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Uyi, Osariyekemwen. "Aspects of the biology, thermal physiology and nutritional ecology of Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae: Arctiinae), a specialist herbivore introduced into South Africa for the biological control of Chromolaena odorata (L.) King and Robinson (Asteraceae)." Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1017916.
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Chromolaena odorata (L.) King and Robinson (Asteraceae) is an invasive weedy shrub native to the Americas that has proven to be a significant economic and ecological burden to many tropical and sub-tropical regions of the world where it impacts negatively on agriculture, biodiversity and livelihoods. A distinct biotype of C. odorata was first recognised as naturalized in KwaZulu-Natal (KZN) province, South Africa, in the 1940s and has since spread to other climatically suitable provinces. Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae: Arctiinae) was released in KZN, South Africa, as a biological control agent against the weed between 2001 and 2009. Although the moth did establish at one out of some 30 release sites, its population level is generally low in the field. This thesis attempts to unravel the reasons for the poor performance of P. insulata in South Africa.Studies of life history traits of P. insulata in the laboratory indicated that the moth possess good biological attributes such as low mortality, high fecundity, egg hatchability and high female mating success. Overall, adult female moths eclosed before their male counterparts suggesting the presence of protogyny. Beyond the contribution of this study to our understanding of the life history traits of erebid moths, it hypothesized that the absence of protandry might have contributed to the low population levels of the moth in the field. To determine if a degree of agent-host plant incompatibility is culpable for the poor performance of P. insulata, insect performance metrics were compared on two distinct C. odorata plants (one from Florida and another from South Africa) in laboratory experiments. Pareuchaetes insulata performance metrics were similar on both plant forms; there were no significant differences in total leaf area consumed, egg and larval development, immature survival rates, feeding index (FI), host suitability index (HSI), growth index (GI), and fecundity between the Floridian and southern African C. odorata plants. In sum, there was no evidence to demonstrate that differences in plant forms in C. odorata are culpable for the poor performance of P. insulata in South Africa.The effects of temperature on the developmental and reproductive life history traits, locomotion performance and thermal tolerance range of P. insulata were studied in order to elucidate the possible role of temperature on the poor performance of the moth. The results showed that at temperatures below 25 °C, mortality increased and development time was prolonged. Fecundity and egg hatchability were negatively affected at a constant temperature of 15 °C. Results futher showed that third instar larvae were unable to initiate movement at 6 °C and locomotor abilities were significantly reduced at 11 °C. In sum, it is hypothesized that both direct and indirect negative impacts of low temperature may partly explain the poor performance of P. insulata in South Africa. Theeffects of seasonal and spatial variations in the leaf characteristics of C. odorata on the performance of P. insulata were investigated. Foliar nitrogen and magnesium concentrations were higher in shaded plants during winter due to low temperatures. Leaves of C. odorata plants growing in the shaded habitat (relative to full sun) and leaves of plants during autumn (relative to winter) were more nutritionally balanced and suitable for herbivore performance. Consequently, P. insulata developed faster, had heavier pupal mass and increased fecundity when reared on shaded leaves (relative to full sun) or when reared on autumn leaves compared to leaves growing in winter. This study demonstrates that low winter temperatures can indirectly affect insect herbivore performance by changing the phytochemistry of host plant and hypothesized that excess nitrogen and possibly magnesium may have detrimental effects on the insect herbivore performance.A cross-feeding experiment was conducted to determine P. insulata response to a change in the diet of offspring due to a shift in plant quality in shaded versus full sun habitats. The results showed that a ‘negative switch’ in herbivore diet (i.e. when progeny from parents reared on shaded leaves were fed on full sun leaves) resulted in high (40%) mortality, prolonged development time and reduced fecundity. Thus full sun foliage is an inferior diet for P. insulata offspring. In laboratory experiments, foliar nitrogen was positively correlated with the performance of P. insulata. From this study, it is demonstrably evident that the poor performance of P. insulata on C. odorata in South Africa is caused by multiple factors such as low temperatures as well as spatio-temporal variations in the leaf characteristic of C. odorata leaves. This study shows the complexity of determining the causes of low populations and apparent low impact of biological control agents and herbivorous insects generally, in the field. The implications of this research to the biological control programme against C. odorata and the direction of future research for the control of C. odorata are discussed.
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Dumalisile, Lihle. "Effects of Chromolaena odorata on mammalian biodiversity in Hhluhuwe iMofolozi Park, South Africa." Pretoria :[s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-07102008-102018.
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Dew, L. Alexander. "Monitoring and managing Chromolaena odorata in a South African savanna reserve : Evaluating the efficacy of current control programs in response to ecological factors and management protocols." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-104590.
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Biological invasions have increased dramatically in the past centuries and are one of the greatest threats to biodiversity today. Invasions occur when organisms are introduced at a location to which they are non-native, and they reproduce and spread, causing damage to the environment. Chromolaena odorata, a herbaceous shrub from the Americas, is one of the most widespread and problematic invasive plant species in the tropics and sub-tropics. The plant is a serious problem in South Africa, where invasive species threaten the nation’s biodiversity and limited water supply. This study combined transect monitoring data of C. odorata with ecological and clearing management data to assess the efficacy of an invasive plant clearing program over its decade of operation in the Hluhluwe-iMfolozi reserve in KwaZulu-Natal, South Africa. Densities and local extent of the C. odorata invasion were significantly reduced during the period of operations of the clearing program. Seasonal effects impacted clearing efficacy, namely a reduction in efficacy during the seed dispersal period. Effort and fire frequency were positively associated with clearing success, and rainfall negatively associated with clearing success. Excluding the northern section of the reserve, where the invasion progressed over the whole landscape, observations of C. odorata were closer to watercourses than randomized points, indicating a water limitation for invasion in most of the park. Management implications drawn from the results include halting clearing during seed-drop months, giving extra attention to areas with more rainfall and other water availability, and incorporating fire with other clearing methods where possible.
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Assemien, Embi Féline Laurenza. "Impact de pratiques agricoles conventionnelles et innovantes sur la fertilité des sols et les acteurs microbiens impliqués dans la zone de savanes humides de Côte d’Ivoire." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1103/document.
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En Afrique de l'Ouest, les sols de savanes humides se caractérisent par des concentrations extrêmement basses de matières organiques, d'azote minéral, de phosphore et de cations basiques, ce qui limite la production primaire. Ce travail a analysé comment des changements particuliers dans les utilisations des terres peuvent influencer le fonctionnement et la fertilité des sols, pour in fine soutenir la production des agroécosystèmes dans cette zone de savane. Six différents types d'utilisation des terres sur 9 parcelles expérimentales répartis à l’échelle du paysage du centre-sud de la Côte d’Ivoire ont été comparé : (i) le brûlis comme pratique traditionnelle ; (ii) la fertilisation chimique comme pratique conventionnelle ; et le mulching comme pratique innovante, testé (iii) sans insertion de légumineuses ou (iv et v) avec insertion de haricot ou soja dans des cycles de rotations culturales ; (vi) le sol nu était considéré comme une situation de référence (le témoin). Le sol a été prélevé dans 54 sous-parcelles, avant et 3 fois après la mise en place des traitements. Sept activités enzymatiques (activités dénitrifiante, nitrifiante, β glucosidase, N-acétyl-β-D-glucosaminidase, phosphatase acide et alcaline, déshydrogénase) du sol, les principales variables du sol (humidité, carbone organique, azote total, pH et Phosphore assimilable), l'abondance et la diversité des communautés microbiennes impliquées dans le cycle de l’azote (bactéries et archées oxydatrices de l’ammonium ; les genres Nitrobacter et Nitrospira qui jouent un rôle clé dans la production de nitrate ; les bactéries réductrices du nitrite porteuses des gènes nirS ou nirK ; et les bactéries réductrices du N2O porteuses de gènes nosZI ou nosZII). Les résultats ont montré que (i) le C. org, le K, le Mg et les activités enzymatiques du sol ont diminué avec la profondeur du sol, indiquant un faible taux d’accumulation des nutriments dans les profondeurs les plus importantes du sol. Par ailleurs, les durées de jachère (0 à 10 ans) n’ont pas significativement affecté la majorité des propriétés du sol, à l'exception de l’Ntot et du K du sol qui étaient élevés dans les vieilles jachères. De plus, le C. org a diminué en fonction de la durée de la jachère tandis que le Mg a suivi une tendance inverse ; (ii) le type d'utilisation des terres a affecté fortement la plupart des activités enzymatiques du sol et les communautés microbiennes impliquées dans le cycle de l’azote; (iii) les pratiques de mulching pourraient avoir un impact positif sur les caractéristiques du sol et les communautés microbiennes, avec pour conséquence le renforcement du maintien de la fertilité des sols et la durabilité de la production agricole à long terme. D’après les résultats obtenus, la pratique de paillage, possiblement avec insertion de légumineuses, pourrait être moins onéreuse et plus adaptée pour augmenter progressivement et de façon durable la disponibilité en azote dans ces agroécosystèmesIn West Africa, humid savanna soils are characterized by extremely low concentrations of organic matter, mineral nitrogen, phosphorus and basic cations, which limit primary production. We analyzed how particular changes in land-uses can influence the functioning and fertility of soils, to support the production of agroecosystems in this savanna zone. We compared six land-use types at 9 experimental plots across a landscape: traditional slash-and-burn; conventional chemical fertilization; and innovative use of mulching (tested with or without inserting legumes in the crop rotation). Bare soil was also considered as a reference situation. Soil was sampled on the 54 sub-plots, before and 3 times after treatment inception. We surveyed seven soil enzyme activities (denitrification, nitrification, β glucosidase, N-acetyl-β-D-glucosaminidase, acid and alkaline phosphatase, dehydrogenase), key soil variables (moisture, organic C, mineral and total N, pH, and available P) and the abundances and diversity of microbial communities involved in the N cycle (bacterial and archaeal ammonia oxidizers; Nitrobacter; Nitrospira; and nirS-, nirK- and nosZ-like denitrifiers). Our results showed that (i) C. org, K, Mg and soil enzymes activities decreased with soil depth, reflecting a low rate of nutrient accumulation in soil depth. In contrast, fallow periods (0 to 10 years) did not significantly affect the majority of soil properties, excepted soil Ntot and K, which were high in old fallows. In addition, C. org decreased as a function of the fallow period, but Mg follow-up an inverse trend; (ii) the land use type strongly affects most soil enzymatic activities and the microbial communities involved in nutrient cycling; (iii) innovative mulching practices have a positive impact on soil characteristics and microbial communities, thereby maintaining the maintenance of soil fertility and the sustainability of agricultural production in the long term. According to our results, the practice of mulching, possibly with the insertion of legumes, could be less expensive and more appropriate to progressively and sustainably increase nitrogen availability in these agro-ecosystems
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Almeida, Neto Mario. "Autocorrelação espacial e variação temporal na fenologia floral, produção e predação de sementes em Chromolaena odorata (Asteraceae)." [s.n.], 2003. http://repositorio.unicamp.br/jspui/handle/REPOSIP/316252.
