No description available.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

In this thesis, I describe three experimental studies that investigate the hotly debated role of competition in structuring communities in unproductive habitats. The studies were done in a boreal forest understory plant community in the southwestern Yukon. The first study was a traditional neighbour removal experiment. Ten of the most common species were transplanted as seedlings into transects with and without neighbours in a factorial design with two levels of water addition and two levels of fertilizer addition. The presence of neighbours increased survival and biomass of 6 species indicating a facilitative effect of neighbouring plants. The second study used the Community Density Series (CDS) methodology. The first of these was a 10-speciesexperimental community established from seed and grown in sandboxes at 6 densities with 2 watering levels and 2 fertilizer levels in a factorial design. At the community level, density dependence was observed at all life stages, but was not consistently competitive or facilitative - both emergence and final per plant shoot mass were density dependent, while survival to the end of the season was inversely density dependent. The effect of water was positive at seed emergence whereas fertilizer negatively affected survival. Species specific responses were also dependent on life stage. The final study was a 4-year CDS in the field using 9 common understory species at 6 densities and 3 fertilizer levels. Density negatively affected the community every year except for the first with competition being important at all densities above x1/8th the average community density. Constant final yield was reached in plots above the naturalx1 density for the last two years of the study. Responses to density were species-specific and 7 species declined with increasing density. No facilitative effects were observed. These studies demonstrate that density dependence is important in structuring this unproductive boreal understory habitat. The CDS approach allows us to quantify both the intensity and importance of plant competition at the community and species levels and to determine whether the importance of these biotic interactions depend on abiotic factors. The results clearly show that species-specific responses to biotic interactions are not necessarily the same as community level responses and if we are to understand community structure, it is necessary to use appropriate methodologies.

Thesis (Ph. D.)--Oregon State University, 2002. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

In this thesis, I describe three experimental studies that investigate the hotly debated role of competition in structuring communities in unproductive habitats. The studies were done in a boreal forest understory plant community in the southwestern Yukon. The first study was a traditional neighbour removal experiment. Ten of the most common species were transplanted as seedlings into transects with and without neighbours in a factorial design with two levels of water addition and two levels of fertilizer addition. The presence of neighbours increased survival and biomass of 6 species indicating a facilitative effect of neighbouring plants. The second study used the Community Density Series (CDS) methodology. The first of these was a 10-speciesexperimental community established from seed and grown in sandboxes at 6 densities with 2 watering levels and 2 fertilizer levels in a factorial design. At the community level, density dependence was observed at all life stages, but was not consistently competitive or facilitative - both emergence and final per plant shoot mass were density dependent, while survival to the end of the season was inversely density dependent. The effect of water was positive at seed emergence whereas fertilizer negatively affected survival. Species specific responses were also dependent on life stage. The final study was a 4-year CDS in the field using 9 common understory species at 6 densities and 3 fertilizer levels. Density negatively affected the community every year except for the first with competition being important at all densities above x1/8th the average community density. Constant final yield was reached in plots above the naturalx1 density for the last two years of the study. Responses to density were species-specific and 7 species declined with increasing density. No facilitative effects were observed. These studies demonstrate that density dependence is important in structuring this unproductive boreal understory habitat. The CDS approach allows us to quantify both the intensity and importance of plant competition at the community and species levels and to determine whether the importance of these biotic interactions depend on abiotic factors. The results clearly show that species-specific responses to biotic interactions are not necessarily the same as community level responses and if we are to understand community structure, it is necessary to use appropriate methodologies.

No description available.

Thesis (Ph.D.)--University of Adelaide, School of Earth and Environmental Sciences, Discipline of Environmental Biology, 2004. / "March 2004" Bibliography: leaves 115-141.

