Invasive plant species in natural ecosystems have been shown to have a wide range of potential impacts on community composition and ecosystem function. Alligator weed (Alternanthera philoxeroides) is invasive in New Zealand and elsewhere. An aggressive competitor and difficult to control, its impacts in productive ecosystems are widely documented. However, little information exists about alligator weed’s effects in natural ecosystems. This thesis therefore investigated potential effects of alligator weed on decomposition and nutrient cycling, as well as on invertebrate and plant communities in a “native” ecosystem, thus integrating effects on ecosystem processes and community composition. These aspects were compared between vegetation dominated by alligator weed or by one of two native sedges, Isolepis prolifer and Schoenoplectus tabernaemontani, in a northern New Zealand lake. In addition, the potential of shading to control alligator weed was assessed. Herbivory by the biocontrol agent Agasicles hygrophila resulted in substantial alligator weed defoliation, differing in timing and magnitude from biomass dynamics of the native sedges. Alligator weed also decomposed faster than either native sedge. Changes in decomposition dynamics led to a shift towards fungivore dominated beetle communities. This illustrates the potentially complex ecosystem effects of biocontrol agents as well as invasive weeds. Alligator weed decomposition rates and invertebrate communities were more similar to those of I. prolifer than S. tabernaemontani. This pattern was attributed to the greater chemical and architectural similarity of alligator weed to I. prolifer compared with S. tabernaemontani. Invasive plants’ impacts may thus be partially influenced by the degree of similarity between the invasive species and the dominant vegetation they invade. Alligator weed was associated with decreased cover of native plants, potentially placing them at greater risk of local extinction. Greenhouse and field experiments showed that shading significantly reduced alligator weed growth. However, clonal support from unshaded areas, and competitive release from less shade tolerant plants, may potentially impede the success of shade based control. This research demonstrates that alligator weed can have a range of complex and multi-trophic effects in a natural ecosystem. Further, characteristics of both invasive and competing vegetation can influence the success of cultural control methods such as shading.

Invasive plant species in natural ecosystems have been shown to have a wide range of potential impacts on community composition and ecosystem function. Alligator weed (Alternanthera philoxeroides) is invasive in New Zealand and elsewhere. An aggressive competitor and difficult to control, its impacts in productive ecosystems are widely documented. However, little information exists about alligator weed’s effects in natural ecosystems. This thesis therefore investigated potential effects of alligator weed on decomposition and nutrient cycling, as well as on invertebrate and plant communities in a “native” ecosystem, thus integrating effects on ecosystem processes and community composition. These aspects were compared between vegetation dominated by alligator weed or by one of two native sedges, Isolepis prolifer and Schoenoplectus tabernaemontani, in a northern New Zealand lake. In addition, the potential of shading to control alligator weed was assessed. Herbivory by the biocontrol agent Agasicles hygrophila resulted in substantial alligator weed defoliation, differing in timing and magnitude from biomass dynamics of the native sedges. Alligator weed also decomposed faster than either native sedge. Changes in decomposition dynamics led to a shift towards fungivore dominated beetle communities. This illustrates the potentially complex ecosystem effects of biocontrol agents as well as invasive weeds. Alligator weed decomposition rates and invertebrate communities were more similar to those of I. prolifer than S. tabernaemontani. This pattern was attributed to the greater chemical and architectural similarity of alligator weed to I. prolifer compared with S. tabernaemontani. Invasive plants’ impacts may thus be partially influenced by the degree of similarity between the invasive species and the dominant vegetation they invade. Alligator weed was associated with decreased cover of native plants, potentially placing them at greater risk of local extinction. Greenhouse and field experiments showed that shading significantly reduced alligator weed growth. However, clonal support from unshaded areas, and competitive release from less shade tolerant plants, may potentially impede the success of shade based control. This research demonstrates that alligator weed can have a range of complex and multi-trophic effects in a natural ecosystem. Further, characteristics of both invasive and competing vegetation can influence the success of cultural control methods such as shading.

Thesis (M.S.)--Montana State University--Bozeman, 2004. / Typescript. Chairperson, Graduate Committee: Roger L. Sheley. Includes bibliographical references (leaves 26-30).

