Made available in DSpace on 2014-06-11T19:23:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-03-05Bitstream added on 2014-06-13T20:10:24Z : No. of bitstreams: 1 rocha_acr_me_rcla.pdf: 18201528 bytes, checksum: 00ea232cd505c19dc6717bfc237f5a83 (MD5) / Universidade Estadual Paulista (UNESP) / Os estudos das diatomáceas do estado de São Paulo são bastante recentes, especialmente os taxonômicos. A grande maioria das referências para esse grupo de algas, incluindo a família Pinnulariaceae, aparece em listas constantes de trabalhos ecológicos e/ou de saneamento ambiental, cujas identificações não são, na maioria das vezes, passíveis de identificação e tampouco as unidades amostrais utilizadas ou as preparações feitas foram preservadas para permitir re-estudo. Em todos esses trabalhos, pouca atenção foi dada ao estudo taxonômico da comunidade perifítica em relação à planctônica. O presente trabalho visou a conhecer os gêneros, espécies, variedades e formas taxonômicas da família Pinnulariaceae que ocorrem nas águas continentais do estado de São Paulo, bem como a variabilidade, em nível de população, das características diacríticas dos táxons, a avaliação de características diacríticas como diagnósticas na separação de táxons, subsidiar a hierarquização das características diagnósticas infragenéricas com vistas a futura revisão taxonômica de gêneros e/ou de espécies e fornecer subsídios a projetos de outras áreas da investigação que demandem o conhecimento prévio da composição florística da diatomoflórula local. O inventário florístico foi realizado a partir de material de ambientes de águas continentais do estado de São Paulo, de modo que as amostras foram selecionadas com o fim de abranger, o mais homogeneamente possível, a área do estado, bem como amostras de material tanto plânctônico quanto perifítico. Foram examinadas 103 lâminas semipermanentes confeccionadas de 101 amostras provenientes de 60 municípios. / Studies on the São Paulo state diatoms are very recent yet, especially those regarding their taxonomy. Most references, including the ones referring to the family Pinnulariaceae, are included in simple lists of ecological and/or sanitary engeneering publications. Many times, taxonomic identifications in these publications do not allow reidentification, because the sampling units or the slide mountings used for the publication were not preserved, making reidentification not anymore possible. In all those papers, little attention was paid to the taxonomic study of the periphytic community comparing to the planktonic one. Present paper aimed (1) at knowing the genera, species, varieties and taxonomic formae of family Pinnulariaceae present in the state of São Paulo continental waters; (2) as well as the variability, at population level, of the diacritic characteristics of different taxa; (3) at evaluating the diacritic features used as diagnostic during separation of different taxa; (4) at subsidizing the hierarchization of the infrageneric diagnostic characteristics aiming at a future taxonomic revision of genera and/or species; and (5) subsidizing projects in others fields of knowledge that will demand previous knowledge of the floristic composition of the diatom flora. Present floristic inventory was carried out using material gathered from freshwater environments all over the state of São Paulo, so that samples were selected would cover, the most homogeneous possible, the São Paulo State area, as well as material from both plankton and periphyton. One hundred and three semipermanent slides were prepared from 101 sample units gathered from 60 municipalities.

