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Phipps, Sarah J. "Biodiversity of ants (Hymenoptera: Formicidae) in restored grasslands of different ages." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4538.
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Thesis (M.S.) University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 27, 2007) Includes bibliographical references.
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Edwards, Grant R. "The creation and maintenance of spatial heterogeneity in plant communities : the role of plant-animal interactions." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239335.
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Mendez-Estrella, Romeo, Jose Romo-Leon, Alejandro Castellanos, Fabiola Gandarilla-Aizpuro, and Kyle Hartfield. "Analyzing Landscape Trends on Agriculture, Introduced Exotic Grasslands and Riparian Ecosystems in Arid Regions of Mexico." MDPI AG, 2016. http://hdl.handle.net/10150/621492.
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Riparian Zones are considered biodiversity and ecosystem services hotspots. In arid environments, these ecosystems represent key habitats, since water availability makes them unique in terms of fauna, flora and ecological processes. Simple yet powerful remote sensing techniques were used to assess how spatial and temporal land cover dynamics, and water depth reflect distribution of key land cover types in riparian areas. Our study area includes the San Miguel and Zanjon rivers in Northwest Mexico. We used a supervised classification and regression tree (CART) algorithm to produce thematic classifications (with accuracies higher than 78%) for 1993, 2002 and 2011 using Landsat TM scenes. Our results suggest a decline in agriculture (32.5% area decrease) and cultivated grasslands (21.1% area decrease) from 1993 to 2011 in the study area. We found constant fluctuation between adjacent land cover classes and riparian habitat. We also found that water depth restricts Riparian Vegetation distribution but not agricultural lands or induced grasslands. Using remote sensing combined with spatial analysis, we were able to reach a better understanding of how riparian habitats are being modified in arid environments and how they have changed through time.
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Hsu, Joanna S. "Potential Effects of Altered Precipitation Regimes on Primary Production in Terrestrial Ecosystems." DigitalCommons@USU, 2011. https://digitalcommons.usu.edu/etd/1053.
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In addition to causing an increase in mean temperatures, climate change is also altering precipitation regimes across the globe. General circulation models project both latitude-dependent changes in precipitation mean and increases in precipitation variability. These changes in water availability will impact terrestrial primary productivity, the fixation of carbon dioxide into organic matter by plants. In my thesis, I addressed the following three questions: 1.) What will be the relative effect of changes in the mean and standard deviation of annual precipitation on mean annual primary production? 2.) Which ecosystems will be the most sensitive to changes in precipitation? 3.) Will increases in production variability be disproportionately greater than increases in precipitation variability? I gathered 58 time series of annual precipitation and aboveground net primary production (ANPP) from long-term ecological study sites across the globe. I quantified the sensitivity of ANPP at each site to changes in precipitation mean and variance. My results indicated that mean ANPP is about 40 times more sensitive to changes in precipitation mean than to changes in precipitation variance. I showed that semi-arid ecosystems such as shortgrass steppe in Colorado or typical steppe in Inner Mongolia may be the most sensitive to changes in precipitation mean. At these sites and several others, a 1% change in mean precipitation may result in a change in ANPP that is greater than 1%. To address how increases in interannual precipitation variability will impact the variability of ANPP, I perturbed the variability of observed precipitation time series and evaluated the impact of this perturbation on predicted ANPP variability. I found that different assumptions about the precipitation-ANPP relationship had different implications for how increases in precipitation variability will impact ANPP variability. Increases in ANPP variability were always directly proportional to increases in precipitation variability when ANPP was modeled as a simple linear or a lagged function of precipitation. However, when ANPP was modeled as a nonlinear, saturating function of precipitation, increases in ANPP variability were disproportionately low compared to increases in precipitation variability during wet years but disproportionately high during dry years. My thesis addresses an existing research gap regarding the long-term impact of increases in interannual precipitation variability on key ecosystem functioning. I showed that increases in precipitation variability will have negligible impacts on ANPP mean and have disproportionately large impacts on ANPP variability only when ANPP is a concave down, nonlinear function of precipitation. My work also demonstrates the importance of the precipitation-ANPP relationship in determining the magnitude of impacts to ANPP caused by changes in precipitation. Finally, my thesis highlights the potential for considerable changes in ANPP variability due to increases in precipitation variability.
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Windhager, Steven. "An assessment of the use of seeding, mowing, and burning in the restoration of an oldfield to tallgrass prairie in Lewisville, Texas." Thesis, Connect to this title online, 1999. http://www.library.unt.edu/theses/open/19992/windhager%5Fsteven/index.htm.
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Psomas, Achilleas. "Hyperspectral remote sensing for ecological analyses of grasslands ecosystems : spectral separability and derivation of NPP related biophysical and biochemical parameters /." Zürich : RSL, Remote Sensing Laboratories, Department of Geography, University of Zürich, 2009. http://opac.nebis.ch/cgi-bin/showAbstract.pl?u20=9783037030202.
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Asandei, Ancuta. "Global warming : carbon-nutrient interactions and warming effects on soil carbon dynamics." Thesis, University of Exeter, 2014. http://hdl.handle.net/10871/17537.
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In order to predict how terrestrial ecosystems will respond to global change, there is growing recognition that we need to better understand linkages between plant and soil processes. Previously the factors and processes with potential to influence the terrestrial carbon (C) cycle have been investigated in isolation from each other. This study investigated the interactions of nutrient availability and warming in controlling the soil carbon dynamics, with regards to the fate of already sequestered carbon in soil, under conditions of increasing atmospheric temperatures. The project objectives were addressed by three independent experiments designed to explain specific components of the carbon-nutrient cycle interactions, and the findings brought together to describe the implications for future soil carbon storage. The main measurements collected throughout this project included soil carbon dioxide (CO2) fluxes, partitioned into autotrophic and heterotrophic components, net ecosystem exchange and respiration fluxes, and background soil moisture and temperature data, backed by gas, soil and biomass analyses. In the two field experiments, these measurements were taken from plots with or without any inorganic nutrient additions or in the presence or absence of legumes providing biological nitrogen addition to the ecosystem. In the laboratory, temperature and nutrient availability were manipulated within the ecosystem. The reduction in decomposition rates, without reduction of productivity as a result of inorganic nutrient additions, indicated the potential for increasing C storage. There was also evidence that nutrient availability controls the strength of the link between plant and soil processes in semi-natural grasslands. The yields, decomposition rates and soil C fluxes recorded in the presence and absence of legumes provided some evidence of N2 fixation, improving ecosystem productivity and soil properties while reducing soil C effluxes, in a managed grassland. In the laboratory, the warming of soils from lysimeters with and without plants, receiving or not receiving fertiliser, supported the findings from field experiments regarding the importance of the soil-plant link in controlling C fluxes. However, C stocks and δ13C analyses showed that over a year’s worth of warming and nutrient manipulations made little difference to the amount of C stored in the soil, indicating that edaphic factors have greater control over the response of C dynamics to increased temperatures.
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Goldas, Camila da Silva. "Distúrbio por fogo nos campos sulinos: artrópodes e hemiptera como bioindicadores." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/117899.
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Distúrbios são eventos que modificam os processos e a biodiversidade presentes em um ecossistema. Estas mudanças dão origem a um processo de sucessão ecológica, onde o tempo de retorno a o estado anterior ao distúrbio e chamado de resiliência. Organismos bioindicadores são ferramentas amplamente utilizadas na compreensão destas relações entre os distúrbios e os ecossistemas. Campos são ecossistemas altamente diversos, que podem possuir importante relação com o distúrbio de fogo, sendo este possivel responsável por modelar sua distribuição e propriedades ecológicas. Os artrópodes são componentes importantes da biodiversidade, e possuem respostas rápidas aos distúrbios, características que os tornam ferramentas importantes no monitoramento desta. Dentre estes a ordem Hemiptera é recorrentemente utilizada como bioindicadora de distúrbios, devido ao fato de sua diversidade estar diretamente ligada à diversidade da vegetação onde estes se encontram. Neste estudo explorei as respostas da comunidade de artrópodes ao distúrbio causado pelo fogo, sendo este o tema do primeiro capítulo desta dissertação, e no segundo capítulo, aspectos da diversidade taxonômica e funcional da ordem Hemiptera (Heteroptera e Auchenorryncha) foram utilizados como ferramentas de compreensão dos efeitos do fogo sobre o ecossistema campestre. O experimento de fogo foi conduzido na Estação Experimental Agronômica da UFRGS em Eldorado do Sul. Instalei sete blocos de unidades experimentais, constituídos por duas parcelas de 10 x 10 m, sendo uma delas queimada em dezembro/2009. Realizei amostragens em quatro períodos: antes da queima e um, seis e 12 meses após a queima. Utilizei armadilhas pitfall no solo (cinco por parcela), e rede de varredura na vegetação (quatro transectos em cada parcela). Os artrópodes coletados foram classificados em ordens e contabilizados. Para a ordem Hemiptera classifiquei os adultos em famílias e os jovens em subordem, e para todos os indivíduos medi atributos morfológicos funcionais. No primeiro capítulo conclui-se que a comunidade de artrópodes responde às mudanças ambientais causados pelo fogo, com respostas distintas entre ordens, e entre os níveis da vegetação e sobre o solo. No solo, a resiliência dos artrópodes foi mais lenta do que em artrópodes da vegetação, provavelmente devido à reconstituição da camada de serrapilheira acontecer posteriormente à regeneração da vegetação, através da deposição de matéria orgânica morta. No segundo capítulo concluo que os efeitos do fogo sobre a vegetação campestre afetaram a comunidade de Hemiptera aumentando a abundância e diversidade deste grupo, padrão este que segue a diversificação da vegetação. Quanto aos atributos, o principal atributo selecionado foi aparelho sugador maior nas áreas queimadas. O período de desenvolvimento em que os organismos se encontram, adulto ou imaturo, parece ter sido mais fortemente selecionado pelas alterações do fogo.Disturbances are events that modify processes and biodiversity present in an ecosystem. These changes lead to an ecological succession process, where the time to return to pre-disturbance state is called resilience. Bioindicators are tools widely used to understand these relationships between disturbances and ecosystems. Grasslands are highly diverse ecosystems and fire disturbance is an important factor there, responsible for shaping their distribution and ecological properties. Arthropods are key biodiversity components, and have fast responses to disturbances. These characteristics make them important tools for biodiversity monitoring. Among arthropods, the order Hemiptera is recurrently used as a bioindicators of disturbance, because their diversity is directly linked to vegetation diversity. This study explored the effects of fire on the arthropod community, which is the theme of the first chapter of this dissertation, and in the second chapter, aspects of taxonomic and functional diversity of the order Hemiptera (Heteroptera and Auchenorryncha) were used to understand the fire effects on the grasslands. Fire experiment was conducted at Estação Agronômica Experimental da UFRGS in Eldorado do Sul. I installed seven blocks of experimental units (two plots of 10 x 10 m) and one plot of each were burned in December 2009. Samplings occurred in four periods: before fire and one, six and 12 months after fire. I used pitfall traps in the soil (five per plot), and in vegetation we use sweep net (four transects in each plot). Arthropods collected were identified into orders. I classified the order Hemiptera adults in families and the young in suborders, and for each individual i measured functional morphological attributes. From the first chapter we conclude that the arthropod assemblage responds to environmental changes caused by fire, with distinct responses among arthropod orders and between the vegetation and ground levels. On the ground, arthropod community resilience is slower than for vegetation arthropods, probably due to a delay in the comeback of the litter soil layer which is subsequent to the regeneration of the vegetation, through deposition of dead organic matter. In the second chapter I conclude that the effects caused by fire affected the Hemiptera community, increasing abundance and diversity of this group. For functional attributes, the sucking apparatus was selected most in burned areas. The developmental period of the organisms, either adult or immature, seems to have been more strongly selected by fire-induced changes.