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Orientador: Thomas Michael LewinsohnDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
Made available in DSpace on 2018-08-03T15:00:40Z (GMT). No. of bitstreams: 1 AlmeidaNeto_Mario_M.pdf: 3490696 bytes, checksum: acc4a9eb38f12cc9199039e1caf0cfdf (MD5) Previous issue date: 2003
Resumo: Estudei a fenologia floral de uma importante espécie de planta invasora em seu habitat nativo. Meu objetivo foi avaliar se parâmetros fenológicos, como a duração, o início, o fim e a sincronia floral das plantas apresentavam alguma estruturação espacial e quais as conseqüências desta estrutura no sucesso de produção de sementes das próprias plantas avaliadas.As plantas apresentaram distribuição espacial agregada entre indivíduos co-específicos e co-genéricos. Encontrei autocorrelação espacial em diferentes parâmetros fenológicos e na produção de capítulos e sementes. Todos os correlogramas significativos mostraram valores positivos de autocorrelação no primeiro intervalo de distância. Isto significa que os parâmetros fenológicos, a produção e a predação de sementes das plantas não estão aleatoriamente distribuídos no espaço. Os parâmetros fenológicos não tiveram influência significativa sobre a predação de sementes ou a proporção de sementes viáveis por planta. Embora este resultado difira do encontrado na maioria dos estudos, sua ausência pode ser explicada como um efeito da resposta dependente de densidade entre plantas. A predação de sementes nas plantas ocorreu de modo inversamente dependente de densidade e também se mostrou espacialmente autocorrelacionada. Esta autocorrelação deve ter ocorrido como um reflexo da estruturação espacial na abundância de capítulos e sementes por planta. Portanto, a autocorrelação espacial na fecundidade das plantas possivelmente gerou este mesmo efeito na resposta dos predadores de sementes. A abundância de capítulos de plantas vizinhas co-específicas e co-genéricas parece ter um efeito aditivo na resposta dependente de densidade dos endófagos de capítulos
Abstract: I investigated the flowering phenology of an important weed in its native habitat, in order to ask if plant phenological parameters, such as onset, end, duration and flowering synchrony, were spatially structured and if so, what are the possible consequences of such structure for plant seed production. Plants were spatially aggregated, at the leveI of both species and genus. I found spatial autocorrelation in several different phenological parameters and in plant fecundity. There was positive autocorrelation mainly between neighbouring plants, which means that floral phenology and plant fecundity are not randomly distributed in space. According to my results, phenological parameters did not affect significantly either seed predation or proportion of viable seeds per plant. Although this result is contrary to most results in previous studies, it may be explained as a density-dependent effect among plants. In this study, seed predation was inversely density dependent as well as spatially autocorrelated. This autocorrelation should be related to spatial structure in the abundance of flower-heads and seeds per plant. Thus, spatial autocorrelation in plant fecundity possibly induced the same effect in seed predator response. Intra-specific and congeneric flower-head abundance probably has an additive effect on seed predation escape
Mestrado
Ecologia
Mestre em Ecologia
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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.
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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.
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Tantsi, Nolubabalo. "Long-term impacts of Chromolaena odorata (L.) invasion and ungulate grazing on ant body size and communities in Hluhluwe-iMfolozi Park, South Africa." Diss., University of Pretoria, 2012. http://hdl.handle.net/2263/30949.
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The present study investigated the impacts of Triffid weed Chromolaena odorata
infestation and ungulate grazing on native ant communities in Hluhluwe-iMfolozi Park
(HiP), in KwaZulu-Natal province, South Africa. HiP is a highly valued park because of its unique biodiversity. However, management of biodiversity in this park is intimidated
by restructuring disturbances produced by invasions by alien plants and grazing.
C. odorata is a highly invasive plant known to invade to an impenetrable extent, out
shading and eliminating all competition of indigenous vegetation to many parts of the
world. The rapid invasion and spread of C. odorata in natural environments, including
large parts of HiP, is making ecosystems unstable as indigenous species decline, thereby
resulting in hampered delivering of ecological services. The re-vegetation of C. odorata
even after control measures has heightened, raises concerns regarding sustainability of
indigenous species.
The increase in populations of herbivores in HiP is of concern as vegetation is
restructured resulting in interruptions in flora and fauna relations. To increase the
understanding of changes associated with these habitat altering disturbances, the effects
of invasions by C. odorata and herbivory on indigenous communities were investigated.
Ants play diverse roles in terrestrial ecosystems and influence composition,
distribution and abundance of other species. Ants are sensitive to changes that influence
food abundance, shelter and microclimate. Ants are also strongly linked to a variety of
vegetation. Therefore, disturbances that result in displacement of indigenous flora impede
the diversity and abundance of indigenous ant species.
Grazing had no effects on ant species diversity but combination of reserve and grass
had a significant influence, while rainfall influenced ant abundance. The presence of high
rainfall promoted high ant diversity and evenness indicating increased foraging and
nesting resources for a variety of ant species. Ant diversity and evenness in areas of high
precipitation could also have been caused by moist soils that encourage vegetation growth
and cover.
Ant abundance was significantly affected by the combination of reserve, grazing and
grass type. High ant abundance was associated with high rainfall, light grazing, and
greater vegetation biomass. High ant abundance in lightly grazed exclosures contributed
to high vegetation diversity. The lack of ants specializing in lawn grass suggests that this
habitat does not contain unique ant communities. However, greater ant diversity found in
these habitats, compared to tall grass, confirms that lawn grass provides optional foraging
areas and is important for management of ants. This study concludes that rainfall or
altitude variations influence ant composition through changes in vegetation growth and
diversity more than herbivory.Dissertation (MSc)--University of Pretoria, 2012.
Animal and Wildlife Sciences
MSc
Unrestricted
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Gunasekera, Taligama Gamaralalage Lalith Gamini. "Physiological studies on growth and development of weed species, with particular reference to Galium aparine L. (Cleavers) and Chromolaena odorata (L.) K. & R." Thesis, Bangor University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334737.
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Atindehou, Ménonvè. "Caractérisation structurale et biologique de nouveaux agents antibactériens naturels actifs dans les infections intestinales : des peptides de la chromogranine A et des principes actifs de Chromolaena odorata." Phd thesis, Université de Strasbourg, 2012. http://tel.archives-ouvertes.fr/tel-00856585.