Made available in DSpace on 2014-06-11T19:23:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-02-25Bitstream added on 2014-06-13T20:29:41Z : No. of bitstreams: 1 riolfi_ta_me_rcla.pdf: 1217162 bytes, checksum: e79f5e161ef779d243d71daceffa7eff (MD5) / 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 / 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

Orientador: Reinaldo Monteiro / Banca: Marco Antonio de Assis / Banca: Osmar Cavassan / Banca: Geraldo Alves Damasceno Junior / Banca: Natália Macedo Ivanauskas / Resumo: A Universidade Estadual de Mato Grosso do Sul - Unidade de Aquidauana (20º28'16' S e 55º47'14' W) situa-se a 12 km do município e apresenta aproximadamente 160 ha de área de preservação permanente, principalmente ao longo da encosta do Morro Paxixi, que integra a paisagem local e marca a linha de contato ocidental entre o planalto e a planície pantaneira. A altimetria varia entre 300 e 600 metros e a vegetação predominante é a de Savana, em suas diferentes fisionomias. Nas áreas mais planas encontram-se o cerrado l.s. (savana arborizada, savana arbórea densa); ao longo da encosta do Morro Paxixi, há mata seca (floresta estacional semidecidual submontana); nas áreas de afloramentos rochosos há vegetação rupestre e xerofítica e mata ciliar (floresta estacional semidecidual aluvial) ao longo do córrego Fundo, que possui sua nascente no Morro Paxixi. Com o objetivo de caracterizar algumas das diferentes fisionomias, foram realizados levantamentos florísticos e fitossociológicos nas formações de cerrado s.s., cerradão e mata semidecídua, com ênfase nos componentes arbustivo-arbóreos. Para tal, foram alocadas um total de 80 parcelas de 10x10m, distribuídas em 30 parcelas na fisionomia de cerrado s.s., 30 na mata semidecídua e 20 no cerradão, onde os indivíduos com CAP ≥ 10 cm foram incluídos. Todos os fragmentos apresentaram-se em solos ácidos, distróficos, e alguns considerados álicos. Nos fragmentos de cerrado s.s. foram identificadas 130 espécies pertencentes a 40 famílias; na fitossociologia foram amostrados 1107 indivíduos, pertencentes a 33 famílias e 88 espécies. A família Vochysiaceae foi a mais importante, enquanto Fabaceae (12), Myrtaceae e Caesalpinaceae (7 espécies cada) foram as mais ricas. O índice de diversidade foi elevado (H'= 3,86), entretanto a análise da composição e estrutura mostrou que cerca de 45% das espécies... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The State University of Mato Grosso do Sul - Unit of Aquidauana (20º28'16' S and 55º47'14' W), is localized at 12 Km of the city and presents about 160 ha of permanent preservation area, mainly throughout the hillside of Paxixi mount, that integrates the local landscape and determines the occidental line of contact between plateaus and plains of Pantanal. Altimetry varies between 300 to 600 meters and the predominant vegetation is the savanna, in their distinct forms. In plainer areas find cerrado s.s. (savanna; woody savanna); throughout the hillside of the Paxixi Mount it has dry forest ( semidecidual forest); in the areas of emergent rocks it has xerofitic and rupestrian vegetation and the humid forest is throughout the Fundo brook, that presents its spring in the Paxixi Mount. With the objective to characterize some of the different physiognomies, floristic and phytosociological surveys were conducted in areas of cerrado s.s., cerradão and dry forest, with emphasis on shrub-arboreal strata. For such, they had been placed a total of 80 plots of 10x10 meters, distributed in 30 plots in cerrado s.s., 30 plots in dry forest and 20 plots in arboreal savanna where the individuals with PBH ≥ 10 cm were included. All the fragments presents acid and distrofic soils, some too alics. In cerrado s.s .were found 130 species belonging 40 families; in phytosociological analysis were found 1107 individuals belonging 33 families and 88 species. Vochysiaceae was the most important family while Fabaceae (12), Myrtaceae e Caesalpinaceae (7 species own) were the most richness. The diversity index was high (H'= 3,86), however the analysis of composition and structure showed that about 45% of species presents less than 5 individuals, became considers numerically rare. The similarity among the Centro- Oeste areas was low, devices the presence of species the woody savanna and dry forest... (Complete abstract click electronic access below) / Doutor