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Le, Stradic Soizig. "Composition, phenology and restoration of campo rupestre mountain grasslands - Brazil." Phd thesis, Université d'Avignon, 2012. http://tel.archives-ouvertes.fr/tel-00942593.
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Global environmental changes, especially land-use changes, have profound effects on both ecosystem functioning and biodiversity, having already altered many ecosystem services. These losses emphasize the need to preserve what remains; however when conservation programs are not sufficient, restoring areas that have been destroyed or disturbed can improve conservation efforts and mitigate damages. This work focuses on campos rupestres, Neotropical grasslands found at altitudes, which are part of the Cerrado (Brazilian savannas). They host a great biodiversity with a high level of endemism and, like other mountain ecosystems, provide valuable ecosystem services, such as water purification and recreational services. They have been and still are being impacted by human activities, such as civil engineering construction, quarrying or mining. The first objective of this thesis was to describe the reference ecosystem in order to aim for a clear restoration target and to monitor progress and success. We show that campos rupestres are composed of at least two distinct plant communities (i.e. sandy and stony grasslands), each having a specific composition and structure, hosting a great biodiversity. Several phenological patterns occur among the herbaceous communities: the majority of species flowers and fruits appear during the rainy season but other patterns can be observed. During our 2-year survey, some dominant species belonging to Poaceae, among others, were not observed reproducing, which implies limited chances to disperse on degraded areas. Campo rupestre vegetation is not resilient following a strong disturbance: several years after the disturbance, almost no native species are encountered on the degraded areas, soils are completely altered and seed bank recomposes only with non-target ruderal species. According to the filter model, a local community is a subset of the regional species pool determined by a set of dispersal, abiotic and biotic filters. Acting on the different filters to influence the plant community was the core of our restoration interventions. We then applied three in-situ restoration protocols (hay transfer, species translocation and turf translocation) to restore both kinds of grassland. Hay transfer does not allow the restoration of campo rupestre vegetation because of soil alteration and mainly because of poor seed quality. Indeed, germination studies show that, while some Xyridaceae and Velloziaceae have a high germinability, some dominant Poaceae, Cyperaceae or Asteraceae species have embryoless, unviable or dormant seeds, which makes seeding less efficient. There is no evidence that fire-related cues enhance germination in campos rupestres. Species translocation is successful for only one species, Paspalum erianthum; for the others, root damages probably impede survival. Finally, turf translocation is the most successful method, since numerous species are re-introduced on degraded areas. However due to the low resilience of pristine campos rupestres where turfs are taken from, turf translocation can only be considered in the case of habitat rescue, in circumstances when complete habitat destruction is otherwise unavoidable. Face to the difficulty to restore these peculiar grasslands, the protection and the conservation of campos rupestres must be made a high priority
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Andrade, Bianca Ott. "Interação solo-vegetação campestre:estudos de caso em diferentes escalas ecológicas." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/148772.
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Enquanto em regiões temperadas o conhecimento sobre a relação solo-vegetação é consolidado, nos trópicos e subtrópicos é preliminar. É urgente a necessidade de se determinar os fatores abióticos que controlam padrões vegetacionais visando dar suporte a estudos de recuperação e conservação. O presente estudo analisa a relação entre fatores abióticos e vegetação campestre na forma de três artigos científicos (capítulos I, II e III) e um artigo de revisão (capítulo IV). Nos primeiros três artigos, analisou-se a variância da vegetação em diferentes escalas ecológicas; e no artigo de revisão, discutiu-se de forma aplicada a variância de fatores bióticos e abióticos em resposta à degradação. Dessa forma, a presente tese objetivou responder as seguintes questões: (I) Que diferenças podem ser observadas dentro de uma mesma espécie quanto à funcionalidade e suas estratégias de alocação sob diferentes graus de disponibilidade de recursos?; (II) Quão variáveis são as propriedades físicas e químicas do solo em diferentes escalas espaciais; e existem propriedades dos solos que podem explicar com maior precisão a distribuição das espécies em diferentes escalas espaciais? (III) Que porcentagem de variância da vegetação pode ser explicada por propriedades pedológicas e climáticas; e quais características de solo e clima melhor explicam esses padrões de vegetação? No capítulo IV é apresentado um modelo conceitual sobre degradação dos campos e sua aplicação aos campos do Rio Grande do Sul (RS). Para responder as questões acima usei dados ao nível de espécie de campos calcáreos da Alemanha (capítulo I); dados ao nível de comunidade em seis áreas campestres do Rio Grande do Sul, sul do Brasil (capítulos II e III); e através da revisão de literatura relacionada à degradação, quanto à capacidade de recuperação dos campos do RS (capítulo IV). Os resultados evidenciaram que: (I) dentro de espécies ficaram evidentes duas estratégias frente à limitação de recursos, enquanto a resposta dos atributos aos diferentes tratamentos se mostrou constante; (II) a variação dos parâmetros do solo relaciona-se à escala espacial aplicada e a variância da vegetação geralmente responde a diferentes parâmetros de solo em diferentes escalas; (III) 45% da variância da vegetação entre biomas nos campos do RS foi explicada por características pedológicas e climáticas, sendo em grande parte governada pela precipitação anual e a porcentagem de saturação por alumínio do solo; e (IV) o modelo conceitual apresenta variações ao longo de dois eixos (biótico e abiótico) e poderá servir de suporte a estudos de conservação e recuperação de campos tropicais e suptropicais, bem como facilitar a tomada de decisões quanto ao manejo e conservação. Como conclusão geral, verificou-se que a vegetação campestre responde a variações ambientais em diferentes escalas espaciais e pode adotar diferentes estratégias para sobrepor filtros ambientais e processos de degradação. O entendimento da relação entre a vegetação e o meio abiótico é de grande importância para tomada de decisões quanto ao emprego de formas alternativas de manejo e conservação.Whereas in temperate regions the abiotic-biotic relationship is well-known, in the tropics and subtropics our understanding is still preliminary. There is an urgent need to determine abiotic factors that control vegetation patterns in order to give support to restoration and conservation approaches. The present thesis analyses the relationship between abiotic factors and grassland vegetation in three original research papers (chapters I, II and III) and a review paper (chapter IV). In the first three papers, vegetation variance in response to abiotic factors was analyzed at different ecological scales; and in the fourth, the variance in biotic and abiotic factors in response to degradation process was discussed with a more applied view. Thus in this thesis the aim is to answer the following questions: (I) Which differences can be found in functional plant traits and allocation strategies within species at different levels of water and nutrient availability?; (II) How variable are physical and chemical parameters in different spatial scales; and are there soil parameters that can more accurately explain plant distribution in different spatial scales? (III) How much of RS grassland vegetation variance can be explained by soil and climatic properties; and which climatic and soil properties better explain these vegetation patterns? In chapter IV a conceptual model of grassland degradation is presented and applied to Rio Grande do Sul (RS) grasslands. To address these questions I used species-level data in a calcareous grassland in Germany (chapter I); community-level data in six sites in RS, South Brazilian grasslands (chapter II and III); and a review of literature studies concerning RS grassland degradation and restorability (chapter IV). The results showed that: (I) at a intraspecific level, the study species showed two allocation strategies in relation to resource stress, while the responses of individual traits to the soil treatments were consistent across species; (II) soil parameters variation are related to the measurement scale applied and the vegetation variance often responds to different soil parameters at different scales; (III) climatic and soil properties explained 45% of vegetation variance between biomes in RS grasslands and the main factors controlling its variance are annual precipitation and percent aluminum saturation; and (IV) the conceptual model is displayed as biotic and abiotic changes along the axes and can serve as a general framework to study degradation and restorability of tropical and subtropical grasslands, and further it may facilitate decisions on alternative management and conservation. As a general conclusion, the grassland vegetation responds to changes in the environment in different scales and may use different strategies to overcome environmental selective forces and degradation process. The understanding of this relationship is of high importance to facilitate decisions on alternative management and conservation.
