Kliknij ten link, aby zobaczyć inne rodzaje publikacji na ten temat: Weed invasion.
Rozprawy doktorskie na temat „Weed invasion”
Utwórz poprawne odniesienie w stylach APA, MLA, Chicago, Harvard i wielu innych
Sprawdź 50 najlepszych rozpraw doktorskich naukowych na temat „Weed invasion”.
Przycisk „Dodaj do bibliografii” jest dostępny obok każdej pracy w bibliografii. Użyj go – a my automatycznie utworzymy odniesienie bibliograficzne do wybranej pracy w stylu cytowania, którego potrzebujesz: APA, MLA, Harvard, Chicago, Vancouver itp.
Możesz również pobrać pełny tekst publikacji naukowej w formacie „.pdf” i przeczytać adnotację do pracy online, jeśli odpowiednie parametry są dostępne w metadanych.
Przeglądaj rozprawy doktorskie z różnych dziedzin i twórz odpowiednie bibliografie.
1
Gosper, Carl R. "Consequences of weed invasion and control on plant-bird interactions and bird communities". Access electronically, 2004. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20050221.155953/index.html.
Pełny tekst źródła
2
Siderov, Kris, i kris siderov@rmit edu au. "An investigation of the invasion dynamics of Asparagus asparagoides at the habitat level using spatial analytical techniques". RMIT University. Mathematical and Geospatial Sciences, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20061010.095929.
Pełny tekst źródłaStreszczenie:
This thesis reports on research that examines the early stage invasion process of Asparagus asparagoides (L.) W. Wight (bridal creeper), primarily a bird-dispersed weed, in a remnant vegetation patch. The study site is on Phillip Island, approximately 100 kilometres south east of Melbourne, Victoria. Asparagus asparagoides invasion of the remnant vegetation reserve is a relatively recent phenomenon. Landscape elements that affect bird dispersal and vegetation types that affect seedling establishment may be important factors that limit or enhance the spread of A. asparagoides. A systematic sampling strategy was adopted and data collected for a variety of landscape and vegetative variables including cover and abundance of A. asparagoides and the data were presented in a Geographic Information System (GIS). Preliminary results show that the distribution of A. asparagoides within a remnant vegetation patch is not random. It appears to have entered the reserve from two boundaries, spreading toward the centre, which to date remains sparsely colonised despite the capacity of this weed to spread rapidly over long distances by birds. A number of other outcomes are noted. Asparagus asparagoides establishment is prevented in pasture where sheep and cattle graze, and paddocks subjected to tillage practices. The exclusion of grazing in fenced off vegetation in pastures demonstrates rapid weed establishment and colonisation several hundred metres from main infestation. Field observation and visual inspection of temporal progress of invasion (using above ground weed density with tuber appearance to infer age) appear to suggest that invasion into remnant is associated with the track network. This age/density assumption is strengthened when spatial distribution is examined using a data set where low-density values for A. asparagoides are removed and compared with a data set using all A. asparagoides density values. The mapping of A. asparagoides in fenced off farm remnants suggests that velocity of spread at 191m/yr is a considerable underestimate. Subsequent analysis shows that the spatial distribution of A. asparagoides is not completely spatially random while intensity surface analysis highlights regions of low and high intensity located near track network. Mapping a density surface within GIS provided confirmatory evidence for the establishment of satellite clusters along the track network. The change in the intensity surface observed using the two data sets (lowdensity values and all density values) is also consistent with an expanding invasion occurring between two time periods. Spatial point pattern analysis using K-function statistics shows that xxii the clustering observed using GIS appears to be occurring at two scales or distances (130m- 160m and 195m-205m). The association between tracks and the invasion process observed in the initial stages of the study is examined. There is a change in density as a function of distance from a track where the density of A. asparagoides appears to reduce the further away from the track a site is and this relationship holds regardless of track width. The final stages of the study look at the development of a predictive model. Visual exploration of the data through mapping in a GIS and field observation made during data collection provide the starting point for the development of logistic models to estimate the probability of A. asparagoides presence. Finally the best overall logistic model is applied to a second independent site to determine the general applicability of the model. A number of variables that impact on the presence of A. asparagoides, particularly during the initial stages of the invasion process, are identified. While all the identified variables and the overall model are statistically significant, the model is found to correctly predict presence/absence in only 67% of cases overall. The model however could be expected to correctly predict the presence of A. asparagoides in 74% of cases and has a false positive rate of 40%. The model is applied at a second independent site and found to have an overall percent correct rate of 80% and correctly predicted A. asparagoides presence in 94% of cases. The variables identified as influential in the early stage of invasion are relatively easy to acquire by simple field survey that does not require specialist skills. When considering the model as a tool for the management of remnant vegetation communities, high false positive rates may lead to limited resources being spent on searching sites where there is no weed. However, a high false negative rate would have a larger impact on the management of the weed since the undetected infestations would form sources for new propagules. The model performs well from this point of view in that it provided low false negative rates at both sites. The value of the predictive model is its ability to provide managers with information regarding specific areas to target for weed eradication and management can use the model to assess the effectiveness of any control measures by going back to obtain new cover density data, then using the model to examine the changes over time. The model also provides a starting point for the development of a generic model of A. asparagoides invasion at sites outside of Phillip Island and could also provide the starting point for developing models that could be used for other bird-dispersed fleshy-fruited weed species.
3
Carruthers, Sandy. "The effects of weed invasion on native plants communities : a case study of the creekbank vegetation communities of Morialta Conservation Park /". Title page, contents and abstract only, 1990. http://web4.library.adelaide.edu.au/theses/09AR/09arc319.pdf.
Pełny tekst źródła
4
Rounsaville, Todd J. "INVASION DYNAMICS OF THE EXOTIC LIANA EUONYMUS FORTUNEI (TURCZ.) HAND.-MAZZ. (WINTERCREEPER)". UKnowledge, 2017. http://uknowledge.uky.edu/biology_etds/40.
Pełny tekst źródłaStreszczenie:
Elevated atmospheric CO2 has been implicated as a driver of increased liana abundance worldwide. Known as disturbance creators and beneficiaries, lianas possess the potential to significantly influence forest ecosystems. I investigated the early-invasion dynamics of Euonymus fortunei (wintercreeper), an evergreen liana that is invading forests in eastern North America, disrupting native plant communities and ecosystem functions.
Wintercreeper is widely cultivated as an ornamental groundcover, frequently invading natural areas via asexual stem growth. Invasion of remote natural areas is dependent upon seed transport and may occur less frequently. I examined the mechanisms of seed dormancy by conducting a ‘move-along’ experiment using fresh and after-ripened seeds. Additionally, I sought to characterize the nature of seed dispersal by birds by deploying seed traps within an invaded forest in central Kentucky. Wintercreeper seeds displayed conditional nondeep physiological dormancy. Although germination occurs at high velocity following cold stratification, a cold period was only facultative to break dormancy. While fresh seeds had greater germination rates (98.6%) compared to after-ripened seeds (85.7%), after-ripened seeds experienced earlier germination (41 days across all treatments). My findings also indicate that bird-mediated seed dispersal occurs throughout the winter from seeds that after-ripen on maternal liana phanerophytes. Overall, these data suggest wintercreeper seeds are capable of dispersing and recruiting in areas with mild to non-existent winters.
The invasion of natural areas by exotic invaders is regulated by biotic and abiotic processes, which influence the invader’s success or failure. I studied the vegetation and soil effects of paired invaded (INV), uninvaded (NAT), and ‘restored’ (RES) sites on the germination and survival of wintercreeper seeds and seedlings. The effect of aril (with vs. without) was also tested, both in the field and in vitro. In the field, total germination and first year survival were 55.6% and 24.2%, respectively, across treatments. Total germination was unaffected by treatments, yet vegetation (P = 0.0016) and aril (P = 0.001) treatments significantly influenced germination rates over time, including delayed germination of seeds with arils. The proportion of germinated seedlings that survived was significantly different based on vegetation (P = 0.054) and aril (P = 0.071) treatments after the first winter of growth, but not prior to the first winter. The proportion of seedling survival was significantly lower among seeds dispersed with an aril and seeds sown within INV treatments; there were no interactive effects.
Finally, I examined how seedling density and growth habit (horizontal vs. vertical) influenced plant survival, growth, and allometry. I also tested extractable soil C, N, P, K, Ca, and Mg prior to planting and after 17 months of soil conditioning. I found evidence that increased planting density negatively influenced growth among individual plants (lower survival, basal diameter, shoot mass, root mass). At the plot level, high-density plantings yielded greater stem length, and shoot, root, and combined biomass, indicating positive frequency dependence for this species. Soil analyses indicated C, N, P, Ca, and Mg significantly increased (P < 0.05) over the course of the experiment. I conclude that in wintercreeper, prominent asexual propagation leads to aggregate populations whose total contributions to above- and belowground biomass are positively correlated with density, even though individual plant fitness is not.