Orientador:, Edson Luiz Lopes Baldin / Coorientador: Leandro do Prado Ribeiro / Banca: Carlos Frederico Wilcken / Banca: Antonio Eduardo Miller Crotti / Resumo: Helicoverpa armigera (Hübner, 1808) (Lepidoptera: Noctuidae) destaca-se pela grande capacidade de dispersão, hábito polífago e por ocasionar expressivos danos em culturas de interesse econômico em todo o mundo. Dentre os métodos de manejo de insetos-praga, o uso de derivados vegetais é considerado uma promissora alternativa ao controle químico, uma vez que estes produtos apresentam mais de um ingrediente ativo em sua composição, dificultando a seleção de insetos resistentes, além de serem provenientes de recursos renováveis. Dentre as famílias botânicas de ocorrência em regiões neotropicais, Annonaceae constitui uma das principais fontes de compostos naturais bioativos. Assim, visando disponibilizar alternativas mais sustentáveis e ao mesmo tempo eficientes para o manejo de Helicoverpa armigera (Hübner, 1808) (Lepidoptera: Noctuidae), avaliou-se a bioatividade de cinco derivados de anonáceas (Annona montana Macfad., A. mucosa Jacq., A. muricata L., A. reticulata L. e A. sylvatica A. St.-Hil.) e do produto comercial à base de acetogeninas de anonáceas (Anosom® 1 EC) sobre lagartas do inseto. Adicionalmente, o composto majoritário do extrato mais ativo foi identificado e também avaliado quanto à sua bioatividade sobre formas neonatas de H. armigera. Constatou-se que o extrato de A. mucosa (CL50: 411,55 mg kg-1 e CL90: 1.479 mg kg-1 ) assim como o Anosom® 1 EC (CL50: 312,08 mg kg-1 e CL90: 1.151 mg kg-1 ) apresentaram significativa atividade inseticida sobre H. armigera, com toxicidade aguda após sete dias de exposição a dieta artificial tratada. A partir do extrato etanólico de A. mucosa realizou-se fracionamento biomonitorado através de diferentes técnicas cromatográficas, permitindo o isolamento da acetogenina bisterahidrofurano roliniastatina-1. Este composto foi testado a uma concentração de 41,55 mg kg-1, ocasionando mortalidade total das larvas de H. armigera ... / Abstract: Helicoverpa armigera (Hübner, 1808) (Lepidoptera: Noctuidae) is a highly polyphagous species with high dispersion ability and adaptability to different crops of economic interest worldwide. Botanical insecticides emerge as a viable alternative to the use of synthetic insecticides for pest management because they have more of a potentially active ingredient in their composition, delaying the selection of resistant insect, moreover come from renewable resources. Among tropical plant families, the Annonaceae has shown great potential as a source of biopesticides. To determine an alternative tool for H. armigera control, this study evaluated the insecticidal activity of ethanolic seed extracts from five species of Annonaceae (Annona montana Macfad., A. mucosa Jacq., A. muricata L., A. reticulata L. e A. sylvatica A. St.-Hil.) and the acetogenin-based commercial bioinsecticide Anosom® 1 EC on larvae of H. armigera larvae. In addition, the major active compound of the ethanolic extract was isolated using various chromatographic techniques and assessed for its bioactivity on H. armigera neonates. In the initial screening assay we verified that the ethanolic seed extract from A. mucosa (LC50 = 411.55 mg kg-1 and LC90 = 1,479 mg kg-1 ) was the most promising one, showing similar effectiveness to Anosom® 1 EC (LC50 = 312.08 mg kg-1 and LC90 = 1,151 mg kg-1 ) against H. armigera at seven days after exposition to treated diet. The acetogenin bis-tetrahydrofuran rolliniastatin-1 was identified as the major compound in ethanolic extract from A. mucosa. This compound was assessed at 41.55 mg kg- 1, causing 100 % of larval mortality on H. armigera neonates for days after exposition to treated diet. After, in a greenhouse trial using tomato plants, the bioactivity of ethanolic extract of A. mucosa was compared to botanical insecticide Anosom® 1 EC (both at LC90) and a synthetic insecticide (Belt® 48 SC) ... / Mestre