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Oliveira, Tamara Esteves de. "Dinâmica da produção de alimentos no bioma pampa." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/163288.
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Esse estudo analisou a dinâmica da produção de alimentos no estado do Rio Grande do Sul e suas consequências para as alterações nas áreas de pastagens naturais no Bioma Pampa. Para tanto, foram analisadas as mudanças no uso da terra nos municípios conforme os Censos Agropecuários de 1975, 1985, 1995/1996 e 2006 e da produção de alimentos de acordo com os relatórios de produção agrícola e pecuária municipais do Instituto Brasileiro de Geografia e Estatística (IBGE). Para analisar as variações na área das culturas e quantidade produzida foi calculado um índice de crescimento relativo. Os municípios foram ordenados conforme a área das categorias em seu território e sua localização por Escalonamento Multidimensional Não Métrico (NMDS). A influência do bioma sobre o uso da terra foi analisada por ENVIFIT e a diferença entre as categorias por PERMANOVA, no software R. No Bioma Pampa ocorreu um decréscimo de 26% nas pastagens naturais desde 1975, apresentando decréscimo de até 12.5%, entre 1975 e 1985. Destacam-se as taxas das lavouras e matas artificiais, em que para lavouras temporárias, apresentaram um crescimento considerável de 1985 para 2005. A influência do Bioma Pampa na composição das categorias de uso da terra manteve-se entre 14 e 15%, havendo diferença entre municípios localizados no Bioma Pampa em todos os anos analisados. Ao longo do tempo foi possível observar uma movimentação significativa das lavouras temporárias e das matas artificiais que principalmente entre 1995 e 2005 começam a integrar a paisagem do bioma. Para enfrentar o desafio de manter atividades agroecológicas em biomas ameaçados o Brasil deve investir em fiscalização, desenvolvendo sistemas de monitoramento capazes de detectar sutis alterações no uso da terra. Por outro lado, a produção de alimentos nesse estado apresentou crescimento na quantidade produzida. Foi observado um crescimento elevado na quantidade produzida de soja, sendo distribuição homogênea em todo o estado. O arroz apresentou redução na quantidade produzida no norte do estado e uma concentração expressiva nas regiões sul e fronteira oeste do estado. Os bovinos mantiveram seu rebanho estável com grande concentração na fronteira oeste. A silvicultura apresentou crescimento em praticamente todo estado, estando sua produção centrada na região sudeste do estado. As lavouras analisadas contribuíram para o PIB do estado e são capazes, hoje e no futuro, de suprir as demandas calóricas do Rio Grande do Sul em caso de necessidades, caso sejam mantidas as características atuais do agronegócio gaúcho. Dessas culturas, a soja foi a que mais disponibilizou calorias e retorno financeiro ao estado, sendo capaz de suprir a demanda local e oferecer excedentes para a exportação. Em todas as culturas, com exceção do milho, o aumento da quantidade de calorias disponibilizadas esteve relacionado ao aumento da área plantada, demandando maiores investimentos e incentivos ao incremento do rendimento das culturas.This study analyzed the food production dynamics in the state of Rio Grande do Sul and its consequences for the changes in the natural grassland areas in the Pampa Biome. To this end, data for land use in the municipalities of Pampa Biome were collected from the Agricultural Censuses of 1975, 1985, 1995/1996 and 2006 as well as the food production data presented at the municipal agricultural and livestock reports published by the Brazilian Institute of Geography and Statistics (IBGE). To analyze the dynamics of the natural grasslands area of natural pastures, the micro-regions were compared every 10 years, the relative growth rate. The comparison between the municipalities was made by the adjusted mean the area allocated for the categories of land use. All municipalities were ranked as the area of the categories in its territory and its location by Multidimensional Scaling Not Metric (NMDS). The influence of the biome on land use was analyzed by ENVIFIT and the difference between the categories by PERMANOVA in Pampa Biome R. In software, there was a 26% decrease in natural pastures since 1975, presenting decrease of up to 12.5% between 1975 and 1985. Noteworthy are the rates of crops and artificial forest in which to temporary crops showed considerable growth from 1985 to 2005. The influence of the Pampa biome in the composition of land use categories remained between 14 and 15%, with significant differences between municipalities in the Pampa biome in all the years analyzed. Over time, it observed a significant movement of temporary crops and artificial forests that mainly between 1995 and 2005 begin to integrate the biome landscape. To face the challenge of maintaining agro-ecological activities threatened biomes in Brazil should invest in surveillance, developing monitoring systems capable of detecting subtle changes in land use. Moreover, the production of food in this state showed an increase in the amount produced. High growth for soy produced, being homogeneously distributed across the state was observed. Rice declined on the amount produced in the northern state and a significant concentration in the south and west of the state border. Cattle kept its stable herd with great concentration on the western border. Forestry grew in almost every state, with its production centered in the southeastern region of the state. The crops analyzed contributed to the state's GDP and are able, today and in the future, to meet the caloric demands of Rio Grande do Sul in the event purposes, if the current features of the gaucho agribusiness are maintained. These crops, soybean was the one that provided calories and financial return to the state, being able to meet local demand and provide surplus for exports. In all crops, except corn, increasing the amount of calories available was related to the increased planted area, requiring greater investments and incentives to increase crop yields.
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Meireles, Leonardo Dias. "Estudos floristicos, fitossociologicos e fitogeograficos em formações vegetacionais altimontanas da Serra da Mantiqueira Meridional, sudeste do Brasil." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/315023.
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Orientador: George John ShepherdTese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: A Serra Fina é o nome de umas das áreas da Serra da Mantiqueira Meridional, uma cadeia montanhosa na divisa geográfica entre Minas Gerais, São Paulo e Rio de Janeiro, sudeste do Brasil. A Serra Fina compreende um dos maciços de rochas alcalinas que forma uma das áreas de maior altitude dessa região com mais de 2.500 metros de altitude em vários locais. Ela apresenta um destacado gradiente altitudinal que permite a ocorrência de diferentes formações vegetacionais altimontanas. Sua vegetação apresenta-se ainda relativamente conservada, mas pouquíssimo conhecida. Nós objetivamos analisar a composição florística de suas formações vegetacionais altimontanas, descrever a estrutura fitossociológica das florestas nebulares, verificar a similaridade dessa floresta com outras florestas montanas brasileiras e verificar como mudanças climáticas quaternárias influenciaram a distribuição geográfica das espécies que as compõem. Nos campos de altitude, matas de candeias e nas florestas nebulares foram coletadas 393 espécies das quais sete são provavelmente novas para a ciência. As famílias Asteraceae, Poaceae, Melastomataceae, Rubiaceae, Cyperaceae, Fabaceae, Myrtaceae, Orchidaceae e Ericaceae apresentaram as maiores riquezas específicas. Duas espécies novas da família Asteraceae restritas aos campos de altitude acima de 2.500 metros de altitude foram descritas e ilustradas e as demais necessitam de estudos detalhados por especialistas. A riqueza específica amostrada denota a importância das áreas de altitude na diversidade da Floresta Atlântica e denotam a importância fitogeográfica da Serra Fina por apresentar um grande número de espécies endêmicas ou com distribuição geográfica restrita e comportar espécies com fortes relações com a flora dos Andes, oeste da América do Sul. As florestas apresentaram características típicas de florestas nebulares como menor riqueza, elevada densidade e um dossel reduzido. Myrsinaceae, Myrtaceae, Symplocaceae e Cunoniaceae foram as famílias de maior valor de importância. As florestas alto-montanas da Serra da Mantiqueira apresentaram alta similaridade florística com florestas nebulares sulinas e em parte com as florestas alto-montanas do interior de Minas Gerais e do topo da Serra do Mar em São Paulo, que apresentam uma composição florística relativamente diferenciada. A similaridade dessas florestas com florestas em altitudes mais baixas é relativamente menor. Os modelos de distribuição potencial para espécies florestais montanas destacaram intensas modificações na área de ocupação dessas espécies em cenários climáticos para o Quaternário Tardio e sugerem que estas espécies possam ter ocorrido em altitudes e latitudes menores e longitudes maiores do que atualmente observado. Esses resultados sugerem que florestas com composição florística similar às atuais florestas alto-montanas possam ter ocupado uma área mais extensa no passado, formando em algumas regiões florestas mais extensas que foram posteriormente fragmentadas e confinadas ao topo de cadeias montanhosas na região leste ao sul do Brasil.