Altogether, this work provides insight into how wintercreeper invasions occur at broad and fine scales. This information will provide a foundation for future wintercreeper studies and aid land managers in their prevention and control strategies.
5
Dunlop, Elizabeth A. "Mapping and modelling the invasion dynamics of Senna obtusifolia at different levels of scale in Australia". Thesis, Queensland University of Technology, 2007. https://eprints.qut.edu.au/16490/1/Elizabeth_Dunlop_Thesis.pdf.
Pełny tekst źródłaStreszczenie:
The invasion of natural environments by alien species is a significant threat to the ecological integrity of these systems. Senna obtusifolia is an aggressive invasive weed recently introduced to Australia that is having significant impacts on grassland ecosystems on the Cape York Peninsula. Currently the species is inadequately managed and so range expansion continues. The invasion potential of S. obtusifolia in Australia remains unknown, as does much about its behaviour and management in natural systems. This project undertakes extensive mapping and modelling of the current and future distributions and the invasion dynamics of S. obtusifolia in Australia to facilitate early detection of outbreak populations and the development of appropriate management strategies.
The mapping and modelling of S. obtusifolia was conducted at three different scales: continental, landscape and local (population). To address these spatial scales, eco-climatic modelling, remote sensing analysis, field experimentation and creation of a model of seed fate was undertaken.
Using the climatic preferences of S. obtusifolia displayed internationally, an eco-climatic model (using CLIMEX software) ascertained that S. obtusifolia has a very large invasive potential in Australia. The predicted geographic distribution comprised the entire eastern and northern Australian coastlines, with spread further inland being largely restricted by a lack of moisture. The regional distribution of S. obtusifolia was not successfully delineated using remote sensing technology. Despite possessing favourable traits for detection by remote sensors, poor data quality and inappropriate image scales prevented the weed from being distinguished from other vegetation by multi-spectral satellite imagery and aerial photography. However, the results indicated that refining the data and the techniques used, single S. obtusifolia populations may be detectable in the future.
Investigation of the invasion dynamics of S. obtusifolia at the local scale involved multiple field surveys and manipulative experiments during 2002-2005. Field work indicated that little variation in population characteristics (e.g. stem density, soil seed reserve, seed production) existed within populations, but there was variability across populations and between years: the variation between years was very significant. The vegetation type adjacent to the weed population did not affect population attributes; however less competitive, more open and disturbed environments may better facilitate the invasion. The compartment model of seed fate reflecting S. obtusifolia population dynamics demonstrated that change in annual rainfall was unlikely to explain the variation evident between populations and years. Instead, the rate at which dormancy is broken in seeds and the intensity and regularity of fire provided a better explanation of the weed's population dynamics.
Early detection of invaders and the prediction of likely sites of invasion provide the most effective means of preventing future invasions. How best to achieve these goals still remains largely unknown. The process undertaken in this study was a relatively quick and reliable method for assessing the seriousness of S. obtusifolia, predicting future outbreaks and for providing clues to long term management. The appropriate use of fire, maintaining high interspecific competition and shade, as well reducing the rate at which dormancy is broken in seeds are all possible methods of managing S. obtusifolia.
6
Dunlop, Elizabeth A. "Mapping and modelling the invasion dynamics of Senna obtusifolia at different levels of scale in Australia". Queensland University of Technology, 2007. http://eprints.qut.edu.au/16490/.
Pełny tekst źródłaStreszczenie:
The invasion of natural environments by alien species is a significant threat to the ecological integrity of these systems. Senna obtusifolia is an aggressive invasive weed recently introduced to Australia that is having significant impacts on grassland ecosystems on the Cape York Peninsula. Currently the species is inadequately managed and so range expansion continues. The invasion potential of S. obtusifolia in Australia remains unknown, as does much about its behaviour and management in natural systems. This project undertakes extensive mapping and modelling of the current and future distributions and the invasion dynamics of S. obtusifolia in Australia to facilitate early detection of outbreak populations and the development of appropriate management strategies. The mapping and modelling of S. obtusifolia was conducted at three different scales: continental, landscape and local (population). To address these spatial scales, eco-climatic modelling, remote sensing analysis, field experimentation and creation of a model of seed fate was undertaken. Using the climatic preferences of S. obtusifolia displayed internationally, an eco-climatic model (using CLIMEX software) ascertained that S. obtusifolia has a very large invasive potential in Australia. The predicted geographic distribution comprised the entire eastern and northern Australian coastlines, with spread further inland being largely restricted by a lack of moisture. The regional distribution of S. obtusifolia was not successfully delineated using remote sensing technology. Despite possessing favourable traits for detection by remote sensors, poor data quality and inappropriate image scales prevented the weed from being distinguished from other vegetation by multi-spectral satellite imagery and aerial photography. However, the results indicated that refining the data and the techniques used, single S. obtusifolia populations may be detectable in the future. Investigation of the invasion dynamics of S. obtusifolia at the local scale involved multiple field surveys and manipulative experiments during 2002-2005. Field work indicated that little variation in population characteristics (e.g. stem density, soil seed reserve, seed production) existed within populations, but there was variability across populations and between years: the variation between years was very significant. The vegetation type adjacent to the weed population did not affect population attributes; however less competitive, more open and disturbed environments may better facilitate the invasion. The compartment model of seed fate reflecting S. obtusifolia population dynamics demonstrated that change in annual rainfall was unlikely to explain the variation evident between populations and years. Instead, the rate at which dormancy is broken in seeds and the intensity and regularity of fire provided a better explanation of the weed's population dynamics. Early detection of invaders and the prediction of likely sites of invasion provide the most effective means of preventing future invasions. How best to achieve these goals still remains largely unknown. The process undertaken in this study was a relatively quick and reliable method for assessing the seriousness of S. obtusifolia, predicting future outbreaks and for providing clues to long term management. The appropriate use of fire, maintaining high interspecific competition and shade, as well reducing the rate at which dormancy is broken in seeds are all possible methods of managing S. obtusifolia.
7
Gatehouse, Hazel A. W. "Ecology of the naturalisation and geographic distribution of the non-indigenous seed plant species of New Zealand". Diss., Lincoln University, 2008. http://hdl.handle.net/10182/1009.
Pełny tekst źródłaStreszczenie:
The naturalisation and subsequent spread of non-indigenous plant species (NIPS) is a major problem for most regions of the world. Managing plant invasions requires greater understanding of factors that determine initial naturalisation and distribution of wild NIPS. By the year 2000, 2252 NIPS were recorded as wild (1773 fully naturalised and 479 casual) in New Zealand. From published literature and electronic herbaria records, I recorded year of discovery of wild populations, and regional distribution of these wild NIPS. I also recorded species related attributes hypothesised to affect naturalisation and/or distribution, including global trade, human activities, native range and biological data; and regional attributes hypothesised to affect distribution, including human population densities, land use/cover, and environmental data. I used interval-censored time-to-event analyses to estimate year of naturalisation from discovery records, then analysed the importance of historical, human activity, biogeographical and biological attributes in determining patterns of naturalisation. Typically, NIPS that naturalised earlier were herbaceous, utilitarian species that were also accidentally introduced and/or distributed, with a wide native range that included Eurasia, naturalised elsewhere, with a native congener in New Zealand. In the year 2000, 28% of wild NIPS occupied only one region, 18% occupied two regions, decreasing incrementally to 2.5 % for nine regions, but with 13.5% occupying all ten regions. I used generalised linear models (GLMs) with binomial distribution to determine predictors of whether a wild NIPS occupied ten regions or not, and GLMs with Poisson distribution for wild NIPS occupying 0 – 9 regions. As expected, the dominant effect was that species discovered earlier occupied more regions. Utilitarian wild NIPS that were also accidentally introduced and/or distributed, and wild NIPS with a native congener tended to be more widely distributed, but results for other attributes varied between datasets. Although numbers of wild NIPS recorded in regions of New Zealand were sometimes similar, composition of wild NIPS was often very different. I used nonmetric multidimensional scaling (NMDS) to determine dissimilarity in composition between regions. Then, after reducing correlation between predictor variables using principal components analyses (PCAs), I tested the importance of regional variables in determining the regional composition of wild NIPS using metaMDS. The density of human populations best explained the dissimilarity in composition, but temperature gradients and water availability gradients were also important. In the year 2000 more than 1100 (60%) of the 1773 fully naturalised NIPS in mainland New Zealand had each been recorded in Northland/Auckland and Canterbury, and at the other end of the scale, Southland and Westland each had fewer than 500 (30%). I used GLMs to analyse the importance of people and environment in determining the numbers of wild NIPS in each region. Because I conducted multiple tests on the same dataset I used sequential Bonferroni procedures to adjust the critical P-value. Only human population density was important in explaining the numbers of NIPS in the regions. Overall, humans were the dominant drivers in determining the patterns of naturalisation and spread, although environment helps determine the composition of NIPS in regions. Incorporating human associated factors into studies of wild NIPS helps improve the understanding of the stages in the naturalisation and spread process.