Orientador: Fernando Roberto Martins / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-11T15:33:15Z (GMT). No. of bitstreams: 1 VanMelis_Juliano_M.pdf: 1390063 bytes, checksum: 7c525d7204f312e3db23b7fb3945a8d3 (MD5) Previous issue date: 2008 / Resumo: As lianas (plantas trepadeiras lenhosas) são importantes componentes nos ciclos biogeoquímicos e da biodiversidade nas florestas tropicais. A partir dos dados estruturais das árvores e lianas em um hectare (23º21¿54¿-23º21¿59¿S; 45º05¿02¿-45º05¿04¿W)de Floresta Ombrófila Densa Atlântica (348-395 m) construímos dois capítulos. O primeiro teve como objetivos estudar variáveis estruturais que determinam a abundância e biomassa acima do solo das lianas (LAGB). Nossas hipóteses eram que havia correlação positiva entre abundância e LAGB com a abundância e biomassa aérea de árvores (AAGB), e negativamente com a abundância de palmeiras e samambaiaçus (grupo sem fuste). Em uma escala continental investigamos quais variáveis geográficas e climáticas determinariam maiores valores absolutos e relativos (contribuição das lianas na biomassa florestal total) de LAGB. Encontramos correlação entre abundância de árvores pequenas e a AAGB com a abundância das lianas pequenas, não sendo encontradas outras correlações relevantes. A biomassa aérea individual dos forófitos e lianas associadas tiveram correlação positiva fraca. Nenhuma variável sozinha explicou os valores absolutos e proporcionais de LAGB na escala continental, apesar da sazonalidade da precipitação ser a mais importante dentre aquelas colocadas. Acreditamos que a sazonalidade da precipitação caracterize florestas com árvores caducifólias, permitindo maior entrada de luz, beneficiando em importância sociológica (abundância e área basal) as lianas nessas florestas. A LAGB na escala fina depende de suportes potencialmente adequados, pois as lianas grandes estão associadas a árvores de grande biomassa. Mas a existência de grandes árvores não necessariamente decorre em maior LAGB. Portanto, destacamos que a susceptibilidade das árvores à escalada das lianas acarretaria maior abundância e LAGB nas florestas tropicais. No segundo capítulo buscamos investigar qual é a relação observada entre a riqueza das espécies lenhosas amostradas com a sua produtividade (SRPR), assumindo a biomassa aérea (AGB) como valor de produtividade. Nossas expectativas foram: a) as lianas têm uma SRPR de forma unimodal, devido à reprodução clonal e ao predomínio da exclusão competitiva; b) as árvores têm uma SRPR linear positiva, devido à complementaridade das espécies; c) a inclusão das lianas altera a SRPR, devido aos seus baixos valores de AGB e alta contribuição para a riqueza; d) a variação de abundância influi na correlação entre a riqueza e a AGB, pois ambas dependem da abundância. Todas as SRPR foram significativas, mesmo com a inclusão da abundância, indicando que a SRPR não é um artefato decorrente de características da comunidade. As lianas apresentaram SRPR unimodal, e as árvore e o conjunto lianas+árvores apresentaram SRPR linear positiva. A inclusão das lianas não alterou a forma monotônica da SRPR nem a inclinação da reta de regressão, mas produziu um intercepto maior, indicando que a inclusão das lianas aumenta a riqueza em qualquer valor de AGB, mesmo com SRPR linear e positiva / Abstract: Lianas (woody climbing plants) are important components in biogeochemical cycles and biodiversity in tropical forests. Two chapters were written from the data of a stand (23º21¿54¿-23º21¿59¿S; 45º05¿02¿-45º05¿04¿W) of lianas and trees in Atlantic Rain Forest (348-395 m). The first chapter aimed at studying structural variables that determine the abundance and lianas above-ground biomass (LAGB) and the correlation of these variables to the above-ground biomass phorophytes on local scale. Our assumptions were that the LAGB and lianas abundance was positively correlated with the above-ground biomass (AAGB) and arboreal abundance, and negatively correlated with the abundance and types of trees without bole (palm and ferns). We also investigated, in continental scale, the geographical and the climatic variables which determine the largest absolute and relative (lianas contribution to total above-ground biomass) LAGB. We found a positive correlation between abundance of small trees and AAGB with the abundance of small lianas, and no correlation between the group without bole and AAGB with LAGB. There was weak positive correlation between the individual phorophytes biomass and associated lianas. At a continental scale any variable alone explained the absolute and proportional LAGB, despite the seasonality of precipitation to be the most important among those released. We believe that the seasonality of precipitation features forests with caducifolius trees, occurring