Watercourses and especially their riparian vegetation are habitats that are very sensitive to spreading of invasive plant species. Rivers create natural migration routes (corridors) and help propagules to spread quickly and easily. The theoretical part of this thesis is focused on plant invasions and covers also the most recent knowledge in the field of invasion ecology. In the practical part of this thesis the spread of invasive neophytes in the riparian vegetation of the Kamenice river in Northern Bohemia is described. The plant species were examined during the field survey along the entire stream of the Kamenice river. In total, common occurence of 7 invasive taxa were recorded, namely Impatiens parviflora, I. glandulifera, Reynoutria japonica, R. sachalinensis, R. bohemica, Solidago gigantea and S. canadensis. The distribution of observed taxa along the stream as well as on the banks was relatively uneven.

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Numerous studies have looked at biotic succession at the aboveground level; however, there are no studies describing fungal community change associated with long-term ecosystem development. To understand ecosystem development, the organisms responsible for shaping and driving these systems and their relationships with the vegetation and soil factors, it is critical to provide insight into aboveground and belowground linkages to ultimately include this new information into ecosystem theory. I hypothesized that fungal communities would change with pedogenesis, that these changes would correlate with vegetation community change, and that they should show change of composition and diversity as the seasons change. Chapter 1 discusses the main topics related to this dissertation. Chapter 2 includes a publication draft that describes a study of sand-dune soil samples from northern Michigan that were analyzed to pinpoint the structural change in the fungal community during the development of the ecosystem. The samples were analyzed by pyrosequencing the soil DNA, targeting the internal transcribed spacer region. Chapter 3 contains a coauthored published paper that describes plant invasion of fields in Virginia to determine how they impact soil bacterial and fungal communities. The bacterial and fungal communities that were invaded by 3 different plant species exhibited similar changes, regardless of plant species, suggesting that some functional traits of invasives may have similar impacts on belowground communities. Chapter 4 remarks the conclusions of this research. / Master of Science / Ecosystems, including the soils underneath, are the environments that surround us perform a large number of critical human-relevant functions (playing roles in production of food, filtration of water for drinking, sequestration of carbon and nitrogen to build soil organic matter, and buffer against flooding). Yet, how these systems naturally develop over time are still in need of detailed study. One particular area of interest and need is the study of belowground fungal communities. It is not commonly known, but plants and ecosystems are highly dependent on the underground web of fungal hyphae that transform nutrients and provide water to plants. A first step in gaining this understanding utilized a natural ecosystem development gradient known as a chronosequence. It was expected that fungal communities would change as soil and ecosystem development progressed and that they would mimic changes in soil and vegetative properties. Discerning if these linkages occur is the first step to assessing how they work together to create ecosystems and their valuable environmental services. Chapter 1 provides a discussion of the main topics in this dissertation. Chapter 2 is at the heart of the dissertation via a study of fungal communities in a developmental soil ecosystem in northern Michigan in addition, in Chapter 3, I include a coauthored published paper that describes plant invasion of fields in Virginia. Chapter 4 remarks on the major conclusions of this Master thesis, supporting the role that vegetation and fungal community change in soil are associated with one another.

Invasive spread of neophyte Impatiens glandulifera in central Europe started approximatelly eighty years ago. First records of dense cover stands come from belt stands in riparian habitats. The scale of invaded habitats and degree of the dominance of I. glandulifera is more diversified nowadays. This thesis is objected on the dominance and fertility of I. glandulifera within different habitat types and scale of invaded habitats in different parts of invaded range within Europe (i. e. in Czech Republic and Switzerland). The results show that the height and cover (substitutes for biomass and dominance) of this neophyte (i) correlates with the character of invaded vegetation (ii) relates to the degree of hemeroby (a measure of human impact) negativelly, and (iii), of course, both the growth and dominance are positively affected by nutrient content. Fertility does not differ among the types of invaded habitats, but goes up with the height of I. glandulifera and decreases with its cover. Invaded habitats comprises ruderal and riparian vegetation, but also wet maedows, forest clearances, beach and slope forests or weed vegetation.