8
Liutkus, Dainius. "Ilgalaikio skirtingo intensyvumo žemės dirbimo poveikis miežių agrocenozei taikant intensyvias technologijas". Master's thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20130621_111609-10533.
Pełny tekst źródłaStreszczenie:
Agronomijos studijų programos magistro baigiamasis darbas 40 puslapių, 10 paveikslų, 2 lentelės, lietuvių kalba.
Tyrimo objektas: paprastojo miežio (Hordeum vulgare L.) vasarinės veislės ,,Simba'' agrocenozė.
Tyrimo tikslas: Įvertinti ilgalaikio skirtingo intensyvumo žemės dirbimo poveikį miežių agrocenozei, taikant intensyvias technologijas.
Tyrimo uždaviniai:
1. Apžvelgti mokslinę literatūrą ir atlikti sisteminę analizę tiriamuoju klausimu.
2. Aprašyti atlikto eksperimento vykdymo sąlygas ir metodus.
3. Tyrimais nustatyti ir įvertinti ilgalaikio skirtingo intensyvumo žemės dirbimo poveikį struktūros patvarumui, miežių sudygimui, pasėlių piktžolėtumui ir miežių produktyvumui.
Tyrimo metodai: mokslinės literatūros apžvalga, loginė analizė ir sintezė, statistinė analizė, palyginamoji analizė, grafinio modeliavimo technikos.
Tyrimo rezultatai:
• Pirmoji dalis pristato Lietuvos ir užsienio autorių mokslinės literatūros analizę. Mokslinė medžiaga atrinkta, susisteminta ir analizuota.
• Antroje dalyje aprašyti koncentruojamasi ties bandymo schema ir parametrais, mokslinio eksperimento variantais ir duomenų analizės stebėjimais ir metodais.
• Trečioji dalis identifikuoja dirvožemio struktūros patvarumą, miežių sudygimą ir stiebų produktyvumą, miežių derlių, pasėlių piktžolėtumą bei miežių produktyvumą.
Nustatyta, kad ilgalaikis skirtingo intensyvumo žemės dirbimas neturėjo esminės įtakos dirvožemio struktūros patvarumui. Nenustatyta esminės įtakos ir miežių produktyvumui... [toliau žr. visą tekstą]Final work of University Undergraduate/Master Studies 47 pages, 9 figures, 2 tables, the Lithuanian language. Object of the research: barley (Hordeum vulgare L.) spring variety Simba'' agrocenoses. Aim of the research: to evaluate the long-term effect of different soil tillage intensity on barley agrocenosis applying intensive technologies. Objectives of the research: 1. Review of the literature and perform a systematic analysis of the relevant issue. 2. Describe an experiment carried out with the conditions and methods. 3. Studies to identify and evaluate the long-term differences in the intensity of tillage effects on structural stability, barley germination, weed infestation and barley productivity. Research methods: review of scientific literature logical analysis and synthesis, statistical analysis, comparative analysis, graphical modelling techniques. Research results: • Part One presents Lithuanian and foreign scientific literature. Scientific material selected, structured and analysed. • Part Two describe the focus is on testing scheme and the parameters of the scientific variants of the experiment and data analysis methods and observations. • Part Three identifies the soil structure stability, barley germination and stem productivity of barley harvest, weed and barley crop productivity. It was established, that tillage intensity had no significant effect on soil aggregate stability and on barley productivity parameters except the number of germinating barley... [to full text]
9
Babin, Courtney H. "Size-dependent patterns of reproductive investment in the North American invasive plant species Triadica sebifera (L.) Small (Euphorbiaceae)". ScholarWorks@UNO, 2017. http://scholarworks.uno.edu/td/2295.
Pełny tekst źródłaStreszczenie:
Knowledge of sex allocation trade-offs with tree growth in insect-pollinated woody plants is limited, particularly in invasive plants. This study examined patterns of growth and reproductive investment in a North American invasive plant species, Triadica sebifera, I hypothesized that the energy limitations of smaller trees may result in the production of more male reproductive structures that are energetically less costly. Diameter at breast height was a significant predictor of seed and catkin mass and regression can describe these relationships across sites. Seed and catkin mass were positively correlated across sites. The relationship between the seed mass:catkin mass ratio and DBH was not significant, nor was seed mass:catkin mass and total investment. Results showed a significant positive relationship between total reproductive investment and tree size across sites. Seed mass:catkin mass ratio and reproduction investment showed substantial variation among individual trees of similar size within sites.
10
Lucero, Jacob Elias. "Cheatgrass (Bromus tectorum), Native Grasses, and Small Mammals in the Great Basin: a Test of the Apparent Competition Hypothesis Facilitated by a Novel Method of Decanting Seeds from a Flotation Solution". BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3405.
Pełny tekst źródłaStreszczenie:
The effect of shared enemies between invasive and native species has been argued to facilitate biological invasions (i.e., the apparent competition hypothesis or ACH). This study investigated a previously untested possibility: whether granivorous small mammals facilitate cheatgrass (Bromus tectorum) invasion by driving food-mediated apparent competition between cheatgrass and native grasses. Specifically, we tested three predictions that must be true if such apparent competition occurs. First, cheatgrass invasion augments total seeds available to granivorous small mammals. Second, density of granivorous small mammals increases in response to increased seed availability (simulated with experimental additions of cheatgrass seeds). Third, granivorous small mammals prefer seeds from native grasses over cheatgrass seeds. We tested these predictions in the Great Basin Desert of Utah, USA. Cheatgrass invasion augmented total yearly seed production. Granivorous small mammals preferred native seeds over cheatgrass seeds. However, neither abundance, richness, nor diversity of granivorous small mammals increased in response to experimental additions of cheatgrass seed. We therefore conclude that granivorous small mammals did not drive food-mediated apparent competition during the study period. The lack of support for the ACH in this study may suggest that the role of small mammal-driven apparent competition is either unimportant in the Great Basin, or that the appropriate indirect interactions between small mammals, cheatgrass, and native grasses have yet to be evaluated. Testing the third prediction required the separation of seeds from the soil matrix. We employed a chemical flotation methodology to recover target seeds from soil, and developed a novel method of decanting target material from the flotation solution. We compared the utility of the novel method to that of a traditional decantation method. Specifically, we compared effectiveness (the proportion of seeds recovered from a known sample), rapidity (the time required to decant that sample), efficiency (the number of seeds decanted per second), and recovery bias (the effect of relative density on seed recovery) between methods. Our proposed method was more effective, more rapid, more efficient, and less biased than the traditional method. Therefore, any future work relying on flotation to analyze seed banks should clearly describe how samples are decanted and should consider the proposed method as a potential means of enhancing the efficiency of chemical flotation.
11
Crider, Kimberly Kay. "BIOLOGICAL CONTROL: EFFECTS OF TYRIA JACOBAEAE ON THE POPULATION DYNAMICS OF SENECIO JACOBAEA IN NORTHWEST MONTANA". The University of Montana, 2010. http://etd.lib.umt.edu/theses/available/etd-03092010-140634/.
Pełny tekst źródłaStreszczenie:
Biological control, using introduced, specialist insects is a common strategy for controlling plant invasions. However, the efficacy of biological control agents in controlling their host plants is rarely quantified population level. I quantified the impact of a specialist biological control agent, the cinnabar moth (Tyria jacobaeae) on its host plant, tansy ragwort (Senecio jacobaea) in northwest Montana. Cinnabar moth damage and its effects on important plant vital rates were tested with and without specialist herbivores. The presence of moth larvae corresponded to a reduction in population growth rates to less than one, compared to herbivore-free controls, indicating the potential for successful biological control by this insect. However, delayed effects of cinnabar moth herbivory on tansy ragwort vital rates were realized during the year following moth herbivory, after the moths had disappeared from the system. Individual damage to flowering plants in 2005 led to increased survival of these plants in the following year compared to controls, by reverting back to a vegetative state. In addition, seed set was reduced in plants that were damaged as juvenile rosettes in 2005 that went on to flower in 2006. When these delayed effects were combined in matrix models, gains in adult survival did not outweigh the decreases in fecundity or transition rates in terms of population growth and our initial conclusions remained unchanged. However, further study revealed that moth larvae were more likely to be depredated by carpenter ants in xeric sites suggesting that moth populations may not be sustained in these areas. Cinnabar moth larvae can be effective in this system provided they consume a large number of seeds (>90%) in consecutive years, but requires that moth populations are established and sustained from year to year. While herbivores do show the ability to control an invasive plant species, this relationship is strongly contextual in this system. This work emphasizes the importance of recognizing the influence of habitat context on the outcome plant-herbivore interactions, specifically in invaded ecosystems.