largest entry of light during the dry season, benefiting lianas in sociological importance (higher values of basal area and abundance) on the forests. On local scale, the LAGB depends of tree potentially suitable, because the large liana, which are the largest contributors of LAGB, are associated with large trees. But the large trees do not necessarily result in greater value of LAGB. Therefore the susceptibility of trees to lianas is a factor that would result in greater abundance and LAGB in tropical forests. The second chapter sought investigate the relationship between richness of trees, lianas both the woody floras with its productivity (SRPR), assuming the above-ground biomass (AGB) as a surrogate of productivity. Our expectations were: a) lianas has a unimodal SRPR, due to clonal reproduction and the dominance of competitive exclusion, b) Trees has a positive linear SRPR, due to the complementarity of species c) the inclusion of lianas changes the SRPR of woody flora, due to its low contribution to the AGB and high contribution to the richness d) the change of abundance influences the correlation between richness and AGB, because both depends on the abundance. All SRPR were statistically significant, even with the inclusion of abundance, indicating that the SRPR is not an artifact due to characteristics of the community. We found a unimodal SRPR for lianas and a positive linear SRPR for trees and of trees and lianas as a whole. The inclusion of lianas not changed the monotonic SRPR nor the inclination of the straight regression, but produced a higher value of intercept, indicating that the inclusion of lianas increases the value of wealth in any AGB, even with positive linear SRPR / Mestrado / Mestre em Biologia Vegetal

The greater photosynthetic nitrogen use efficiency (PNUE) of C4 compared with C3 plants may explain the relative success of C4 grasses in nutrient poor environments. This study compared the responses in photosynthetic parameters, leaf nitrogen and biomass allocation between the C3 and C4 subspecies of Alloteropsis semialata supplied soil nitrogen at three levels. Photosynthesis was assessed by means of CO2 response curves and the leaf nitrogen content assayed. Plants were destructively harvested, leaf areas determined and the dry biomass of functional plant components was measured. Results confirmed that the higher PNUE of C4 plants allowed them to accumulate more biomass than C3 plants at the high nitrogen level, despite smaller leaf areas. The greater productivity of C4 plants enabled them to invest more in storage and sexual reproduction than in leaves when compared to the C3 plants. In contrast the C3 plants invested biomass in less efficient and more nitrogen demanding leaves and bigger root systems. PNUE and photosynthetic rates were not significantly affected by nitrogen-limitation in either subspecies and the major response was a decrease in biomass accumulation and an increase in biomass allocation to roots. This altered root to shoot ratio was accompanied by a lowered allocation to sexual reproduction in the C4 subspecies, but an unaltered allocation to leaves, while in the C3 subspecies there was a decrease in leaf allocation. In a further experiment, the C4 subspecies was supplied three levels of nitrogen provided as nitrate, or alternatively as ammonium plus nitrate, and leaves were excised to within 5 cm of the ground at the start of treatment. Prior to flowering, photosynthesis was assessed by means of CO2 response curves and the plants were destructively harvested. Leaf areas and the dry biomass of functional plant components were determined, and at levels of nitrogen supply higher than those found in savanna soils the rate of photosynthesis was increased. Leaf re-growth was reduced by severe nitrogen limitation and co-provision of nitrate and ammonium had no significant effect other than increased tillering. Both subspecies of Alloteropsis semialata are adapted to nutrient poor environments and maintain photosynthetic rates by reducing leaf area. The C4 subspecies is likely to show greater resilience in disturbance-prone environments by exploiting its higher PNUE to allocate greater resources to storage and sexual reproduction, while the C3 subspecies is usually found in environments with closed canopies which favour vegetative growth, and allocate greater resources to leaves and roots.