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Les premières souches bactériennes résistantes aux antibiotiques sont connues depuis 70 ans et se sont multipliées ces dernières années posant un grave problème de santé publique. Parmi les nombreux types d'infections induites par ces bactéries, nous nous sommes intéressés aux infections intestinales qui peuvent dégénérer en maladies inflammatoires de l'intestin et cancers. Notre travail de thèse a consisté à proposer des outils thérapeutiques dans le traitement des pathologies intestinales infectieuses : des peptides antimicrobiens dérivés de la chromogranine A et des extraits de plantes de la médecine traditionnelle béninoise. La chromogranine A est une protéine libérée par les cellules nerveuses, neuroendocrines et immunitaires au cours d'un stress et maturée en peptides. Des peptides actifs contre quatre souches bactériennes pathogènes (Klebsiella oxytoca, Salmonella enterica, Shigella sonnei et Vibrio cholera non O1) ont été identifiés et l'interaction bactérie-peptide analysée. L'étude de la combinaison peptide-antibiotique montre que la cateslytine permet de réduire les doses d'antibiotiques nécessaires. Ensuite, nous avons étudié l'implication de deux peptides sur un modèle de cellules neuroendocrines, les cellules BON. La chromofungine provoque la stimulation des cellules BON en induisant un influx de calcium extracellulaire, tandis que la catestatine est capable de bloquer l'activité de la chromofungine.Après un screening des extraits de 14 plantes du Bénin, nous avons isolé deux molécules, la sinensétine et l'O-tétraméthyléther scutellaréine, responsables de l'activité antibactérienne de Chromolaena odorata contre les pathogènes étudiés.
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Fonche, Florentin Mongeng. "The impact of alien plant invasions on biodiversity in South Africa : the case of alien Acacia species in the Gauteng and Chromolaena odorata in the KwaZulu Natal Provinces." kostenfrei, 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=978419995.
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Autfray, Patrice. "Effets de litières sur l'offre en azote d'origine organique dans des systèmes de culture de maïs à couvertures végétales Etude de cas dans la zone à forêt semi-décidue de Côte d'Ivoire." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2002. http://tel.archives-ouvertes.fr/tel-00825211.
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Un dispositif agronomique pérennisé entre 1995 et 1999 avec des systèmes de culture de maïs à couvertures végétales a été installé dans la zone écologique à forêt semi-décidue de Côte d'Ivoire. L'offre en N d'origine organique est étudiée dans le cadre de systèmes de culture de maïs, avec une durée de jachère de 6 mois (SC6MJ) et 18 mois (SC18MJ). Les jachères sont occupées soit par Chromolaena odorata (subspontanée), soit par Pueraria phaseoloides (introduite). Ces quatre systèmes sont comparés à deux témoins, un sans Chromolaena pour les SC6MJ et un avec brûlis de Chromolaena pour les SC18MJ. Les systèmes à couvertures végétales sont gérés en couvertures vivantes avec des herbicides et leur pérennité est assurée par une reprise de croissance des espèces avant la récolte de la céréale. Les systèmes à SC6MJ bénéficient d'une fertilisation modérée en phosphore. L'étude réalisée pose comme hypothèses de départ que (i) les déterminants de l'offre à court terme (cycle cultural) et à moyen terme (effets cumulés) dépendront principalement des quantités et de la qualité des litières de surface d'origine des jachères (ii) ces effets se concentreront à la surface du sol. Le potentiel de minéralisation des litières au laboratoire est corrélé avec leur rapport C/N, plus faible pour Pueraria (C/N entre 20 à 23) que pour Chromolaena (C/N entre 25 à 43). En 1998 la vitesse de disparition des litières suivie avec des " sacs de décomposition " est beaucoup plus rapide qu'en 1999 en relation au début du cycle de décomposition avec le régime pluviométrique. Les deux années la quantité de litières présentes après la coupe détermine le taux de décomposition à moyen terme des litières. Ces dynamiques, modélisées sur deux années, permettent de distinguer un compartiment de litières à disparition rapide et un compartiment à disparition lente. La comparaison des pertes en C dans des " sacs de décomposition " à maille différente montre que l'activité de la mésofaune et de la macrofaune du sol pourrait être responsable de la disparition de 50 % des litières au début du processus de décomposition et de 35% à la fin du processus de décomposition. Leur action de fragmentation et d'incorporation au sol des litières (meules des termites champignonnistes situées à la surface du sol) permet une disparition comparativement plus rapide des litières de Chromolaena que celles de Pueraria. L'application des modèles aux données obtenues sur les mobilisations en N des jachères en relation avec les besoins de la culture en N indique (i) un risque " d'asynchronie " en début de cycle (ii) une offre insuffisante en fin de cycle pour les SC6MJ (iii) peu de différenciation entre l'offre de Chromolaena et celle de Pueraria. L'offre en N in situ du sol en surface (0-10 cm) en 1998 et 1999, estimée pendant des périodes de 90 jours durant le cycle du maïs par des mesures et des incubations de sol, est corrélée pour les SC6MJ avec les mobilisations en N du maïs dans les parties aériennes. C'est le traitement avec Pueraria qui les deux années satisfait le mieux les besoins en N de la culture et cette offre est comparable à celle des SC18MJ. L'offre en N varie peu selon les traitements des SC18MJ. Le régime pluviométrique intervient (i) à une échelle pluriannuelle, en déterminant, l'intensité du pic de minéralisation en N minéral du sol et les accumulations en N dans les parties aériennes des jachères (ii) à l'échelle de la campagne en interaction avec les litières en surface et l'activité des systèmes racinaires des couvertures végétales. La litière de Pueraria semble mieux conserver l'humidité du sol et le système racinaire de Chromolaena mobiliser de plus fortes quantités d'eau. En situations hydriques limitantes, la minéralisation nette est corrélée aux humidités de sol. Les litières semblent être à l'origine en 1998 de l'augmentation de la biomasse microbienne du sol en surface créant ainsi une source potentielle d'immobilisation temporaire de N. En 1998 l'offre en N estimée par minéralisation nette indique une meilleure synchronie avec les besoins de la culture malgré une pluviométrie plus abondante en début de cycle par rapport en 1999. Une étude utilisant l'abondance naturelle 15N permet d'estimer que la litière de Pueraria peut contribuer fortement à la nutrition azotée de la culture, de 30 à 41% en 1998 et de 64 à 87% en 1999 dans le cadre du système de culture à jachère de 6 mois. Les différenciations sur les matières organiques du sol (MOS) indiquent un début d'effet sur les stocks évalués sur 0-10 cm en moyenne à 2.34 t ha-1 N pour les SC6MJ et en moyenne à 2.83 t ha-1 N pour les SC18MJ. Pour les SC6MJ la différence obtenue entre les apports et les pertes sur quatre années suggère que Chromolaena conserve mieux les stocks en C et N que Pueraria. La comparaison avec une jachère forestière située hors dispositif indique que la disponibilité en matériaux facilement minéralisables dans nos agrosystèmes est (i) réduite en fin de saison des pluies (ii) diminuée par la pratique du brûlis (iii) peu augmentée par la pratique de la jachère. Les études sur des incubations de longue durée (106 et 85 jours) montrent des effets significatifs sur les modélisations faites par ajustement aux points expérimentaux sur les cinétiques de respiration et de minéralisation nette cumulées (exprimées en proportion par rapport au C et N total du sol). Elles permettent d'identifier d'importants facteurs de différenciation au niveau du compartiment des MOS à taux de renouvellement élevé. Pour les SC6JM ce compartiment représente une part plus importante avec Pueraria, certainement en relation directe avec des apports cumulés de plus grande qualité biochimique (rapport lignine / N). La durée de la jachère n'améliore pas la disponibilité en N facilement minéralisable indiquant ainsi un blocage de C et N au niveau du sol de nature physique et/ou biochimique.
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Erasmus, Daniël Jacobus. "Achene biology and the chemical control of Chromolaena odorata." Thesis, 1985. http://hdl.handle.net/10413/10530.
Full text
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Yi-ying, Tseng, and 曾怡頴. "Seasonal Dynamic Change in Spectrum of Mikania micrantha and Chromolaena odorata." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/46076226375124912967.
Full textAbstract:
碩士國立屏東科技大學
森林系所
99
As an island country, Taiwan has unique ecosystem and abundant natural resources. However, invasive plants impact the forest ecosystem in Taiwan in both economy and biodiversity aspects. In order to assess the possibility of remote sensing monitoring for invasive herb species through utilising GER1500 this research regularly measured the reflectance spectrum of Mikania micrantha and Chromolaena odorata. Seasonally dynamic variations of the reflectance spectrum were also observed. By simulating the wave band range of multispectral scanner and hyperspectral scanner and by ANOVA, distinguishability between Mikania micrantha and Chromolaena odorata while distribute mapping with a multispectral scanner can be manifested. Further, through stepwise discriminant analysis, the best timing and specific wave band for mapping Mikania micrantha and Chromolaena odorata with a hyperspectral scanner can be found. Results indicated that the visible light reflectance rate of Mikania micrantha and Chromolaena odorata rises with fading; whereas the near-infrared light reflectance rate decreases with it. The lowest visible and near-infrared light reflectance rate happened in January. The highest visible light reflectance rate was detected in February. The highest near-infrared light reflectance rate was detected in July.The reflection peak of Mikania micrantha is 553-554 nm. The absorption valley in red light is 670 nm. REP was 718 nm regardless seasons, but would blue shift to 716 nm in February. As for Chromolaena odorata, February and March present the lowest visible and near-infrared light reflectance rate. December had the highest visible light reflectance rate. October had the highest near-infrared light reflectance rate. The green light reflection peak is 551-553 nm. The absorption valley in red light is 667-674 nm. REP was 716-718 nm. However, it would blue shift to 700-701 nm from January to March, and would red shift to 718 nm in April. According to multispectral scanner wave band simulation, the wave bands with distinguishability were mostly detected in red light and near-infrared light, and mainly happened in November, after the florescence. This suggests that the phenology change of Mikania micrantha and Chromolaena odorata can act as a vital reference for partial mapping by utilising remote detection. Based on the simulation of hyperspectral scanner by stepwise discriminant analysis, distinguishability of remote detection is found. Reflectance spectrum data obtained in March has the best classification accuracy. Specific wave bands could be 400-410, 649-659, 704-724, 737-746, and 818-828 nm. This reflectance spectrum data can be applied for remote sensing.image mapping.