12
Norton, Eric. "Camelthorn: A Homeowners Guide". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005. http://hdl.handle.net/10150/144799.
Pełny tekst źródłaStreszczenie:
2 pp.Camelthorn is an invasive weed classified as a noxious weed in Arizona. The weed has the potential to cause serious damage for private landowners and their property. This fact sheet provides the means for landowners to identify and take steps to control and eliminate this weed.
13
Mastalerz, Allison. "The role of ornamental gardening in forest plant invasions across an urban-rural gradient in Southwestern Ohio". University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1377866412.
Pełny tekst źródła
14
Howery, Larry D., Ed Northam, Walt Meyer, Jennifer Arnold, Emilio Carrillo, Kristen Egen i Mary Hershdorfer. "Non-Native Invasive Plants of Arizona". College of Agriculture, University of Arizona (Tucson, AZ), 2016. http://hdl.handle.net/10150/625545.
Pełny tekst źródłaStreszczenie:
84 pp. / First Edition Published 2001The noxious weed problem in the western United States has been described as, a biological forest fire racing beyond control because no one wants to be fire boss. Indeed, when small weed infestations are left unchecked, they can grow exponentially and spread across the land much like a slow-moving biological wildfire. However, land consumed by fire usually recovers and is often more productive than before the fire occurred. On the other hand, land consumed by noxious weeds may be irreversibly changed and never again reach its full biological potential. Reviewed 12/2016, First Edition Published 2001
15
Hansen, Steen Ole. "Interactions between the invasive weed Heracleum mantegazzianum and associated insects /". [S.l.] : [s.n.], 2005. http://www.zb.unibe.ch/download/eldiss/05hansen_so.pdf.
Pełny tekst źródła
16
Christensen, Stephanie. "Establishing Weed Prevention Areas and evaluating Their Impact". DigitalCommons@USU, 2011. https://digitalcommons.usu.edu/etd/851.
Pełny tekst źródłaStreszczenie:
The spread of invasive weeds continues to be a serious economic and environmental threat. Weed prevention has the potential to stop weeds before they become well established in an area conserving time, energy, and resources. Unfortunately, weed prevention is often overlooked. Weed Prevention Areas (WPAs) are a relatively new tool developed to help improve the application of weed prevention. They are cooperatively managed areas that focus on implementing prevention and early detection strategies at a community level. The purpose of this research was to establish baseline data that will be used to evaluate the overall effectiveness of the WPA concept, as well as to produce materials to assist individuals with the development of a WPA. Two rural communities, with new WPAs, were each paired with a non-WPA community for data collection purposes. On-the-ground GPS vegetation inventories were conducted to determine the initial abundance and distribution of selected invasive weed species. This information was then used to demonstrate how to prioritize species and sites within a WPA in order to utilize limited resources more efficiently. A mail-back survey was also conducted to evaluate landowners' current opinions and activities in regards to prevention and control. In general, weed prevention was viewed as an important part of integrated weed management, but fewer than half of all respondents applied prevention strategies on their property. The failure to implement prevention strategies was attributed to limited funding and resources, a lack of weed prevention knowledge, and a high level of perceived risk. The knowledge gained from this research was then used to create Step-By-Step Guidelines for Establishing a Weed Prevention Area. These Guidelines provide interested individuals the resources necessary to successfully organize a WPA in their community. In addition, four wildland weed mapping methods were evaluated to identify their strengths and weaknesses. There was no difference in the estimation of patch size or location between the buffered point, screen-drawn, and perimeter walked methods. In most situations, time and distance factors favor the selection of either the buffered point or screen-drawn method. If patch shape is an important consideration, the perimeter-walked or buffered point method should be selected.
17
Davis, Philip Browning. "The invasion potential and competitive ability of Camelina sativa (L.) Crantz (camelina) in rangeland ecosystems". Thesis, Montana State University, 2010. http://etd.lib.montana.edu/etd/2010/davis/DavisP0510.pdf.
Pełny tekst źródłaStreszczenie:
Camelina sativa (L.) Crantz (large-seeded false-flax) is a recently introduced oilseed crop in Montana and has potential for large scale production for the biofuel market. However, due to weedy characteristics, the invasive potential of this species is of concern. A need exists to create a pre-entry protocol to accurately assess risk to minimize uncertainty inherent in qualitative weed risk assessment approaches. We assessed the probability of C. sativa to invade rangeland ecosystems of southwest Montana to address this concern. The objectives of this study were to 1) quantitatively assess the invasion potential of C. sativa by collecting demographic data over two years and developing a population dynamics model, 2) compare experimental results and modeling outcomes to predictions suggested by a qualitative weed risk assessment system, and 3) assess the impact of growing conditions on the relative competitiveness of C. sativa and Brassica napus (L.) (canola). Objective 1 was carried out in two contrasting rangeland ecosystems to assess the effects of disturbance and seeding season on emergence, survival, and fecundity rates of C. sativa. Population growth (lambda) was forecasted by developing a population dynamics model. Resulting lambda values from simulations using observed data never exceeded 0.03 and the maximum time to extinction was six years. The low lambda values indicate that the threat of invasion by this species in the studied ecosystems is low. Objective 2 compared quantitative results to predictions from the Australian weed risk assessment (WRA) model. In contrast to experimental results, outcomes from the WRA suggested that this species should not be allowed entry into the region. These opposing results highlight the need for a more comprehensive approach to weed risk assessment. Objective 3 was conducted over three trials in two greenhouses. A replacement series design was used to estimate the effects of soil conditions and the presence of an invasive weed, Bromus tectorum (L.) (cheatgrass, downy brome), on the competitive outcomes between C. sativa and canola. Replacement series diagrams determined that competition occurred and that canola was the superior competitor in all treatments, thus providing further evidence that the invasion potential of C. sativa is low.
18
Bell, Graeme Douglas Milton. "Regulation of gene expression in invasive and non-invasive Compositae weeds". Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/26226.
Pełny tekst źródłaStreszczenie:
Gene expression divergence between populations has been linked to adaptive morphological evolution and is thought to be a factor in the invasive success of certain weedy plants. Understanding the genetic basis of these regulatory changes can identify genes that have been under selection during adaptation to a new environment or new species interactions. A high-throughput sequencing approach was used to study the regulatory basis (cis and/or trans) of gene expression differences between native and invasive populations of Cirsium arvense (Canada thistle) by exploring patterns of differential gene expression and sequence variation. Parent and hybrid allele-specific expression ratios were compared to infer the relative effects of cis- and trans-regulatory change. Genes differentially regulated in cis are considered candidate genes involved in adaptation or weediness because there is evidence for selection acting primarily on cis-regulatory variation. Illumina sequencing of cDNA libraries derived from parents and hybrid pools resulted in a total of 82,713,256 paired-end (2x100bp) reads and 83.4% of these were mapped to a reference C. arvense transcriptome of 88,374 unigene sequences. Expression analysis and variant (SNPs and Indel) calling was performed to score the nature of regulatory divergence for the first 900 contigs, representing ~1% of the total dataset. Of the 40 high-confidence cases, 7 showed cis-effects, 6 showed trans-effects, 9 had varying degrees of both cis and trans, and 18 showed non-intermediate hybrid effects. A set of contigs that had high similarity to 63 known or confirmed stress-related genes, previously identified in studies of sunflower and Canada thistle, was also assayed for allelic imbalance. Of these, 2 cases showed a cis-effect, 2 showed both cis- and trans-effects, and 2 revealed hybrid effects. Contig 23614, an auxin-response transcription factor, was differentially regulated due to cis-effects and has been previously confirmed as drought-stress gene in both sunflower and C. arvense. This research identifies changes in gene expression that are driven by differential selective pressures in native and invasive populations. It also advances our understanding of the nature of genetic changes that drive gene expression evolution.
19
Dixon, Gemma Michelle. "Allelopathic potential of the alien invader weed Campuloclinium macrocephalum(Less) D.C". Diss., Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-10052009-111802/.
Pełny tekst źródła
20
Theile, H. Lenore. "Invasion of contrasting ecosystems by alien plant species /". [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18380.pdf.
