Made available in DSpace on 2016-06-02T19:29:57Z (GMT). No. of bitstreams: 1 5173.pdf: 2537344 bytes, checksum: 189e9f5fe14dc2946f00d093ab36ee54 (MD5) Previous issue date: 2013-04-12 / Universidade Federal de Sao Carlos / The aims of this thesis were: to investigate the heterogeneity of soils and to evaluate the contribution of clonal growth to the population dynamics of woody species under contrasting soil conditions. In the Cerrado-Pantanal ecotone (15º43 S; 56º04 W), the soil possesses typical features from both the soil of Cerrado in the Central Plateau and the soil of the Pantanal Plain. Given the variability of soil and pluviosity, our hypothesis is that clonal growth is the demographic parameter that most contributes to the population growth rate () of five woody species in this ecotone area. This study was carried out in five Cerrado areas. We identified four soil categories; three of them typic Litoplinthic Petric Plintosol, typic Dystrophic Yellow Latosol and Dystrophic Yellow Latosol with plinthite had not yet been described for the study site. The chemical attributes aluminum saturation, magnesium, calcium, pH and manganese explained 38.7% of the variability of the soils in the study sites. The spatial distribution of the edaphic attributes was heterogeneous. These attributes differed between the soils in the Cerrado Pantanal ecotone and the soils of Cerrado in the Central Plateau and of the Pantanal Plain. The population dynamics of Curatella americana, a dominant species with wide geographical distribution, was evaluated in Petric Plintosol (P) and in Yellow Latosol (L), in the dry and rainy seasons. Sexual reproduction and seedling growth were higher in P, whereas clonal growth was higher in L. The population growth rate (λ) was higher in P. The adult survival rate exerted the strongest effect on λ for the two soil categories and the dry and rainy seasons. The interaction between soil category and pluviosity exerted the strongest effect on λ. We also analyzed the dynamics of species with small populations (Bowdichia virgilioides and Roupala montana) and large populations (Curatella americana and Caryocar brasiliense), to determine which demographic parameters characterize woody clonal species with different sizes. For the species with small populations, the rate of sexual reproduction and the density of all life stages were smaller, whereas the clonal growth was higher. Small populations were more susceptible to variations in soil and pluviosity. The rates that most contributed to the λ of Bowdichia virgilioides and Roupala montana in L and P were: respectively, the survival of young ramets and immatures, in the dry season; and for both species, the survival of adults, in the rainy season. For C. americana and C.brasiliense, the survival of adults was the parameter that most contributed to λ, independently of soil category and season. The study indicated an heterogeneity of the superficial layer of the soil and of the soil categories that occur in this area. Soils with contrasting attributes exerted an important effect on the dynamics of woody clonal species. The survival of young and immature individuals, originated from clonal growth, was the rate that most contributed to the λ of the small-sized populations of woody clonal species B. virgilioides and R. montana , whereas the survival of adults was the rate that most contributed to the λ of the large-sized populations C. americana and C. brasiliense. / Os objetivos desta tese foram: investigar a heterogeneidade de solos e verificar qual a contribuição do crescimento clonal para a dinâmica de populações de espécies lenhosas sob condições edáficas contrastantes. Em Cerrado, zona de ecótono com o Pantanal (15º43 S; 56º04 W), o solo é constituído por características inerentes tanto ao solo de Cerrado do Planalto Central como da Planície do Pantanal. Diante da variabilidade de características edáficas e da pluviosidade, a hipótese é que o crescimento clonal apresente-se como o parâmetro demográfico que mais contribua para a taxa de crescimento populacional () de cinco espécies lenhosas nesta zona de ecótono. O estudo foi realizado em cinco remanescentes de Cerrado. Identificou-se quatro classes de solo, sendo que três destas Plintossolo Pétrico Litoplíntico típico, Latossolo Amarelo distrófico típico e Latossolo Amarelo distrófico com plintita ainda não haviam sido descritas para a região em estudo. Saturação por alumínio, magnésio, cálcio, pH e manganês explicaram 38,7% da variabilidade de solos. Houve heterogeneidade na