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Mgobozi, Mandisa Pride. "Spider community responses to Chromolaena odorata invasion, grassland type and grazing intensities." Diss., 2008. http://hdl.handle.net/2263/26800.
Full textAbstract:
Biological indicators measure components of the biota and are used to give general information about complex ecosystems in which they occur, playing key roles in conservation planning and management. This study illustrates the impact of habitat change by factors that are extrinsic to the habitats in question and the importance of spider responses in aiding management decisions. The spider responses illustrated existence of environmental change and represent responses of other biota. The conclusions drawn from this study have important management implications for protected areas with grazing herbivores and occurrence of alien invasive plants. Grazed sites showed the highest abundance, diversity and species richness, while ungrazed had the lowest. The implications from this study are that no grazing has negative implications on lower trophic levels, whereas grazing seems to result in favourable conditions for optimal abundance, diversity and species richness. The higher abundance, diversity and species richness associated with grazed sites could result from increased ground cover, greater variation in habitat structure, increased plant diversity and enhanced soil/plant nutrient concentrations. But, ungrazed sites in turn become more monotonous and provide less habitat diversity. However, the characteristic species for each grazing intensity level demonstrates the difficulty in making generalizations for management even for closely related species. The results further opposed the assumption that grazing lawns are a result of overgrazing and thus highly undesirable. This grassland type in comparison to tall bunch grassland displayed the highest spider diversity and species richness. This evidence further supports the conclusion that grazing lawns are steady state communities of their own and not a sub-set of any other grassland type. Therefore, veld management decisions that eradicate grazing lawns are negative for the park as the fauna and flora associated with this grassland type will be lost, leading to cascading effects. Additionally, this study illustrated that habitat modification by invasion of invasive alien plant species has detrimental consequences for the endemic fauna. C. odorata invasion results in a monotonous habitat structure. Consequently, structural heterogeneity is a primary determinant for spider diversity as opposed to abundance of prey, because plant height and architecture drive spider colonization. Therefore, removal of alien invasive weeds results in returning a system to close approximation of its condition prior to disturbance with both structure and function recreated. Assemblage patterns can be selected as endpoints to measure the ecological rehabilitation; thus, the non-significant differences in assemblage patterns of the control versus cleared sites imply that the system is rehabilitating with clearing without further management intervention. This study adds to the limited information on the implications of grazing intensities, grassland types, short and long-term invasion and clearing of an alien invasive plant on spider communities. CopyrightDissertation (MSc)--University of Pretoria, 2008.
Animal and Wildlife Sciences
unrestricted
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Wessels, Mathias Fittschen. "The role of fire and mechanical clearing in the management of Chromolaena odorata." Thesis, 2006. http://hdl.handle.net/10413/5492.
Full textAbstract:
The effects of fire and mechanical clearing were investigated for their potential in assisting with
the eradication of Chromolaena odorata (previously Eupatorium odoratum). The study was
divided into two focus areas, the first focused on mechanical clearing of dense stands of C.
odorata on three sites and the second focused on the long term influences of a single burn on C.
odorata plants in the different size categories. For mechanical clearing, two key issues were
investigated; namely whether this type of clearing procedure was effective in dense C. odorata
stands and whether rehabilitation was necessary in these cleared areas. The study was conducted
from July 2002 to June 2004. The area was subject to a severe drought throughout the duration
of the study. The severe drought had a large influence on the result in both focus areas. A
bulldozer was found to be a very effective at clearing dense C. odorata stands. Results from the
mechanical clearing study showed that there was still a large viable grass seed population in the
areas that had been covered by a dense stand of C. odorata plants for over three years. Thus,
indigenous plants were able to re-colonize the area after removal of C. odorata without human
intervention, even thought the area was experiencing a severe drought. The density of C. odorata
seedlings emerging in the cleared areas was far lower than expected. The C. odorata density in
the permanent plots, for seedlings that germinated in the first season after clearing (SeptemberOctober
2002), was only 0.25,0.03 and 0.72 per 5 m2 in the three sites respectively by the end of
the study in June 2004. For the C. odorata seedlings that germinated in the second season
(September-October 2003) the density was, 0.5, 0.56 and 1.06 per 5 m2 in the three sites
respectively by the end of the study in June 2004. It was suspected that the drought influenced
seed germination. Unfortunately the number of C. odorata seedlings was so low, that no
significant relationship could be found between grass and C. odorata seedling density. By the
end of the study the grass fuel mass in all the rehabilitated sites was already over 3000 kg ha-1,
even though the area was experiencing a severe drought. This grass fuel load, when burnt, will
assist land managers in controlling C. odorata plants, especially seedlings. Very few other alien
invasive plant species emerged in the cleared areas. At the Mhlosinga site, Senna pendula made
up less than one percent of the herbaceous species composition and only a single Ricinus
communis plant was recorded. No alien plant species were recorded on the other two sites.
Results from the burning trials revealed that plants in all the size categories were affected by fire.
Greater fuel masses and fire intensities were required to kill larger C. odorata plants relative to
smaller ones. Fire was found to be very effective at eliminating small and medium size C.
odorata plants. Fire applied as a once off treatment had a significant long-term effect on the C.
odorata population. The following fuel loads were required to achieve 80% mortality in this
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study: for small plants a fuel load of over 4000 kg ha-I, for medium plants a fuel load over 4200
kg ha-I and for large plants a fuel load over 4600 kg ha-I. Little difference could be detected
between a head or a back burn, as both fire types had their own advantages and disadvantages.
Although some of the C. odorata plants in the burnt plots had not perished by the time of the
first investigation, following the burn (February 2003), by the time of the second investigation
(June 2004), many of these plants had eventually succumbed. These results highlighted the fact
that plants which are damaged by fire were more likely to persish during an extended droughts
period, than plants which were not subjected to fire. Results from the control plots, in the
burning trials, for medium and large plants showed dramatic increases in density over time.
Tagged individuals from the control plots did reveal that some of the medium and large plants
did die during the drought, although the amount was negligible when compared to the number of
new plants growing into the new size categories. A large proportion of the small plants in the
control plots also survived the drought with many of them even growing into the medium
category. The difference between the control plots and the burnt plots was obvious and
significant, especially once the fuel mass exceeded 3783 kg ha-I. Results from this study show
that fire can be used as a very effective tool in assisting land managers to control C. odorata in
open savanna bushveld.Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.
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Dumalisile, Lihle. "Effects of Chromolaena odorata on mammalian biodiversity in Hluhluwe-iMfolozi Park, South Africa." Diss., 2008. http://hdl.handle.net/2263/26178.
Full textAbstract:
This study investigated the effects of the Triffid weed Chromolaena odorata on small and large mammals in Hluhluwe-iMfolozi Park. C. odorata is a widespread invasive alien plant that poses threat to the highly maintained natural vegetation in HiP and most other protected areas in KwaZulu-Natal. Following the opinion that the effects of invasive alien plants on all levels of biodiversity need to be recognised for their effective control, we compared small and large mammal species richness and diversity between areas with differing C. odorata invasion durations, areas with differing clearing times and an area with no history of invasion as a control area. Small mammal trapping was done using Sherman live traps and mark-recapture techniques. Track counts were used to estimate large mammal species abundance, richness and diversity. The control area had higher small mammal species richness and diversity than the invaded areas, which suggests that invaded areas were not suitable habitats for small mammals. It was also found that small and large mammal species richness and diversity decreased with the increase in invasion duration, which shows that the more time C. odorata is left to establish the more disturbance it causes to the habitat. We found the uninvaded treatment to have the highest diversity of large mammal species than all the invaded treatments, which suggests that large mammalian species show some degree of avoidance to the invaded areas. We also found that there were significant differences between the treatments with regard to large mammal species diversity indices. Some of the large mammalian species appeared to neither avoid nor prefer invaded areas. It is hypothesized that they use invaded areas to hide away from predators as most of them fall prey to many carnivores. Also, C. odorata invaded areas could provide suitable shelter from climatic extremes. The treatments cleared of C. odorata showed an increase in both small and large mammalian species richness and diversity, suggesting that clearing of this plant helps in rehabilitation of the ecosystem. However, large mammal species composition in the cleared treatments remained different to preinvasion state, which suggests that the habitat may remain changed for a long time after clearing. Managers of conservation areas should therefore prioritise alien plant removal in order to maintain healthy ecosystems.Dissertation (MSc (Wildlife Management))--University of Pretoria, 2009.