Petróleo Brasileiro S.A. / As espécies de corais invasores, Tubastraea tagusensis e T. coccinea foram acidentalmente introduzidos no Brasil através de plataformas de petróleo. O rápido crescimento e estágio reprodutivo, competição contra espécies nativas, defesas químicas contra predadores e competidores naturais e uso amplo em diferentes substratos utilizados contribuem para o sucesso e expansão de Tubastraea spp. na costa brasileira. O presente estudo teve dois objetivos principais: 1) investigar uma metodologia que resulte em uma maior eficiência e custo-benefício nos processsos de monitoramento dos corais invasores Tubastraea spp. no litoral brasileiro; 2) mapear a distribuição geográfica, caracterizar as populações e estudar o efeito da inserção dos corais na comunidade bêntica de costões rochosos do litoral norte do estado de São Paulo (LNSP). O primeiro avaliou quatro metodologias, comparando o método do censo visual, e outras três metodologias que utilizam fotografia e filmagem. O método do censo visual mostrou ser mais eficiente na obtenção dos resultados quando comparado com os outros métodos, principalmente para identificar pequenos organismos. Contudo, seu tempo em campo e seus custos foram maiores. O segundo utilizou o método visual para estudar o efeito da inserção dos corais invasores na comunidade local do LNSP. Ainda, foi realizado um monitoramento espacial semi-quantitativo em larga escala para caracterizar a distribuição espacial dos corais invasores; transectos com quadrados amostrais foram usados para estimar a densidade de Tubastraea ao longo da profundidade, e transectos e arcos graduados empregados para estimar a ocorrência de colônias em diferentes inclinações do substrato, no LNSP. Os corais invasores estão aumentado sua distribuição, causando diversos impactos nas comunidades e nos organismos nativos. T. tagusensis é comumente encontrado dominando diversos costões rochosos, com uma densidade maior em ambientes mais profundos e com maior ocorência em substratos de inclinções verticais e negativas no LNSP. A erradicação e/ou controle do coral invasor é recomendado no litoral brasileiro, principalmente onde as populações estão isoladas ou ainda são pequenas. / The invasive coral species, Tubastraea tagusensis and T. coccinea were accidentally introduced into Brazil by oil platforms. The rapid growth and reproductive stage, competition against native species, chemical defenses against natural predators and competitors and ample use of different substrates contribute to the success and expansion of Tubastraea spp. on the Brazilian coast. This study had two aims: 1) investigate a methodology that results in more efficient and cost-effective monitoring of the Tubastraea spp. invaders on the Brazilian coast, 2) map the geographical distribution, characterize the populations and study the effect of corals insertion in the community on the northern coast of São Paulo (LNSP). The first aim evaluated four methods by comparing the visual census method and three other methods that use photography and filming. The visual census method proved to be more efficient in achieving the results compared with other methods, primarily to identification of smaller organisms; however, time in the field and costs were higher. The second aim used the visual method to study the effect of insertion of coral invaders into the community. Also, a semi-quantitative monitoring of spatial scale to characterize the spatial distribution of coral invaders was carried out; transects with squares were used to estimate the density of Tubastraea spp. along the depth gradient, and transects and graduated arcs employed to estimate the occurrence of colonies at different inclinations of the substrate, in LNSP. The invader corals are increasing their distribution, causing several impacts on native communities and species. T. tagusensis is actually found dominating several rocky shores, with a higher density deeper and in a vertical and negative substrates slopes in LNSP. Eradication and/or control of the invasive corals are recommended on the Brazilian coast, especially where populations are isolated or are still small.