Pełny tekst źródła
21
Brock, Marcus T. "Invasion of high alpine ecocystems by the exotic dandelion Taraxacum officinale (Asteraceae) /". free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p3115529.
Pełny tekst źródła
22
Meffin, Ross. "Invasion success and impacts of Hieracium lepidulum in a New Zealand tussock grassland and montane forest". Lincoln University, 2010. http://hdl.handle.net/10182/1808.
Pełny tekst źródłaStreszczenie:
Invasive species represent a major concern; they can result in serious ecological and economic losses and are recognised as one of the most serious threats to global species diversity. Plant invasions are of particular concern in New Zealand, which has high proportions of both naturalised and endemic plant species. In this thesis I focussed on the invasive plant Hieracium lepidulum, an exotic weed introduced from Europe to New Zealand prior to 1941. It is invasive in a variety of habitats in the South Island, where it has steadily increased in distribution and abundance over the last 50 years, and is thought to have detrimental impacts on native plant communities. I investigated factors influencing its invasion success and tested for impacts on native plant communities, making extensive use of existing plots into which H. lepidulum was experimentally introduced in 2003. I examined how community richness, turnover, resource availability and propagule pressure of the invader interacted to determine the invasion success of H. lepidulum. Results differed markedly above and below treeline. Above treeline, plots with higher richness and turnover were more invaded; below treeline, plots with higher available light were more invaded. In both habitats, these findings were modified by the influence of propagule pressure; at low propagule pressure, site characteristics were non-significant in explaining invasion success, while at higher propagule pressure these effects became significant. To test for impacts resulting in altered community composition and structure, I looked for changes in community richness, diversity and evenness subsequent to H. lepidulum introduction. As impacts may be more apparent at fine spatial scales, I made measurements at a 5 x 5 cm cell scale in addition to the established 30 x 30 cm plot scale. Plot species richness increased from 2003 to 2009 and a component of this increase was associated with H. lepidulum density. Other relationships between the plant community and H. lepidulum were generally non-significant. Results showed that H. lepidulum has had no negative effects on community richness, evenness or diversity. Despite being able to opportunistically colonise grassland sites with high turnover, and forest sites subject to canopy disturbance, dependant on propagule pressure, it appears H. lepidulum has not impacted community composition or structure.
23
McReynolds, Kim, i Cori Dolan. "Invasive Plants on Small Acreage Properties in Arizona". College of Agriculture, University of Arizona (Tucson, AZ), 2017. http://hdl.handle.net/10150/625562.
Pełny tekst źródłaStreszczenie:
3 pp. / Originally published 01/2010.Invasive plants are plants that have been accidentally or intentionally introduced to an area outside their original range and become problematic in their new environment by interfering with native or desirable species. Landowners can help prevent the spread and assist in controlling these invasive plants. Revised 11/2016. Originally published 01/2010.
24
Repath, Charles Fitts. "Evaluating and monitoring invasive plant processes". Thesis, Montana State University, 2005. http://etd.lib.montana.edu/etd/2005/repath/RepathC0505.pdf.
Pełny tekst źródła
25
Oppermann, Alison. "Introduced plant invasion in small remnants of native vegetation /". Title page, contents and abstract only, 1992. http://web4.library.adelaide.edu.au/theses/09ENV/09envo62.pdf.
Pełny tekst źródła
26
Weede, Oliver [Verfasser]. "Wissensbasierte Planung für die minimal-invasive Chirurgie / Oliver Weede". Karlsruhe : KIT Scientific Publishing, 2013. http://www.ksp.kit.edu.
Pełny tekst źródła
27
Lopez, Anthony J. "PREDICTING INVASIVE RANGE OF Eucalyptus globulus IN CALIFORNIA". DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1517.
Pełny tekst źródłaStreszczenie:
Eucalyptus globulus is the subject of intense debate in California. Its invasive potential, aggressive growth, reproductive biology, and association with fire make the prediction of spread important in California. Two modeling simulations, Climex and Maxent, will illustrate the distribution and potential growth range of E. globulus in California based on climate and presence. Modeling the potential range of growth will predict invasive spread. The anticipated result is the continued spread of E. globulus in coastal regions with adequate moisture and suitable climate. Predicting the range of E. globulus in California dictates management strategy and is key for preventing further introduction, establishment, and dispersal.
28
Boersma, Nicholas Neal. "Natural weed controls potential of the invasive shrub Rhamnus cathartica and improvement of corn gluten meal /". [Ames, Iowa : Iowa State University], 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1481846.
Pełny tekst źródła
29
Kasdirin, Hyreil. "Adaptive bio-inspired firefly and invasive weed algorithms for global optimisation with application to engineering problems". Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/15905/.
Pełny tekst źródłaStreszczenie:
The focus of the research is to investigate and develop enhanced version of swarm intelligence firefly algorithm and ecology-based invasive weed algorithm to solve global optimisation problems and apply to practical engineering problems. The work presents two adaptive variants of firefly algorithm by introducing spread factor mechanism that exploits the fitness intensity during the search process. The spread factor mechanism is proposed to enhance the adaptive parameter terms of the firefly algorithm. The adaptive algorithms are formulated to avoid premature convergence and better optimum solution value. Two new adaptive variants of invasive weed algorithm are also developed seed spread factor mechanism introduced in the dispersal process of the algorithm. The working principles and structure of the adaptive firefly and invasive weed algorithms are described and discussed. Hybrid invasive weed-firefly algorithm and hybrid invasive weed-firefly algorithm with spread factor mechanism are also proposed. The new hybridization algorithms are developed by retaining their individual advantages to help overcome the shortcomings of the original algorithms. The performances of the proposed algorithms are investigated and assessed in single-objective, constrained and multi-objective optimisation problems. Well known benchmark functions as well as current CEC 2006 and CEC 2014 test functions are used in this research. A selection of performance measurement tools is also used to evaluate performances of the algorithms. The algorithms are further tested with practical engineering design problems and in modelling and control of dynamic systems. The systems considered comprise a twin rotor system, a single-link flexible manipulator system and assistive exoskeletons for upper and lower extremities. The performance results are evaluated in comparison to the original firefly and invasive weed algorithms. It is demonstrated that the proposed approaches are superior over the individual algorithms in terms of efficiency, convergence speed and quality of the optimal solution achieved.
30
Bentivegna, Diego Javier. "Integrated management of the invasive weed, cut-leaved teasel (Dipsacus laciniatus L.) along a Missouri highways". Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5549.
Pełny tekst źródłaStreszczenie:
Thesis (Ph. D.)--University of Missouri-Columbia, 2008.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on July 22, 2009) Includes bibliographical references.
31
Burnham, Jeffrey S. "Native Bunchgrass and Invasive Weed Establishment in Low Nutrient Rangeland Soils with Nitrogen and Phosphorus Manipulation". DigitalCommons@USU, 2010. https://digitalcommons.usu.edu/etd/793.
Pełny tekst źródłaStreszczenie:
Competition between native perennial grasses and Bromus tectorum has been studied for many years. Recently, soil nutrients have been immobilized in an effort to preferentially inhibit growth of B. tectorum relative to native species. Most of this work has focused on soil N, but interactions with soil P are less studied and may be important as well. Additionally, although competitive effects and nutrient responses of several Centaurea spp. are well documented, data are lacking on the competitive effects that Centaurea virgata exerts on the establishment of native and exotic communities. A field experiment and a greenhouse experiment were conducted to evaluate influence of N and P on the native perennial bunchgrass Pseudoroegneria spicata in competition with B. tectorum and C. virgata. Chapter 2 describes the effects of nutrient immobilization and subsequent 2 x 2 factorial additions of N and P. Treatments were applied to transplanted individuals of the study species in monocultures and mixtures. Analysis of variance (ANOVA) was performed on shoot dry mass, soil water content, and physiological responses including photosynthetic rate, stomatal conductance, and transpiration. Results suggest that B. tectorum may be P-limited in certain circumstances, and that physiological activity of all species is subject to interactions between available N and P. In Chapter 3, I assess response of the study species to 2 x 2 factorial additions of N and P on a very low-nutrient soil in a greenhouse. Relative effects of different species mixtures on P. spicata are reported. I report ANOVA results of tiller number, leaf number, specific leaf area, shoot dry mass, root dry mass, and water addition. Results indicate that N and P co-limit P. spicata and B. tectorum, and to a lesser extent, C. virgata. B. tectorum showed the highest percentage response to fertilization. Land managers may be more successful establishing native grasses if they can minimize soil fertility.
