local residents who use trails for recreation (Davids 1970). The summit reaches a height of 1210 m above sea level (asl) and much of the preserve is above 883 m asl. Average temperatures range between Figure 1. Within each black area, several Japanese spiraea populations were measured during the 2011 growing season at Buffalo Mountain Natural Area Preserve in Virginia (map courtesy of the Virginia DCR). 20 C in the summer to 1 C in the winter (Conner 2009). Total annual precipitation in Floyd County averages 104 cm. Field Work During ground surveys to identify current boundaries of Japanese spiraea populations, we walked the preserve on foot, using a targeted approach that focused our sampling on areas with a high risk of invasion such as forest edges, roads, right-of-way cuts, and waterways. We spent less time sampling areas with low risk of invasion such as side slopes or remote areas of the preserve with less potential for human disturbance. Once a population of Japanese spiraea was located, we used adaptive cluster sampling (Salehi and Brown 2010) and concentrated additional sampling effort in areas surrounding existing populations. For each population, its location was recorded with a global positioning system and the size was measured by recording length of the longest diameter and width of the diameter perpendicular to the first axis. Maximum population height was measured by recording the height of the tallest individuals to ascertain the height at which sunlight was intercepted. Total ground cover was estimated for each population with cover classes. A subset of 15 Japanese spiraea populations was randomly selected for additional measurements to be compared with 15 adjacent paired-plots without Japanese spiraea, but having similar topographic position and aspect. The size, shape, and orientation of the adjacent plots were variable and were determined by the boundaries of the paired Japanese spiraea population. Within each plot, percent canopy cover, soil moisture, and soil depth to bedrock were recorded. Canopy cover was measured using a canopy-sampling tube (a scope-like viewing tube with cross-hairs) and a point-intercept sampling method (Mueller-Dombois and Ellenberg 1974). Percent soil moisture was measured using a soil moisture probe (Hydrosense AP Moisture Probe). During measurement of soil depth to bedrock, soil samples were collected for hand texturing and testing of soil ph, buffer ph, percent acidity, percent base saturation, cation exchange capacity (CEC), boron, calcium, copper, iron, magnesium, manganese, 436 Natural Areas Journal Volume 33 (4), 2013

3 phosphorus, potassium, and zinc. Soil analyses were performed at the Virginia Tech Soil Testing Lab. Data analysis We used a paired t-test to compare plotlevel characteristics of canopy cover, soil moisture, soil depth, and soil chemistry between plots with and without Japanese spiraea. A comparison was considered significant if P < We used multiple linear regression in JMP (SAS Inc., Cary, NC) to identify potential relationships between plot-level environmental variables and area, height, and cover of Japanese spiraea populations. We excluded elevation, slope, and aspect because paired plots were intentionally selected to have similar topographic positions. RESULTS At BMNAP, populations of Japanese spiraea were found primarily in powerline corridors, abandoned roads, and streambeds (Figure 1). Populations of Japanese spiraea were most concentrated in the southwestern corner of the preserve, south of Route 758, because it contained several large populations of Japanese spiraea. This area was an intersection point for three conditions that increase the likelihood of successful Japanese spiraea establishment: a creek, a road, and an adjacent pasture. Occasional, small populations were found at saddle and side-slope positions. Populations ranged in size from 58 m 2 to 3565 m 2 and stem heights from 1.0 m to 2.5 m. Percent cover occupied by Japanese spiraea ranged from 5% to 90%. There was significantly less canopy cover in plots with Japanese spiraea than without Japanese spiraea (t = 1.76, P = 0.02; Table 1). There was no significant difference among paired plots for soil moisture or depth to bedrock. Calcium was significantly higher (P = 0.04) in plots containing Japanese spiraea (988 mg kg -1 ) compared to plots without Japanese spiraea (616 mg kg -1 ). For all other soil variables tested, there were no significant differences between paired plots (Table 1). Regression models show that the environmental variables are not good predictors of Japanese spiraea s area (Adjusted R 2 = 0.07), height (Adjusted R 2 = -0.48), or cover (Adjusted R 2 = -0.22). DISCUSSION Forest disturbances create canopy gaps and allow non-native understory species to establish in the increased light; and, once established, these non-native species can prevent successful regeneration of native plants (Burnham and Lee 2010; Aronson and Handel 2011). At BMNAP, canopy gaps are traditionally occupied by herbaceous species. In canopy gaps having experienced recent disturbance, Japanese spiraea appears to have a competitive advantage compared