Plant Ecol (2010) 211:65–77 DOI 10.1007/s11258-010-9773-2 Establishment of the invasive perennial Vincetoxicum rossicum across a disturbance gradient in New York State, USA Kristine M. Averill • Antonio DiTommaso • Charles L. Mohler • Lindsey R. Milbrath Received: 23 October 2009 / Accepted: 7 April 2010 / Published online: 22 April 2010 Ó Springer Science+Business Media B.V. 2010 Abstract Vincetoxicum rossicum (pale swallow- tillage and herbicide-only plots [1.6 ± 0.5%]. Of those wort) is a non-native, perennial, herbaceous vine in seedlings that emerged, overall survival was high at the Apocynaceae. The species’ abundance is steadily both locations (70–84%). Similarly, total (above ? increasing in the northeastern United States and belowground) biomass was greater in herbicide ? till- southeastern Canada. Little is known about Vincetox- age and herbicide-only plots than in mowed and icum species recruitment and growth. Therefore, we control plots at both locations. Thus, V. rossicum was conducted a field experiment in New York State to successful in establishing and surviving across a range address this knowledge gap. We determined the of disturbance regimens particularly relative to other establishment, survival, and growth of V. rossicum old field species, but growth was greater in more during the first 2 years after sowing in two old fields disturbed treatments. The relatively high-establish- subjected to four disturbance regimens. We hypothe- ment rates in old field habitats help explain the sized that establishment and survival would be higher invasiveness of this Vincetoxicum species in the in treatments with greater disturbance. At the better- northeastern U.S. and southeastern Canada. drained location, overall establishment was 15 ± 1% [mean ± standard error] and did not differ among Keywords Biotic resistance Á Dog-strangling vine Á treatments. At the poorly drained location, establish- Environmental gradient Á Invasibility Á ment varied by treatment; mowed and control plots had Pale swallow-wort Á Weed ecology greater establishment [10 ± 2%] than herbicide ? Introduction K. M. Averill Á A. DiTommaso (&) Á C. L. Mohler Department of Crop and Soil Sciences, Cornell A species must overcome a cascade of limiting factors University, Ithaca, NY 14853, USA to become invasive (Gordon 1998; Williamson 2006). e-mail: [email protected] Enough propagules must be transported from the native range for a population to establish. Recruitment Present Address: K. M. Averill is a critical phase in the invasion process, during which Department of Crop and Soil Sciences, The Pennsylvania high rates of mortality may occur (Jesson et al. 2000; State University, University Park, PA 16802, USA Lockwood et al. 2005); it is driven largely by biogeographical and ecological factors (Williamson L. R. Milbrath USDA-ARS Robert W. Holley Center for Agriculture 2006). Gurvich et al. (2005) suggest that once an and Health, Ithaca, NY 14853, USA invader becomes established, the invaded habitat must 123 66 Plant Ecol (2010) 211:65–77 satisfy only one or a few characteristics to ‘‘trigger’’the held constant the propagule pressure (number of spread and invasion of the species. Abiotic constraints individuals per unit area) (Lockwood et al. 2005) and play a dominant role in invasibility of habitats and, in time since introduction (by using one sowing date). suitable environments, invasives must additionally We also controlled for autecology by only examining overcome biotic constraints (Gerhardt and Collinge one species and genetic variation because propagules 2007). Early successional habitats, such as old fields, were collected from one population. Using only one are particularly prone to invasion due to their vulner- population was valid because genetic similarity is able state of transition (Johnson et al. 2006). high among introduced V. rossicum populations in One area of focus in the plant invasion literature is New York (Douglass 2008; Douglass et al. 2009). We the attempt to find commonalities among habitats that varied the intensity of old field disturbance. We used increase their susceptibility to invasion. Disturbance mowing, herbicide applications, and tillage to deter- allows a direct or indirect increase in available mine the response of V. rossicum to different distur- resources (Sousa 1984), including light, nutrients, and bance regimes. This approach tested the fluctuating water previously utilized by the resident vegetation resource hypothesis of invasibility (Davis et al. 2000), (Canham and Marks 1985). Even brief disturbances which proposes that plant species may successfully allow a pulse of resources to be released that can establish in novel habitats when their propagules temporarily reduce competition and increase suscep- encounter