distribuição espacial dos atributos edáficos. Tais atributos diferiram entre os remanescentes e entre solos de Cerrado do Planalto e da Planície do Pantanal. A dinâmica populacional de Curatella americana, espécie dominante e de ampla distribuição geográfica, foi avaliada em Plintossolo Pétrico (FF) e em Latossolo Amarelo (LAd), nas estações seca e chuvosa. A reprodução sexuada e o crescimento de plântulas foram maiores em FF, enquanto o crescimento clonal foi maior em LAd. A taxa de sobrevivência de adultos exerceu maior efeito sobre para as duas classes de solo e estações seca e chuvosa. A interação entre classe de solo e pluviosidade exerceu maior efeito sobre Também foi avaliada a dinâmica das populações de Bowdichia virgilioides e Roupala montana, Curatella americana e Caryocar brasiliense, para determinar quais parâmetros demográficos caracterizam espécies lenhosas clonais com diferentes tamanhos populacionais. A taxa de reprodução sexuada e a densidade de todos os estádios foram menores, enquanto o crescimento clonal foi maior para pequenas populações de espécies lenhosas. Pequenas populações foram mais suscetíveis às variações de solo e de pluviosidade. As taxas que mais contribuíram para de B. virgilioides e R. montana em LAd e em FF foram a sobrevivência de rametas jovens; na estação seca foi a sobrevivência de rametas jovens e de imaturos para as respectivas espécies e na estação chuvosa foi a sobrevivência de adultos para ambas as espécies. Para C. americana e C.brasiliense, a sobrevivência de adultos foi o parâmetro que mais contribuiu para independente da classe de solo e da estação do ano. O estudo comprovou a heterogeneidade da camada superficial do solo e das classes de solo que constituem esta área. Solos de características contrastantes exercem importante efeito sobre a dinâmica de espécies lenhosas clonais. A sobrevivência de indivíduos jovens e de imaturos, provenientes do crescimento clonal, foi a taxa que mais contribuiu para de populações pequenas de lenhosas clonais B. virgilioides e R. montana - ao passo que a sobrevivência de adultos contribuiu para de populações grandes C. americana e C.brasiliense.

Submitted by Luciana Sebin (lusebin@ufscar.br) on 2016-09-15T12:55:24Z No. of bitstreams: 1 TeseRNB.pdf: 4016225 bytes, checksum: f19817cea28780fc143ece6a86758413 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-23T18:14:57Z (GMT) No. of bitstreams: 1 TeseRNB.pdf: 4016225 bytes, checksum: f19817cea28780fc143ece6a86758413 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-23T18:15:06Z (GMT) No. of bitstreams: 1 TeseRNB.pdf: 4016225 bytes, checksum: f19817cea28780fc143ece6a86758413 (MD5) / Made available in DSpace on 2016-09-23T18:15:12Z (GMT). No. of bitstreams: 1 TeseRNB.pdf: 4016225 bytes, checksum: f19817cea28780fc143ece6a86758413 (MD5) Previous issue date: 2014-06-09 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A community can be defined purely as a group of individuals in a certain area? Since the beginning of ecology as a science, many authors have proposed theories to explain the structure of plant communities and therefore the spatial variation. However, although the accumulated knowledge has advanced to challenge the theories with each other, we have not reached many consensus within the community ecology. Likewise it has not been an easy task to establish physical or functional boundaries between the plant communities in the field, has also not been easy to establish boundaries between theories, approaches and influences of diferents areas of science, such as the biogeografia and evolution. Although some researchers have been working on attempts to establish an integrated theory was not only achieved little success and earned the antipathy of many trends or incited passions in scientific circles. On the one hand, the structure of the plant community may be the result of chance that accumulates over time and space, or by environmental heterogeneity due to specific ecological adaptations of different species. On the other hand, the gradient study indicates recognition of closed communities separated by transitional areas whose influence among communities, such highly dynamic areas, regulate their diversity, as endemic center would be essential for management and maintenance actions. Thus, the thresholds may reflect discontinuities on many different levels, but all kinds of limits can help to draw the line where there is success or failure in the prevalence of survival, growth and reproduction, sufficient to prevent the extinction of a species. In