Slow spread of the aggressive invader, Microstegium vimineum (Japanese stiltgrass)

Abstract

Microstegium vimineum (Japanese stiltgrass) is a non-native weed whose rapid invasion threatens native diversity and regeneration in forests. Using data from a 4 year experiment tracking new invasions in different habitats, we developed a spatial model of patch growth, using maximum likelihood techniques to estimate dispersal and population growth parameters. The patches expanded surprisingly slowly: in the final year, the majority of new seedlings were still within 1 m of the original patch. The influence of habitat was not as strong as anticipated, although patches created in roadside and wet meadow habitats tended to expand more rapidly and had greater reproductive ratios. The long-term projections of the patch growth model suggest much slower spread than has typically been observed for M. vimineum. The small scale of natural dispersal suggests that human-mediated dispersal, likely influenced by forest road management, is responsible for the rapid spread of this invasive species.

Predicting Microstegium vimineum invasion in natural plant communities of the southern Blue Ridge Mountains, USA

“…The long-distance dispersal must primarily occur along roads or be associated with human activity (Fig. 4; I) as these are known movement corridors, were important factors in our modelling, and have been ubiquitous in other studies (Cheplick 2010;Christen and Matlack 2009;Cole and Weltzin 2004;Clay 2006, 2009;Mortensen et al 2009;Rauschert et al 2010). The exact mechanism and dispersal kernel for long movements remain unknown (Warren et al 2011b), and our data were insufficient to shed any light on this process (i.e., we cannot identify likely sources of nascent populations).…”

“…Microstegium vimineum has been in the eastern United States since 1917 (Fairbrothers and Gray 1972), and Kuhman et al (2010) documented this species in 100 % of 25 Southern Appalachian watersheds surveyed and in 84 % of roadside plots. Longdistance dispersal must occur because this species could not otherwise have become so widely distributed, given the slow dispersal rates reported in finescale studies (Huebner 2010b;Mortensen et al 2009;Rauschert et al 2010). The long-distance dispersal must primarily occur along roads or be associated with human activity (Fig.…”

“…The exact mechanism and dispersal kernel for long movements remain unknown (Warren et al 2011b), and our data were insufficient to shed any light on this process (i.e., we cannot identify likely sources of nascent populations). However, these events must be infrequent and stochastic because efforts to quantify dispersal along roads have demonstrated very slow spread (Huebner 2010b;Mortensen et al 2009;Rauschert et al 2010;Warren et al 2011a).…”

“…The mechanism for this dispersal also remains unknown (Warren et al 2011b) but must be secondary dispersal as M. vimineum seeds generally fall very close to the maternal plant (Huebner 2010b;Rauschert et al 2010;Warren et al 2011a). Human activity is likely responsible for intermediate-distance dispersal along roads and trails (Cole and Weltzin 2004;Rauschert et al 2010). Flooding and water flow paths that intersect a source population also have the potential to move propagules (Mehrhoff 2000;Miller and Matlack 2010;Warren et al 2011a).…”

Performance and reproduction of an exotic invader across temperate forest gradients

“…If plots lacking M. vimineum represent dispersal limitation (Gibson et al 2002, Christen and Matlack 2009, Miller and Matlack 2010, Rauschert et al 2010) and/or time since invasion (Richardson and Pysek 2006), (H 1a ) we hypothesize that there will be little difference in environmental variables between invaded and uninvaded plots. However, if environmental variables limit or prevent M. vimineum establishment and persistence (H 1b ), we expect significant differences in environmental variables between invaded and uninvaded habitats.…”