to native herbaceous species, allowing it to monopolize available light. In these areas, Japanese spiraea can occupy up to 90% of the understory. No difference was noticed in the dominant tree species between areas with Japanese spiraea present from areas where it was not present. Four native woody species found on Buffalo Mountain (Copenheaver et al. 2004) with a height advantage over Japanese spiraea are rhododendron (Rhododendron maximum L., height of 10 m), eastern redbud (Cercis canadensis L., Table 1. Comparison of various characteristics found at plots with Japanese spiraea and adjacent plots without Japanese spiraea. Asterisk notes a statistically significant difference (P < 0.05) between the two values based on a t-test. Volume 33 (4), 2013 Natural Areas Journal 437

4 height of 12 m), witch hazel (Hamamelis virginiana L., height of 20 m) and serviceberry (Amelanchier arborea (Michx. f.) Fernald, height of 11 m) (Gleason and Cronquist 1991); though these species may not dominate the understory in areas without Japanese spiraea, based on our observations, they do not co-occur with Japanese spiraea. These taller shrubs have a competitive height advantage over Japanese spiraea, indicating taller species may more successfully compete for a light resource, thus excluding shorter species, such as Japanese spiraea, from an area. In areas where Japanese spiraea outcompetes herbaceous species, wildlife habitat (LeMaitre et al. 2011) and vigor of other plants may be degraded. Research in Nova Scotia has shown that in areas where Japanese spiraea has a high importance value, it tends to be associated with other invasive species such as privet (Ligustrum ovalifolium) and Norway maple (Acer platanoides); however, in a site where Japanese spiraea was absent, the most important woody species was a native shrub, red-osier dogwood (Cornus stolonifera) (Turner et al. 2005). This indicates that Japanese spiraea may serve as one of several indicator species of invasional meltdown (Simberloff and von Holle 1999). Preventing initial establishment of non-native species is the best way to minimize the likelihood that a species will damage an ecosystem. However, following successful establishment at a site, such as in the case of Japanese spiraea at BMNAP, it is essential to develop a long-term monitoring plan to ensure a species does not develop into a more serious conservation issue (Blossey 1999). Successful monitoring of non-native species includes creating a spatial database of populations based on field measurements or remotely sensed data and concentrating monitoring efforts in areas of highest risk for future invasion (Swain et al. 2011). Repeated sampling aids in tracking the spatial and temporal distribution of non-native species and is necessary to alert land managers of where and when control efforts should be directed (Spyreas et al. 2010). At BMNAP, Japanese spiraea does not currently pose a threat to the grassy balds or the eastern redcedar glades; however, its proximity to wet areas at the lower elevations identifies it as a greater threat to the mafic seeps. Japanese spiraea is of greatest concern in these areas such as the southwestern portion of the preserve because populations are more frequent and create more competition for available resources. Given that the presence of Japanese spiraea seems to be independent of abiotic conditions, preventing human actions that would result in canopy disturbance near these seeps will be crucial for preventing the spread of Japanese spiraea. Additionally, monitoring should continue in areas where Japanese spiraea exists (Figure 1), in areas of high risk for future establishment (riparian zones and recently disturbed areas), and within the grassy balds, eastern redcedar glades, and mafic seeps. Identifying the current extent of Japanese spiraea and whether it presents a direct threat to the conservation goals of BMNAP represent the first stage of stopping this biological invasion before they become a serious conservation issue (Martine et al. 2008). Our results suggest the current distribution of Japanese spiraea appears to be closely tied to historical disturbances and independent of environmental conditions. Therefore, the importance of minimizing disturbance in areas of high conservation value will be the key for successful control and management of Japanese spiraea at Buffalo Mountain. ACKNOWLEDGMENTS We thank John Peterson and David Walker for giving their time and effort to assist with field work and data collection. We also express our thanks to the Virginia Tech Department of Recreational Sports for providing funding for this project. Finally, we extend a sincere thank you to Claiborne Woodall and the Virginia Department of Conservation and Recreation s Natural Heritage Program for allowing us the opportunity to work at Buffalo Mountain Natural Area Preserve. Jeffrey J. Feldhaus completed his M.F. at Virginia Tech in the Department of Forest Resources and Environmental Conservation in He is currently at the same institution pursuing a Ph.D. Carolyn A. Copenheaver is an Associate Professor in the Department of Forest Resources and