Abstract: The "Serra Fina" is the name given to a block of the Serra da Mantiqueira, a mountain chain that forms the boundary between the states of Minas Gerais, São Paulo, and Rio de Janeiro, southeastern Brazil. The Serra Fina largely corresponds to a massif of alkaline rocks and forms the highest part of the range, rising to more than 2500m at several points. It offers an exceptionally extensive altitudinal gradient, with the occurrence of several high-montane vegetation formations. These formations are still relatively well-conserved, but are very poorly known. The main objectives of the present study were to analyze the floristic composition of some of the high-montane vegetation types, describe and analyze the phytosociological structure of the cloud forests, determine the degree of similarity between these forests and other montane forests in Brazil and to investigate possible explanations of the patterns seen, especially with regard to climate changes in the quaternary. A total of 393 species, of which seven are probably new to science, were collected in the grasslands, "candeia" scrub and cloud forests. The greatest species-level richness was found in the families Asteraceae, Poaceae, Melastomataceae, Rubiaceae, Cyperaceae, Fabaceae, Myrtaceae, Orchidaceae and Ericaceae. Two new species of Asteraceae, confined to grasslands above 2500m have been described and illustrated, and the remainder await more detailed studies by specialists. The species richness encountered demonstrates the importance of the contribution of high altitude areas to the overall diversity of the Atlantic Forest of eastern Brazil, and the phytogeographic importance of the Serra Fina with a large number of endemic species or species with restricted distributions with strong links to the Andean flora of western South America. The forests showed a number of characteristics typical of cloud forests, such as low richness, high density and a reduced canopy, with Myrsinaceae, Myrtaceae, Symplocaceae and Cunoniaceae as the most important families. The Serra da Mantiqueira upper montane forests showed their greatest floristic similarity to be with the cloud forests of southern Brazil and to some extent with the upper montane forests of the interior of Minas Gerais and the crest of the coastal range ("Serra do Mar") in São Paulo, though with a somewhat differentiated floristic composition. Similarities with the surrounding forest matrix at lower altitudes were much less. Models of potential distribution for montane forest species using scenarios for Late Quaternary conditions suggest that extensive modifications of currently observed distributions are likely to have occurred, with many species occupying much lower altitudes and latitudes, together with much greater longitudes. These results suggest that forests similar in composition to current upper montane forests may have occupied much more extensive areas in the past, forming an almost continuous forest that has subsequently been fragmented and confined to high mountain areas in the east-south Brazil.
Doutorado
Doutor em Biologia Vegetal
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Ford, Hilary. "Biodiversity, ecosystem function and ecosystem service provision in saltmarsh and sand dune grasslands." Thesis, Bangor University, 2012. https://research.bangor.ac.uk/portal/en/theses/biodiversity-ecosystem-function-and-ecosystem-service-provision-in-saltmarsh-and-sand-dune-grasslands(d96624cd-2324-40db-9ce8-ee30ada754fc).html.
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Coastal grasslands, such as salt marshes and sand dunes, provide many important ecosystem services including 'supporting services' (soil formation, primary productivity and nutrient cycling), 'provisioning services' (fresh water supply, food and fibre products, biochemical or genetic resources), 'regulating services' (equable climate, pollution control, flood prevention, invertebrate pollination and pest regulation) and 'cultural services' (recreation, education and aesthetic appreciation). Historically, salt marsh and sand dune grasslands were commonly used as agricultural livestock grazing land. Currently, some of these coastal grasslands are 'conservation grazed' (i.e. extensively grazed to maximise plant diversity and to provide a suitable habitat for over-wintering bird species), others have been 'abandoned' (i.e. large herbivores removed) due to the removal of agricultural subsidies or remain historically 'un-grazed'. Grazing management of coastal grasslands influences biological and physical habitat characteristics, ecosystem function, biodiversity and ecosystem service delivery. Understanding the impact of grazing is therefore vital to enable future robust management recommendations. Biodiversity is often used as an indicator of ecosystem health and ecosystem service provision with conservation priorities allocated accordingly. It is therefore essential to critically assess just how important biodiversity is to the provision of ecosystem services within a wide range of habitats. The review chapter draws together evidence for this argument from salt marsh and sand dune habitats with the conclusion that functional diversity and composition are more important than biodiversity per se (Chapter 2). The experimental chapters of this thesis deal with the impact of grazing upon temperate salt marsh and sand dune grassland biodiversity and ecosystem service provision. 'Grazed' (cattle grazed < 8 cm) and historically 'un-grazed' upper salt marsh plots were compared. 'Fully grazed' (ponies 0.2 ha⁻¹, cattle 0.05 ha⁻¹ and rabbits 45 ha⁻¹), 'rabbit grazed' and 'un-grazed' (for 8 years) fixed sand dune grassland plots were also evaluated. Firstly, how grazing management affected ecosystem service provision of sand dune grassland was examined, by measuring a wide range of biophysical variables as proxies for ecosystem services (Chapter 3). 'Supporting' and 'regulating' services were provided predominantly by the un-grazed, 'provisioning' and 'cultural' services by the extensively grazed grassland. Secondly, the impact of short sward cattle grazing on the abundance, composition and diversity of the ground dwelling invertebrate community of an upper salt marsh was assessed using pitfall traps (Chapter 4). The findings showed that both cattle grazed and un-grazed saltmarsh habitat should be maintained to maximise invertebrate abundance and diversity and provide suitable habitat for coastal specialists. Thirdly, greenhouse gas emissions from grazed and un-grazed salt marsh were measured monthly for one year. Additionally, below-ground gas sampling tubes were used to measure soil methane concentrations (Chapter 5). Carbon dioxide efflux was greater from the un-grazed marsh soil but 'hotspots' of methane efflux were only found on the grazed marsh. Finally, the influence of grazing on the soil microbial community of both salt marsh and sand dune grasslands was measured by microbial biomass (fatty acid phospholipids: PLFAs), bacterial growth rate (Leucine incorporation) and respiration rates (Chapter 6). Microbial biomass, PLFA markers and bacterial growth rate were all influenced by grazing management. In summary, this work concludes that grazing management clearly affects biological and physical habitat characteristics, biodiversity, ecosystem function and ecosystem service delivery (Chapter 7). Management of coastal grasslands evidently involves trade-offs between biodiversity conservation and multiple ecosystem service provision.
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Lee, Mark. "Air pollution and climate change effects on grassland ecosystems." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9697.
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Grassland ecosystems extend across a substantial area of the world’s surface, providing many valuable ecosystem services including carbon sequestration, biodiversity preservation and food provision. Global and local environmental changes are anticipated in the future, including shifts in climatic conditions and changes to the composition of the atmosphere. This thesis adds to our understanding of how grassland communities respond to air pollution and climate change using two key methodologies. Firstly, a suite of environmental variables were measured in calcareous grassland ecosystems along transects adjacent to roads. This allowed quantification of plant compositional changes and identification of the likely drivers of plant compositional changes nearer roadsides. Evidence of road-derived changes to air quality, soil biogeochemistry and hydrology at roadsides are presented. The key messages being that road proximity was associated with increased abundances of nitrophilic species and also of species not typical of calcareous habitats. Secondly, a mesotrophic grassland ecosystem was exposed to a factorial combination of end-of-century rainfall regimes (+ 15 % winter rainfall and – 30 % summer rainfall) based on IPCC 4th Assessment projections and nitrogen enrichment. Plant productivity and species composition were resistant to nitrogen enrichment throughout the three year study. Above-ground plant biomass declined in rainfall manipulated plots by the third year, with evidence of increasing forb abundance and declining grass abundance. These data can assist projections of grassland responses to environmental change in the future and inform management decisions aimed at preventing decline in natural grasslands and declines in the ecosystem services that grasslands currently provide.
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Fry, Ellen Louise. "Climate change implications for grassland ecosystems : a biodiversity approach." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/9076.
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Grassland species assemblages are vulnerable to changes in rainfall patterns, with consequences of change including less species-rich communities, and changes in carbon, nitrogen and hydrological cycles. Research has indicated that increasing species diversity can lead to better resource and water use efficiency, and experiments are now targeted at identifying species characteristics that can modify ecosystem responses to climate change. This thesis aimed to evaluate the extent plant functional diversity can modify the effect of climate change in a field experiment on acid grassland in South-East England. Other climate scenarios, namely spring and summer drought, and highly variable rainfall were tested concurrently, and a modelling technique was developed to predict ecosystem functions from abiotic and plant trait-based variables. Climate change treatments generally decreased rates of ecosystem processes such as mineralisation and ecosystem respiration. Plots dominated by perennial plant species exhibited lower rates of processes such as net ecosystem CO2 exchange and soil respiration under climate stress. Results suggest annual plants are adapted to take advantage of very small rainfall input, and are less affected by climate change, thus generally maintaining overall ecosystem function through times of drought. A spring and summer drought regime was associated with slowing of ecosystem processes. This treatment was more deleterious to ecosystem function than increasing rainfall variability, where process rates did not differ discernibly from ambient, although plants suffered a higher level of dieback in general. While climate change could have detrimental effects on all aspects of ecosystem function, using information regarding species traits which are more resistant to climate change may aid grassland management in order to preserve more vulnerable species. Experiments such as these are vital to further understanding of the links between plant community composition and ecosystem function in order to target management schemes and policy to reduce the effects of climate change.
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Milton, Adrian Mark. "Heavy metals in contaminated grassland ecosystems : distribution, transfer and effects." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266222.
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Rudge, Stephen Alan. "The biological transport of radionuclides in grassland and freshwater ecosystems." Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292164.
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Stevens, Carly. "Ecosystem properties of acid grasslands along a gradient of nitrogen deposition." Thesis, Open University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406902.
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Sixty-eight randomly selected grasslands belonging to the National Vegetation Classification group U4 (Festuca ovina-Agrostis capillaris-Galium saxatile grassland) were studied during the summers of 2002 and 2003 along a gradient of atmospheric N deposition ranging from 6 to 36 kg N ha-1 yr-1 to investigate potential damage caused by acidification and eutrophication. At each site vegetation was surveyed and samples were taken from the topsoil and subsoil. Above-ground plant material was collected from three species: Agrostis capillaris, Galium saxatile and Rhytidiadelphus squarrosus. Species richness showed a negative linear trend with N deposition, with a reduction of 1 species for every 2.5 kg N ha -1 yr-1. At the current mean N deposition in Europe this gave a reduction in species richness of 23% from a projected pristine condition. Forbs accounted for the majority of this decline, showing reductions in both cover and abundance along the N-deposition gradient. Grasses showed a decrease in species richness, but an increase in cover, indicating increased dominance of a few species. Using canonical correspondence analysis, several individual species were identified as being positively and negatively associated with N deposition. Soil pH declined along the N-deposition gradient. This was also associated with increased mobilisation of aluminium, arsenic and lead. Nitrate concentration in the soil did not increase with increasing N inputs, possibly due to rapid plant uptake and its mobility in the soil profile. Soil extractable ammonium concentration showed a significant positive correlation with N inputs. A weak relationship was also identified between the C:N ratio in the soil and N inputs. Potential ammonium mineralization showed considerable variation across the sites. There was no correlation between aboveground tissue Nand N deposition for any of the three species examined. A weak correlation was identified between tissue Nand soil C:N for G. saxatile. Tissue N:P ratios gave no clear indication of nutrient limitation. The relative merits of different indicators ofN-deposition are discussed.