Insect pests represent major threats to food production, biodiversity conservation, and human and animal health. Currently, the most widespread strategy to control their populations is through the spraying of synthetic chemical insecticides. However, the overuse of these compounds has had significant negative environmental consequences. Additionally, our reliance on insecticides has resulted in major reductions in their efficacy through pest-evolved resistance. To successfully manage insect pests, while avoiding environmental degradation, thus requires the development of novel, more sustainable, pest management strategies. Recent advances in our understanding of recombinant DNA methods and molecular biology have allowed the application of transgenic tools to pest management. Here, synthetic genes can be engineered, transformed into the genomes of pest species, and transported into wild target populations through the natural mating behaviour of the insect. A strategy in which these transgenes are lethal to those insects inheriting them in the field is known as RIDL – Release of Insects carrying a Dominant Lethal. A variant of RIDL limits this lethality to females – female specific RIDL (fsRIDL) – which explicitly targets the reproductive capacity of a target population. The aim of this thesis is to investigate the application of such an fsRIDL strategy to the diamondback moth (Plutella xylostella L.). This economically important pest of brassica crops is highly adept at developing resistance to insecticides and is considered extremely difficult to manage effectively. I present findings which demonstrate the power of diamondback moth lines transformed with fsRIDL transgenes to eliminate target pest populations, and combine synergistically with other transgenic control strategies such as Bt crops in counteracting the evolution of pesticide resistance. Additionally, an exploration into an alternative gene expression system to that used in current RIDL strategies – the Q system – suggests that not all expression systems will be suitable for transgene control within this highly specific framework. It is hoped that this work will contribute towards the effective control of the diamondback moth, and form a model for the sustainable control of other lepidopteran species through genetic pest management.

Petróleo Brasileiro S.A. / As espécies de corais invasores, Tubastraea tagusensis e T. coccinea foram acidentalmente introduzidos no Brasil através de plataformas de petróleo. O rápido crescimento e estágio reprodutivo, competição contra espécies nativas, defesas químicas contra predadores e competidores naturais e uso amplo em diferentes substratos utilizados contribuem para o sucesso e expansão de Tubastraea spp. na costa brasileira. O presente estudo teve dois objetivos principais: 1) investigar uma metodologia que resulte em uma maior eficiência e custo-benefício nos processsos de monitoramento dos corais invasores Tubastraea spp. no litoral brasileiro; 2) mapear a distribuição geográfica, caracterizar as populações e estudar o efeito da inserção dos corais na comunidade bêntica de costões rochosos do litoral norte do estado de São Paulo (LNSP). O primeiro avaliou quatro metodologias, comparando o método do censo visual, e outras três metodologias que utilizam fotografia e filmagem. O método do censo visual mostrou ser mais eficiente na obtenção dos resultados quando comparado com os outros métodos, principalmente para identificar pequenos organismos. Contudo, seu tempo em campo e seus custos foram maiores. O segundo utilizou o método visual para estudar o efeito da inserção dos corais invasores na comunidade local do LNSP. Ainda, foi realizado um monitoramento espacial semi-quantitativo em larga escala para caracterizar a distribuição espacial dos corais invasores; transectos com quadrados amostrais foram usados para estimar a densidade de Tubastraea ao longo da profundidade, e transectos e arcos graduados empregados para estimar a ocorrência de colônias em diferentes inclinações do substrato, no LNSP. Os corais invasores estão aumentado sua distribuição, causando diversos impactos nas comunidades e nos organismos nativos. T. tagusensis é comumente encontrado dominando diversos costões rochosos, com uma densidade maior em ambientes mais profundos e com maior ocorência em substratos de inclinções verticais e negativas no LNSP. A erradicação e/ou controle do coral invasor é recomendado no litoral brasileiro, principalmente onde as populações estão isoladas ou ainda são pequenas. / The invasive coral species, Tubastraea tagusensis and T. coccinea were accidentally introduced into Brazil by oil platforms. The rapid growth and reproductive stage, competition against native species, chemical defenses against natural predators and competitors and ample use of different substrates contribute to the success and expansion of Tubastraea spp. on the Brazilian coast. This study had two aims: 1) investigate a methodology that results in more efficient and cost-effective monitoring of the Tubastraea spp. invaders on the Brazilian coast, 2) map the geographical distribution, characterize the populations and study the effect of corals insertion in the community on the northern coast of São Paulo (LNSP). The first aim evaluated four methods by comparing the visual census method and three other methods that use photography and filming. The visual census method proved to be more efficient in achieving the results compared with other methods, primarily to identification of smaller organisms; however, time in the field and costs were higher. The second aim used the visual method to study the effect of insertion of coral invaders into the community. Also, a semi-quantitative monitoring of spatial scale to characterize the spatial distribution of coral invaders was carried out; transects with squares were used to estimate the density of Tubastraea spp. along the depth gradient, and transects and graduated arcs employed to estimate the occurrence of colonies at different inclinations of the substrate, in LNSP. The invader corals are increasing their distribution, causing several impacts on native communities and species. T. tagusensis is actually found dominating several rocky shores, with a higher density deeper and in a vertical and negative substrates slopes in LNSP. Eradication and/or control of the invasive corals are recommended on the Brazilian coast, especially where populations are isolated or are still small.