this context, the objective of this work is especially to propose a new old way to look at the structure of plant communities, trying to recognize the principles of the proposed theories from the scale of influence on spatial variation in community composition. Still, considering the current context of environmental changes caused by human activities, we will evaluate the effect of artificial transitions in the structure and diversity of communities. Furthermore, given the important contribution of ecotonal areas as endemic centers, we evaluate the contribution of the occurrence of threatened species in these areas for the Brazilian ecosystems conservation status. In this analysis, greater focus was given to the Cerrado, as the Brazilian Phytogeographic Domain presenting transition areas with almost all other ecosystems, with the exception of Pampa. Our results indicated a greater heterogeneity among the grasslands than in the savanna, but in thin scales both guard similarity close to 1, with a higher similarity between samples than expected by chance. This allows us to consider that the fine-scale continuum theory applies to structuring of communities and its spatial variation. In a coarser scale, communities vary as of continuum, in which the case studied in Itirapina Ecological Station, the continuum is represented by the part of Coutinho's gradient ("Grassland – Savanna - Forest") as Grassland-Forest. However, within a mosaic of ecotones and homogeneous types of vegetation, we find gradients nested with the refinement of the scale. In this case, the influence of the scale in approaches to the structuring of the Cerrado communities could be related to fractals, from the recognition of repeated linked units. Considering the intense fragmentation of the Cerrado vegetation, the invasibility of the communities and the biodiversity loss by invasive alien species, it is necessary to carefully evaluate the effect of artificial transitions in the structure of plant communities and establish 3 effective measures of management of invasive grasses for the focus of established invasion. Still, one must consider the ecosystem conservation status are significantly influenced by the heterogeneity that should be considered in priority actions for conservation. / Uma comunidade pode ser definida puramente como o conjunto de indivíduos de determinada área ? Desde o ínicio da Ecologia enquanto ciência, muitos autores vêm propondo teorias que expliquem a estruturação das comunidades vegetais e, portanto, da variação espacial. Entretanto, ainda que o conhecimento acumulado tenha avançado com a contestação das teorias entre si, não alcançamos muitos consensos dentro da ecologia de comunidades. Da mesma forma que não tem sido uma tarefa fácil estabelecer limites físicos ou funcionais entre as comunidades vegetais em campo, também não tem sido fácil estabelecer fronteiras entre as teorias, abordagens e influências de principios de outras áreas da ciência, como por exemplo, a biogeografia e evolução. Ainda que alguns pesquisadores tenham se debruçado sobre tentativas para o estabelecimento de uma teoria integrada, não só foi alcançado pouco sucesso como ganhou a antipatia de diversas tendências ou acirrou ânimos no meio científico. Por um lado a estrutura da comunidade vegetal pode ser resultado do acaso que se acumula ao longo do tempo e do espaço, ou da heterogeneidade ambiental devido a adaptações ecológicas únicas de espécies diferentes. Por outro lado, o estudo de gradientes indica o reconhecimento de comunidades fechadas separadas por áreas de transição, cuja influência entre as comunidades, como áreas muito dinâmicas, regulam sua diversidade e, como centro de enemismos seriam essenciais para ações de gestão e conservação. Assim, os limites podem refletir descontinuidades em muitos níveis diferentes, mas todos os tipos de limites podem ajudar a desenhar a linha onde há sucesso ou fracasso no predomínio de sobrevivência, crescimento e reprodução, suficientes para evitar a extinção de uma espécie. Nesse contexto, o objetivo deste trabalho é sobretudo o de propor um nova velha forma para o olhar para a estrutura das comunidades vegetais, buscando reconhecer os princípios das teorias propostas a partir da influência da escala na variação espacial da composição das comunidades. Ainda, considerando o atual contexto de transformações ambientais causadas por atividades antrópicas, avaliaremos o efeito de transições artificiais na estrutura e diversidade das comunidades. Além disso, diante da importante