Το Θέμα της Μεταπτυχιακής Εργασίας Ειδίκευσης αφορά την οργάνωση ενός Προγράμματος Παρακολούθησης των υφιστάμενων οικοτόπων στο Εθνικό Πάρκο Λιμνοθαλασσών Μεσολογγίου- Αιτωλικού, του κάτω ρου και εκβολών ποταμών Αχελώου και Ευήνου καθώς και των Νήσων Εχινάδων. Ειδικότερα στο πρώτο μέρος της Εργασίας γίνεται ανάλυση των υφιστάμενων οικοτόπων της προστατευόμενης περιοχής με περιγραφή των αβιοτικών και βιοτικών στοιχείων των οικοσυστημάτων που συνιστούν το τοπίο της περιοχής. Στη συνέχεια οργανώθηκε ένα σύστημα βιοπαρακολούθησης με ένα ψηφιακό σχεδιασμό μόνιμων επιφανειών δειγματοληψίας, στις οποίες προτάθηκαν οι απαραίτητες βάσεις δεδομένων με εισαγωγή των διαφόρων μετρήσεων τους. Τέλος στο τρίτο μέρος γίνεται αξιολόγηση των οικοτόπων σε σχέση με τις επιδράσεις που έχουν πραγματοποιηθεί σε αυτούς μέσα από την παράθεση φωτογραφικού υλικού, ώστε στη συνέχεια να απεικονιστεί η έντασή τους αλλά και η επιρροή τους στις ζώνες του Δικτύου Natura 2000 εντός του Εθνικού Πάρκου και ανάλογα με αυτές να ακολουθήσουν προτάσεις διαχείρισης και προστασίας και τα συμπεράσματα. / The theme of the Graduate Degree Working on the organization of a monitoring program of existing habitat at the National Park Lagoons Messolongi-Aitolikou the lower reaches and estuaries Acheloos Evinos and Islands Echinades. Especially in the first part of the project is an analysis of current habitat of the protected area with a description of abiotic and biotic components of ecosystems that make up the landscape. Then run a biomonitoring system with a digital design permanent sampling plots, which offered the necessary databases to introduce the various measurements. Finally the third part has an evaluation of habitats in relation to the effects that have made ​​them through photographs so then visualize the intensity and the influence zones of the Natura 2000 network within the National Park and as with these proposals to follow the management and protection and conclusions.

Submitted by Rosana Amâncio (rosana.amancio@ufcg.edu.br) on 2018-07-12T21:53:47Z No. of bitstreams: 1 AMANDA GONÇALVES SANTOS - DISSERTAÇÃO PPGCNBio 2016..pdf: 3551999 bytes, checksum: db596e2a882aff72633f305307857dee (MD5) / Made available in DSpace on 2018-07-12T21:53:47Z (GMT). No. of bitstreams: 1 AMANDA GONÇALVES SANTOS - DISSERTAÇÃO PPGCNBio 2016..pdf: 3551999 bytes, checksum: db596e2a882aff72633f305307857dee (MD5) Previous issue date: 2016-07-14 / CNPq / Os nematódeos são os metazoários mais abundantes do planeta. Estima-se que três quartos, ou mais, de todos os animais da terra são nematódeos. Podem ser encontrados em todos os habitats que forneçam fontes de carbono orgânico disponíveis. Variam de acordo com a sensibilidade a poluentes e perturbação ambiental. Por esses motivos vem sendo utilizados, como ferramenta para biomonitoramento de ecossistemas. A resolução taxonômica diminui o problema do “impedimento taxonômico”, causado pela carência de pesquisadores nesta área e pela dificuldade na identificação dos organismos nos níveis taxonômicos mais baixos. Assim, objetivou-se comparar as estruturas populacionais nematofaunística, pelo uso de resoluções taxonômicas em três ambientes costeiros, a fim de ampliar a utilização da “resolução taxonômica” e enfatizar a sua importância como uma boa ferramenta de suporte as pesquisas de cunho taxonômico, principalmente nas que envolvam o monitoramento ambiental. Foram realizadas coletas em período chuvoso e seco, em ponto fixo da praia, do recife e do estuário de Pirangi do Sul - RN, Brasil. Os nematódeos encontrados foram identificados até o nível de espécie. Foram encontrados 46 gêneros e 56 espécies, pertencentes à 15 famílias, sendo 9 espécies novas para a ciência. As análises estatísticas mostraram que os níveis taxonômicos utilizados apontam diferenças na organização da comunidade, entre as estações de coleta, com exceção do nível específico. As diferenças também foram observadas para análises espaciais, com exceção do nível de ordem. A classificação até o nível de gênero se mostra taxonômicamente suficiente para interpretar os dados da comunidade nematofaunística da região de Pirangi do Sul-RN, para análises espaciais. / Nematodes are the most abundant metazoans in the planet. It is estimated that three-quarters or more of all land animals are nematodes. They can be found in all habitats that provide sources of organic carbon available. They still vary according to the sensitivity to pollutants and environmental disturbance. For these reasons it is being used as an instrument for biomonitoring ecosystems. The taxonomic resolution reduces the problem of "taxonomic impediment" caused by the scarcity of researchers in this area and the difficulty in identifying organisms at lower taxonomic levels. Thus, this study aimed at comparing the nematofaunistic population structures through the use of taxonomic resolutions in three coastal environments in order to expand the use of taxonomic resolution and emphasize its importance as a good resource support in the researches of taxonomic aspects, especially in those involving environmental monitoring. Samplings in rainy and dry season were made, in a fixed point at the beach, of the reef and estuary of Pirangi do Sul - RN, Brazil. The found nematodes were identified up to the species level. They were found 46 genera belonging to 15 families and 56 species being 9 of them new to science. Statistical analyzes showed that the taxonomic levels used in this research point to differences in the community´s organization, among the sampling stations, except the specific level. Differences were also observed for spatial analysis, with the exception of the order level. Classification up to the genus level has shown taxonomically enough to interpret the data nematofaunistic community of Pirangi-RN southern region for spatial analysis.