Animal and Wildlife Sciences
unrestricted
17
"The effect of elevated atmospheric CO2 on the growth and physiology of Chromolaena odorata." Thesis, 2008. http://hdl.handle.net/10413/449.
Full textAbstract:
Rising atmospheric CO2 (Ca) concentrations have generated concern among scientists, mainly because of CO2’s role as a greenhouse gas and its influence on plant growth and development. Previous research has suggested that future CO2 enriched atmospheres may enhance the success of invasive aliens. Chromolaena odorata is an example of an invasive alien proving to be a serious threat to indigenous vegetation in South Africa, and effective control measures are desperately needed to curb infestations in the future. The current study aimed at assessing the response of C. odorata to elevated Ca and interactive factors, and was divided into two trials. During PART A, C. odorata was grown in competition with 2 grass species: Eragrostis curvula and Themeda triandra (selected for their differential preferences to nutrient availability). All three species were potted in a greenhouse at the University of KwaZulu-Natal (Howard College). There were 16 pots in total, and each pot contained four C. odorata plants, four T. triandra seedlings, and four E. curvula seedlings. Eight pots were exposed to elevated Ca (~700ppm), and eight pots were exposed to ambient Ca (~370ppm). The pots at each Ca treatment were further divided: four received high nutrient treatments (3L per addition), while the other four received low nutrient treatments (300 ml per addition). Studies on growth (e.g. plant height, dry weight, etc.), as well as physiology (e.g. Jmax), were undertaken. Results showed that generally, plants responded positively to high nutrient treatments. In contrast, elevated Ca did not affect growth or any of photosynthetic parameters of C. odorata significantly, but did reduce stomatal limitations. During PART B, C. odorata plants were grown monospecifically to assess whether there was a “chamber effect” associated with planting density. Pots at both Ca treatments contained either four C. odorata or two C. odorata seedlings. Growth and physiology were assessed. The fact that elevated Ca did not affect any of the photosynthetic parameters studied, suggests that photosynthetic down-regulation did not occur. This, together with the fact that no increase in stomatal limitations were observed in elevated Ca, implies that enhancement of photosynthetic assimilation could have occurred in C. odorata plants exposed to CO2 enrichment. Results from this study (PART A and PART B), when compared to previous research on this species, suggests that CO2 enrichment may enhance the success of monoculture populations of C. odorata. However, other species may gain competitive advantages over C. odorata occurring in mixed communites, under CO2 enriched environments. In addition, results of this study support the prediction that increasing Ca will reduce the importance of carbon as an external limiting resource, and that the extent of a plant’s response to Ca enrichment will depend on resources other than CO2. If increases in temperature caused by elevated Ca increases nutrient availability in the soil, then Ca could indirectly enhance the success of C. odorata occurring in mixed communities.Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2008.
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Thiombiano, Amadou, and 田巴諾. "Life History and Host Specificity of Pareuchaetes pseudoinsulata on Chromolaena odorata in Quarantine Laboratory." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/94132996334008817591.
Full textAbstract:
碩士國立屏東科技大學
熱帶農業暨國際合作系所
96
This study was aimed at determining the life history and evaluating the host specificity of the leaf-feeding moth, Pareuchaetes pseudoinsulata Rego Barros on Siam weed Chromolaena odorata (L.). The immature stages of P. pseudoinsulata could be divided into egg, 6 discernable larval instars as well as pre-pupal and pupal stages. The efficiency of P. pseudoinsulata feeding on C. odorata from 5th to 6th instar was observed with a mean consumption by each larva ranging from 28 to 97% of leaf area. The fecundity of P. pseudoinsulata was affected by the variation of temperatures, and the mean number of laid eggs was 217.2, 284.6 and 129.2 eggs per female at 24, 28 and 32ºC, respectively. Two host specificity tests of P. pseudoinsulata were carried out. The results of consumption on C. odorata test showed mutual interference among P. pseudoinsulata caterpillars. The amount of leaf consumed was dominant in Treatment 3 (T3, the 6th instar larvae on plants with different age) and at 28ºC with leaf area damage 32.47 cm2/larva/day. However, the lowest consumption was observed in T1 (the 5th instar larvae on same age plants) and at 32ºC with leaf area consumed 9.69 cm2/larva/day, 28.93 %. Host preference of P. pseudoinsulata on C. odorata (P1) and other plants species, Ageratum conyzoides L. (P2), Ageratum houstonianum Mill (P3) and Eupatorium formosanum Hay (P4) showed that P. pseudoinsulata larvae are more effective the greatest amount on feeding C. odorata than other plants species. Under 24, 28 and 32ºC, it was 4.82, 4.52 and 4.53 cm2/larva/day for P1, 1.96, 2.29 and 2.13 cm2 /larva/day for P2, 2.73, 2.83 and 2.89 cm2 /larva/day for P3 and 2.13, 3.13 and 2.66 cm2/larva/day for P4, respectively. Based on these results under favorable conditions for the growth of C. odorata, P. pseudoinsulata performed well. Therefore, the release of this natural enemy will serve as an effective biological control and greatly reduce the invasive weeds in Taiwan. However, field experiment of this leaf-feeding moth on C. odorata is suggested before its definitive release into infested areas of Taiwan.
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Howison, Ruth Alison. "Food preferences and feeding interactions among browsers and the effect of an exotic invasive weed Chromolaena odorata on the endangered black rhino (Diceros bicornis), in an African savanna." Thesis, 2009. http://hdl.handle.net/10413/7976.
Full textAbstract:
Biodiversity changes, often resulting from climate change, land transformation, and the
transportation of organisms across geographical barriers are among the most important human
induced global changes. To optimize the spatial allocation of conservation efforts, and how to
best protect indigenous species, requires an understanding of the principal determinants that
structure ecological communities and ecosystems. We studied community-level interaction
among a diverse assemblage of specialist and generalist browsers in an African savanna.
Hluhluwe-iMfolozi Park (HiP), South Africa, hosts a complete assemblage of vertebrate species
across all trophic levels and contains a diverse guild of large browsers. Using species abundance
distributions (SADs) we graphically illustrate the diversity and abundance of woody species that
comprise six structural habitat types within HiP. We calculated the Shannon-Wiener index and
Pianka’s niche overlap to characterise the utilization of forage across habitat types among
different browser groups. By using individual plant traits we investigated mechanisms of
resource partitioning. We specifically investigated the effect of the temporal expansion of an
exotic invasive plant (Chromolaena odorata) on the critically endangered black rhino using GIS
and statistical analyses. We found that lower lying habitat types were important forage resources
for browser species and individual plant traits that are highly correlated with digestibility
strongly predicted browser preference. Black rhino used different strategic and metabolic
mechanisms to successfully compete within the same forage height range of other, smaller,
browsers. C. odorata has negatively impacted forage species utilization and has led to a spatial
reorganization of the population of black rhino. This may partly explain the recent decline in the
population. The principles within metapopulation management can be used to successfully
conserve endangered species. High diversity of browse across three dimensions (diversity,
abundance and maximum height) relative to area facilitates a high diversity and abundance of
different browsing herbivores. Therefore the spatial configurations of resources ranging from
topological attributes to the individual plant traits are essential to maintaining viable populations
of many co-occurring species within conservation areas of limited extent.Thesis (M.Sc.)-University of KwaZulu-Natal, 2009.
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Goodall, Jeremy Marshall. "Monitoring serial changes in coastal grasslands invaded by Chromolaena odorata (L.) R.M. King and Robinson." Thesis, 2000. http://hdl.handle.net/10413/10246.
Full textAbstract:
The objective of this study was to describe the impacts of the density of Chromolaena odorata
(chromolaena) on species composition in coastal grasslands and to investigate serial changes in
the vegetation following the implementation of a burning programme. The thesis deals with key
ecological concepts and issues, so a comprehensive literature review is included.
Chromolaena invades coastal grasslands that are not burnt regularly (i.e. biennially). Grasslands
that were not burnt for 30 years were seral to secondary forest. The successional pathway from
open grassland to closed canopy forest varied according to soil type. Coastal grasslands on
Glenrosa soils were characterised by savanna at an intermediate stage between the grassland and
forest states. Shading ended the persistence of savanna species (e.g. Combretum molle,
Dichrostachys cinerea and Heteropyxis natalensis) in forest, whereas forest precursors (e.g.