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Cenini, Valeria Laura. "Linkages between soil enzyme activities and critical ecosystem processes in grasslands." Thesis, Ulster University, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.692819.
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Soils are important life-supporting systems to human society and their long-term sustainability is high on both the scientific and political agenda. However soil functioning remains poorly understood because of the difficulty in studying complex biogeochemical interactions, which mostly occur belowground. This PhD study aims to improve the understanding of plant-soil-microbial interactions in grassland ecosystems. First, it was addressed how key microbial functions (i.e. extracellular enzyme activities) might respond to common management practices (e.g. nutrient fertilization) and to land use change (i.e. conversion from arable to grassland). Second potential linkages between enzyme activities and critical ecosystem processes such as soil carbon (C) and nitrogen (N) sequestration were investigated.
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Kossmann, Guido. "Plant functional traits and ecosystem functions in experimental grassland stands." Bayreuth : Bayreuth Center of Ecology and Environmental Research, 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=979898854.
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Gamnitzer, Ulrike. "Kinetic characterisation of respiratory carbon pools in a grassland ecosystem." kostenfrei, 2010. https://mediatum2.ub.tum.de/node?id=956652.
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Kossmann, Guido. "Plant functional traits and ecosystem functions in experimental grassland stands." Bayreuth Bayreuth Center of Ecology and Environmental Research, 2005. http://deposit.d-nb.de/cgi-bin/dokserv?idn=979898854.
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Hempel, Stefan. "Diversity and functioning of arbuscular mycorrhizal fungi in semi-natural grassland ecosystems /." Leipzig : Helmholtz Centre for Environmental Research - UFZ, 2008. http://www.ufz.de/data/ufzdiss_15_2008_9591.pdf.
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Joel, Geeske. "Responses of grassland ecosystems to elevated CO₂: single and multi-species components /." May be available electronically:, 2000. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Mason, Norman, and n/a. "Functional diversity and ecosystem-level processes in a short-tussock grassland." University of Otago. Department of Botany, 2006. http://adt.otago.ac.nz./public/adt-NZDU20061024.114054.
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Increased functional diversity has been linked to an increase in ecosystem level processes (ELPs), such as productivity, ecosystem reliability and invasion resistance. However, there has been no exact definition of functional diversity and it is not known which indices are appropriate for its measurement. Consequently, continuous indices have rarely been applied in examination of relationships between functional diversity and ELPs and little is known of the mechanisms linking functional diversity to ELPs. This thesis begins by providing an exact definition of functional diversity, identifying its primary components and devising appropriate continuous indices for the measurement of these components. These indices are used to examine relationships between functional diversity and three ELPs - biomass production, the reliability of biomass production and invasion resistance. Initially these examinations are conducted using a mechanistic community assembly and dynamic model. This model is based on physiological and morphological character data for species occurring in the short-tussock grassland communities of the Luggate field experiment, in the southern South Island, New Zealand. Finally, relationships between functional diversity, mean annual community cover and the reliability of cover are examined in the Luggate field experiment.
Functional composition (i.e. the actual functional characters of the species within a community) appeared to exercise the greatest influence on ecosystem reliability in the community assembly and dynamic model. However, there was evidence that functional diversity increased the reliability of productivity via the co-variance effect. Functional composition also exercised the greatest influence over mean annual productivity in the model, almost completely accounting for the negative relationship between functional diversity and mean annual productivity. These results are respectively analogous to the positive and negative selection effects seen in species richness / ELP relationships. Both functional diversity and functional composition influenced community invasion resistance in the model. Here, increased functional diversity acted to increase community resistance to invasion. In the Luggate field experiment, neither functional diversity nor functional composition was related to mean annual cover, though species richness was positively related to it. Increased functional diversity acted to increase the reliability of cover. However, this did not appear to occur via the co-variance effect, but as a result of increased functional diversity increasing consistency in the species composition of experimental plots through time.
These results demonstrate that studies examining functional diversity must account for the effects of species identity. A framework is proposed to accommodate selection effects associated with functional diversity / ELP relationships. The usefulness of the co-variance effect as a testable mechanism linking functional diversity to ecosystem reliability in the field is questionable, as there is no objective way of measuring it.
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Scherer-Lorenzen, Michael. "Effects of plant diversity on ecosystem processes in experimental grassland communities /." Bayreuth : Bayreuther Institut für Terrestrische Ökosystemforschung (BITÖK), 1999. http://www.gbv.de/dms/bs/toc/31133928x.pdf.
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Bagherzadeh, Mahtaab. "CAN INCREASING GRASS-FUNGAL ENDOPHYTE SYMBIOTIC DIVERSITY ENHANCE GRASSLAND ECOSYSTEM FUNCTIONING?" UKnowledge, 2018. https://uknowledge.uky.edu/pss_etds/105.
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The relationship between biodiversity and ecosystem functioning is important in maintaining agroecosystem sustainability. Plant-microbe symbioses, such as exists between the grass tall fescue (Schedonorus arundinaceum) and the asexual fungal endophyte Epichloë coenophiala, can be utilized to enhance agroecosystem functions, such as herbivore resistance. “Novel” E. coenophiala strains that vary in the production of mammal- and insect-toxic compounds have been identified, inserted into tall fescue cultivars, and are planted in pastures globally. Novel fungal endophyte-tall fescue associations may have divergent ecosystem function effects. This study assessed effects of different fescue-endophyte symbiotic combinations on pasture ecosystem function, including aboveground (fescue biomass, plant species richness, alkaloid synthesis, arthropod abundance) and belowground (soil microbial biomass, soil enzyme activity, trace gas fluxes) parameters. Results showed no significant effects of increasing symbiotic diversity within a fescue stand on aboveground measurements, bar arthropod abundance and alkaloid synthesis. Most soil parameters quantified had significant symbiotic diversity effects. For example, soil microbial biomass decreased whereas soil enzyme activity increased with increasing symbiotic diversity. Overall, our results suggested that increasing symbiotic diversity had weak to moderate effects on aboveground processes and stronger effects on certain belowground processes, indicating that symbiotic diversity can impact ecosystem functions and warrants further research.
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Nogueira, Carla de Almeida. "Responses and mechanisms of a mediterranean grassland ecosystem to nutrient addition." Doctoral thesis, ISA/UL, 2018. http://hdl.handle.net/10400.5/17509.
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Doutoramento em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de AgronomiaGlobal changes, resulting from anthropogenic activities, are increasing precipitation variability, drought and nutrient inputs into ecosystems. These global change drivers are expected to induce changes in grassland species richness and composition and functional structure and diversity which may in turn affect ecosystem functioning. This is particularly important for the Mediterranean basin, a climate change hotspot. Understanding how these changes affect grassland structure and functioning is critical to anticipate impacts of global change, improve management actions and develop land management strategies and restoration tools to mitigate grassland degradation. Through a pot greenhouse experiment, we applied three levels of extended autumn drought and two levels of nitrogen deposition to grassland communities. The severe drought originated a shorter growing season, and led to lower net ecosystem exchange and gross primary productivity, which translated into reduced productivity. Drought induced changes in functional group proportion and delayed plant phenology. Nitrogen addition did not affect productivity, diversity or phenology. However, nitrogen interacted with the severe drought treatment to attenuate the negative effects on total carbon fluxes. A 5-year nutrient addition field experiment was also conducted. Nitrogen, phosphorus and potassium were added in a factorial way to establish three treatments of one, two and three added nutrients, including controls. Grassland productivity was co-limited by multiple nutrients and precipitation. Nutrient addition decreased species richness and interacted with climatic variability to alter functional group composition. Resilience to disturbance was not affected by nutrient addition, as resistance that decreased with nutrient enrichment due to lower species richness was cancelled out by increased recovery due to the dominance of competitive graminoids. Community functional structure was affected by nutrient addition and precipitation and, for some traits, by their interaction and was the main determinant of productivity. Functional diversity was affected by precipitation, with drought negatively affecting community functional diversity
N/A
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Ibañez, Raffaele Mercedes. "Vegetation drives greenhouse gas exchange, and carbon and nitrogen cycling in grassland ecosystems." Doctoral thesis, Universitat de Lleida, 2020. http://hdl.handle.net/10803/669268.