Submitted by Chaylane Marques (chaylane.marques@ufpe.br) on 2015-03-10T18:14:39Z No. of bitstreams: 2 PDF_FINAL.pdf: 2698581 bytes, checksum: f98f1938375301d4161c74863e04c652 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-03-10T18:14:39Z (GMT). No. of bitstreams: 2 PDF_FINAL.pdf: 2698581 bytes, checksum: f98f1938375301d4161c74863e04c652 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2012 / CNPQ / A fragmentação e a perda de habitats são as mais importantes transformações ambientais que afeta significativamente a abundância e a distribuição de espécies nas paisagens atuais. O objetivo deste estudo foi avaliar a influência desses dois processos sobre as comunidades de samambaias ocorrentes em uma paisagem fragmentada de Floresta Atlântica em Alagoas (Brasil). Foram amostrados dez fragmentos e em cada um deles foram marcadas quatro parcelas de 10x20m para a coleta dos dados biológicos. O Generalized Linear Models (GLMs) foi aplicado para avaliar os efeitos das variáveis físicas (extensão de área núcleo, forma, quantidade de microhabitats e isolamento) sobre a riqueza, abundância e diversidade das samambaias. Para a analise de composição foi realizada uma análise de ordenação MDS e aplicado o teste de permutação ANOSIM, além de testes de freqüências para presença de grupos ecológicos específicos. Foram encontradas oitenta espécies de samambaias distribuídas em 18 famílias e 36 gêneros. O GLMs mostrou que todas as variáveis descritoras analisadas explicam as variações na riqueza e diversidade entre os fragmentos analisados, no entanto, não indicou influência sobre a abundância das espécies. Não foi observado formação de grupos florísticos, sendo os aspectos ecológicos importantes na distribuição das espécies entre os fragmentos. Os resultados constataram que a fragmentação e a perda de habitat exercem influência negativa sobre a composição, riqueza e diversidade de samambaias na região analisada, representada pela restrição de habitats adequados para ocorrência das espécies mais sensíveis às mudanças causadas pelo desmatamento, supressão de área núcleo e efeitos de homogeneidade do habitat.