32
Bain, Kandee. "VARIATION BETWEEN PERIPHERAL AND CENTER ACHENE MORPHOLOGY AND ATTRIBUTES OF ACHENE GERMINATION IN THE INVASIVE SPECIES, CENTAUREA MELITENSIS". CSUSB ScholarWorks, 2015. https://scholarworks.lib.csusb.edu/etd/256.
Pełny tekst źródłaStreszczenie:
Invasive species are often successful and problematic because of their ability to persist in disturbed and undisturbed environments despite weed management practices. Understanding reproduction and dispersal strategies in these species can aid in developing management approaches to help control their spread. Centaurea melitensis, a nonnative invasive with European origins, is found in disturbed areas of southern California. It produces three different types of flower heads that develop at different times and at different locations on the plant during the growing season. The chasmogamous (CH) flower heads are located at the top of the plant, the initial cleistogamous (iCL) heads are located at the base of the plant and at some branch and axillary points, and the final cleistogamous (fCL) heads are located along the stem and at some branch points. This pattern differs from that in Centaurea solstitialis, its most closely related congener, which develops one type of flower head with two morphologically distinct achenes within each flower head: peripheral and center achenes. The overall objective of this study was to examine potential differences between peripheral and center achenes of Centaurea melitensis, including morphological differences in dispersal features, potential differences in response to temperature, tendency to disperse, dormancy and viability. The approach involved selecting whole plants from the field and separating peripheral and center achenes from each of the three head types. Morphological differences were assessed by measuring mass, fruit length, fruit width, pappus length, pappus width, and elaiosome features. Temperature response patterns were evaluated by exposing peripheral and center achenes to temperatures ranging from 5 C to 30 C and measuring germination. Tendency of different achene types to remain in the flower heads was assessed by comparing ratios of peripheral to center achenes in heads immediately after maturation (March to June) to the ratios remaining in heads in early fall (September). Viability and dormancy testing was performed using a cut test and tetrazolium chloride tests in conjunction with germination tests. Results of these studies indicate that peripheral achenes of Centaurea melitensis were lighter and narrower, with shorter pappi and smaller elaiosomes than center achenes. Peripheral achenes responded similarly to their center counterparts in germination response to temperature, but the pattern differed among head types. Broad temperature optima were observed within the fCL and CH heads and a narrow optimum was observed in iCL. There was no evidence that the peripheral achenes remained in the heads longer than the center achenes. Ratios of peripheral to center achenes were 3.8:1 in CH heads, 2.23:1 in iCL heads, and 1.94:1 in fCL heads. Peripheral achenes were more likely to be dormant while maintaining viability than center achenes were. The results of this study, therefore, indicate that peripheral and center achenes of Centaurea melitensis differ morphologically. Dispersal features, such as pappi and elaiosomes, were more highly developed in center achenes than in peripheral achenes, but these differences were not reflected in differences in behavior to the extent we could measure it (i.e., the tendency to remain in heads or the germination responses to temperature). Differences between peripheral and center achenes of Centaurea melitensis trended in the same direction as differences seen in its closely related congener, Centaurea solstitialis, which has center achenes that disperse more readily than peripheral achenes. However, the differences observed in Centaurea melitensis were not as pronounced as those seen in Centaurea solstitialis.
33
Littlefield, Joanne. "Invasive Weeds on Rangeland: Controlling Sweet Resin Bush and Yellow Star-Thistle". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2002. http://hdl.handle.net/10150/622248.
Pełny tekst źródła
34
Meela, Moraba Macdonald. "Evaluation of alien invasive weedy plants for activity against plant pathogenic fungi". Diss., University of Pretoria, 2009. http://hdl.handle.net/2263/23195.
Pełny tekst źródłaStreszczenie:
Plant fungal pathogens are a major threat to food security worldwide. The most important method of protecting plants against fungal attack is the use of fungicides, but the development of resistance towards synthetic fungicides is of great concern. Moreover, the health risks associated with the use of chemical fungicides increase the need to search for safe, efficacious and environmentally friendly fungicides. Plants produce antifungal agents by secondary metabolism to protect themselves from fungal attack, and therefore many plant species have substantial antifungal activity. The use of plant extracts could enable the development of inexpensive and environmentally acceptable fungicides based on locally available natural products. This study was undertaken to investigate weedy and invasive plant species for antifungal activity against plant pathogens in order to develop a useful product using a widely available resource. Acetone leaf extracts of seven invasive species (Chromoleana odorata, Ipomoea alba, Tecoma stans, Passiflora suberosa, Passiflora subpeltata, Aristolochia sp, Solanum seaforthianum) were screened against eight plant fungal pathogens viz Rhizoctonia solani, Fusarium oxysporium, Penicillum janthinellum, Penicillum expansum, Aspergillus parasiticus, Aspergillus niger, Pythium ultimum and Phytophthora nicotiana, using microdilution assay and bioautography. The acetone extract of Tecoma stans had reasonable antifungal activity with an average minimal inhibitory concentration (MIC) value against all the fungi of 550 ìg/ml and clear zones on bioautograms indicating inhibition of fungal growth of a compounds with an Rf of 0.082 in BEA against several of the fungal pathogens. Due to the clear compound on bioautography and availability of Tecoma stans, this species was selected for further work. Bioassay-guided fractionation of the leaves of the Tecoma stans dichloromethane (DCM) extract obtained from solvent-solvent fractionation resulted in one major compound, oleanolic acid. The isolated compound had antifungal activity with an average MIC value of 130 ìg/ml against the 10 plant pathogenic fungi and clear bands with an Rf value of 0.082 on bioautograms, indicating fungal growth inhibition. It was surprising that the MIC value of the crude DCM extract was as high as that of the only compound with antifungal activity based on bioautography. These results clearly indicated the possibility of synergisms especially since the average total activity of the extract was nearly 6.5 times higher than that of oleanolic acid with total activity values of 60154 ml for the extract and 9262 ml for oleanolic acid. Cellular cytotoxicity of DCM extract and oleanolic acid was investigated using tetrazoliumbased colorimetric assay (MTT) on Vero monkey kidney cells. The toxicity of the extract and oleanolic acid was determined by LC50 values. The DCM extract and oleanolic acid were toxic with and LC50 of 0.413 mg/ml and 0.129 mg/ml respectively, lower than that of berberine the toxic compound used as control. However therapeutic index which can be defined here as the LC50 in (ìg/ml)/MIC in (ìg/ml), indicated that though the extract and oleanolic acid were toxic, they could be used under controlled conditions against infections of certain of the fungal pathogens. The crude extract had a high therapeutic index value of 21 against microorganisms T. harzianum, R. solani, F. oxysporium and P. expansum; and oleanolic acid had high therapeutic index values of 16 and 64 of against T. harzianum and R.solani respectively. This high therapeutic index value of crude extract and oleanolic acid means that, crude extract and oleanolic acid may be used for treatment of infections by these tested fungi with very little toxicity under controlled conditions. Oleanolic acid had very low antibacterial activity (MIC >250 ìg/ml). against two Grampositive (Staphylococcus aureus, ATCC 29213 and Enterococcus faecalis, ATCC 29212) and two Gram-negative bacteria (Escherichia coli, ATCC 27853 and Pseudomonas aeruginosa, ATCC 25922). Animal pathogenic fungi were more resistant than the plant fungal pathogens. Based on the good activity of the DCM crude extract, the surprising selectivity in activity against different fungi coupled with reasonably good therapeutic indexes and the wide availability of T stans leaves opens up the possibility that a commercial product to protect plants against certain pathogens may be developed from T. stans leaves. CopyrightDissertation (MSc (Veterinary Science))--University of Pretoria, 2008.
Paraclinical Sciences
unrestricted
35
Diop, Ousseynou. "Management of invasive aquatic weeds with emphasis on biological control in Senegal". Thesis, Rhodes University, 2007. http://hdl.handle.net/10962/d1005414.