contribuição das zonas ecotonais como centros de endemismos, avaliaremos a contribuição da ocorrência de espécies ameaçadas nessas zonas para o estado de conservação dos ecossistemas brasileiros. Nessa análise, maior foco foi dado ao Cerrado, visto que é o Domínio Fitogeográfico brasileiro apresentando áreas de transição com quase todos os outros ecossistemas, com exceção do Pampa. Nossos resultados indicaram uma maior heterogeneidade entre as formações campestres do que no savânicas, porém em escalas finas ambas guardam similaridade próximas de 1, sendo maior a similaridade entre as amostras do que a esperada ao acaso. Isso nos permite considerar que em escala fina a teoria do continuum se aplica a estruturação das comunidades e sua variação espacial. Em uma escala mais grossa, as comunidades variam como continuum, sendo nesse caso de estudo, na Estação Ecológica de Itirapina (EEI), o gradiente é representado por parte do gradiente de Coutinho (Campestre- Savânica-Floresta), como "Campestre-Savanica". No entanto, dentro de um mosaico de ecótonos e tipos de vegetação homogênea, encontramos gradientes aninhados com o refinamento da escala. Nesse caso, a influência da escala para as abordagens sobre a estruturação das comunidades de Cerrado poderiam estar relacionadas a teoria dos fractais, a partir do reonhecimento de repetições de unidades em cadeia. Considerandose a fragmentação intensa do cerrado, a invasibilidade das comunidades, e a perda de diversidade por invasão de espécies exóticas, é preciso cautelosamente avaliar o efeito de transições artificiais na estrutura das comunidades vegetais e estabelecer medidas eficientes de manejo de gramíneas invasoras para os focos já estabelecidos de invasão. Ainda, é preciso considerar que o estado de conservação dos ecossistemas são 2 influenciados significativamente pela heterogeneidade que deve ser considerada em ações prioritárias para a conservação.

Spatial distribution and seasonal succesion of phytoplankton along the longitudinal axis of a eutrophic Římov reservoir was investigated in 2007. Inflow, transitional and lacustrine zones were distinquished in the reservoir according to physical, chemical and biological parameters. Using a functional group concept, typical phytoplankton assemblages were found.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-09-28T18:50:41Z No. of bitstreams: 1 mariavivianadefreitas.pdf: 1128422 bytes, checksum: 682d6ddcf9760bc573a210a6d3df8501 (MD5) / Approved for entry into archive by Diamantino Mayra (mayra.diamantino@ufjf.edu.br) on 2016-09-30T13:51:53Z (GMT) No. of bitstreams: 1 mariavivianadefreitas.pdf: 1128422 bytes, checksum: 682d6ddcf9760bc573a210a6d3df8501 (MD5) / Made available in DSpace on 2016-09-30T13:51:53Z (GMT). No. of bitstreams: 1 mariavivianadefreitas.pdf: 1128422 bytes, checksum: 682d6ddcf9760bc573a210a6d3df8501 (MD5) Previous issue date: 2010-12-14 / FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais / A análise de convergência de renda passou nos últimos vinte anos por diversos desenvolvimentos teóricos e empíricos. Todavia, a variedade de modelos, idéias e resultados presentes na literatura são provas cabais da importância acadêmica dessa linha de pesquisa e sua notável evolução. Neste contexto, o presente trabalho investigou a hipótese de convergência condicional numa perspectiva espacial local contribuindo, dessa forma, à literatura vigente por ocasião da busca de resultados que não sejam apenas globais, mas que provêem informação sobre o coeficiente para cada país. A taxa de crescimento do produto por trabalhador é a variável dependente utilizada para 148 países no período quinquenal compreendido entre os anos 1985 e 2005. Além das variáveis explicativas “básicas” relacionadas na literatura de convergência (PIB inicial, crescimento populacional e capital físico), variáveis explicativas adicionais foram incluídas, tais como: capital humano, expectativa de vida, gastos do governo, grau de abertura ao mercado internacional e medida de distorções do mercado. Conforme classificação da WEO/FMI, há uma nítida divisão entre países desenvolvidos e países emergentes e subdesenvolvidos o que sugere a existência de regimes espaciais distintos. A heterogeneidade espacial extrema foi tratada pela estimação de regressões ponderadas geograficamente (RPG). Os resultados da Análise Exploratória de Dados Espaciais indicaram a presença de dependência espacial global para a taxa de crescimento do PIB por trabalhador para os 148 países amostrados, em um padrão de concentração. Os resultados