The Brazilian pepper tree (BP, Schinus terebinthifolius), introduced to the United States in the 1800s, has since become a category one invasive plant in Florida, aggressively spreading to 3000 km2 of prime habitat. There is a serious dearth of knowledge on whether the rhizobiome plays any roles in the displacement of native flora and the range expansion of BP. This thesis discusses the well-established plant invasion mechanisms of the BP and highlights key emerging mechanisms and gaps in (a) the current understanding of the molecular, below-ground processes of BP invasion and (b) studies on the potential role of microbial interactions in the success of BP invasion already established for other select invasive species, and the intervention of soil metagenomic studies to elucidate plant invasive mechanisms. These poorly studied mechanisms could further explain the aggressive spread and resilience of BP and contribute significantly to the development of effective and sustainable control measures, enabling appropriate strategies for restoring native plants. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Thesis (MSc (Logistics))--University of Stellenbosch, 2008. / The primary question considered in this study is whether a small population of a biological species introduced into a resource-heterogeneous environment, where it competes for these resources with an already established native species, will be able to invade successfully. A two-component autonomous system of reaction-diffusion equations with spatially inhomogeneous Lotka-Volterra competitive reaction terms and diffusion coefficients is derived as the governing equations of the competitive scenario. The model parameters for which the introduced species is able to invade describe the realized niche of that species. A linear stability analysis is performed for the model in the case where the resource heterogeneity is represented by, and the diffusion coefficients are, two-toned functions. In the case where the native species is not directly affected by the resource heterogeneity, necessary and sufficient conditions for successful invasion are derived. In the case where the native species is directly affected by the resource heterogeneity only sufficient conditions for successful invasion are derived. The reaction-diffusion equations employed in the model are deterministic. However, in reality biological species are subject to stochastic population perturbations. It is argued that the ability of the invading species to recover from a population perturbation is correlated with the persistence of the species in the niche that it occupies. Hence, invasion time is used as a relative measure to quantify the rate at which a species’ population distribution recovers from perturbation. Moreover, finite difference and spectral difference methods are employed to solve the model scenarios numerically and to corroborate the results of the linear stability analysis. Finally, a case study is performed. The model is instantiated with parameters that represent two different cultivars of barley in a hypothetical environment characterized by spatially varying water availability and the sufficient conditions for successful invasion are verified for this hypothetical scenario.

My PhD thesis is focused on study of plant-soil interactions. Chapter 1 is focused on general introduction to the interactions between plants and soil biota in terms of relationships between soil organisms and aboveground biomass as well as root biomass. Chapter 2 is focused on food interaction of Folsomia candida and soil microscopic fungi (Penicillium chrysogenum, Penicillium expansum, Absidia glauca, and Cladosporium herbarum). Fungi were grown separately on Petri dishes or on different litter type (oak, alder and willow) separately as well. Laboratory experiments showed that food preference was more influenced by different litter types than fungal species. In chapter 3 was studied long-term production of hybrid sorrel and its effect on the composition of the soil meso and macrofauna, basal soil respiration, microbial biomass and composition of cultivable fraction of soil microscopic fungi in comparison with oilseed rape and cultural meadow. There was found that long-term production of hybrid sorrel affects the composition of soil fauna, while the microbial activity of the soil was more affected by agriculture practices, especially tillage. In chapter 4 was studied the effect of native (Salix viminialis and Phalaris arudinacea) and introduced (Reynoutria sachalinensis, Silphium perfoliatum and...