Pełny tekst źródłaStreszczenie:
In 1985 the Diama Dam was built near the mouth of the Senegal River to regulate flows during the rainy season and prevent the intrusion of seawater during the dry season. This created ideal conditions upstream of the dam wall for invasion by two highly invasive aquatic weeds, first by water lettuce Pistia stratiotes Linnaeus (Araceae) in 1993, and then by salvinia Salvinia molesta D.S. Mitchell (Salviniaceae) in 1999. This study was focused on the management of P. stratiotes and S. molesta. Following successes that were achieved elsewhere in the world, biological control programmes involving two weevil species were inaugurated against both weeds and research was focused on several aspects. These included pre-release studies to determine the weevils' host-specificity and impact on the plants in the laboratory, their subsequent mass-rearing and releases at selected sites and post-release evaluations on their impact on the weed populations in the field. Both programmes, which reprepresented the first biocontrol efforts against aquatic weeds in Senegal, proved highly successful with severe damage inflicted on the weed populations and complete control achieved within a relatively short time span. A laboratory exclusion experiment with N. affinis on P. stratiotes showed that in treated tubs, the weevil strongly depressed plant performance as measured by the plant growth parameters: mass, rosette diameter, root length, number of leaves and daughter plants whereas control plants were healthy. Field releases started in September 1994 and water coverage by P. stratiotes at Lake Guiers was reduced by 25% in January 1995 and 50% in April 1995. A general decline of 65% in water coverage by P. stratiotes was observed in June 1995 and by August 1995, eight months after releases P. stratiotes mats were destroyed. Further, although no releases were made there, good results were obtained within 18 months at Djoudj Park water bodies, located 150 km NW from Lake Guiers indicating the potential of the weevil to disperse long distances. In 2005, P. stratiotes reappeared and the weevil N. affinis has located and controlled all of these P. stratiotes recurrences after new releases. In 1999, S. molesta covered an estimated area of 18 000 ha on the Senegal River Left Bank and tributaries (Senegal) and 7 840 ha on the Senegal River Right Bank (Mauritania). Military and Civil Development Committee (CCMAD) and community volunteers made an effort to control S. molesta using physical removal, but this costly and labour-intensive approach was unsustainable. Hence, biological control was adopted by Senegal and Mauritania to manage the weed. Host range tests to assess feeding by C. salviniae on S. molesta and non-target plants and carried out on 13 crop species showed that no feeding damage was observed on the latter and weevils only fed on S. molesta. Field releases of some 48 953 weevils at 270 sites were made from early January 2002 to August 2002. Within one year, weevils were established and were being recovered up to 50 km from the release sites. In a case study conducted at one of the release sites, the S. molesta infestation was reduced from 100% to less than 3% 24 months after release. These results are discussed in the context of the weeds’ negative impact on aquatic systems and riverside communities, and in the involvement of these communities in the programmes.
36
Seier, Marion K. "Evaluation of two fungal pathogens as classical biological control agents of the invasive weed Mimosa pigra in Australia /". [S.l. : s.n.], 1998. http://www.gbv.de/dms/bs/toc/252701771.pdf.
Pełny tekst źródła
37
Itholeng, Kebalepile Benedict Itholeng. "The indigenous knowledge of the local community towards weeds and alien invasive plants in the Dinokana area, North-West Province, South Africa / by Kebalepile Benedict Itholeng". Thesis, North-West University, 2007. http://hdl.handle.net/10394/2129.
Pełny tekst źródła
38
Lewis, Glennis M. "Protecting Canada's natural ecosystems from invasive alien plant species: Is sub-national weed control legislation up to the task?" Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27388.
Pełny tekst źródłaStreszczenie:
Invasive alien plant species pose a serious threat to Canada's natural ecosystems. It is the thesis of this paper that sub-national laws are important tools in combatting such species that are naturalized and spreading within provincial and territorial boundaries. Weed control acts in British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, Nova Scotia, and Prince Edward Island and the plant health protection acts in New Brunswick, and Newfoundland and Labrador are a strong basis to combat invasive alien plant species.
However, since these laws were enacted for weeds in agro-ecosystems, they are not up to the task of protecting natural ecosystems from invasive alien plant species. In some provinces and territories, there is a need to fill gaps in the law and ensure that it applies in a clear and uniform manner to all natural ecosystems. Numerous other revisions are recommended to make applicable provincial and territorial laws more effective.
39
Hutchison, Melissa Alice Sarah. "Interactions between habitat fragmentation and invasions: factors driving exotic plant invasions in native forest remnants, West Coast, New Zealand". Thesis, University of Canterbury. School of Biological Sciences, 2009. http://hdl.handle.net/10092/3218.
Pełny tekst źródłaStreszczenie:
Habitat fragmentation and biological invasions are widely considered to be the most significant threats to global biodiversity, and synergistic interactions between these processes have the potential to cause even greater biodiversity loss than either acting alone. The objective of my study was to investigate the effects of fragmentation on plant communities in native forest fragments, and to examine potential interactions between these effects and invasions by exotic plants at multiple spatial scales. I examined edge, area and landscape effects on plant invasions using empirical data from fragmented landscapes on the West Coast of New Zealand. My research revealed significant interactions between the amount of native forest cover in the landscape and the strength of edge and area effects on plant communities in forest fragments. The dominance of exotic plants in the community was highest at forest edges and decreased towards fragment interiors, however the interiors of very small fragments were relatively more invaded by exotic plants than those in larger fragments, reflecting a significant interaction between edge and area effects. Similarly, exotic dominance increased in more heavily deforested landscapes, but this effect was only apparent in very small fragments (<2 ha). The combined effects of small fragment size and low forest cover in the landscape appear to have promoted invasions of exotic plants in very small remnants. I explored the mechanisms underlying edge-mediated invasions in forest fragments and examined whether propagule availability and/or habitat suitability may be limiting invasions into fragments. Experimental addition of exotic plant propagules revealed that landscape forest cover interacted with edge effects on germination, growth and flowering rates of two short-lived, herbaceous species, and this appeared to be driven by elevated light and soil phosphorus levels at edges in heavily deforested landscapes. I also examined the role of traits in influencing plant responses to forest fragmentation. Different traits were associated with exotic invasiveness in edge and interior habitats of forest fragments, indicating that the traits promoting invasiveness were context dependent. Traits also had a major influence on responses of native plants to forest fragmentation, with generalist species appearing to benefit from fragmentation, as they can utilise both forest and open habitats, whereas native forest specialists have been negatively impacted by fragmentation.
40
Hari, Krishnan Ramesh Kannan. "Invasion of Lantana into India: analyzing introduction, spread, human adaptations and management". Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1001756.
Pełny tekst źródłaStreszczenie:
Objectives and Research Questions 1. To reconstruct the history of invasion of Lantana in India from where, by who, and when was Lantana species introduced into India?, given its long history in the country, is it still spreading or has it become more or less stable? 2. To study the human adaptation to Lantana invasion: socioeconomic causes and consequences of the use of Lantana as an alternative source of livelihood for forest dependent communities in southern India; how have local communities adapted to the invasion?; what are the key determinants that may have driven communities to use Lantana?; what are the economic consequences of the use of Lantana by local communities? 3. To critically review local practices and forest policy for the management of Lantana in southern India.; how has the use of Lantana by local communities impacted its local regeneration?; does the use of Lantana in local context have implications for its management?; what has been the role of the Forest Department and its policies in managing Lantana?
41
Holly, D. Christopher. "Multi-scale evaluation of mechanisms associated with the establishment of a model invasive species in Mississippi Imperata cylindrica /". Diss., Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-06052008-155216.
Pełny tekst źródła
42
DeGomez, Tom. "Invasive Plants in Arizona's Forests and Woodlands (Climate Change and Variability in Southwest Ecosystems Series)". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2007. http://hdl.handle.net/10150/146956.
Pełny tekst źródłaStreszczenie:
5 pp.This is part of the series on climate variability
Climate change appears to have an effect on invasive species in the forests and woodlands of Arizona. Many invasive plants have been documented. Land managers and educators will find this publication informative.
43
Von, Senger Inge. "An assessment of the genetic diversity and origin of the invasive weed Chromolaena Odorata (L.) King and Robinson in South Africa". Thesis, Rhodes University, 2002. http://hdl.handle.net/10962/d1003802.
Pełny tekst źródłaStreszczenie:
Chromolaena odorata (L.) King and Robinson is an alien invasive weed to most of the Old World tropical regions of the earth, including South Africa where it is morphologically distinct from most other C. odorata plants examined from both its native and invasive range. It is thought that these morphological differences are related to difficulties encountered in successful establishment of biological control agents on the South African population of C. odorata. It has been postulated that the source population of the South African population will harbour potential biocontrol agents that will be suited to successful establishment on the South African plants. Several morphological, cytological and isozyme studies have been attempted to identify the source population of the South African population, but these have failed to identify the origin of the South African population. In this dissertation two PCR-based methods were attempted, in an investigation into whether the morphological differences and difficulties in establishment of biocontrol agents have a genetic basis. The two techniques attempted were: Inter Simple Sequence Repeat (ISSR) amplification, and DNA sequencing. Results could not be obtained using the ISSR method, and the reason for this was not discovered despite extensive trials. The internal transcribed spacer region and the external transcribed spacer region sequences were obtained from five samples, and compared. It was found that the ETS region gave more phylogenetic signal at the intraspecific level than the ITS region. However, due to difficulties in amplification of the external transcribed spacer region, work here focussed on obtaining Internal Transcribed Spacer sequences for 61 samples. Each of the samples sequenced had a unique ITS sequence, displaying a high level of intraspecific genetic diversity. The degree of this diversity is discussed with reference to the possible influences of polyploidy and concerted evolution on genetic structure. The ITS data indicated that some of the physical traits used to define ‘morphotypes’ of C. odorata were not correlated to genotype. From discussion and comparison of morphological character distributions and the ITS-based phylogeography it is suggested that the geographical origin of the South African population is Greater Antilelan, rather than from the continents of North and South America, which is where the Australasian, West African and Mauritian infestations are suggested to have originated.