Environmental Conservation at Virginia Tech. Her research focuses on dendrochronology, disturbance ecology, and land-use history. Jacob N. Barney is an Assistant Professor of Invasive Plant Ecology in the Department of Plant Pathology, Physiology, and Weed Science at Virginia Tech where he studies invasive plants, risk assessment, and bioenergy crop ecology. LITERATURE CITED Alpert, P The advantages and disadvantages of being introduced. Biological Invasions 8: Aronson, M.F.J., and S.N. Handel Deer and invasive plant species suppress forest herbaceous communities and canopy tree regeneration. Natural Areas Journal 31: Blossey, B Before, during, and after: the need for long-term monitoring in invasive plant species management. Biological Invasions 1: Bradley, B.A., D.M. Blumenthal, R. Early, E.D. Grosholz, J.J. Lawler, L.P. Miller, C.J.B. Sorte, C.M. D Antonio, J.M. Diez, J.S. Dukes, I. Ibanez, and J.D. Olden Global change, global trade, and the next wave of plant invasion. Frontiers in Ecology and Environment 10: Britton, K., B. Illman, and G. Man Prevention. Pp in M.E. Dix and K. Britton, eds., A Dynamic Invasive Species Research Vision: Opportunities and Priorities General Technical Report WO-79/83, U.S. Department of Agriculture, Forest Service, Washington, D.C. Burnham, K.M., and T.D. Lee Canopy gaps facilitate establishment, growth, and reproduction of invasive Frangula alnus in a Tsuga canadensis dominated forest. Biological Invasions 12: Colautti, R.I., and D.M. Richardson Subjectivity and flexibility in invasion terminology: too much of a good thing? Biological Invasions 11: Conner, R.K Soil Survey of Floyd County, Virginia. USDA Natural Resources Conservation Service, Washington, D.C. 438 Natural Areas Journal Volume 33 (4), 2013

5 Copenheaver, C.A., N.E. Fuhrman, L.S. Gellerstedt, and P.A. Gellerstedt Tree encroachment in forest openings: a case study from Buffalo Mountain, Virginia. Castanea 69: Davids, R.C The Man Who Moved a Mountain. Fortress Press, Philadelphia, Pa. Essl, F Ausbreitung und beginnende Einbürgerung von Spiraea japonica in Österreich. Botanica Helvetica 115:1-14. Gleason, H.A., and A. Cronquist Manual of Vascular Plants of Northeastern North America and Adjacent Canada, 2 nd ed. The New York Botanical Garden, Bronx. LeMaitre, D.C., M. Gaertner, E. Marchante, E.J. Ens, P.M. Holmes, A. Pauchard, P.J. O Farrell, A.M. Rogers, R. Blanchard, J. Blignaut, and D.M. Richardson Impacts of invasive Australian acacias: implications for management and restoration. Diversity and Distributions 17: Lockwood, J.L., P. Cassey, and T. Blackburn The role of propagule pressure in explaining species invasions. Trends in Ecology and Evolution 20: Martine, C.T., S. Leicht-Young, P. Herron, and A. Latimer Fifteen woody species with potential for invasiveness in New England. Rhodora 110: Miller, D.R., and G.L. Miller A new species of Puto and a preliminary analysis of the phylogenic position of the Puto group within Coccoidea (Homoptera: Pseudococcidae). Jeffersoniana 4:1-35. Mueller-Dombois, D., and H. Ellenberg Aims and Methods of Vegetation Ecology. J. Wiley, New York. Pimentel, D., L. Lach, R. Zuniga, and D. Morrison Environmental and economic costs of non-indigenous species in the United States. Bioscience 50: Pysek, P., and D.M. Richardson Traits associated with invasiveness in alien plants: where do we stand? Ecological Studies 193: Remaley, T Japanese spiraea. Fact Sheet, Plant Conservation Alliance s Alien Plant Working Group, Great Smoky Mountains National Park, Gatlinburg, Tenn. Salehi, R., and J.A. Brown Complete allocation sampling: an efficient and easily implemented adaptive sampling design. Population Ecology 52: Simberloff, D., and B. von Holle Positive interactions of nonindigenous species: invasional meltdown? Biological Invasions 1: Spyreas, G., B.W. Wilm, A.E. Plocher, D.M. Ketzner, J.M. Matthews, J.L. Ellis, and E.J. Heske Biological consequences of invasion by reed canary grass (Phalaris arundinaceae). Biological Invasions 12: Sullivan, K.A., and A.M. Ellison The seed bank of hemlock forests: implications for forest regeneration following hemlock decline. Journal of the Torrey Botanical Society 133: Swain, S., S. Narumalani, and D.R. Mishra Monitoring invasive species: detecting purple loosestrife and evaluating biocontrol along the Niobrara River, Nebraska. GI- Science & Remote Sensing 48: Turner, K., L. Lefler, and B. Freedman Plant communities of selected urbanized areas of Halifax, Nova Scotia, Canada. Landscape and Urban Planning 71: Vila, M., J.L. Espinar, M. Hejda, P.E. Hulme, V. Jarosik, J.L. Maron, J. Pergl, U. Schaffner, Y. Sun, and P. Pysek Ecological impacts of invasive alien plants: a meta-analysis of their effects on species, communities, and ecosystems. Ecology Letters 14: Wellman, W.R Chemical control of Japanese spiraea (Spiraea japonica) in Big South Fork National River and Recreation Area. University of Kentucky, Lexington. Wilson, R.L., and W.A. Hoch Identification of sterile, noninvasive cultivars of Japanese spiraea. Hortscience 44: Volume 33 (4), 2013 Natural Areas Journal 439

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