Livestock in southern Brazil is sustained largely by native pastures, which have large species diversity. This area is part of the Pampa biome. However, invasive species Eragrostis plana (tough lovegrass) threat to native grasslands of this biome. Becomes necessary to develop alternative methods of control of this species, since conventional control practices, although fairly efficient, has no as a principle the preservation of native vegetation. The present work aimed to study the control of tough lovegrass through biocontrol method for isolation of potentially pathogenic fungi, as well as the allelopathic effects of aqueous extract of carqueja (Baccharis trimera) on the germination of tough lovegrass. The fungi were isolated from seeds of tough lovegrass and incubated for eight days of growth at 25 °C and a photoperiod of 12 hours, then identified to genus chamber. Five genera were identified: Alternaria sp., Curvularia sp., Aspergillus sp., Penicillium sp. e Fusarium sp. To test the interaction of these fungi with the seeds of E. plana, fungi inoculation was performed in seeds through deposition technique, which were previously sterilized with 1% NaClO, and seeded on two types of substrates: filter paper (in vitro experiment) and substrate and sand mixture (ex vitro experiment). Treatments consisted of the five identified fungi, inoculated separately in seeds of E. plana. The genera showed that the best results were: Fusarium sp., Curvularia sp. e Penicillium sp. The carqueja belongs to the Asteraceae family, possessing compounds with many properties. Among the compounds present in B. trimera can highlight the presence of flavonoids, tannins, fatty acids, steroids, triterpenoids. To evaluate the allelopathic effect of B. trimera on E. plana different doses of the crude aqueous extract (CAE) of carqueja were applied on the seeds of tough love-grass. The concentrations where 0; 25; 50; 75 and 100 g.L-1. The experiments were conducted in vitro and ex vitro. The High-performance liquid chromatography (HPLC) was also conducted to identify the compounds present in the CAE. Were found in larger amounts: caffeic acid, chlorogenic acid, ellagic acid and isoquercitina. In the in vitro experiment the inhibition of the germination appeared from the concentration of 25 g.L-1 upwards, causing a diminishing germination with increasingly higher concentrations of the CAE. In the ex vitro experiment the reduction of emergence was lower, but was statistically significant. The data show that the carqueja extracts interfere on the development of the tough lovegrass by reducing leaf length and the dry mass of the aerial part and of the roots. / A pecuária na Região Sul do Brasil é sustentada, em grande parte, por pastagens nativas, que apresentam grande diversidade de espécies. Esse território faz parte do bioma Pampa. A espécie invasora capim-annoni ameaça essas pastagens. Torna-se necessário o desenvolvimento de métodos alternativos de controle dessa espécie, pois práticas convencionais de controle, embora relativamente eficientes, não tem a preservação da vegetação nativa como princípio. O presente trabalho teve por objetivo estudar o controle de capim-annoni, através do biocontrole por método de isolamento de fungos potencialmente fitopatogênicos, bem como dos efeitos alelopáticos do extrato aquoso de carqueja (Baccharis trimera) sobre a germinação do capim-annoni. Os fungos foram isolados a partir de sementes de E. plana e incubados por oito dias em câmara de crescimento, a 25 °C e fotoperíodo de 12 horas, em seguida identificados até gênero. Foram identificados cinco gêneros: Alternaria sp., Curvularia sp., Aspergillus sp., Penicillium sp. e Fusarium sp. Para testar a interação desses fungos com as sementes de E. plana, foi realizada a inoculação dos fungos nas sementes através da técnica de deposição, sendo elas previamente desinfestadas com NaClO 1%, e semeadas em dois tipos de substratos: papel-filtro (experimento in vitro) e mistura de substrato e areia (experimento ex vitro). Os tratamentos constaram dos cinco fungos identificados, inoculados separadamente nas sementes de E. plana. Os gêneros que apresentaram os melhores resultados foram Fusarium sp., Curvularia sp. e Penicillium sp. A carqueja, pertencente à família Asteraceae, apresenta vários compostos na sua composição. Dentre os compostos presentes em B. trimera pode-se destacar a presença de flavonóides, taninos, ácidos graxos, esteróides, triterpenóides. Para avaliar o efeito alelopático de B. trimera em E. plana foram aplicadas diferentes doses de extrato bruto aquoso (EBA) de carqueja nas sementes de capim-annoni. As concentrações foram 0; 25; 50; 75 e 100 g.L-1. Os experimentos foram conduzidos in vitro e ex vitro. Também foi realizada a técnica Cromatografia Líquida de Alta Eficiência (HPLC) para identificar os compostos presentes no EBA. Foram encontrados em maior quantidade: ácido cafeico, ácido clorogênico, isoquercitina e ácido elágico. No experimento in vitro a inibição da germinação deu-se a partir da concentração 25 g.L-1, sendo que a germinação diminuiu conforme a concentração do EBA aumentou. No experimento ex vitro a redução da emergência de plântulas foi estatisticamente significativa. Os dados obtidos mostram que os extratos de carqueja interferem no desenvolvimento do capim-annoni para comprimento de folhas e massa seca de parte aérea e raiz.

With the majority of Earth’s population living in coastal areas, estuarine ecosystems have been particularly affected by anthropogenic disturbances. My dissertation research focused on three interrelated types of human disturbance that affect estuaries: Anthropogenic alteration of freshwater inflow, the introduction of invasive species, and habitat alteration. Using the LoxahatcheeRiver(Jupiter, FL) as a model system, my goal was to understand how these disturbances affect estuarine organisms, particularly fishes. One of the most ecologically harmful disturbances affecting estuaries is anthropogenic alteration of freshwater inflow (and resulting changes in salinity patterns). To identify effects of freshwater inflow on the behavior of an ecologically and economically important fish (common snook Centropomus undecimalis), I conducted a 19-month acoustic telemetry study. Common snook were more abundant and made more frequent upstream migrations during the wet season, but freshwater inflow did not appear to be the proximate cause for these behaviors. Increased estuarine salinity resulting from anthropogenic flow alteration may have facilitated the second type of disturbance that I address in this dissertation; the invasion of non-native Indo-Pacific lionfish into estuarine habitats. During the course of my dissertation research, I documented the first ever estuarine invasion by non-native lionfish. Using mark-recapture, I identified high site fidelity in lionfish, a trait that may aid future control efforts. The extremely low minimum salinity tolerance that I identified in lionfish appears to have allowed the species to colonize far upriver in estuaries with anthropogenically modified salinity patterns. Anthropogenic salinity alteration has also led to a severe degradation of oyster reef habitats in theLoxahatcheeRiver. As a foundation species, oysters provide food, shelter, and nursery habitat for a wide variety of estuarine organisms, including many ecologically and economically important fishes. Increasingly, degraded oyster reef habitats have been the focus of restoration efforts. I identified a relatively rapid (< 2 years) convergence between restored and natural oyster reef communities, and documented the importance of vertical relief in restoration success. My dissertation research is critical for the management and conservation of coastal rivers inFlorida, while more broadly informing restoration and management decisions in many other estuarine and coastal ecosystems.

