Thesis (M.S.)--Texas State University--San Marcos, 2009. / Vita. Reproduction permission applies to print copy: Blanket permission granted per author to reproduce. Includes bibliographical references (leaves 49-55).

Thesis (M.S)--Ohio University, March, 2005. / Includes bibliographical references (p. 135-158)

Thesis (Ph. D.)--Wageningen University, 2006. / Thesis propositions sheet inserted. "Author's publications": p. 194-196. Includes bibliographical references (p. 151-180).

Thesis (M.S)--Ohio University, March, 2005. / Title from PDF t.p. Includes bibliographical references (p. 135-158)

Thesis (M.S.)--Humboldt State University, 2007. / Includes bibliographical references (leaves 37-38). Also available via Humboldt Digital Scholar.

Thesis (Ph.D. (Zoology and Entomology)) - Rhodes University, 2007.

Thesis (M.Sc.(Agric.))(Plant Production)--University of Pretoria, 2006. / Includes bibliographical references. Available on the Internet via the World Wide Web.

Thesis (M.S. in environmental science)--Washington State University, May 2007. / Includes bibliographical references (p. 30-33).

The increased movement of plants around the world is a serious and impactful environmental consequence of increased human dominance globally. Some of these plants will become established in new areas, some will proliferate, and some will become invasive causing environmental and socio-economic damage. Environmental processes contribute to plants becoming introduced, established and invasive. However, humans have an increasingly important role in all stages of the invasion process. In particular, the social processes that shape decision making, such as knowledge, risk perceptions, values and attitudes, can influence people’s behaviour that might lead to increased or decreased spread of invasive non-native plants (INNP). The social processes contributing to individual decision-making can be particularly influential in domestic gardens as it is the individual(s) responsible for that garden that decides how it is managed. Furthermore, the socio-economic impacts of INNP can be particularly acute in domestic gardens. In addition to the direct impacts of INNP in domestic gardens, an increase of their abundance therein could be detrimental to the health and well-being benefits gardens can provide, such as increased connectedness to nature. Invasion ecology is a rapidly growing area of research, however, key gaps in knowledge remain. In particular, little research has been done on INNP in domestic gardens and the perceptions of risk people have about the impacts they can have therein. This thesis applies an interdisciplinary approach to address these gaps. Japanese knotweed Fallopia japonica, is used as a case study throughout as it exemplifies many of the environmental and socio-economic impacts of INNP, many of which are particularly acute in domestic gardens. Identifying the processes contributing to the spread of INNP will help develop mitigation strategies to reduce their spread and therefore impact - this is the focus of chapters two to six. Chapter two explores the predictors of presence and abundance of Japanese knotweed at a 1km resolution within Cornwall, UK, finding that building density is the strongest predictor, followed by biophysical variables (minimum and maximum monthly temperature), and then socio-economic status of the residents within the 1km grid-cell. Chapter three considers one social process that might be contributing to the spread of INNP - the movement of propagules within soil. One of the key results of this chapter is that the abundance of invasive and naturalised species was significantly higher in garden than in housing development samples. This suggests that informal movement of soil between gardens poses a greater risk of spreading invasive plants than do commercial sources. Chapter three highlights the importance of high levels of identification skills of INNP to reduce their spread, however no previous research has tested INNP identification levels amongst the public. Chapter four explores this idea, finding that less than 20% of the public could identify Japanese knotweed. Even if people can identify INNP, if it is present in their garden they may not know how to manage it correctly and details of the impacts it can have therein. Chapter five analyses internet-based information about the management advice and impacts of INNP, determines the authors of this discourse, and considers whether and how this could be confusing to those responsible for managing domestic gardens. Analysis identified extensive variation in document structure, topics discussed, references and links to other sources, and language style; sometimes this variation was between and sometimes within author categories. A key conclusion from chapter five is that some internet-based information sources might potentially contribute to amplification (or attenuation) of risk perceptions, that could in turn lead to inappropriate management actions, resulting in increased spread of INNP. Chapter six uses a survey approach to explore risk perceptions of INNP in domestic gardens further. The results suggest differences in perceived risk of Japanese knotweed depends on people’s occupation, their direct experience of the species in a domestic context, their geographical proximity to the risk, their age and level of education. Greater understanding of the impacts INNP can have within domestic gardens will help assess the level of risk, plan mitigation strategies and design risk communication. This is the focus of chapter seven, which focuses on the economic impacts within domestic gardens. Results indicate that the magnitude and frequency of the risks Japanese knotweed poses in domestic gardens are much lower than anticipated based on media coverage, and compared with public perception. The results of this thesis have several important implications: (1) To mitigate potential inaccurate perceptions of INNP, governmental authorities need to provide clear and accurate communication about the impacts of INNP and how best to manage them. (2) When resources are limited, identifying the areas of society where knowledge is lowest or perceptions most inaccurate can help awareness and educational campaigns to be more impactful, thus reducing spread and impacts of INNP. (3) Implementation of the recommendations to reduce the spread and impacts of INNP within domestic gardens given within this thesis could contribute towards preserving the health and well-being benefits gardens can provide. Overall this thesis demonstrates further evidence of the need to consider the human causes and solutions to INNP and the need for knowledge on this topic to be applied by a diverse range of stakeholders.

This study was conducted to provide insight into the response of Achyranthes japonica to management tools in the form of complete shoot removal (clipping) and herbicide application at Cypress Creek National Wildlife Refuge (CCNWR) in southern Illinois. Field herbicide experiments indicate that A. japonica is susceptible to foliar applications of systemic, broad leaf herbicides. The removal of A. japonica by herbicide, however, did not allow for re-establishment of the surrounding plant community in years 2011 and 2012. Seedlings at node stage 3, 4 and 6 were able to regrow following complete shoot removal indicating that this species can sustain perennial growth when it develops three nodes and that the node stage at which plants were clipped did not affect their regrowth potential. In the greenhouse, A. japonica was able to regrow following complete shoot removal at the 3 node stage and the number of branches and apical nodes on a plant are the best predictors of the regrowth potential for this species. Achyranthes japonica's susceptibility to foliar applications of systemic herbicides in the greenhouse was high. Herbicide titration results indicate that of the six herbicides tested (2,4-D ester, triclopyr, glyphosate, aminopyralid, triclopyr+fluroxypyr, and aminopyralid+metsulfuron) triclopyr required the least amount of active ingredient to reduce the growth of A. japonica by 50% (GR-50). Results overall suggest that A. japonica reaches perennial growth by the time it has three nodes, making clipping as a management tool only successful if done before plants have developed three nodes. Achyranthes japonica perennial plants are highly susceptible to foliar applications of broad leaf systemic herbicides making them a good management tool in the field.