Thesis--Zürich. / "Arbeit aus dem botanischen Museum des eidgenössischen Polytechnikums in Zürich." "Separatabdruck aus dem Jahrbuch der St. Gallischen Naturwissenschaftlichen Gesellschaft, 1903." "Auch erschienen als: drittes. Heft der Botanischen Exkursionen und pflanzengeographischen Studien aus der Schweiz." Includes bibliographical references (p. 169-171).

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This study shows how the feeding behaviour of the increasing number of geese impacts their fragile breeding grounds in the Arctic region of Svalbard and, ultimately, may affect the geese themselves.  On arrival in their breeding grounds in spring, pink-footed geese, in common with other goose species, forage for below-ground plant parts.  This grubbing behaviour disturbs tundra ecosystems.  This thesis investigates the extent and distribution of grubbing on Svalbard, its impact on tundra ecosystems and feedbacks to the goose population in the long term. Grubbing geese reduce the abundance of plants, including moss, in tundra vegetation and cause the loss of substantial quantities of soil carbon.  A multi-habitat field manipulation experiment demonstrated that the impact of grubbing varies between communities; wetter communities with high moss cover are less negatively affected, but these are more likely to be grubbed by geese, particularly in valley bases and low lying coastal areas.  Using data collected in this project, the long-term effect of geese on tundra was simulated.  This resulted in predictions that geese will cause substantial degradation of their habitat if the population increases by another 50% to 75,000. Due to the negative effect of grubbing on vegetation, the long-term sustainable size of the population of pink-footed geese breeding on Svalband is estimated to be 95,000, less than 30% of the number expected based on the tundra’s productivity.  Pink-footed geese are therefore “ecosystem engineers” of the tundra, as they affect resource availability and “carrying capacity engineers”, as by degrading their own habitat they reduce the size of the goose population that it can support.

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Plant interactions (e.g., competition, facilitation) are critical drivers in community development and structure. The Stress Gradient Hypothesis (SGH) provides a predictive framework for how plant species interactions vary inversely across an environmental stress gradient, predicting that facilitation is stronger with increasing levels of stress. The SGH has been supported in numerous ecosystems and across a variety of stress gradients, but recent research has demonstrated contradictory results. These discrepancies have led to SGH revisions that expand its conceptual framework by incorporating additional factors, such as other stressor types and variations in species life history strategies. In this dissertation, I examine a further modification of the SGH by proposing and testing a Multiple Stress Gradient Hypothesis (MSGH) that considers how plant interactions vary along a continuous gradient of two co-occurring stressors using mangrove and salt marsh communities as a case study. In Chapter 1, I outline the predictive framework of a MSGH, by creating a series of predictions of species interactions. The components of the MSGH predict that stressors of similar types (e.g., resource and nonresource) will have similar effects and be additive. On the other hand, varying species life history strategies and life stages will lead to extremes of plant interactions. In Chapter 2, I performed a series of experiments to test the various components of the MSGH. In Chapter 3, I performed a large-scale observational study to test whether multiple co-occurring stressors altered the cumulative effects on plant interactions, and if these stressors should be grouped (e.g., resource and non-resource, abiotic and biotic, etc.) to enhance predictability. From a series of studies conducted herein, I concluded that co-occurring stressors are important factors that control complex species interactions as shown in my MSGH modeling approach. Further, future theories need to incorporate species-specific and stressor specific grouping when modeling how species interactions shape communities. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2013.

