Wetland value is threatened by invasive plant species such as Reed Canarygrass (Phalaris arundinacea). Hence the research objectives of this project were to determine if reed canarygrass abundance has an effect on plant species diversity and assess the effectiveness of novel treatments on reed canarygrass control in a constructed wetland. Four treatments (mowing, herbicide, mowing plus herbicide, and a control) followed by broadcast seeding were applied to regulate growth of reed canarygrass. Principal components analysis, biodiversity measures, and ANOVA were used to identify community composition, quantify biodiversity values and identify treatment differences respectively. Results indicated differences in species composition between east and west blocks of the study site, reed canarygrass abundance appears to keep plant species diversity low, indigenous species were rare, and reed canarygrass was resistant to treatments.The results of this study are not surprising considering there is little evidence that treatments for reed canarygrass control are effective.

Invasive species are one of many important environmental issues facing Canadians today. A great deal of research has explored both the scientific and social aspects of invasive species. However, the cumulative research has not yet thoroughly explored people’s thoughts and feelings about, or perceptions of, invasive species and the influence these may have on management of, or policy decisions regarding, invasive species. This thesis research project was designed to assess the attitudes and perceptions that high school students have towards invasive species and to determine to what extent learning about invasive species alters their connection with nature. The study group was comprised of students from four Grade 11 Environmental Science classes from three high schools within the city of Guelph, Ontario. The students received regular classroom instruction from their teachers covering the course content, including invasive species. Students also made weekly visits to a local nature centre, providing them with hands-on learning experiences related to the course content. Students responded to an 80-question survey that assessed their knowledge of local invasive species and attitudes towards them as well as students’ connection to nature. Their connection to nature was assessed using a modified version of the Connectedness to Nature Scale (Mayer & Frantz, 2004). The surveys were administered by the classroom teachers in October, 2010, prior to the presentation of instructional material covering invasive species and then again in December, 2010 when the presentation of instructional material concerning invasive species was complete. The results showed that the students’ knowledge of invasive species upon entering the course was quite low and each of the classes witnessed a significant increase in knowledge. The survey results did not reveal any change to the students’ connection to nature; however, they did reveal three underlying themes in students’ attitudes towards invasive species: a concern about invasive species as a threat or problem; feelings of acceptance towards invasive species; and feelings of anxiety about invasive species. These attitudes remained relatively unchanged after the course.

The horticultural industry is responsible for approximately half of the invasive plant introductions in North America. To reduce these introductions, voluntary initiatives are preferred over government regulations. This thesis aims to evaluate the effectiveness of two types of voluntary initiatives. At the gardener level, I investigated the effectiveness of alternative species promotion campaigns, called “Grow Me Instead” programs. Adult gardeners visiting the Royal Botanical Gardens in Hamilton, Ontario, as well as customers at two garden centres, participated in a conjoint analysis which measured their preferences for various traits of potential ground cover species. Results showed that gardeners generally prefer plant species having invasive characteristics, suggesting these programs may not be as effective as initially believed. At the retailer level, this study aimed to build upon the work done by Burt and colleagues (2007) to obtain further understanding of the relative strength of internal (ethical motivations) and external (legislation, stakeholder pressures and economic opportunities) factors for motivating participation in voluntary initiatives. Telephone interviews were conducted with 30 industry professionals from southern Ontario to assess their adoption of the St. Louis Voluntary Codes of Conduct. Results found that participation rates of industry professionals in southern Ontario were lower for every specific initiative than those interviewed by Burt et al. (2007). Industry professionals presently experience the most pressure to participate from a sense of personal responsibility and the desire to create a green business image. Pressure was significantly higher from these sources than from pressure from employees. Together these two studies identified several barriers to the efficacy of voluntary initiatives as well as some reasons for optimism. To ensure the success of future voluntary initiatives, efforts must be made to encourage these two groups to work together. Understanding how both retailers and gardeners respond to voluntary initiatives will assist in the development of more effective programs and lead to fewer horticultural invasive species introductions in the future.