Canthium inerme, Maytenus undata and Protorhus longifolia) only established where fire was
absent. Chromolaena infestations were characterised by multi-stemmed adult plants of variable
height (i.e. 1-3 m), depending on soil type. Regic sands did not support stratified woody
vegetation and chromolaena infestations were self-supporting, reaching a maximum height of
1.5 m. Glenrosa soils supported tree communities and chromolaena reached more than 3 m in
places. The density of chromolaena affected species composition in grasslands with moderate to
dense stands (> 5 adult plants m ¯² or >50000 shrubs ha ¯¹). Chromolaena stands became monospecific when the number of adult plants exceeded 7 m ¯². Succession to forest also ceased
once chromolaena became thicket-forming.
Fire-induced mortality of the chromolaena depended on grass fuel loads. Grass cover of 30% (c.
1 000 kg ha ¯¹) was required to achieve 80% mortality of the parent infestation after the initial
burn. Dense infestations could only be killed by running head-fires from adjacent grasslands
into thickets. Under conditions where head-fires could not be used, infestations were slashed
and burnt at the height of the dry season (July to August) to achieve an 80% kill rate. Seedlings
were killed (99%) by annual burning in sparse (≤ 10000 shrubs ha ¯¹) to moderate
< 50 000 shrubs ha ¯¹) infestations. The suppression of chromolaena and other alien species,
establishing on bare ground after clearing dense infestations, required chemical control until
grass cover was sufficient (i.e. 1 000 kg ha ¯¹) to effect uniform burning. Certain secondary alien
invaders (e.g. Lantana camara, Psidium guajava and Solanum mauritianum) persisted by
coppicing profusely after fire and herbicides need to be integrated into burning programmes
when these species occur. Grasslands on regic sands (e.g. Ischaemum fasciculatum, Panicum
dregeanum and Themeda triandra) were more resilient to the modifying effects of woody
vegetation, than grasslands on Glenrosa soils. Grasslands on Glenrosa soils did not revert to an
open state but persisted as ruderal savanna grassland (e.g. Eragrostis curvula, Hyparrhenia
tamba and Cymbopogon validus) once fire-resistant tree species (e.g. Combretum molle and
Heteropyxis natalensis) had established.
Depending the objectives for land management and the vegetation's condition, coastal
grasslands can be rehabilitated and managed in multiple states, i.e. grassland, savanna or forest
communities. A state-and-transition model based on the empirical data recorded in the study is
presented and shows chromolaena altering vegetation states from open grassland to chromolaena
dominated thicket. The model illustrates chromolaena thickets as the dominant phase of a moist
coastal forest/savanna succession, irrespective of soil type, in absence of appropriate land
management practices (e.g. control burning and integrated control of alien vegetation). This
model should aid in planning strategies for the control of chromolaena in subtropical grasslands in South Africa.Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.
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Gareeb, Milly. "Investigation into the mortality of potted Chromolaena odorata (L.) R. M. King & H. Robinson (Asteraceae)." Thesis, 2007. http://hdl.handle.net/10413/462.
Full textAbstract:
The neotropical semi-woody perennial shrub Chromolaena odorata (L.) King and Robinson (Asteraceae: Eupatorieae) has become a serious invasive weed in the sub-tropical regions of southern Africa, resulting in the initiation of an insect biocontrol research programme at Cedara in the KwaZulu-Natal province. The programme has experienced difficulties in growing and maintaining healthy potted C. odorata plants for research, for almost ten years. In an attempt to identify possible causes of mortality, plants were grown on elevated grids in two trials; (winter-spring 2003) and (autumn-winter 2004) in Durban (subtropical region, within the natural range of C. odorata) and Cedara (temperate region, outside its natural range). Plants that established at all sites, in Trials 1 and 2, did not display any visual symptoms associated with mortality; however, results from Trial 1 indicated that plants grown in a tunnel at Cedara were physiologically stressed evidenced by lower transpiration rates despite higher vapour pressure deficits, compared with plants grown in a tunnel in Durban. Environmental stress was further indicated by the chlorophyll fluorescence ratio and a change in allocation of total non-structural carbohydrate (TNC) within Cedara-grown plants compared with Durbangrown plants. An attempt to relate mortality symptoms of unhealthy C. odorata plants with TNC content of the roots was unsuccessful but unhealthy plants had lower levels of N, P and K than healthy plants. Although mortality seem to be exacerbated by pathogenic fungi in saturated soil, infection was reduced by treating the soil with Previcur N and Benlate drench. Morphological adaptations of plants exposed to waterlogged soils include hypertrophied lenticels and new lateral roots; these were observed on the stem base of unhealthy C. odorata plants placed on the ground, that had reached a critical stage of die-back or had died back and re-sprouted. Examination of the root anatomy of C. odorata plants indicated an absence of cortical aerenchyma (interconnected system of air spaces), which may explain plant mortality in waterlogged pots wherein levels of oxygen in the soil may be reduced. C. odorata stock plants at Cedara have been placed on elevated grids since August 2004 and two years later plant mortality has been significantly reduced. Presently, the only feasible option is to grow potted C. odorata plants on elevated grids at Cedara because this allows for adequate drainage, aeration of soil and air-nipping of roots, and spacing plants on the grids also improves penetration of light.Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2007.
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Kang, Chang-Jung, and 康昌榮. "Ecophysiological Studies on the Seed Germination of Chromolaena odorata (L) R. M. King & H. Rob." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/07362300640834641976.
Full textAbstract:
碩士國立嘉義大學
農學研究所
99
The purposes of this study were to test the ecological characteristics of seed germination and to evaluate the effects of herbicide on the seed germination and seeding growth of Chromolaena odorata (L) R. M. King & H. Rob., and a comparison of seedling vigor of Bidens pilosa, Mikania micrantha, and C. odorata (L) R. M. King & H. Rob. was performed. The seeds were germinating at a constant temperature between 20 and 40℃, and the constant temperature resulting in the optimum germination was at 30℃, the germination percentage higher than 60 %. As using an alternating temperature between 25/20 and 45/40℃, the optimum germination occurred at 35/30℃, and the germination percentage was 85.87%. The seed germination of C. odorata (L) R. M. King & H. Rob. would be higher at the alternating temperature than the constant temperature. The seeds of C. odorata (L) R. M. King & H. Rob. could germinate under the water potential from 0 to -0.8 MPa but did not germinate under the -1.0 MPa. The optimum water potentials were 0 and -0.1 MPa, and then the seed germination percentages was 81.20% and 84.93 %. The seeds of C. odorata (L) R. M. King & H. Rob. could germinate under the treatments of NaCl solutions (0 - 1.0 %). The germination percentage of seed was decreasing with increase of NaCl concentration. The seeds under the treatment of 0 % NaCl solution showed the highest germination of 86% and as NaCl concentration increasing up to 1.2 %, the seeds did not germinate. Under the pH treatments, the seeds of C. odorata (L) R. M. King & H. Rob. can germinate at the pH values from 4 to 11. And the seeds under the pH values 6 and 7 could show the germination percentage higher than 80 %. Under the irradiation treatments, there was 85 % seed germination of C. odorata (L) R. M. King & H. Rob. during the exposure of white light. But, the lowest germination percentage was 8 % under the dark treatment. Furthermore, the partial oxygen condition and enough irradiation resulted in 89% seed germination of C. odorata (L) R. M. King & H. Rob. However, there would be not seed germination at the non-oxygen condition. Under the treatments of bury depth, the emergence percentage of seeds was decreasing with increase of buried depth. With 0 cm bury depth, there was the highest emergence, and seed would not germinate with the bury depth more than 1.5 cm. Under the herbicide treatments, alachlor (45.1 % emulsion) 400x resulted in the seed germination of C. odorata (L) R. M. King & H. Rob. lower than 1 % but during the pendimethalin (34 % emulsion) 200x, 300x and 400x, the seed germination was higher than 70%. Glyphosate 50x, 75x and 100x could reduce the seed germination to lower than 7% and paraquat 120x, 160x and 200x could reduce the seed germination to lower than 5%. After use of paraquat, the shoot fresh weight and root fresh weight of C. odorata (L) R. M. King & H. Rob. were ranged from 0.093 g to 0.135 g and from 0.151 g to 0.209 g, respectively. Compared with the controls for shoot fresh weight and root fresh weight (1.315 g and 0.872 g) respectively, paraquat 120x resulted in the lowest shoot fresh weight and root fresh weight. After use of glyphosate, the shoot fresh weight and root fresh weight of C. odorata (L) R. M. King & H. Rob. were ranged from 0.510 g and 0.671 g and from 0.362 g and 0.435 g, respectively. Compared with the controls for shoot fresh weight and root fresh weight (1.315 g and 0.872 g) respectively, glyphosate 50x resulted in the lowest shoot fresh weight and root fresh weight. In the comparison of seedling vigor of B. pilosa, M. micrantha, and C. odorata (L) R. M. King & H. Rob., B. pilosa had the best seedling vigor and M. Micrantha presented the moderate; however, C. odorata (L) R. M. King & H. Rob. was inferior to B. pilosa and M. Micrantha.