econométricos indicam a presença de efeitos não-observados, sendo mais adequada a estimação por efeitos fixos. O modelo espacial global que melhor se ajusta aos dados é o modelo de defasagem espacial confirmando a hipótese de convergência a uma velocidade encontrada na ordem de 2,07% ao ano. Como esperado, o investimento em capital físico assim como em capital humano e a inserção no mercado internacional atuam positivamente sobre o crescimento econômico. Atuando de maneira oposta estão os gastos do governo e a medida de poder de paridade de compra. Além disso, constatou-se que a taxa de crescimento do país vizinho é um fator relevante do crescimento de um determinado país. Considerando os regimes espaciais, o melhor modelo espacial estimado para os países desenvolvidos foi o de erro espacial. A hipótese de convergência foi, mais uma vez, confirmada, alcançando uma velocidade de 1,92% ao ano. O investimento privado influencia de maneira substancial o desenvolvimento alcançado pelos mesmos ao contrário da atuação insignificante do governo. Quanto à heterogeneidade espacial extrema, por intermédio da estimação por regressões ponderadas geograficamente, foram verificadas diferenças significativas quando consideradas as respostas locais, específicas a cada país. O mapeamento dos resultados de velocidade de convergência local e meia-vida local demonstrou considerável concentração geográfica. Ademais, as evidências internacionais e as estimativas desta dissertação validam a hipótese de convergência teorizada pela vertente neoclássica de crescimento econômico. A velocidade de convergência de, aproximadamente, 2% ao ano parece ser, portanto, “uma constante onipresente”. / Income convergence analysis has undergone in the last twenty years several theoretical and empirical developments. However, the variety of models, ideas and results put forward in literature are a compelling evidence of the relevance of this kind of research and its notorious evolution. Within this context, this study investigated the conditional convergence hypothesis in a local perspective, thereby contributing to the current literature estimating not only global results but providing information about each country coefficient. The growth rate of GDP per worker is the dependent variable for 148 countries over a five-year period between 1985 and 2005. In addition to the “basic” explanatory variables related to convergence literature (initial GDP, population growth and physical capital), other explanatory variables were included, such as: human capital, life expectancy, government spending, international markets opening degree and market distortions measurement. According to WEO/IMF classification, there is a clear division among advanced economies and other emerging markets and developing countries. This specification suggests the existence of different spatial regimes. The extreme spatial heterogeneity was handled by Geographically Weighted Regressions estimation (GWR). The results obtained by Exploratory Spatial Data Analysis indicated spatial dependence for global growth rate of GDP per worker across 148 countries in the form of a concentration pattern. The econometric results indicate unobserved effects suggesting a better fit when fixed effects are considered in the estimation. The best global spatial model is the spatial lag model confirming the convergence hypothesis and providing an estimate of 2.07% speed per year. As expected, investment in physical capital and human capital and the international market insertion act positively on economic growth. On the contrary, government spending and purchasing power parity measurement impact negatively. Moreover, the neighbors’ economic growth rate is an important factor in growth of a particular country. As to spatial regimes, the best model for advanced economies is the error spatial model. Once again convergence hypothesis was confirmed, reaching a 1.92% speed per year. Private investment influences substantially the development attained by the advanced ones, as opposed to the insignificant role played by the government. Addressing the extreme spatial heterogeneity by means of GWR approach, significant differences were verified when considering local relationships, specific to each country. Mapping results of local speed of convergence and local half-life demonstrated considerable geographic concentration. Besides, international evidences validate the convergence proposed by neoclassical economists. The speed of convergence around 2% per year seems to be “a ubiquitous constant”.