This study focused on an invasive riparian reed grass, Arundo donax L., a clonal plant of the family Poaceae that is widely distributed in North America. Water availability, including water taken up from the roots locally or transported from the neighboring ramets, may affect the performance of A. donax in riparian zones. The first objective was to find out how moisture gradients affected the performance of A. donax in riparian zones. I measured leaf photosynthetic rate, leaf δ13C ratio, and plant growth-related parameters across two summer growing seasons at four transects perpendicular to the water course on the Rio Grande in South Texas. The second objective was to find out whether physiological integration existed in A. donax and how resource sharing, if any, affected plant growth. A rhizome severing experiment was conducted on five paired plots to compare growth-related parameters between plots with rhizomes severed and intact at 3, 7, and 11 weeks after treatment. Heavy water (δ 2H ~1800‰) was applied on three 1-m2 area over 3 successive days and rhizome samples were collected beyond the watering zone after 5, 24, and 48 hours of last watering. At short-term scales, A. donax performance was adversely affected by both drought and inundated conditions; over longer time scales, plant performance decreased as water availability declined in general, but biomass and stem density were similar across moisture gradients. I also found evidence of physiological integration in A. donax. Water was transported through interconnected rhizomes at least 3.5 m; transport distances averaged 1.67 m. Rhizome severing stimulated higher ramet production initially but over longer periods produced shorter thinner stems with lower flood tolerance. However, after 11 weeks of re-growth, plot-level biomass was similar between plots with severed and intact rhizomes. These results suggest that performance of A. donax is affected by water availability in riparian zones; however, clonal plant plasticity, water use efficiency, and clonal integration ameliorate impacts of water stress on the performance of A. donax. Such traits enhance its resource use, which could potentially increase competitive ability rate of establishment, and extent of this invasive species in heterogeneous riparian environments.

Invasive species are problematic but their control can be difficult. When the history and dynamics of invasive populations are unknown, analytical techniques utilising genetic data can provide information to management. The application of these techniques has typically been limited to species with restricted dispersal or to localised geographic scales. Here these techniques are used in conjunction with traditional approaches to study the invasion of a highly vagile species over a continental scale. Originally introduced to eastern Australia, the common starling (Sturnus vulgaris) is expanding westward and has reached the southeast agricultural region of Western Australia (WA). Spatial, temporal and museum samples representing historical incursions into WA were used in genetic analyses to answer questions important to WA management agencies. Where possible, multiple marker classes were used to evaluate their relative ability to address these questions, including microsatellites, mitochondrial DNA (mtDNA), and a nuclear gene. Between two and four genetic groups were identified in Australia, and the localities on the edge of the range expansion (ERE) were consistently genetically differentiated from all others. Levels of genetic exchange between groups appeared to be low, suggesting that localised control may be effective. Analyses of historical samples indicated patterns of genetic exchange are temporally stable. This suggests that starlings will continue to arrive from the east, requiring vigilance from management. Consistently, a negative relationship was found between genetic diversity and date of first record, which may help in the future to distinguish ineffective surveillance from recent colonisations. Genetic evidence of female-biased dispersal indicated that control strategies preferentially targeting females may more efficiently limit dispersal than those targeting both sexes equally. Variants private to particular genetic groups were identified; tracking the spread of these variants may assist future monitoring programs in understanding ongoing exchange between groups. One mtDNA variant private to ERE localities showed dramatic temporal change, which could not be adequately explained by genetic drift or admixture, but may be explained by selection. Microsatellites were most useful in determining origins and identifying dispersers, mtDNA sequences provided a unique tool for ongoing monitoring of dispersal, and nuclear sequences had high levels of gene diversity and resolution of population structure.

Thesis (M.S.)--Indiana University, 2008. / Title from screen (viewed on April 23, 2008). Department of Earth Sciences, Indiana University-Purdue University Indianapolis (IUPUI). Advisor(s): Gabriel M. Filippelli, Catherine J. Souch, Gary D. Rosenberg. Includes vitae. Includes bibliographical references (leaves 85-87).