44
Buru, Joshua Comrade. "Comparative biology of two forms of an invasive vine, Dolichandra unguis-cati (L.) Lohmann (Bignoniaceae): implications for weed spread and biocontrol". Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/102084/1/Joshua%20Comrade_Buru_Thesis.pdf.
Pełny tekst źródłaStreszczenie:
This thesis is a comparative study of two distinct forms ('long pod' and 'short pod') of an invasive vine, cat’s claw creeper. The two forms have differing prevalence rates in Australia. The thesis examines important plant traits that could explain this variation in prevalence between the forms. The thesis covers seed biology, anatomical and growth traits, together with physiological traits in response to two levels of light, water and nutrients resources. In addition, the study assesses preferences of two bio-agents (insects) against the two forms of cat’s claw creeper to ascertain bio-control efficacy. This is because in Australia, the same insects are used to control both forms. The outcome of the study is a prospectus of traits that help explain why the short pod form is more widespread than the long pod form. Short pod possesses many of the traits that are associated with fast growing plants that easily colonize habitats. Generally, insects feed and lay eggs on both forms.
45
Larson, Daniel. "Non-indigenous freshwater plants : patterns, processes and risk evaluation /". Uppsala : Dept. of Environmental Assessment, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200715.pdf.
Pełny tekst źródła
46
Reed, Garret W. "Solarization as a means to eliminate invasive plant species and target the seedbank". Scholarly Commons, 2009. https://scholarlycommons.pacific.edu/uop_etds/735.
Pełny tekst źródłaStreszczenie:
The Calaveras River is a unique riparian habitat in San Joaquin County, influenced by both tidal water from the San Francisco Bay and impounded rainwater from the New Hogan Dam. The Calaveras River is one of the few river systems in California that does not benefit from snowpack melt. This dynamic system has changed dramatically in both its species composition and hydrodynamic regime due to years of human influences. What was once a thriving population of native plant species has become an environment dominated almost completely by aggressive exotic invasive species. The goal of this project was to remove the nonnative plant habitat by the most cost effective and least labor intensive means. The study area was along a section of river that bisects the University of Pacific campus in Stockton, California. From years of invasive species presence a deep seedbank has developed within the soil which acts to reduce the effectiveness of native plant reintroductions. A technique known as "solarization" was used to eliminate the seedbank and to facilitate the survival of native plants. Tarps were used to eradicate existing plants followed by disturbance of the soil and watering to induce germination of subsoil weed seeds. As the new plant seedlings emerge, tarps are reapplied to eliminate that generation of seedbank plants. After four time series of tarping and watering, a significant difference was found between control plots and treatments utilizing the solarization technique. Treatment 2, which consisted of tarping without weight, was determined to best target the seedbank after four repetitions and resulted in reducing invasive species in the seed bank.
47
Lindsay, Elizabeth A. "The impact of Chrysanthemoides monilifera spp. rotundata (bitou bush) on coastal ecosystem processes". Access electronically, 2004. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20041222.143610/index.html.
Pełny tekst źródła
48
Van, der Laan Michael. "Allelopathic interference potential of the alien invader plant Parthenium hysterophorus". Diss., Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-04042007-134659.
Pełny tekst źródła
49
Scarr, Lowell Martin. "Assessing the value of public investment into biological control research for invasive alien plants : the ARC PPRI Weeds Research Division". Thesis, Rhodes University, 2016. http://hdl.handle.net/10962/d1020604.
Pełny tekst źródłaStreszczenie:
This study investigates the economic impact of the ARC PPRI Weeds Research Division. The Division researches appropriate methods of biological control for invasive alien plants (IAPs). These plants pose an increasing threat to environmental integrity and ecosystem service provision impacting on economic potential. Since the work of the Division is considered a public good, a predominantly descriptive approach has been adopted for the valuation process. A combination of quantitative cost analysis and a qualitative study of the impacts of research and invasive alien plants is used to deal with the challenges associated with non-market valuation. The study found that investment into the Weeds Division is a valuable activity that supports the long-term growth potential of the South African economy. The role of a well-functioning environment is highlighted as an essential base for the creation of sustained growth opportunities in any society. It was determined that investment into the Division should be increased into the future to support efficient spending of scarce state funds. Biological control research was found to provide strategic future growth potential, creating opportunities for the development of a competitive advantage in the biotechnology and environmental management sectors. The study adds to the increasing move towards a more holistic view of economic valuation, taking factors other than pure finance and econometrics into consideration. This is an important shift in prevailing economic thought, as a realisation is reached that a single, or even triple, bottom line is an outdated and insufficient decision making basis.
50
Hely, Sara Elizabeth Lorraine Biological Earth & Environmental Sciences Faculty of Science UNSW. "The responses of C4 invasive grass Eragrostis curvula and C3 native grass Austrodanthonia Racemosa under elevated CO2 and water limitation". Awarded by:University of New South Wales, 2008. http://handle.unsw.edu.au/1959.4/35671.
Pełny tekst źródłaStreszczenie:
The concentration of atmospheric carbon dioxide (CO2) in the atmosphere has increased by 35% since pre-industrial levels. Projections for the next 100 years indicate an increase to levels between 490 and 1260 parts per million by volume (ppm) of CO2, equating to a 75 % to 350 % increase in concentration since the year 1750. Associated with this increase in [CO2] will be a 1.4 to 5.8?? C increase in lower atmospheric temperature. While past research has attempted to address the effects of such climatic changes on individual plant responses, predictions of plant responses at the ecosystem level are still highly uncertain. Difficulties lie in the enormous variation of plant responses to climate change variables among and within species, and between and within environmental conditions. Past research assumed that plants using either the C3 or C4 metabolic pathways would respond differently but predictably to climate-change variables based on their metabolic pathway. Recent evidence has suggested however, that the added interactions of external environmental variables and species-specific sensitivities to climate change make it difficult to predict plant and ecosystem responses to climate change. To investigate the mechanisms behind responses of Australian grasses to climate change, 2 pot experiments was conducted using growth cabinets to compare the effect of elevated CO2 and water-limitation on the invasive C4 grassland plant, Eragrostis curvula (E. curvula), native Australian C3 grassland plant, Austrodanthonia racemosa (A. racemosa), and wheat species, Triticum aestivum (T. aestivum). The experiment was run at ambient levels of CO2 maintained at 390 ppm compared to elevated levels of 740 ppm. Imposed restrictions to water supply consisted of gradually drying the soil down to 30 % available soil water (ASW) followed by re-wetting to 50 % ASW. Well-watered conditions for the experiment consisted of gradually drying the soil down to 50 % ASW, followed by rewetting to 95 % ASW. Plants were grown in mixtures and monocultures, consisting of 9 plants equally spaced in a grid design. The three significant findings of the thesis were that: 1) the metabolic pathway (C3 versus C4) was not always an accurate predictor of biomass accumulation under elevated CO2 in the plants studied. Previous research suggested that CO2-stimulation of photosynthesis in C3 plants would lead to greater increases in biomass under elevated CO2 compared to C4 plants, though both C3 and C4 plants could benefit from any reduction in stomatal conductance under dry conditions at elevated CO2. The results from the experiments in this thesis showed a strongly significant biomass response to elevated CO2 in both dry and wet conditions for C4 grass E. curvula. The C3 grass A. racemosa in dry conditions, did not. It was speculated that without the CO2-induced water conservation effect, the C3 grass experienced photosynthetic down-regulation and this precluded a positive biomass response under elevated CO2. 2) the magnitude and direction of biomass response to elevated CO2 was dependant on factors such as resource-availability and the phenotypic variability of the plants species. 3) critical analysis of results from this thesis, combined with past research on plant responses under elevated CO2 showed a tendency for researchers to repeatedly test plants from the Poaceae family, or close relatives of the Poaceae family. As a result, when past data were corrected for this lack of independence, there was no relationship between the evolution of the C3 and C4 metabolic pathway and biomass response to elevated CO2. Instead, other factors (such as growth rate, plant height, leaf number, etc) were presented as being more important in determining biomass response. These observations were supported by results found in this thesis.