Made available in DSpace on 2014-06-11T19:30:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-02-28Bitstream added on 2014-06-13T20:01:15Z : No. of bitstreams: 1 kissmann_c_dr_rcla.pdf: 812203 bytes, checksum: 55b5329cab91716f1f1d2528dec508db (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / As espécies Styrax ferrugineus Ness & Mart., S. camporum Pohl. e S. pohlii A. DC. apresentam distintos padrões de ocorrência. S. ferrugineus é comumente encontrada no Cerrado sensu strictu (s. str.), enquanto S. camporum apresenta ampla distribuição no Cerrado sensu latu (s.l.), especialmente nas bordas dos fragmentos e S. pohlii é abundante nas florestas ripárias e de galeria. As performances germinativas das sementes e ecofisiológicas das plantas destas três espécies foram avaliadas através de experimentos de enterrio das sementes e plantio recíprocos em fragmentos de Cerrado s.str, Cerradão (clareira e sub-bosque) e mata ripária, os quais diferem em disponibilidade hídrica no solo e na atmosfera e luminosidade. Simultaneamente, o crescimento e desempenho fotossintético de S. pohlii em resposta ao alagamento do solo foram estudados em casa de vegetação. As sementes das três espécies germinaram em todos os locais experimentais onde foram enterradas. Porém, as plantas jovens de S. ferrugineus e S. camporum não sobreviveram às condições de baixa irradiância e alta disponibilidade de água no solo, encontradas na floresta ripária. A sobrevivência e o sucesso de S. pohlii neste ambiente parece estar relacionado ao rápido crescimento inicial da parte aérea, para obtenção de luz, e à adaptação que ela apresenta em resposta ao alagamento do solo. S. pohlii foi capaz de sobreviver a alagamentos sazonais e mostrou rápida recuperação fisiológica após inundação artificial. S. camporum apresentou maior eficiência fotossintética, crescimento e biomassa quando as plantas foram cultivadas sob altas irradiâncias, em comparação a ambiente sombreados, o que explica o maior número de indíviduos nas bordas em comparação ao interior dos fragmentos de Cerrado. Os dados de trocas gasosas, fluorescência e crescimento de... / The species Styrax ferrugineus Ness & Mart., S. camporum Pohl. and S. pohlii A. DC. show distinct geographical distribution patterns. S. ferrugineus is commonly found in the Cerrado sensu stricto (s. str.), whereas S. camporum is widely distributed in the Cerrado sensu lato (s. l), especially at the edge of vegetation fragments, and S. pohlii is abundant in riparian and gallery forests. Seed germination performances and ecophysiological performances of plants of these three species were assessed through reciprocal burial and planting experiments in a Cerrado s. str. fragment, a Cerradão fragment (gap and understory conditions) and in a riparian forest remnant, where water and light resources are differently availabe. Concurently, growth and photosynthetic parameters of S. pohlii potted plants in response to soil flooding was assessed in a greenhouse experiment. Seeds from each of the tree species were able to germinate in every experimental condition where the seeds were buried. Nevertheless, young plants of S. ferrugineus and S. camporum did not survive the low irradiance and high soil water availability found in the riparian forest. The survival and the success of S. pohlii in such environment seems to be related to a faster shoot initial length in order to capture sunlight, and to the adjustment that this species exhibits in reponse to different levels of soil flooding, enabling this species to fast recover from flooding periods. S. camporum showed higher photosynthetic performance, growth and biomass production when it was cultivated under high irradiances in comparison to shaded environments. These results explain the higher number of individuals of this species observed at the edge in comparison to the interior of Cerrado fragments. Gas exchange, fluorescence and growth parameters measured on S. pohlii and S. ferrugineus... (Complete abstract click electronic access below)

Orientadora: Alessandra Fidelis / Coorientador: Jaime Baeza / Banca: Vânia Regina Pivello / Banca: Marcelo Fragomeni Simon / Banca: Marco Antonio de Assis / Banca: Sergio Tadeu Meirelles / Resumo: Queimadas descontroladas e de grandes proporções estão entre as principais ameaças à biodiversidade do Cerrado. A época da queima é um dos elementos do regime do fogo, e estudos sobre seus efeitos na dinâmica da vegetação pós-fogo podem auxiliar no uso de queimas prescritas como ferramenta de manejo. Desta forma, o objetivo desta tese foi avaliar os resultados da época da queima no comportamento do fogo e na dinâmica da vegetação herbácea-arbustiva de uma área de campo sujo. Os experimentos foram realizados na Reserva Natural Serra do Tombador (Goiás). Primeiramente, comparamos o comportamento do fogo nas diferentes