Theses (M.S.)--University of Hawai'i at Hilo, 2008. / Advisor : Mautz, William Bibliography : p.39-42.

In this thesis I investigated various factors that might affect species diversity and the relations between predator/parasitoid and host, using mainly insects as a model group. These factors were agricultural practices, landscape composition, climate change and invasive species.

Historically, the tallgrass prairie (TGP) was the largest ecosystem in North America, but today only about 10-15% of the original extent exists today. Some areas have experienced more extreme loss, for example in the state of Illinois less than 0.01% of high-quality native tallgrass prairie remains. Non-native invasive species are a recent phenomenon that threatens the integrity of surviving TGP communities. Ecotypes of dominant C4 grasses are the basis of numerous cultivars, many of which are utilized in prairie restorations. In this study, the effects of three invasive species (Bromus inermis, Schedonorus phoenix, and Poa pratensis) on two lowland (`Alamo' and `Kanlow') and three upland (`Blackwell', `Cave in Rock', and `Trailblazer') cultivars of the dominant C4 grass Panicum virgatum were tested. Two simple pair-wise greenhouse experiments were established in which cultivars were sown as a monoculture or as a mixture of the cultivars with one of three invasive species. Pots were subjected to one of two water treatments with three replicates of each treatment combination. Response variables (height, number of leaves, tiller density, and biomass) and resources (soil moisture, soil pH, soil electrical conductivity, and light intensity) were measured. The greenhouse studies showed that response variables were affected by the presence of invasive species and that the time of growth affected resource levels. Resources are allocated to different areas (i.e growth and reproduction) when competition and stress are implemented on the dominant species. This study was the first to experimentally test for the presence of the physiological stress marker, trigonelline, in a prairie grass. Trigonelline was highest in upland cultivars under low moisture and highest in lowland cultivars under low moisture treatments. The results of these greenhouse studies suggest that invasive species may differentially affect cultivars of Panicum virgatum that may be sown in a prairie restoration. Performance of the P. virgatum cultivars was dependent on the timing of growth, the pot size, the invasive species, as well as soil moisture level. Therefore, when choosing a cultivar source for restoration, resources (i.e. soil moisture) should be looked into to maximize the output of the cultivar.

The timing of biological events in autumn, or autumn phenology, is an important factor in many ecosystem processes. Leaf senescence terminates the growing season, fruiting is important for seed dispersal and frugivorous wildlife, bird migration concludes the breeding season and is a high-mortality event, and insect diapause ends the active season for insects. Climate change and the spread of invasive species have the potential to shift autumn events and ecological processes. However, autumn has been neglected in the phenology literature, and there are many gaps in our knowledge of basic phenological patterns in this season, as well as how they are affected by anthropogenic changes. To address these gaps, I first synthesized the literature on how climate change affects autumn phenology. I found that shifts in autumn phenology can alter reproductive capacities, exacerbate invasions, increase disease transmission rates, reshuffle enemy-prey dynamics, and alter interactions between species. With a focus on autumn interactions between birds and fleshy-fruited plants, my colleagues and I then observed patterns of fruit phenology, using herbarium specimens of 55 species collected across New England, and over 400 species in the living collections of 5 international botanical gardens. Last, I monitored fleshy fruit phenology and abundance at Manomet, a migratory stopover site in coastal Massachusetts, and compared those patterns to seeds identified from landbird fecal samples collected across the autumn season. I found that the sequence of fruiting is moderately consistent from year to year and place to place, and has a significant phylogenetic signal. In wild plants, invasive species fruit, on average, nearly one month later than native species. Considering many landbirds are migrating through New England later over time and in warm years, this suggests birds are increasingly likely to encounter invasive fruits during late-autumn migration. However, bird diets do not reflect the increased availability of invasive fruits in late-autumn; rather, birds show a preference for native fleshy fruits throughout the autumn season. These findings add to our knowledge of how climate change and species invasions affect autumn synchrony, and highlight the importance of native, rather than invasive, fruits as a food source for migratory landbirds. / 2019-11-07T00:00:00Z