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Los pastos son el hábitat más extenso del mundo, siendo fundamentales para la mitigación del cambio climático. Sin embrago, las predicciones sobre emisiones de gases de efecto invernadero (GEI), ciclo del carbono (C) y del nitrógeno (N), todavía están marcadas por una alta incertidumbre, la cual subyace en gran medida en las interacciones entre suelo y vegetación. La presente tesis investiga cómo la vegetación influye sobre el intercambio de GEI y la dinámica del C y el N, en términos de fenología, estructura, composición y diversidad. Para este fin, se han seleccionado pastos a lo largo de un gradiente climático (desde pastos alpinos del Pirineo hasta dehesas en el suroeste de la Península Ibérica). El intercambio de GEI se determinó combinado medidas continuas (eddy covariance) y discretas (cámaras de suelo). La dinámica del C y el N, se aproximó mediante el contenido de C y N, y el ratio isotópico de 13C y 15N. Los resultados mostraron que la vegetación influyó sobre el intercambio de GEI y la dinámica del C y N a lo largo del gradiente climático y de gestión. En ambientes de montaña la fenología condicionó las interacciones entre intercambio de CO2 y vegetación, en función del estrato altitudinal. En dehesas, la estructura compuesta por árboles y pasto, condicionó las emisiones de CO2 y N2O, siendo importante la especie de árbol. El contenido de C y N, y la discriminación contra 13C y 15N incrementó bajo copa en comparación con el pasto abierto. Dicha estructura determinó la composición de grupos funcionales de plantas, éstos presentando particularidades en la adquisición y uso de C y N. Así mismo, la composición de la vegetación influyó sobre el intercambio de GEI. Las legumbres incrementaron la asimilación neta de CO2 y las emisiones de N2O; la composición de especies influyo sobre la respiración y el intercambio de N2O. La interacción entre cereales y legumbres incrementó la asimilación neta de CO2 en comparación con monocultivos de cereal, como resultado de una mayor asimilación bruta pero no mayor respiración. La inclusión de la vegetación mejoró la comprensión sobre los mecanismos que afectan al intercambio de GEI y la dinámica del C y el N.Les pastures són l’hàbitat més extens del món, essent fonamentals per a la mitigació del canvi climàtic. Tot i així, les prediccions respecte a les emissions de gasos d’efecte hivernacle (GEH) i cicle del carboni (C) i del nitrogen (N), estan encara marcades per una gran incertesa, la qual recau en bona part en les interaccions entre el sòl i la vegetació. Aquesta tesi investiga com la vegetació influeix sobre el intercanvi de GEH i la dinàmica del C i el N, en termes de fenologia, estructura, composició i diversitat. Per a aquesta finalitat, es van seleccionar pastures al llarg d’un gradient climàtic (des de prats alpins del Pirineu fins a deveses al sud-oest de la Península Ibèrica). El intercanvi de GEH es va determinar mitjançant mesures continues (eddy covariance) i discretes (cambres de sòl). La dinàmica del C i el N, es va aproximar mitjançant el contingut de C i N, i el rati isotòpic de 13C i 15N. Els resultats mostraren que la vegetació va influir sobre el intercanvi de GEH i la dinàmica del C i N al llarg del gradient climàtic i de gestió. En ambients de muntanya la fenologia va condicionar les interacciones entre el intercanvi de CO2 i la vegetació, en funció del estrat altitudinal. A les deveses l’estructura composta per arbres i pastures, va condicionar les emissions de CO2 i N2O, essent important l’espècie d’arbre. El contingut de C i N, i la discriminació contra 13C i 15N va incrementar sota copa en comparació amb la pastura oberta. Aquesta estructura va determinar la composició de grups funcionals de plantes, els quals presentaren particularitats en l’adquisició i ús de C i N. Així mateix, la composició de la vegetació influí sobre el intercanvi de GEH. Les lleguminoses incrementaren l’assimilació neta de CO2 i las emissions de N2O; la composició d’espècies va influir sobre la respiració i el intercanvi de N2O. La interacció entre cereals i lleguminoses incrementà l’assimilació neta de CO2 en comparació amb monocultius de cereal, com a resultat d’una major assimilació bruta però no major respiració. En general, la inclusió de la vegetació va millorar la comprensió sobre els mecanismes que afecten al intercanvi de GEH i la dinàmica del C i el N.
Grasslands are the most widespread habitat in the world, and play a crucial role in climate change mitigation. However, predictions about greenhouse gas (GHG) fluxes, and carbon (C) and nitrogen (N) cycling, are still marked by great uncertainty, which in good part lies on soil – vegetation interactions. Accrdingly, this thesis investigates the role of vegetation, in terms of phenology, structure and diversity, as a driver of GHG exchange, C and N cycling in grasslands along a climatic gradient (mountain grasslands and dehesa ecosystems) and under diffrent management regimes. GHG recording was done combining continuous (eddy covariance) and discrete chamber based measurements. C and N cycling was assessed using C and N content, and 13C and 15N isotope ratios as a proxy. Our results showed that vegetation influenced GHG fluxes and C and N cycling along the climatic gradient and management regimes. In mountain environments, phenology determined interactions between CO2 exchange, vegetation and environmental variables, depending on the elevation belt. In dehesa ecosystems, the tree – open grassland structure drove CO2 and N2O fluxes, with some differences among tree species. Moreover, the different plant functional types, presented marked differences in their C and N acquisition and use strategies. Legumes enhanced net CO2 uptake and N2O emissions; as well as cereal – legume interactions enhanced net CO2 uptake compared to cereal monocultures. Overall, the inclusion of vegetation structure and diversity improved the understanding of mechanisms affecting GHG exchange, and C and N cycling.
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Joshi, Jasmin Radha. "On the importance of biodiversity in European grassland ecosystems : dissertation zur naturwissenschaftlichen Doktorwürde... /." Zürich : [Universität Zürich], 2000. http://catalogue.bnf.fr/ark:/12148/cb39932119z.
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Bergquist, Kiersten. "Ecosystem Functioning In Restored Grassland As Influenced By Ecotypic Variation, Precipitation, And Biodiversity." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/theses/2800.
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The restoration of degraded tallgrass prairies can mitigate climate change due to the carbon accrued during the development of grasslands. The focal species, dominant grass Andropogon gerardii, can assist the recovery of grassland ecosystem functioning. Climate, local adaptation, and biodiversity have been found to impact the accrual of carbon in grasslands. This study examined the difference in ecosystem functioning between ecotypes along a dry to mesic precipitation scale. The study site for this project was at the Southern Illinois University Agriculture Research Center in Carbondale, Illinois. The field site was planted with seeds originating from dry to mesic ecotypes, and the resulting ecosystem functioning was analyzed. It was found that the Kansas non-local ecotypes had significantly higher biodiversity, while the local Illinois sites demonstrated local adaptation with A. gerardii. Aboveground plant biomass was higher in the local sites, but there was no difference in carbon accrual between any of the ecotypes. While ecotypic variation in a dominant species will usually differentially influence ecosystem functioning, in this case, high biodiversity and local adaptation result in similar carbon inputs in grassland soil. It is necessary to analyze the carbon content of the soil in the drier field sites in order to determine if major differences in rainfall leads to differences in carbon accrual. If the goal of restoring a tallgrass prairie in southern Illinois is to assist with climate change mitigation, then it does not make a significant difference if the dominant species is sourced locally or non-locally.
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Prescott, C. V. "Factors responsible for the maintenance of the chalk grassland plagioclimax on Shorehill Down, Kemsing, Kent." Thesis, University of Greenwich, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384730.
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Stein, Claudia. "Biodiversity and ecosystem functioning: regional and local determinants of plant diversity in montane grasslands /." Leipzig : UFZ, 2008. http://www.ufz.de/data/ufzdiss_11_2008_9590.pdf.
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Kossmann, Guido [Verfasser]. "Plant functional traits and ecosystem functions in experimental grassland stands / Guido Kossmann." Bayreuth : Bayreuth Center of Ecology and Environmental Research, 2006. http://d-nb.info/979898854/34.
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Krutsinger, Roxane. "Evaluation of Grassland Restoration Success in Illinois Using Indicators of Ecosystem Function." Thesis, Southern Illinois University at Edwardsville, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1556741.
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Grasslands are known to have been an important ecosystem in the Illinois landscape prior to European settlement. They have been severely impacted by changes in land use such as the conversion of native grasslands to agricultural land for the production of crops and livestock. Grassland ecosystems are known to provide several essential ecosystem functions that are important for the maintenance of the ecosystem and for human survival. Some of the ecosystem functions associated with grasslands include: nutrient cycling, carbon sequestration, and the cleansing of environmental contaminants from water or soil. As grasslands are converted to agricultural use, their ability to perform these ecosystem functions are greatly impaired or lost completely. Due to their recognized importance, grassland restoration projects have been given high priority by conservationists and governmental agencies around the world. Some grassland restorations aim to restore the native vegetation including the great species richness that grasslands, and prairie ecosystems in particular, are known for. Other projects, like the Conservation Reserve Program (CRP), aim to restore one of the vital ecosystem functions that grasslands provide. The measure of success for a grassland restoration has largely been evaluated using species composition and indices of species richness and evenness. These types of measurements do not directly assess the ability of a restoration site to perform the ecosystem functions of a native grassland. The aim of this study is to determine if ecosystem function is recovered over time since restoration. This will be accomplished using a chronosequence of grassland restorations at the Nature Institute in Godfrey, IL ranging from 1 year to 25 years since restoration. Several indicators of ecosystem functioning will be assesses at each site including: soil bulk density, soil organic matter, and peak standing crop. The differences in these characteristics among the sites were analyzed by one-way ANOVA followd by Tukey’s HSD test if significant. All properties were analyzed using linear regression to assess their fit to a linear model. Soil bulk density was found to moderately but significantly decrease in response to time since restoration (p = 0.0049) indicating a recovery from soil compaction and improved soil structure. Differences were detected in soil organic matter among the sites, but no linear trend in response to time since restoration was detected. Similarly with peak standing crop, differences were detected among the sites, but no linear trend with time since restoration. The lack of a predictable recovery in soil characteristics over time was attributed to differences in historical land use. In order to strengthen this study in the future, analysis of a remnant prairie and older restoration sites should be examined.
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Mendola, Meredith Lynne. "Regional-climate and Local-microbial Controls on Ecosystem Processes During Grassland Restoration." OpenSIUC, 2013. https://opensiuc.lib.siu.edu/theses/1338.