abstract: Geographically Weighted Regression (GWR) has been broadly used in various fields to model spatially non-stationary relationships. Classic GWR is considered as a single-scale model that is based on one bandwidth parameter which controls the amount of distance-decay in weighting neighboring data around each location. The single bandwidth in GWR assumes that processes (relationships between the response variable and the predictor variables) all operate at the same scale. However, this posits a limitation in modeling potentially multi-scale processes which are more often seen in the real world. For example, the measured ambient temperature of a location is affected by the built environment, regional weather and global warming, all of which operate at different scales. A recent advancement to GWR termed Multiscale GWR (MGWR) removes the single bandwidth assumption and allows the bandwidths for each covariate to vary. This results in each parameter surface being allowed to have a different degree of spatial variation, reflecting variation across covariate-specific processes. In this way, MGWR has the capability to differentiate local, regional and global processes by using varying bandwidths for covariates. Additionally, bandwidths in MGWR become explicit indicators of the scale at various processes operate. The proposed dissertation covers three perspectives centering on MGWR: Computation; Inference; and Application. The first component focuses on addressing computational issues in MGWR to allow MGWR models to be calibrated more efficiently and to be applied on large datasets. The second component aims to statistically differentiate the spatial scales at which different processes operate by quantifying the uncertainty associated with each bandwidth obtained from MGWR. In the third component, an empirical study will be conducted to model the changing relationships between county-level socio-economic factors and voter preferences in the 2008-2016 United States presidential elections using MGWR. / Dissertation/Thesis / Doctoral Dissertation Geography 2020

Wildlife management and natural resource policy decisions are increasingly being made at the landscape level. Understanding the relationship between modification and the pattern of land classes may minimize potential impacts and enhance the complement of wildlife species. Twenty-four expressions were selected for landscape analysis that describe the spatial heterogeneity, fragmentation, edge characteristics, and connectivity of pattern. Metric relationships were characterized across a variety of landscapes. Cluster analysis organized the metrics into classes quite different from the classification categories used in the literature. Cluster membership reflected the number of land classes, the amount and distribution of forest cover, number of forest patches, patch position, patch shape, patch radius, and edge length. Cartographic modeling was used to determine how modification influenced landscape pattern. The models depicted spatial relationships resulting from proposed landscape changes. Timber harvest schemes with a few large units and those in clustered arrangements led to less fragmentation than those schemes with several small units or those dispersed across the landscape. The placement of roads had either an invasive or partitioning effect on landscape pattern. Discriminant analysis rated the effectiveness of pattern expressions for environmental assessment. Metric effectiveness differed among the timber harvest, road expansion, and deforestation modification schemes. The utility and limitations of each expression was discussed. Sensitivity analyses examined the effects of changing spatial scale on pattern description. Scale influence was dependent upon landscape complexity, distribution of land classes, and the size and shape of those classes. The loss of ability to detect localized variability, to differentiate among spatial patterns, and to represent boundary detail accompanied the use of large pixels (420m²). There was evidence that spatial scale influences habitat evaluation. Semivariogram analysis assessed the constancy of expression behavior during changes in scale and presented the limits of tolerance for using large pixels in pattern analyses. The variability observed suggested that pattern misrepresentation occurred at coarse resolution levels. The successful application of landscape analysis depends on the ability to quantify pattern. By analyzing and understanding selected aspects of landscape pattern, I have examined how wildlife management can be enhanced through a knowledge of the landscape. / Ph. D.

One of the key concerns in spatial analysis and modelling is to study and analyse similarities or dissimilarities between places over geographical space. However, ”global“ spatial models may fail to identify spatial variations of relationships (spatial heterogeneity) by assuming spatial stationarity of relationships. In many real-life situations spatial variation in relationships possibly exists and the assumption of global stationarity might be highly unrealistic leading to ignorance of a large amount of spatial information. In contrast, local spatial models emphasise differences or dissimilarity over space and focus on identifying spatial variations in relationships. These models allow the parameters of models to vary locally and can provide more useful information on the processes generating the data in different parts of the study area. In this study, a framework for localising spatial interaction models, based on geographically weighted (GW) techniques, has been developed. This framework can help in detecting, visualising and analysing spatial heterogeneity in spatial interaction systems. In order to apply the GW concept to spatial interaction models, we investigate several approaches differing mainly in the way calibration points (flows) are defined and spatial separation (distance) between flows is calculated. As a result, a series of localised geographically weighted spatial interaction (GWSI) models are developed. Using custom-built algorithms and computer code, we apply the GWSI models to a journey-to-work dataset in Switzerland for validation and comparison with the related global models. The results of the model calibrations are visualised using a series of conventional and flow maps along with some matrix visualisations. The comparison of the results indicates that in most cases local GWSI models exhibit an improvement over the global models both in providing more useful local information and also in model performance and goodness-of-fit.