The aquatic macrophyte Crassula helmsii is a non-native species and classed as 'invasive' in the UK. This study was carried out in an attempt to provide empirical evidence as to whether the establishment and growth of Crassula helmsii has a measurable impact on the ecology of invaded sites. Dispersal and distribution patterns across England were explored using databases and GIS interpretation. Ecological impact was measured by comparing invaded sites with uninvaded control sites on a range of habitats and waterbody types across Kent and East Sussex. The analysis of spread patterns provided evidence that the plant is likely to have been dispersed due to the horticultural trade, as well as natural vectors into neighbouring habitats. Macrophyte analysis showed that species losses did not occur when C. helmsii was present. Changes to species composition did occur, with rarer plant species being associated with the presence of C. helmsii. Freshwater macroinvertebrates showed no change in either species number or species rarity. The seed banks of invaded and control sites showed no difference, but active management was shown to reduce the total number of seeds in the soil significantly. The water chemistry of invaded and uninvaded sites showed a relationship between the presence of C. helmsii and reduced total organic nitrogen. The results of this study show that the expected species loss associated with non-native species may not be occurring with C. helmsii. Active management may be impacting the ability of native species to recolonise. Further work on other habitats and waterbodies across a wider geographic range are required to explore whether this is a localised effect.

Doctor of Philosophy / Department of Biology / David C. Hartnett / In perennial grasslands, the belowground population of meristems (the bud bank) plays a fundamental role in local plant population structure and dynamics. I tested the “meristem limitation hypothesis” prediction that bud banks increase along an increasing precipitation/productivity gradient in North American grasslands. I sampled bud populations quarterly at six sites across a 1,100 km gradient in central North America. Bud banks increased with average annual precipitation, which explained 80% of variability in bud banks among sites. Seasonal changes in grass bud banks were surprisingly similar across a 2.5-fold range in precipitation and a 4-fold range of aboveground net primary productivity (ANPP). Secondly, I tested the hypothesis that tallgrass prairie plants respond to increases in a limiting resource (nitrogen) through demographic effects on the bud bank. I parameterized matrix models for individual genets, considering each genet as a population of plant parts (buds and stems). Nitrogen addition significantly impacted bud bank demography of both Sporobolus heterolepis and Koeleria macrantha. In 2005, emergence from the bud bank and growth rates (λ) of the tiller population were significantly higher in S. heterolepis genets that received nitrogen. In contrast, nitrogen addition decreased λ in K. macrantha. Both prospective and retrospective analyses indicated that bud bank dynamics are the key demographic processes driving genet responses to nutrient availability. Lastly, I tested the hypothesis that the effects of fire and grazing on plant species composition and ANPP are mediated principally through demographic effects on bud banks. I found that plants respond to fire and grazing with altered rates of belowground bud natality, bud emergence, and both short-term (fire cycle) and long-term changes in bud density. The size of the bud bank is an excellent predictor of long-term ANPP, supporting my hypothesis that ANPP is strongly regulated by belowground demographic processes. Meristem limitation due to water or nutrient availability or management practices such as fire and grazing may constrain grassland responses to inter-annual changes in resource availability. An important consequence is that grasslands with a large bud bank may be the most responsive to future climatic change or other phenomena such as nutrient enrichment, and may be most resistant to exotic species invasions.