Made available in DSpace on 2016-06-02T19:31:42Z (GMT). No. of bitstreams: 1 2411.pdf: 1852790 bytes, checksum: 59e732f774f4acfec1f2c3148f4d6104 (MD5) Previous issue date: 2009-03-26 / Pittosporum undulatum Vent., an Australian tree implicated in supression of tree recruiment in many ecosystems, is found invading secondary Araucaria forests in subtropical Brazil. The first chapter of this study aimed to investigate the role of allelopathy in the invasive proccess, accessing germination and growth of Bauhinia forficata Link. in presence of secondary metabolites from cheesewood leaves. Leachates in concentrations of 20%, 15%, 10% and 5% (w/v), extracts from dry material (10%; 7,5%; 5% and 2,5%) and coumarin solutions (2,5 mM; 1,25 mM; 0,625 mM and 0,3125 mM) were prepared. Petri-dishes germination bioassays, with countings done at each 12 hours, allowed to determinate both germinabilty and germination rate; polyethylene glicol (PEG 6000) solutions were used to evaluate osmotic effects. For seedlings growth, the three highest concentrations of each solution were tested and after seven days root and shoot lenght were measured. While germinability was only sensitive to extracts from dry material, the germination rate showed a dose-dependent curve for all solutions. In seedlings, roots were the most sensitive structure and severe morfo-anatomic anomalies were observed. The main purpose of the second chapter was to investigate the use of Pittosporum undulatum Vent. (cheesewood) leaves as a possible sustainable alternative for barnyard grass control. Leachates in concentrations of 20%; 15%; 10%; 5% and 2,5% (w/v), aqueous extracts from powdered leachated and non- eachated leaves (10%; 7,5%; 5%; 2,5% and 1,25%), coumarin solutions (2,5 mM; 1,25 mM; 0,625 mM and 0,3125 mM) and Roundup Original® according to label informations were prepared. Polyethylene glycol were also used. Both germinability and germination rate were determined by germination biossays, with countings done at each 12 hours. In growth experiments, seedlings were exposed for seven days, when root and shoot length were measured. All solutions, with exception of coumarins, caused only small inhibitory effects on germination. In relation to the growth, all treatments but control caused necrose, absence of hairs and dose-dependent lenght reduction in radicles. Hipocotiles were affected by phenolic compound, extracts from non-leachated leaves and gliphosate. Although the allelopathic effects, ecophisiological aspects relative to Pittosporum undulatum still need to be cleared before its leaves can be used as a herbicide. / A árvore australiana Pittosporum undulatum Vent. (Pittosporaceae) é encontrada diminuindo o recrutamento de espécies nativas em formações secundárias de Floresta Ombrófila Mista no sul do Brasil. O objetivo do primeiro capítulo desse estudo foi verificar a ação alelopática da espécie no processo invasivo, investigando a sensibilidade de sementes e plântulas de Bauhinia forficata Link. (pata-de-vaca) à compostos foliares de pau-incenso. Foram preparados extratos aquosos lixiviados nas concentrações de 20%, 15%, 10% e 5% (m/v), extratos aquosos obtidos do pó de folhas lixiviadas (10%; 7,5%; 5% e 2,5% ) e soluções de cumarina a 2,5 mM; 1,25 mM; 0,625 mM e 0,3125 mM. Bioensaios em placas de Petri, com contagens realizadas a cada 12 horas, permitiram determinar a germinabilidade e velocidade de germinação; soluções de polietileno glicol (PEG 6000) foram preparadas para analisar os efeitos osmóticos. Nos bioensaios de crescimento, utilizaram-se as três concentrações mais elevadas de cada solução, sendo, após sete dias, medidos o comprimento radicular e de parte aérea. Enquanto a germinabilidade mostrou-se sensível apenas aos extratos de pó de folhas, a velocidade de germinação apresentou resposta dose-dependente para todas as soluções testadas. Quanto ao crescimento, a radícula foi a estrutura mais sensível aos efeitos alelopáticos, sendo observadas alterações morfo-anatômicas. No segundo capitulo, objetivou-se investigar o uso de material foliar de pau-incenso como alternativa ao manejo do capim-arroz, uma gramínea resistente a herbicidas que traz problemas a plantações de arroz e à biodiversidade de planícies úmidas em todo o mundo. Foram preparados extratos aquosos foliares lixiviados nas concentrações de 20%; 15%; 10%; 5% e 2,5% (m/v), extratos aquosos obtidos do pó de folhas lixiviadas e não-lixiviadas (10%; 7,5%; 5%; 2,5% e 1,25%), soluções de cumarina a 5mM; 2,5 mM; 1,25 mM; 0,625 mM e 0,3125 mM e solução de Roundup® Original seguindo as recomendações do fabricante. Soluções de PEG também foram utilizadas. Para bioensaios de germinação, as contagens foram realizadas a cada 12 horas, sendo determinadas as porcentagens e velocidades germinativas; para o crescimento, plântulas de sete dias submetidas aos compostos tiveram medidos seus comprimentos de radícula e parte aérea. A germinação, apesar de fortemente inibida pela cumarina, foi pouco sensível às demais soluções. Quanto ao crescimento, as radículas analisadas apresentaram necrose, ausência de pêlos e redução dose-dependente do comprimento para todos os tratamentos com exceção do controle. Os hipocótilos foram afetados pelo composto fenólico, glifosato e extratos aquosos de folhas não-lixiviadas. Apesar da ação alelopática, aspectos ecofisiológicos relativos ao pau-incenso ainda devem ser esclarecidos para que suas folhas possam ser usadas como herbicida.