unexploited resources such as light, mois- tibility to invasion (Davis et al. 2000; Davis and ture, or nutrients. We predicted that V. rossicum Pelsor 2001; Yang et al. 2008). Many non-indigenous establishment success and growth would be the lowest species can establish by taking advantage of such in the control treatment, where competition would be disturbed habitats (Gray et al. 1987; Hobbs 1989; strongest (intact old field community), and that Hobbs and Huenneke 1992; Orians 1986). Vincetox- establishment and growth would increase with icum rossicum (Kleopow) Barbar. = Cynanchum increasing disturbance intensity. rossicum (Kleopow) Borhidi (pale swallow-wort) is one invader that we hypothesized would have a high potential for exploiting resources after disturbances. Materials and methods Thus, V. rossicum was the focus of the experiments reported here. Study species In order to improve management of invasive plants, the use of manipulative field experiments that aid in Vincetoxicum rossicum (Apocynaceae, subfamily determining which habitats or plant communities can Asclepiadoideae) is native to the Ukraine and South- resist or are susceptible to invasion has been proposed western Russia where it grows on stony meadow (Bergelson et al. 1993; Davis et al. 2000; Levine and steppe habitats and on rock outcrops (DiTommaso D’Antonio 1999). However, the multiple interacting et al. 2005b). The species was introduced into North factors that contribute to invasion success need to be America in the late-1800s (Moore 1959), probably as considered in such studies (Hobbs and Humphries an escaped ornamental (Sheeley and Raynal 1996). Its 1995). In the experiment reported here, we adhered to current distribution extends from the Atlantic coast the research framework proposed by Barney and west to southern Michigan and northern Indiana, and Whitlow (2008) in their state factor model for from southern Ontario, Canada, south to southern biological invasions. They presented five state factors, Pennsylvania (DiTommaso et al. 2005b; Sheeley and including propagule pressure, introduced habitat, Raynal 1996). V. rossicum is a twining herbaceous invader autecology, source environment and genetic perennial vine that can grow up to 3 m long in one variance, and time since introduction, and suggested growing season (Averill et al. unpublished) and that more experimental evidence with consideration exhibits relatively high fecundity (Averill et al. for these state factors is required to elucidate invasion unpublished; Sheeley 1992; Smith et al. 2006). The success and provide managers with a more holistic species reproduces and invades new sites by seed, but view of the invasion (Barney and Whitlow 2008). In plants can also grow and expand via buds on root our 2-year study, we controlled for four of the five crowns (Averill et al. unpublished; DiTommaso et al. state factors, while manipulating a fifth factor. We 2005b). V. rossicum seeds, like other members in the 123 Plant Ecol (2010) 211:65–77 67 Apocynaceae, have silky, parachute-like appendages elevation 317 m). V. rossicum is uncommon at both (coma) that assist in wind dispersal. Seeds are often locations; only one mature plant was found 20 m polyembryonic, giving rise to as many as six multiple from the hill top experiment. Despite the ability of seedlings independently of seed mass (Cappuccino V. rossicum to thrive in low light environments, et al. 2002; DiTommaso et al. 2005b). This invasive management in high light habitats is of foremost vine has shown variable emergence and survival in concern, since reproductive output and plant expan- field and glasshouse conditions (Cappuccino et al. sion is greater in such environments (Averill et al. 2002; DiTommaso et al. 2005a; Ladd and Cappuccino unpublished; Hotchkiss et al. 2008; Smith et al. 2005). Emergence (50–72%) and survival (71–100%) 2006). Prior to the start of our study, the hill top and were high in a relatively undisturbed 5-year old field plateau locations had not been mowed for 1 and in Ontario, Canada (Ladd and Cappuccino 2005). 5 years, respectively. Mature V. rossicum plants exhibited 99–100% sur- In November 2007, we collected soil samples from vival during a 4-year field study (Averill et al. each location to determine pH, soil organic matter unpublished), demonstrating that, once established, (SOM) derived from loss on ignition (Storer 1984), these plants have high survival rates. and percentage moisture. The hill top location is on a Vincetoxicum rossicum is increasingly problematic Mardin channery silt loam (course-loamy, mixed, in a range of habitats including old fields, pastures, active, mesic typic fragiudepts), which is a moder- no-tillage agricultural fields, Christmas tree planta- ately well-drained soil with