A vegetation survey, based on plant communities, was conducted on the Ezemvelo Nature Reserve. The aim of the study was to identify, describe and classify plant communities of Ezemvelo Nature Reserve, and interpret them ecologically. The information derived from this study can then be used in the management of the Reserve. The floristic composition and habitat information were recorded in 210 sample plots. The data was captured in the TURBOVEG database and classified using the TWINSPAN numerical classification algorithm. The resulting phytosociological tables were compiled and organised using the MEGATAB computerised table management programme according to Braun-Blaunquet procedures. The data was also subjected to a Detrended Correspondence Analysis (DECORANA), processed by the PCOrd numerical ordination programme, to confirm the results of the classification. The ordination also illustrates any environmental gradients controlling the existence and distribution patterns of the different plant communities. Twenty-two major plant communities and 4 sub-communities were identified, described, and ecologically interpreted. The localities of the plant communities are indicated on map, compiled by using GIS. The plant communities on the Reserve are distributed in a mosaic of woodlands, grasslands and wetlands, based on the heterogeneous habitats created by the variations in topography, which is typical of Bankenveld vegetation. / Dissertation (MSc (Botany))--University of Pretoria, 2007. / Plant Science / MSc / unrestricted

The objectives of this study were to obtain quantitative and qualitative data on the vegetation and environmental factors of the Cariboo Zone and to synthesize these data into an ecosystematic classification. Sample plots were chosen selectively according to criteria based on uniformity and discreteness. Vegetation was studied using the phyto-sociological methods of the Zürich-Montpellier School. On all plots data were also obtained for edaphic and physiographic factors. Based on floristic composition and environmental data the 131 plots were synthesized into a flexible ecosystematic classification in which eight orders, twelve alliances, twenty associations and six subassociations were described. The order Pseudotsugetalia menziesii with three associations dominated most of the forested areas, occurring on subhygric to subxeric habitats. The order Piceetalia glaucae with three associations occurred only marginally; always on subhygric to subhydric habitats. The order Koelerio -Agropyretalia spicati with eight associations dominated the grassland areas, occurring on fine textured soils of aeolian origin. The order Puccinellietalia airoidis with two associations dominated the saline-alkaline habitats. The orders Betuletalia glandulosae, Salicetalia, Scirpetalia validi, and Caricetalia rostratae were represented by single associations of restricted distributions. Soils representative of all six orders of the Canadian Soil Classification system were distinguished with Chernozemic and Brunizolic soils the most common. Melanization appeared to be the dominant soil-forming process and the soils were generally rich having high cation exchange capacities, high amounts of exchangeable cations and alkaline reactions. An examination of the population structures of the major tree species showed that Pseudotsuga menziesii had the widest amplitude and formed the climax forest cover over much of the Cariboo Zone. Picea glauca had a narrower amplitude and Pinus contorta and Populus tremuloides reached dominance only as pioneer species. Selected ecosystem units were characterized microclimatically. The Agropyrion spicati occupied microclimatically warm areas while the floristically related Stipion columbianae was present in areas with a cool microclimate. The Antennario - Poetum secundae and Stipetum richardsonii, although bordering associations, occupied microclimately distinct habitats. Forest communities were shown to develop at higher elevations where a cool microclimate prevails. Based on species significance data, plots were objectively grouped by the weighted-pair-group and the weighted-variable-group methods of cluster analysis. The resulting hierarchical arrangements of plots paralleled very closely the subjectively derived ecosystematic classification. On the dendrogram obtained by the weighted-variable-group method, associations were distinguished and their degree of homogeniety and ecological relationships were demonstrated. The forest-grassland boundary in the Cariboo Zone was assessed to be relatively stable and to be controlled by available soil moisture as related to soil texture. It was apparent though, that minor fluctuations in the boundary as a result of grazing and fire occur. Detailed topographic relationships of the associations were demonstrated and it was apparent that topography, which represents a complex of physiographic factors, is important in controlling the distribution of associations. Successional changes appeared to be operating at a slow rate and thus most of the associations described were in a stable condition. The Agropyretum spicati most closely approximated the climatic climax association, occurring on ridges and slopes. Other stable associations were rated as edaphic or topographic climaxes. The successional relationships of the associations were demonstrated within a monoclimax concept in which it was assumed that ultimately all associations would change into the climax as a result of soil weathering and peneplanation of the land. It was concluded that the gynecological approach and classification methods used allowed the presentation of data in an ecosystematic format which could be directly applied to range or forest management but could also serve as a basis for more detailed scientific studies. / Science, Faculty of / Botany, Department of / Graduate