[Truncated abstract] Mediterranean southwest Australia, a global biodiversity hotspot, has nutrient deficient soils, exacting climatic conditions and is species rich with 7380 native vascular plant species, of which 49% are endemic. The region is expected to experience one of the world's highest degrees of biodiversity loss and change in the coming decades, with introduced species presenting a major threat. Limited knowledge is available on the mechanisms of ecosystem change associated with invasion and fire in this biodiversity hotspot region. Banksia woodland, an iconic complex species-rich natural ecosystem is one of the major vegetation types of the coastal sandplain, extending from 15 to 90 km inland and 400 kms along the west coast. The following hypothesis was tested to explore the ecological impacts of invasion: Is invasion of Banksia woodland by the introduced species Ehrharta calycina and Pelargonium capitatum accompanied by an alteration in ecosystem properties and processes, whereby the degree of change is related to fire frequency and abundance of introduced species? Different vegetation conditions, i.e. Good Condition (GC), Medium Condition (MC), Poor Condition invaded by Ehrharta calycina (PCe) and Poor Condition invaded by Pelargonium capitatum (PCp) were utilized for field assessments. ... In the soil seed bank, species numbers and germinant density decreased significantly for native and seeder (fire sensitive) species between GC sites and invaded sites. Surprisingly 52% of germinants at GC sites were from introduced species, with much of the introduced soil seed bank being persistent. Native species were dominated by perennial shrubs, herbs and sedges, while introduced species were dominated by perennial and annual grasses and herbs. Invasion by introduced species, associated with frequency of fire, altered the ecosystem, thus disadvantaging native species and improving conditions for even greater invasion within the Banksia woodland. Significantly higher soil phosphorus P (total) and P (HCO3) were found at PCe and PCp sites compared to GC sites. Leaf nutrient concentrations of phosphorus were significantly higher, and potassium and copper significantly lower in PCe and PCp sites, with introduced species having significantly greater concentrations than native species (except Manganese). This study demonstrated the key role of phosphorus in the Banksia woodland, in contrast to other research which identified nitrogen as the major nutrient affected by invasion. Higher levels of soil and leaf phosphorus, loss of species diversity and function, changes in fire ecology and canopy cover and a limited native soil seed bank make restoration of a structural and functional Banksia woodland from the soil seed bank alone unlikely. Without management intervention, continuing future fire is likely to result in a transition of vegetation states from GC to MC and MC to PC. The knowledge gained from this study provides a better ecological understanding of the invasive process. This enhanced understanding will enable the development of adaptive management strategies to improve conservation practices within a biodiversity hotspot and reduce the impact of the key threatening process of invasion.