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Root productivity likely has consequences for the composition, activity, and recovery of soil microbial populations and the belowground processes mediated by these organisms. In tallgrass prairie, ecotypic variation potentially exists in response to a strong precipitation gradient across the Great Plains. Thus, ecotypic variation within a species may differentially affect belowground net primary productivity (BNPP), the associated soil microbial community, and may scale up to affect ecosystem processes. The goals of this study were to elucidate: (1) whether ecotype, environment, or an ecotype by environment interaction regulate BNPP of a dominant species (Andropogon gerardii) collected from and reciprocally planted in common gardens across a precipitation gradient, and (2) whether variation in BNPP scales to affect microbial biomass and ecosystem processes. I quantified root biomass, BNPP (using root ingrowth bags), soil microbial biomass, and nutrient mineralization rates in root-ingrowth cores below six population sources of A. gerardii (2 Illinois, 2 eastern Kansas, and 2 central Kansas) established in southern Illinois, eastern Kansas, and central Kansas. An ecotype effect was found on above and belowground net primary productivity, but these findings did not translate to soil response variables. Microbial populations themselves may affect the productivity and composition of prairie species. In a second study, soil ecological knowledge (SEK) was tested by applying a native prairie soil slurry amendment to restoration plots to determine efficacy of this method as a restoration practice. The goals of this two year study were to elucidate: (1) whether a slurry amendment of prairie soil would increase above and belowground productivity and belowground ecosystem processes in a prairie restoration, and (2) to evaluate whether differences in plant diversity will scale to affect belowground productivity and ecosystem processes. I quantified aboveground net primary productivity (ANPP) and species composition, as well as root biomass, belowground net primary productivity (BNPP), soil microbial biomass, and nutrient mineralization rates in root-ingrowth cores installed in treated and control plots. A treatment effect was noted on root biomass and total PLFA biomass; however, there was no treatment effect on cover, ANPP, or soil microbial processes. Though the soil microbial community did represent native prairie soil, there was poor establishment of prairie plant species. These factors may be due to the limited time available for data collection and the lack of precipitation in the second growing season. Longer studies may be necessary to fully examine the effects of soil slurry amendments as restoration tools.
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Luckett, Kathryn. "The biodiversity-ecosystem function relationship in natural grassland communities at Silwood Park." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/32584.
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Biodiversity is a central concept in ecology, fundamental to how we conceive of the natural world, measure human impacts on it, and orient conservation efforts to protect it. When species are lost, their links are lost, and functions for which they are responsible can be lost as a result. There is evidence of an intuitive link between diversity and function, where more diverse systems should generally include a greater number of functions with a greater amount of redundancy built into them, but defining this link has proven difficult. This is an important challenge in ecology, however, because the function and stabilizing role of biodiversity is one of the most important arguments for its preservation. This thesis examines the role of biodiversity in ecosystem function and community stability grassland communities across Silwood Park. The experiment uses natural gradients in plant diversity, measured in a number of alternative ways. Species richness can be an imperfect metric for investigating the link between diversity and ecosystem functioning but can be used as a proxy for more complex diversity measures in grassland communities at Silwood Park. There was no general relationship between plant species richness and plant biomass, and a negative relationship between plant richness and soil mesofaunal biomass. An extreme flooding event negatively impacted some soil mesofauna and not others whilst increasing biomass yield during the following year. Plant biomass stability was independent of species richness and soil mesofaunal biomass varied with either plant richness or plant biomass depending on the definition of stability being used. The inclusion of relative abundance and phylogenetic information allows us more predictive power when looking at the biodiversity-ecosystem function relationship for both primary and secondary production. Experiments such as DExtER are vital to understanding the role of diversity in natural communities.
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Coulthard, Bethany L., Ramzi Touchan, Kevin J. Anchukaitis, David M. Meko, and Fatih Sivrikaya. "Tree growth and vegetation activity at the ecosystem-scale in the eastern Mediterranean." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/625304.
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Linking annual tree growth with remotely-sensed terrestrial vegetation indices provides a basis for using tree rings as proxies for ecosystem primary productivity over large spatial and long temporal scales. In contrast with most previous tree ring/remote sensing studies that have focused on temperature-limited boreal and taiga environments, here we compare the normalized difference vegetation index (NDVI) with a network of Pinus brutia tree ring width chronologies collected along ecological gradients in semiarid Cyprus, where both radial tree growth and broader vegetation activity are controlled by drought. We find that the interaction between precipitation, elevation, and land-cover type generate a relationship between radial tree growth and NDVI. While tree ring chronologies at higher-elevation forested sites do not exhibit climatedriven linkages with NDVI, chronologies at lower-elevation dry sites are strongly correlated with NDVI during the winter precipitation season. At lower-elevation sites, land cover is dominated by grasslands and shrublands and tree ring widths operate as a proxy for ecosystem-scale vegetation activity. Tree rings can therefore be used to reconstruct productivity in water-limited grasslands and shrublands, where future drought stress is expected to alter the global carbon cycle, biodiversity, and ecosystem functioning in the 21st century.
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Orford, Katherine Anne. "Cascading inter-trophic interactions in the provision of ecosystem services : a grassland experiment." Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680373.
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Understanding how species' interactions impact upon the composition and functioning of ecological communities is central to conservation biology. The overarching objective of this thesis is to aid the enhancement of biodiversity and ecosystem services by investigation of bottom-up ecosystem processes in an agricultural context; specifically in conventionally managed grasslands. Grassland for livestock production is a dominant form of land-use throughout Europe. Its intensive management threatens biodiversity in agricultural landscapes. Given its extensive cover, modest increases to conventional grassland biodiversity could have considerable positive impacts on the provision of ecosystem services, such as pollination, to surrounding habitats. The impact of conventional grassland diversity and management on the functional diversity and ecosystem service provision of pollinator communities was investigated. This relationship was assessed using a field-scale experiment in which grassland seed mixes and sward management were manipulated. This was complemented by surveys on ten working farms which possessed a natural gradient of plant diversity within SW England and phytometer experiments (assessing fruit production and seed set of strawberry, broad bean and red campion). The impact of grassland diversity on the ecosystem service of herbivorous pest control was also investigated via a bio-assay experiment on the working farms which assessed parasitism of a surrogate pest; the firethom leaf minor. Increasing plant species richness, by the addition of both legumes and forbs, was associated with significant enhancements in the functional diversity of grassland pollinator communities. This was associated with increased temporal stability of flower-visitor interactions at the community level. Increased sward richness was correlated with an increase in the pollination of the phytometer species strawberry and red campion but not broad bean. Enhanced pollinator functional diversity of more diverse pastures was a potential mechanism for improved pollination of the strawberry phytometers. Increased sward richness under grazing management was associated with increased pollinator biomass and thereby potential resources for insectivores. Visitation networks revealed pasture species Taraxacum sp. and Cirsium arvense to have the highest pollinator visitation frequency and richness, though Cichorium intybus was highlighted as a potential target species for pasture seed mixes due to its agronomic benefits. Finally, increased pasture plant species richness was positively associated with parasitism of the surrogate pest by parasitoids. Results of this study further our understanding of the relationship between plant diversity and invertebrate community functioning, helping us to manage ecosystem services within agro-ecosystems. An additional objective was to assess the importance of different taxa in the pollination process following the observation that non-syrphid Diptera are frequently neglected in the literature. Data from 32 pollen-transport networks and 69 pollinator-visitation networks was analysed to compare the importance of various flower-visiting taxa as pollen-vectors. The non-syrphid Diptera and Syrphidae were compared in detail to determine if neglect of the former in the literature is justified. No significant difference in pollen loads was found between the syrphid and non-syrphid Diptera in terms of pollen count and specialisation. It was estimated that non-syrphid Diptera carry 87% of total pollen carried by farmland Diptera. As important pollinators such as bees and hoverflies have suffered serious declines, it would be prudent to improve our understanding of the role of non-syrphid Diptera as pollinators.
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Silva, Vasco Manuel Almeida da. "Assessing the relationship between habitats conservation status and ecosystem services in Natura 2000." Doctoral thesis, ISA, 2020. http://hdl.handle.net/10400.5/21197.
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Doutoramento em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de Agronomia. Universidade de LisboaNatura 2000 is the pan-European network of protected areas and classifies different habitat types, including shrub-grasslands as of conservation interest. The use and management to which these habitat types are subject potentially affect their conservation status and the ecosystem services they generated, including regulating services as carbon storage or wildfire prevention. Wildfire prevention is an important ecosystem service in the Mediterranean region and management practices such as grazing or prescribed burning have been applied in several shrub-grassland areas in Natura 2000. These practices are known to reduce fuel vegetation, but little is known about their effects on the conservation status of these habitats. The main goal of this thesis was to investigate if there are potential trade-offs between fire hazard reduction and conservation in different shrub-grassland habitat types. For this, we assessed changes on plant species composition, vegetation structure, aboveground biomass and potential fire behaviour in plots treated with grazing or prescribed burning in two Natura 2000 sites located in central-west Portugal. Moderate grazing has effectively contributed to the conservation of some shrub-grassland habitat types through reduction of wildfire hazard and maintenance of favourable conservation status. In contrast, higher grazing and browsing pressure negatively affected the conservation status by altering plant species composition and structure of the analysed habitat. Likewise prescribed burning reduced fuel loads and minimized short-term fire hazard, but negatively affected the conservation status of the habitat types considered. Results showed that there are potential management conflicts between fire prevention and conservation in Natura 2000 and that these trade-offs must be considered during fuel management decisions
N/A
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Chinchilla, Soto Isabel. "Linkages between leaf traits and productivity in two resource-limited ecosystems." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/8933.