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Howison, Owen Erik. "How do alien plants invade : an analysis of the historical spread and potential distribution of the invasive alien plant Chromolaena odorata in and around Hluhluwe Game Reserve." Thesis, 2009. http://hdl.handle.net/10413/8357.
Full textAbstract:
Alien plant invasions and human-induced land transformations are the two most important factors
contributing to loss of biodiversity, and Chromolaena odorata (C. odorata) is one of the world’s
worst invader plants. It impacts negatively on biodiversity conservation, forestry and agriculture
due to its rapid rate of spread, fast growth and hence an ability to transform habitats. It was
introduced into KwaZulu-Natal, South Africa in the mid-1940s, and has spread north and
southwards along the coastline and adjacent interior. In 1961 it was observed in Hluhluwe Game
Reserve, and has invaded and transformed large parts. In this thesis I use C. odorata distribution
maps from 1978 to 2001 to investigate invasion pathways, and whether these are related to
species or habitat characteristics. Invasion in the twelve vegetation types identified in the Reserve
showed two patterns. In some vegetation types invasion expanded linearly, while in others there
were three phases of invasion, driven by interactions between habitat suitability, habitat
fragmentation and propagule pressure. Expansion of existing invasions (phalanx or wave
invasion) through short distance seed dispersal was the primary mode of spread, rather than the
formation of new infestations (guerrilla or diffuse invasion). Known distribution of dense stands
was used to develop a spectral signature and run a supervised classification of satellite images. I
utilized the dense stands and other GIS data sets of climate, altitude, solar radiation, distance from
roads, distance from rivers and normalized differential vegetation index from 1973 and 2001 to
determine a probability model, and assess the impact of the invasion on biodiversity conservation.
The supervised classification underestimated the extent of the invasion, as C. odorata is a cryptic
understory species in some habitats. Supplementation by using multiple regression to develop a
probability model, and combining these into one map provided a realistic result. I used this map
and GIS data sets of vegetation types and protected areas to assess the impact of the invasion on
biodiversity conservation. This showed that C. odorata was preferentially impacting sensitive
areas, and the conservation of threatened vegetation types is not guaranteed by including them in
protected areas.Thesis (M.Sc.)-University of KwaZulu-Natal, 2009.
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"Autocorrelação espacial e variação temporal na fenologia floral, produção e predação de sementes em Chromolaena odorata (Asteraceae)." Tese, Biblioteca Digital da Unicamp, 2004. http://libdigi.unicamp.br/document/?code=vtls000296152.
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Anyasi, Raymond Oriebe. "Bioremediation of polychlorinated biphenyls (PCBs)-contaminated soil by phytoremediation with Chromolaena odorata(L) R.M. King and Robinson." Diss., 2012. http://hdl.handle.net/10500/6103.
Full textAbstract:
The ability of Chromolaena odorata propagated by stem cuttings and grown for six weeks in the greenhouse to thrive in soil containing different concentrations of PCB congeners found in Aroclor and transformer oil, and to possibly remediate such soil was studied under greenhouse conditions. Chromolaena odorata plants were transplanted into soil containing 100, 200, and 500 ppm of Aroclor and transformer oil (T/O) in 1L pots. The experiments were watered daily at 70% moisture field capacity. Parameters such as mature leaves per plant, shoot length, leaf colour as well as the root length at harvest were measured. C. odorata growth was negatively affected by T/O in terms of shoot length and leaf numbers, but no growth inhibition was shown by Aroclor.
At the end of six weeks of growth, Plants size was increased by 1.4 and 0.46%, but decreased at -1.0% in T/O, while increases of 45.9, 39.4 and 40.0% were observed in Aroclor treatments. Mean total PCB recoveries were 6.40, 11.7, and 55.8μg in plants tissues at Aroclor treated samples resulting in a percentage reduction of PCB from the soil to 2.10, 1.50, and 1.10 at 100, 200, and 500mg/kg Aroclor treatments respectively. There was no PCB recovery from plants in transformer oil treatments as a result of its inhibition to growth. Root uptake was found to be the probable means of remediation of PCB-contaminated soil by C. odorata, this was perhaps aided by microbes. This study has provided evidence on the ability of C. odorata to remediate PCB contaminated soil. However, the use of C. odorata for phytoremediation of PCB contaminated soil under field condition is therefore advised.Environmental Sciences
M.Sc. (Environmental Science)
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Naidoo, Kubendran Kista. "Ecophysiological studies of the invasive weed Chromolaena odorata (L.) King and Robinson and its control in KwaZulu-Natal." Thesis, 2013. http://hdl.handle.net/10413/11221.
Full textAbstract:
Despite increased interest in the control and spread of the alien weed, Chromolaena odorata, little is known of its photosynthetic characteristics under field conditions. The aim of the study was to obtain a better understanding of the ecophysiological attributes of C. odorata that contribute to its invasive success.
Photosynthetic performance of C. odorata was evaluated by monitoring diurnal changes in gas exchange, chlorophyll a fluorescence and plant water relations. Gas exchange characteristics of plants growing in exposed and shaded environments, as well as seasonal patterns, were evaluated. The response of C. odorata to water stress was also determined.
Chromolaena odorata exhibited high CO2 uptake rates with no light saturation. Shade plants had significantly larger leaf surface areas and greater concentrations of total chlorophyll, total carotenoids and chlorophylls a and b than sun plants. Relatively high photosynthetic uptake rates in C. odorata may allow for greater carbon gain in high light environments thus contributing to increased growth and spread of the species. Chromolaena odorata can successfully acclimatise to low photosynthetic photon flux density (PPFD), thus, outcompeting less tolerant species under low light conditions.
Leaf conductance, CO2 uptake, transpiration and chlorophyll fluorescence parameters in winter were tightly coupled to summer. Plants had higher water use efficiency (WUE) in summer compared to winter, probably to maximise CO2 uptake and minimise water loss.
There was a progressive decrease in leaf water potential with increase in water stress in water stressed (WS) plants. The leaves of WS plants showed signs of severe wilting 10 days after the onset of stress compared to well watered (WW) plants. Increased proline concentration and leaf wilting probably increase (WUE) and may be an adaptive strategy to protect against dehydration injury.The effects of the herbicide, glyphosate, on gas exchange and translocation were studied. Glyphosate treatment decreased leaf conductance leading to a reduction in CO2 uptake and transpiration. Glyphosate is a mobile herbicide that is transported from leaves to roots and caused death of plants within a week of treatment.
The potential antimicrobial properties of the weed were evaluated using selected bacteria and fungi. Crude leaf extracts exhibited some antibacterial and antifungal activity. Extracts from the weed are unlikely to be useful antimicrobial sources due to low concentrations of active compounds.
A co-ordinated strategy, taking into account the high plasticity of the weed, is needed to curtail the spread of C. odorata. The ecophysiological responses to environmental conditions should be considered when planning management and control strategies for C. odorata.Ph.D. University of KwaZulu-Natal, Durban 2013.
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Wang, Tzu-Hui, and 汪慈慧. "Host range of Pareuchaetes pseudoinsulata Rego Barros (Lepidoptera: Arctiidae) and its population parameters on the weed, Chromolaena odorata (L.) (Compositae)." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/93810333525446144342.
Full textAbstract:
碩士國立屏東科技大學
熱帶農業暨國際合作研究所
93
Chromolaena odorata (L.) introduced around 1989 to southern part of Taiwan as a medicinal plant, has become an invasive weed, spreading to such counties as Pingtung, Kaohsiung, Tainan, Chiayi, Yunlin, Changhau, Taichung, and Taitung. An arctiid moth, Pareuchaetes pseudoinsulata Rego Barros, was introduced from Guam in June 2004 and was immediately isolated for study host specificity and other research in a quarantine laboratory at National Pingtung University of Science and Technology. The life history of P. pseudoinsulata feeding on C. odorata was studied at three different temperatures. Developmental time from egg to adult was 69.5, 40.7 and 39.4 days for female; and 66.8, 38.9 and 41.0 days for male, at 24, 28 and 32℃, respectively. Under the temperatures of 24, 28 and 32℃, the longeyity of P. pseudoinsulata was 13.1, 7.6 and 3.8 days for female, and 11.1, 5.8 and 3.8 days for male, respectively. Pre-oviposition periods and fecundity for P. pseudoinsulata averaged 54.4, 37.4 and 38.1 days, and 389.3, 261.8 and 159.0 eggs per female, respectively. Population parameters were caculated from the life table data for 24, 28 and 32℃. Under the respective temperatures, the net reproduction rates (R0) of P. pseudoinsulata were 279.9, 176.1 and 14.5; the mean generation time (T) were 57.9, 38.0 and 34.2 days; the intrinsic rates of increase (rm) were 0.099, 0.138 and 0.078; the finite rates of increase (λ) were 1.103, 1.146 and 1.082；Doubling times (t) were 7.1, 5.1 and 8.8 days. The age-stable distribution of P. pseudoinsulata under the three different temperatures was significantly different. The larval stage was dominant at 24℃. The larval and adult stages were dominant at 28℃. The larval and pupal stages were dominant at 32℃. In the feeding study, the amount of leaf consumed was the greatest at the late larval stage; each larva consumed 0.57, 0.69 and 0.24g at 24, 28 and 32℃, respectively. A total of 135 plant species in 55 families have been screened by forced feeding for delineating the host specificity of P. pseudoinsulata. Of the plant species screened, larvae of P. pseudoinsulata were found feeding on C. odorata (L.), Ageratum conyzoides L., A. houstonianum Mill, and Eupatorium formosanum Hayata. However, they did not feed or not attempt to feed on 132 other plant species screened.