Made available in DSpace on 2016-06-02T19:31:57Z (GMT). No. of bitstreams: 1 3571.pdf: 899759 bytes, checksum: 288158cbdc684b122136771cdf6c46f3 (MD5) Previous issue date: 2011-02-16 / Universidade Federal de Minas Gerais / In this study it was evaluated the aerobic and anaerobic decomposition of submerged macrophytes Egeria densa Planch. and Hydrilla verticillata (L.f.) Royle, major weeds in tropical reservoirs. It was evaluated the decay of organic matter, mineralization, humification degree of the leached, fiber content, conductivity and pH of the process and activity of cellulase enzymes, peroxidase and xylanase. Mathematical models have indicated relations between enzymatic patterns with decay of organic matter and carbon cycling. Analysis of ANCOVA and ANOVA were used to evaluate differences in the decay processes of the species. The two species showed the same heterogeneous pattern of decay of organic matter and carbon mineralization, however, different patterns of decay patterns of the fiber fraction. Incubations of both species had low values of half life for the mineralization of POC, low mineralization of DOC and high enzymatic activity, especially peroxidase, correlated to high rates of decay of fiber content, mainly lignin. The incubations of the two species exhibited different oxygen consumption, probably due to the different composition of fibers. It was conclude that these macrophytes found in tropical reservoirs may cause changes in the environment metabolism. In this context it is important to study the decomposition of invasive species and their cycles for modeling parameterization of patterns of nutrient cycling in these environments. / Nesse trabalho foi avaliada a decomposição aeróbia e anaeróbia das espécies submersas Egeria densa Planch. e Hydrilla verticillata (L.f.) Royle, importantes invasoras em reservatórios tropicais. Foi analisado o decaimento de matéria orgânica, mineralização do carbono, grau de humificação do material lixiviado, conteúdo de fibras, condutividade, pH e atividade das enzimas celulase, peroxidase e xilanase. Modelos matemáticos indicaram relações entre os padrões enzimáticos e os decaimentos de matéria orgânica e ciclagem do carbono. Análises de ANCOVA e ANOVA foram utilizadas para avaliar diferenças nos processos de decomposição das espécies. As duas espécies apresentaram o mesmo padrão heterogêneo de decaimento da matéria orgânica e de mineralização do carbono; porém, diferentes padrões de decaimento quanto às fibras. As incubações das duas espécies apresentaram baixos tempos de meia vida para a mineralização do COP, baixa mineralização do COD e alta atividade enzimática, principalmente quanto à peroxidase, correlacionada às altas taxas de decaimento dos teores de fibras, principalmente lignina. As incubações das duas espécies apresentaram diferentes consumos de oxigênio, provavelmente relacionados à diferente composição de fibras. Concluiu-se que essas macrófitas encontradas nos reservatórios tropicais possam ocasionar alterações no metabolismo do ecossistema. Neste contexto, é fundamental o estudo da decomposição das espécies invasoras e modelagem dos seus ciclos para parametrização dos padrões de ciclagem de nutrientes nestes ambientes.