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Leaf traits have long been used to classify and characterise species in natural ecosystems. In addition, leaf traits provide important information about plants’ strategies for the use of resources and can be used to improve our understanding of ecosystem level processes such as nutrient cycling and carbon allocation. To explore the linkages between leaf traits and productivity, we worked in two resource-limited ecosystems (a grassland and a forest), and used leaf traits to understand how species respond to changes in available resources and their relationship to ecosystem processes. We worked in a species rich limestone-grassland located in central England, which has been subjected to long-term climatic manipulation (winter warming, summer drought and extra summer rainfall). We characterised species composition in terms of their identity, abundance and leaf structural properties (nitrogen content and leaf mass per area (LMA)) in the main treatments and the control. We found that change in species abundance was the most important factor to understand the differences in productivity (above ground biomass and total foliar nitrogen). We then measured CO2 exchange at ecosystem level, using a chamber technique, and assessed the treatments’ effect on the gross primary productivity (GPP) and ecosystem respiration (Reco). GPP and Reco were controlled by soil moisture and above ground biomass but also influenced by the conditions experienced during the growing season prior to the measuring period. Our second location was a post-disturbance chronosequence in a seasonally dry tropical forest in Costa Rica and we used leaf level gas exchange measurements to explore the role of nitrogen (N) and phosphorus (P) on the temporal-spatial variation of photosynthesis of dominant species. We found that photosynthetic efficiency was strongly linked to leaf N and P content, but that there was an important seasonal pattern on this relationship likely associated to P remobilization. Additionally we found seasonal changes in resources (water, nutrients) had a larger impact on the photosynthetic parameters than changes along the chronosequence. The two ecosystems studied for this thesis are contrasting in their physiognomy, species composition and climate, but are also characterised by species whose structural traits (high LMA and high C:N ratio) are likely to have a significant impact on the nutrient cycling processes. We learned that leaf traits provide important information about species strategies and their usage of resources and they can also aid to address questions at ecosystem level in time and space, either through simple aggregation or as emergent properties. Additionally, the traits explored are important input information to up-scale processes from leaf to the ecosystem level, a step needed to address the effect changes in resources will have on the seasonally dry tropical forest and grasslands, which represent a significant fraction of the total global carbon storage.
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McDonald, M. Christine, of Western Sydney Hawkesbury University, and Faculty of Agriculture and Horticulture. "Ecosystem resilience and the restoration of damaged plant communities : a discussion focusing on Australian case studies." THESIS_FAH_HOR_McDonald_M.xml, 1996. http://handle.uws.edu.au:8081/1959.7/683.
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An examination was undertaken of the literature and restoration cases for 4 major Australian vegetation types (sclerophyll; rainforest; grassland; and wetland) to explore the proposition that ecological resilience may govern recovery after anthropogenic damage, and/or provide a fundamental guide and measure of success for ecological restoration. Also, primary data were collected from highly degraded sites (5 sclerophyll, 3 rainforest, and 4 grassy sites) to assess recovery after restoration treatment. These were supplemented with questionnaire data from practitioners working at a wider range of rainforest and sclerophyll sites, and reports from practitioners working on grassland and wetland sites. In all 4 vegetation types, species generally fell into two main groups : longer-lived 'resprouters' and shorter-lived 'obligate seeders'. But different resilience models were identified for the 4 vegetation types. The sclerophyll type exhibited higher in situ resilience but lower migratory resilience than the rainforest type, which was facilitated by flying frugivore dispersal to perch trees. Self-perpetuation was more tightly coupled with disturbance in the sclerophyll, grassland and wetland types than rainforest; and therefore 'designed disturbance' played a more obvious role in enhancing recovery within these types, than in rainforest. Results suggest that resilience (as both an ecosystem property and a theoretical concept) is fundamental to the practice of ecological restoration. Some prediction of resilience potential of particular degraded sites (and prediction of the degree and type of restoration subsidy needed) can be based on knowledge of : individual species' recovery mechanisms; resilience models for individual vegetation-types; and the site's colonisation potential and impact historyDoctor of Philosophy (PhD)
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Ding, Yan. "Environmental Dynamics of Dissolved Black Carbon in Aquatic Ecosystems." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/846.
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Black carbon (BC), the incomplete combustion product from biomass and fossil fuel burning, is ubiquitously found in soils, sediments, ice, water and atmosphere. Because of its polyaromatic molecular characteristic, BC is believed to contribute significantly to the global carbon budget as a slow-cycling, refractory carbon pool. However, the mass balance between global BC generation and accumulation does not match, suggesting a removal mechanism of BC to the active carbon pool, most probable in a dissolved form. The presence of BC in waters as part of the dissolved organic matter (DOM) pool was recently confirmed via ultrahigh resolution mass spectrometry, and dissolved black carbon (DBC), a degradation product of charcoal, was found in marine and coastal environments. However, information on the loadings of DBC in freshwater environments and its global riverine flux from terrestrial systems to the oceans remained unclear.
The main objectives of this study were to quantify DBC in diverse aquatic ecosystems and to determine its environmental dynamics. Surface water samples were collected from aquatic environments with a spatially significant global distribution, and DBC concentrations were determined by a chemical oxidation method coupled with HPLC detection. While it was clear that biomass burning was the main sources of BC, the translocation mechanism of BC to the dissolved phase was not well understood. Data from the regional studies and the developed global model revealed a strong positive correlation between DBC and dissolved organic carbon (DOC) dynamics, indicating a co-generation and co-translocation between soil OC and BC. In addition, a DOC-assistant DBC translocation mechanism was identified. Taking advantage of the DOC-DBC correlation model, a global riverine DBC flux to oceans on the order of 26.5 Mt C yr-1 (1 Mt = 1012 g) was determined, accounting for 10.6% of the global DOC flux. The results not only indicated that DOC was an important environmental intermediate for BC transfer and storage, but also provided an estimate of a major missing link in the global BC budget. The ever increasing DBC export caused by global warming will change the marine DOM quality and may have important consequences for carbon cycling in marine ecosystem.
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Shinneman, Douglas J. "Determining restoration needs for piñon-juniper woodlands and adjacent ecosystems on the Uncompahgre Plateau, western Colorado." Laramie, Wyo. : University of Wyoming, 2006. http://proquest.umi.com/pqdweb?did=1212779251&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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McLaren, Jennie Renée. "The influence of plant functional groups on ecosystem functions in a grassland in northern Canada." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/22315.
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Human development, climate change, diseases and habitat degradation and loss are resulting in species extinction rates up to a thousand times faster than pre‐human levels. Biodiversity ecosystem functioning research examines how this loss of species and changes in the composition of plant communities are likely to influence numerous ecosystem functions. The effects of biodiversity loss on ecosystem properties may also be highly dependent on the identity of the organisms lost. I investigated the influence of plant functional group identity in determining ecosystem properties. I established a removal experiment in a grassland in northern Canada in 2003 with four treatments: a no‐removal control and independent removal of forbs, graminoids and legumes. As biodiversity loss is occurring in concert with environmental change, I crossed removals with a fertilizer and a mycorrhizal reduction (fungicide) treatment to determine the context dependency of effects. I showed that graminoids have the largest influence on ecosystem properties in this community, despite not being the most abundant group. Short‐term (4 years) biomass compensation for the removals showed no compensation for graminoid removal, but after 7 years there was full biomass compensation for this treatment. Light interception, soil moisture, and soil nutrients were all largely determined by the presence of graminoids in the plant community, and surprisingly legumes had very few effects on any ecosystem property. Graminoids also showed plant‐driven environmental effects on leaf decomposition, although no removal treatment resulted in changes in the decomposition of roots. Graminoids promoted decomposition of leaf litter through 2 mechanisms: influence on the decomposition microenvironment and changes in the litter composition. Finally, I have demonstrated that very few of the effects of functional group identity were context dependent on either fertilization or fungicide treatments. These
results highlight the importance of considering plant functional group identity when predicting the
effects of species loss, and indicate that plant identity, more so than dominance, determines effects on ecosystem properties.
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Bach, Elizabeth Marie. "Biotic and Abiotic Drivers of Soil Microbial Community Recovery and Ecosystem Change during Grassland Restoration." Available to subscribers only, 2009. http://proquest.umi.com/pqdweb?did=1967908731&sid=2&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Lunch, Claire Kerl. "Primary productivity in an annual grassland ecosystem : responses to global change and local environmental variation /." May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Currie, Gwen. "The impact of megaherbivore grazers on grasshopper communities via grassland conversion in a savannah ecosystem." Bachelor's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/24945.
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Grasshoppers are sensitive indicators of the state of disturbance of grassland ecosystems. This study examined the grasshopper communities inside a game reserve, comparing those found on frequently grazed areas with communities inside plots that exclude megaherbivores. The vegetation inside the protected plots was found to differ from the openly grazed areas in terms of grass height and aerial cover, but not in % greenness or richness of forb species. Grass species varied with locality rather than grazing impact. Total numbers of grasshoppers did not differ significantly between the two contrasting areas (100.2 in vs 93.5 out), however grasshopper species richness did, with the outside, short-grass plots having on average 17 different species, and the inside tall-grass plots a higher mean of 24.5. Grasshopper communities responded primarily to grass height and vegetation cover, but not to grass species or greenness of vegetation.
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Bradford, John B. "The influence of climate, soils, and land-use on primary productivity and cheatgrass invasion in semi-arid ecosystems submitted by John B. Bradford." Access citation, abstract and download form; downloadable file 13.42 Mb, 2004. http://wwwlib.umi.com/dissertations/fullcit/3131658.
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Plum, Nathalie Madeleine. "Worms and wetland water the role of lumbricids and enchytraeids in nutrient release from flooded grassland ecosystems." Berlin Logos-Verl, 2005. http://deposit.ddb.de/cgi-bin/dokserv?id=2757258&prov=M&dok_var=1&dok_ext=htm.
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