The eMpofana riparian rehabilitation project (eMRRP) is a pilot project started by Umgeni Water (UW) to demonstrate how effective the removal of invasive alien vegetation is in improving the water yield of a catchment. The disturbance of the country's vulnerable wetland and riparian zones is a major factor contributing to water· stress. The study area was eMpofana riparian areas of Kwazulu-Natal midlands. The study was conducted to establish perceptions of property owners and project employees on eMpofana riparian rehabilitation project with regard to control of invasive alien vegetation. Apart from· these two categories of stakeholders, others whose perceptions were included in the study are one official each from MONDI, SAPPI, the National Working for Water Programme (WFWP) and Kwazulu Natal Nature Conservation Services. However, property owners and project employees were· the main respondents of study. Although all .stakeholders play a crucial role in the project, property owners were selected because clearing takes place on their properties. Similarly project employees perceptions were vital as they are physically involved in clearing invader species and are direct beneficiaries of the project through job creation; To enable interviewees to give their perceptions on various steps on the project cycle; the following key issues were selected; Awareness, Process, Water, Biodiversity, . Tourism, Capacity building, Support, and Sustainability of control of alien invasive plants. Based on these key issues, a questionnaire was drawn. There were fifty-two respondents: 25 property owners and 27 project employees.. The approach used in the study was survey research, and social science methods were employed. Survey research was chosen for this research because of its capacity to provide appropriate data on perceptions of stakeholders of the eMpofana project. The method is useful in a variety of situations such as providing solution to a problem of public policy, provide required data for managing a business or simply for testing hypotheses developed by scientists in the social world. The questions on awareness of the eMpofana riparian rehabilitation project (eMRRP). and the National Working for Water Programme{WFWP) revealed low awareness levels of the two projects. Almost half (48%) property owners indicated little awareness of the national WFWP and almost the same percentage i.e. 42% had little awareness of the provincial WFWP. Also 96% of eMpofana project employees indicated no awareness of the WFW national level and 70% said they were not aware of the WFW provincial level. Given that WFW is a national programme with over 200 alien plant control progratmhes countrywide, one wonder why awareness was so low among the respondents. As for involvement in the project conceptualisation, none of the respondents interviewed indicated involvement in that project phase. However all the project employees indicated that the project was successful (85% very successful and 15% successful). Fifty six per cent property ~wners indicated very strong 'support mainlybecause ofreestablishment of biodiversity through ridding the riparian areas of iilvader species. Ninety-five per cent of the project workers indicated that UW solely supports the eMpofana project and that that support is mainly financial. As for job creation, 88% project workers were of the view that eMpofana riparian project was very successful in creating jobs. It is worth noting that both property owners and the employees shared the same view on water users and project employees being the main beneficiaries of the project. The impact of clearing invader species oil water by the eMRRP was rated as being very significant. Moreover, 52% employees and 44% property owners felt that the project's main beneficiaries were water users in the cities and property owners themselves. As for linkage with the National WFW programme, the perceptions of property owners and project employees revealed a general preference for eMpofana project to continue running independently. On. succesSes achieved in various project phases, most property owners felt the planning phase of the project was the most successful, even though most of them were not involved in the phase. Thirty per cent of the employees felt execution was successful followed by financing, 30%. As the responses from both property owners and employees show, most respondents (property owners and project employees) were of the view that the project goal of reinstating biological diversity was very important. The property owners were of the view that the re-establishment of the naturalness of the area would contribute favourably towards tourism in the area, which they rated very high. The rating explain why property owners also rated biodiversity conservation and the naturalness of the area equally high. On the other hand, Umgeni Water's top priority is water security and the differing priorities between UWs and eMRRP could be seen as a weakness of the project. However, as a holistic view of biodiversity conservation necessitates protection of water resource in the area, the difference could be synchronised to become a strength ofthe eMRRP (see recommendations). The eMRRP has opportunities on a number of areas such as the opportunity to participate in the national campain on control of invader species by teaming up with WFWP and other stakeholders. Also joinirig this partnership would accord eMRRP stakeholders the pride of contributing to the national campaign on control of invader species. Although there is marked success made by UW in planning, financial support, job creation, gender equity in the eMRRP, there is need to address sustainability of the project. In conclusion, it is clear that the eMRRP started off with most stakeholders having low awareness ofits activities and those ofWFW Programme. However, by clearing invasive alien plants in eMpofana riparian areas, the project has gained support from property owners and its employees. Property owners support the project mainly because of possible re-establishment of naturalness of the area (biological diversity) and the employees give their support mainly because of the employment that they receive. However, the goal of sustainability of the eMRRP is likely to remain elusive as long as priorities are not harmonised: property owners' priority (based on benefits drawn) is biodiversity conservation whereas that of UW is water security. / Thesis (M.Env.Dev.)-University of Natal, Pietermaritzburg, 2000.

Fallopiajaponica (Houtt.) Ronse Decraene (Japanese knotweed), an introduced, invasive, rhizomatous perennial plant, has become an increasing problem for nature conservation and land management in both rural and urban areas in the British Isles. In the native range of the plant, Japan, Taiwan and northern China, a number of varieties are recorded. Three congeners of F. japonica are present in the British Isles, F. sachalinensis, F. japonica var. conipacta and F. baldschuanica in addition to a hybrid F. x bohemica. An investigation by postal survey of the distribution of the hybrid F. x bohemica has identified 131 records for the British Isles. Both male and female plants of F. x bohemica have been recorded. Current understanding suggests that only female plants of F. japonica are present in the British Isles, inferring that the only means of reproduction is through vegetative regeneration. High rates of regeneration were recorded in this study for stem and rhizome material for both F. japonica and F. x bohemica in an aquatic and terrestrial environment. Implications of vegetative regeneration are discussed in terms of current management practices and future methods of control. A combination of digging with a mechanical excavator followed by spraying with the herbicide glyphosate decreased the time required to achieve an effective level of control of F. japonica compared to spraying alone. Fragmentation of the rhizome system through digging resulted in an increase in stem density allowing a more effective delivery of herbicide. Implications in terms of costs for F. japonica treatment on sites awaiting re-development are discussed. Analysis of data collated from surveys of F. japonica in Swansea using a Geographical Information System suggest that the primary habitats infested are waste ground and stream and river banks. Results suggest that disturbance, both by natural means and by human intervention has been the primary cause of spread of F. japonica in the British Isles. Management strategies are proposed which take account of these results and measures are put forward to help prevent future infestations.