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Dube, Nontembeko. "Investigation of the biology and cross-breeding of populations of Pareuchaetes insulata (Lepidoptera : Arctiidae) and the implications for the biological control of Chromolaena odorata (Asteraceae) in South Africa." Thesis, 2008. http://hdl.handle.net/10413/10777.
Full textAbstract:
Larvae of Pareuchaetes insulata were released in South Africa for the biological control of the invasive weed Chromolaena odorata. Pareuchaetes insulata has proved to be a difficult agent to establish in the field in South Africa, for various possible reasons. Populations collected from Florida and Jamaica (their aboriginal home) were released separately at several sites each in South Africa, but only one population (Florida) was definitely established. It is possible that adults from this established population interbred with adults from the Jamaican population released at nearby sites.
The aims of this study were to determine whether there were any differences in biology between the two populations and whether hybridization affected the fitness of either. Trials involved: (i) pure-breeding of both Florida (F) and Jamaica (J) populations; (ii) cross-breeding of the two populations and; (iii) back-crossing of the hybrids with the parent populations. The fitness of these populations was determined by measuring adult longevity and fecundity, egg viability, and larval development and survival rates.
The F population was superior to the J population in most of parameters measured, including fecundity. Hybridization of these populations reduced the fitness of the F population. It is unknown whether these differences in fitness reflect differences in their native regions, laboratory cultures or response to South African C. odorata. It appears that different populations of P. insulata have different levels of fitness, and that hybridization negatively affects the fitness of stronger populations. The lower fitness of the J population may have reduced its likelihood of establishing successfully, and even reduced the fitness of the established F population where the populations came into contact. These results caution that the possible consequences of mixing different genotypes of a biocontrol agent species should be properly investigated prior to their release in the same country.Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.
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Malahlela, Oupa. "Intergrating environmental variables with worldview-2 data to model the probability of occurence of invasive chromolena odata in forest canopy gaps : Dukuduku forest in KwaZulu-Natal, South Africa." Thesis, 2013. http://hdl.handle.net/10413/10562.
Full textAbstract:
Several alien plants are invading subtropical forest ecosystems through canopy gaps,
resulting in the loss of native species biodiversity. The loss of native species in such habitats
may result in reduced ecosystem functioning. The control and eradication of these invaders
requires accurate mapping of the levels of invasion in canopy gaps. Our study tested (i) the
utility of WorldView-2 imagery to map forest canopy gaps, and (ii) an integration of
WorldView-2 data with environmental data to model the probability of occurrence of
invasive Chromolaena odorata (triffid weed) in Dukuduku forest canopy gaps of KwaZulu-
Natal, South Africa. Both pixel-based classification and object-based classification were
explored for the delineation of forest canopy gaps. The overall classification accuracies
increased by ± 12% from a spectrally resampled 4 band image similar to Landsat (74.64%) to
an 8 band WorldView-2 imagery (86.90%). This indicates that the new bands of WorldView
such as the red edge band can improve on the capability of common red, blue, green and
near-infrared bands in delineating forest canopy gaps. The maximum likelihood classifier
(MLC) in pixel-based classification yielded the overall classification accuracy of 86.90% on
an 8 band WorldView-2 image, while the modified plant senescence reflectance index
(mPSRI) in object-based classification yielded 93.69%. The McNemar’s test indicated that
there was a statistical difference between the MLC and the mPSRI. The mPSRI is a
vegetation index that incorporates the use of the red edge band, which solves a saturation
problem common in sensors such as Landsat and SPOT.
An integrated model (with both WorldView-2 data and environmental data) used to predict
the occurrence of Chromolaena odorata in forest gaps yielded a deviance of about 42% (D2 =
0.42), compared to the model derived from environmental data only (D2 = 0.12) and
WorldView-2 data only (D2 = 0.20). A D2 of 0.42 means that a model can explain about 42%
of the variability of the presence/absence of Chromolaena odorata in forest gaps. The
Distance to Stream and Aspect were the significant environmental variables (ρ < 0.05) which
were positively correlated with presence/absence of Chromolaena in forest gaps.
WorldView-2 bands such as the coastal band (λ425 nm) yellow band (λ605 nm) and the nearinfrared-
1 (λ833 nm) are positively and significantly related to the presence/absence of
invasive species (ρ < 0.05). On the other hand, a significant negative correlation (ρ < 0.05) of
near-infrared-2 band (λ950 nm) and the red edge normalized difference vegetation index
(NDVI725) suggests that the probability of occurrence of invasive Chromolaena increases forest gaps with low vegetation density. This study highlights the importance of WorldView-
2 imagery and its application in subtropical indigenous coastal forest monitoring.Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.
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Nzama, Sindisiwe N. "Population and behavioural studies on Calycomyza eupatorivora spencer (Diptera : Agromyzidae), a biological control agent of Chromolaena odarata (L.) King and Robinson (Asteraceae) in South Africa." Thesis, 2011. http://hdl.handle.net/10413/10096.
Full textAbstract:
Chromolaena odorata (L.) King and Robinson (chromolaena, triffid weed) (Asteraceae: Eupatorieae) is one of the most problematic weeds in the subtropical northeastern parts of South Africa. Calycomyza eupatorivora Spencer (Diptera: Agromyzidae) was introduced as a biological control agent for the control of this weed. No study has yet been done to quantify field populations of C. eupatorivora since its establishment in 2003. The aim of this study was therefore to measure aspects of the field population and laboratory behaviour of C. eupatorivora on C. odorata.
The first objective was to determine the percentage leaf area mined by larvae of C. eupatorivora on C. odorata plants exposed to three densities of mated flies, and also to determine the number of mines produced by these different densities, and their distribution on the plant. It also attempts to determine the relationship between chromolaena leaf quality and usage by C. eupatorivora. The maximum percentage of leaf area damaged was 37.5% for one of the trials involving five pairs of flies. Mean percentage leaf area damaged was slightly higher with five (28.5%) than ten pairs (22.0%) of adults and was lowest with one pair (6.5%), but these differences were not significant. In relation to the mean number of mines per plant, five and ten pairs of flies caused slightly more mines than one pair. The other significantly different parameter was number of leaves mined per plant, which was higher for five pairs. Within a plant, C. eupatorivora probably selects a subset of leaves with certain chemical and physical characteristics for oviposition since certain leaves were left unmined while others received multiple eggs. Percentage water content did not differ between mined and unmined leaves, but clear patterns were shown by acid detergent lignin which was higher in unmined leaves and nonstructural carbohydrates which were much higher in mined leaves. It is likely that leaf age plays a role in its suitability.
The second objective was to quantify C. eupatorivora infestation levels, by counting and examining larval leaf mines, on C. odorata in the field at four times ('seasons' - September, December, March and July) over a 12-month period, and at three study sites that each included two habitats, viz. open and shady. At each of these six sampling sites, line transects were laid out and plants/branches sampled along them. Both plant/branch height and the number of leaves increased between September and March, and plants in the open habitats were taller and had more leaves than those in the shaded habitats. At the third site, the shady habitat supported taller plants with more leaves compared to the same habitat at the other sites. There was a steep increase in the number of C. eupatorivora mines from December to March. The mean number of mines, both total and in relation to leaves available, was highest in March, and was higher in the shaded habitats compared to the open habitats. The mean number of mines per damaged leaf was slightly higher in December compared to the other seasons, and was also higher in the open than the shaded habitats. Mean larval mortality was high (70%) in September but decreased to 32% in December, and increased again in late summer. The overall levels of mining by C. eupatorivora were low, with less than 5% of leaves sampled having mines. Taken together, the laboratory and field trials suggest that C. eupatorivora is restricted to a subset of the leaves of C. odorata for its development; that the field population is unable to make full use of the resource of young, palatable leaves that develop in early- to mid-summer because it only becomes large in late summer; and that the high mortality rate of young larvae negatively affects both the population of the fly and the level of damage to the plant. Given that these results were obtained in an area where the population of C. eupatorivora is relatively high, it is unlikely that the fly is having anything more than a negligible effect on C. odorata in South Africa at present.Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.
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Fonche, Florentin Mongeng [Verfasser]. "The impact of alien plant invasions on biodiversity in South Africa : the case of alien Acacia species in the Gauteng and Chromolaena odorata in the KwaZulu Natal Provinces / vorgelegt von Florentin Mongeng Fonche." 2005. http://d-nb.info/978419995/34.
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