épocas de queima, dando subsídios para seu uso como ferramenta de manejo. Além disso, investigamos o efeito das épocas de queima nos padrões de recuperação/acumulação da biomassa (total, morta e viva), na fenologia (da comunidade e dos grupos funcionais: graminóides, herbáceas não graminóides e arbustos) e na dinâmica dos diferentes elementos da vegetação herbácea-arbustiva (solo nu, biomassa morta, graminóides, herbáceas e arbustos). Para tal, parcelas experimentais (30x30m) foram estabelecidas e queimadas em maio (queima precoce, início da estação seca), julho (queima modal, meio da estação seca), outubro (queima tardia, final da seca) e controle (não queimada, 4 réplicas/tratamento, total de 16 parcelas). Dentro de cada parcela experimental, dez subparcelas foram sorteadas e estabelecidas (1x1m) para análise da dinâmica e acompanhamento do padrão fenológico pós-fogo. As coletas de biomassa foram realizadas em cinco subparcelas de (0,5x0,5m), sorteadas aleatoriamente na borda das parcelas. O comportamento do fogo (ex: intensidade, taxa de propagação e altura da chama) não diferiu entre as épocas da queima, mas a porcentagem de material combustível morto ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Uncontrolled wildfires are one of the major threats to Cerrado biodiversity. Fire season is a component of fire regime and studies regarding fire season effects on vegetation dynamics can provide information on whether fire should be used as a management tool. Therefore, the aim of this study was to evaluate the effects of fire season on fire behavior and the dynamics of the herbaceous vegetation in a campo sujo area. The study was conducted at the Reserva Serra do do Tombador (Goiás). We first compared fire behavior in each fire season, aiming to provide information for the use of fire as a management tool. Furthermore, we investigated the effects of fire season in the patterns of biomass regeneration/accumulation (total, dead and live), phenology (community and functional groups: graminoids, forbs and shrubs) and in the dynamics of the different components of the herbaceous vegetation (bare soil, dead biomass, graminoids, forbs and shrubs). For such, plots (30 x 30 m) were established and burned in May (early-, at the beginning of the dry season), July (mid-, at the middle of the dry season), October (late-dry season fire, at the end of the dry season) and control (unburned, C, 4 replicates/treatment; total of 16 plots). In each plot, we randomly established and fixed ten subplots (1x1m) for the vegetation dynamics and phenology studies. Biomass sampling was done in five subplots (0.5x0.5m) randomly established in each plot. Fire behavior (e.g.: fire intensity, rate of spread and flame height) did not differ between fire seasons, but percentage of dead fuel was greater in the mid and late-dry season fires. Fire intensity was mainly influenced by the combination of percentage of dead fuel and fuel load. Live biomass regeneration was not affected by any fire season, while differences in total biomass composition ... (Complete abstract click electronic access below) / Doutor

Orientador: Leonor Patrícia Cerdeira Morellato / Coorientador: Marcio Silva Araújo / Banca: José Maria Gómez / Banca: Isabel Alves dos Santos / Banca: Paulo Roberto Guimarães Júnior / Banca: Vinicius Lourenço Garcia de Brito / Resumo: Indivíduos coespecíficos utilizam de forma diferente os recursos do nicho disponíveis às suas populações, e essas variações intraespecíficas (inter e intrapopulacionais) influenciam muitos processos ecológicos, principalmente as interações planta-animal. Em plantas com polinização biótica, a floração (época e intensidade) é uma importante adaptação aos períodos de maior abundância dos vetores de pólen, e está relacionada à atratividade aos polinizadores. A relação evolutiva entre polinizadores e caracteres florais das espécies e, ocorrência das "Síndromes de polinização" vem sendo historicamente testada, e geralmente, é confirmada a existência de uma relação direta entre um conjunto de caracteres florais e os polinizadores principais das espécies. Neste contexto, utilizando como modelo de estudo Trembleya laniflora Cong., uma espécie de Melastomataceae endêmica dos campos rupestres da porção sul da Cadeia do Espinhaço, Minas Gerais (Brasil), com populações naturalmente isoladas em afloramentos rochosos, e que apresenta características florais (flores grandes e brancas) que diferem do padrão observado para a família, tivemos como objetivo deste trabalho: (i) entender a importância ecológica e evolutiva dos distintos caracteres florais de Trembleya laniflora para a sua polinização e sucesso reprodutivo; (ii) avaliar a ocorrência de variação intraespecífica interpopulacional na ecologia reprodutiva da espécie, testando os fatores bióticos e abióticos que determinam tais diferenç... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Conspecific individuals vary in their use of available resources within the population, and intraspecific variations (inter and intrapopulation) in species traits play a fundamental role in many ecological processes, primarily the plant-animal interactions. The flowering activity (time and intensity) is an important adaptation to the periods of larger abundance of pollen vectors, enhancing the plant attractiveness to pollinators. The evolutionary relationship between pollinators and floral traits and the occurrence of "Pollination Syndromes" has been historically tested, and the existence of a direct relationship between a set of floral traits and the main pollinators has been generally confirmed. In this context, using as study model Trembleya laniflora Cong. (Melastomataceae), an endemic species, naturally isolated on rock outcrops from the rupestrian grasslands of South Espinhaço Range, Minas Gerais (Brazil), presenting floral characteristics (large and white flowers) that differ from the pattern observed for the family, we aimed: (i) to investigate the ecological and evolutionary importance of the distinct floral traits of Trembleya laniflora for its pollination and reproductive success; (ii) to observe and evaluate the occurrence of interpopulational intraspecific variation in the reproductive ecology of the species, testing the biotic and abiotic drivers for their reproductive success; and (iii) to evaluate intrapopulational intraspecific variation in flowering phenolog... (Complete abstract click electronic access below) / Doutor

Orientador: Ciro Cesar Zanini Branco / Coorientador: Orlando Necchi Júnior / Banca: Rogério Antonio Krupek / Banca: Rosana Marta Kolb / Resumo: As características fotossintéticas em relação à irradiância de produtores primários de riachos (comunidade perifítica, macroalgas, briófitas e angiospermas) foram analisadas através das técnicas de evolução do oxigênio dissolvido e fluorescência da clorofila. A partir dessas técnicas foram construídas curvas F-I (fotossíntese-irradiância) e seus parâmetros foram analisados. Altos valores de Ik (saturação) e baixos de α (eficiência fotossintética) e β (fotoinibição) sugeriram que espécies de Chlorophyta e a comunidade perifítica se mostraram como organismos de sol, enquanto que Rhodophyta, Xanthophyta, briófitas e as angiospermas se comportaram como organismos de sombra, o que foi refletido por baixos valores de Ik e moderados a altos de α e β. Cyanobacteria, por sua vez, apresentou comportamento intermediário em termos de adaptação luminosa. O parâmetro ΔF/Fm' mostrou que apenas Cyanobacteria e comunidade perifítica estavam aclimatadas às condições luminosas do local onde foram coletadas. Baixos valores do parâmetro de compensação (Ic) foram encontrados para todas as espécies indicando que elas conseguem manter um metabolismo autotrófico mesmo em irradiâncias muito baixas. Os valores de Fmax (fotossíntese máxima) mostraram que Chlorophyta apresentou maior potencial para serem considerados melhores produtores em ambientes lóticos, porém L. majuscula e S. arcangeli apresentaram os maiores valores de F/R (fotossíntese/respiração no escuro). Isso, associado ao fato de que essas algas podem acumular uma grande biomassa em riachos, sugere que as cianobactérias podem ser consideradas como sendo potencialmente melhores produtoras nesses ambientes / Abstract: Photosynthetic characteristics in response to irradiance of stream primary producers (periphyton, macroalgae, bryophytes and angiosperms) were analyzed by oxygen evolution and chlorophyll fluorescence techniques. From these techniques P-I (photosynthesisirradiance) curves were constructed and their parameters analyzed. High values of Ik (saturation), low of α (photosynthetic efficiency) and β (photoinhibition) suggested that Chlorophyta and periphyton were sun adapted, while Rhodophyta, Xantophyta, bryophytes and angiosperms were shade adapted, reflected by low Ik and moderate to high α and β. Cyanobacteria, on the other hand, were intermediate groups in terms of light adaptations. ΔF/Fm' parameter revealed that only Cyanobacteria and periphyton were acclimated to light conditions where they were collected. Low values of compensation parameter (Ic) were found in all species which indicate that they can keep an autotrophic metabolism even under very low irradiances. Pmax values (maximum photosynthesis) showed that Chlorophyta presented greater potential to be considered best producer in lotic environments, but Lyngbya majuscula and Scytonema arcangeli presented the higher values of P/R (photosynthesis/dark respiration). This, associated to the fact these algae can accumulate large biomass suggest that blue-green algae can be regarded as being potential best producers in that environment / Mestre