This thesis deals with factors structuring phytoplankton flagellates. The aim of the thesis was to investigate the role of microhabitats in spatio-temporal differentiation of lentic communities of these flagellates, which has not been rigorously examined to date. The study was conducted during 2010-2013 in the shallow littoral sites of Horní rybník, Rybníčky u Podbořánek Nature Reserve. Phytoplankton flagellates showed cyclic seasonal dynamics, which was reflected by significantly different community structure and species richness during the season. In contrast, silica-scaled chrysophytes showed a non- cyclic seasonal dynamics. The impact of the season was strongly correlated with the impact of fluctuating environmental factors - pH, conductivity and temperature. Gradient of interrelated environmental factors between the northern and southern shore together with microhabitat - substrate type played the major role and accounted for 64.4 - 75.8 % variability in the data. Microhabitat type (plankton, metaphyton, epipelon) significantly affected species richness and community structure also in the course of the season. A large number of species was assessed to prefer a certain type of microhabitat. These preferences were observed at both species and generic levels, and even at the level of the main taxonomic...

Besides spatial heterogeneity, an important component of diversity of the protist communities is also the variation in species assemblages through time (temporal turnover). Spatial and temporal variation in patterns of distribution and abundance of lentic microphytobenthos assemblages is often large and occurs at relatively small spatial scale. Desmids (Zygnematophyceae) often constitute a characteristic part of the microphytobenthos of peat bogs. Despite their important role in primary production and fact that they are useful indicators of ecosystem uniqueness, investigations of their seasonality and spatial distribution are scarce. In my thesis I have investigated if desmid epipelic communities are driven rather by neutral or niche-based processes, and I also focused on the factors affecting their diversity, seasonal dynamics and spatial patterns at the local spatial scale. The study was conducted at the two different types of biotopes - minerotrophic lowland peat bogs (Doksy region) and ombrotrophic raised bogs (Jizera Mountains region). Seasonal changes in species composition and diversity of assemblages were not evident. This may be affected by a monopolization effect and also that local abundance of species was positively correlated with population persistence, which suggests that high local...

Made available in DSpace on 2015-03-04T18:50:45Z (GMT). No. of bitstreams: 1 Dissertacao.pdf: 667521 bytes, checksum: bb065dd72ee7f7268f022ef94b81d208 (MD5) Previous issue date: 2007-03-12 / Uma metapopulação pode ser definida como uma população regional de populações locais geograficamente distintas, interconectadas por migração. Dentro deste contexto, modelos de dinâmica metapopulacional espacialmente implícitos descrevem a taxa de variação da proporção de manchas ocupadas por uma ou mais espécies por meio de um balanço entre os processos de colonização de manchas vazias e extinção de manchas ocupadas. O modelo metapopulacional de Levins prevê que mesmo na presença de habitat adequado, uma espécie pode se extinguir regionalmente, de forma determinística, se a intensidade de extinção for maior do que a intensidade de colonização. Além disso, este modelo sugere a existência de uma quantidade limiar de habitat remanescente, abaixo do qual a extinção regional determinística da espécie ocorre. Características importantes da dinâmica espacial, tais quais, efeito Allee, efeito resgate, colonização externa, qualidade da matriz, efeito anti-resgate e heterogeneidade de manchas podem ser incluídas em variantes do modelo de Levins. Uma outra extensão natural desses modelos é o agrupamento das manchas com relação ao seu estado de ocupação em modelos de metapopulações de espécies interativas, dando origem aos modelos de metacomunidades. Estudos de dinâmica de metacomunidades permitem a análise das relações entre a diversidade de espécies e a heterogeneidade ambiental no nível da paisagem, bem como as implicações de interações diretas e indiretas para a estrutura de comunidades.