Orientadores: Ricardo Ribeiro Rodrigues, Flavio Antonio Maes dos Santos / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-14T22:21:13Z (GMT). No. of bitstreams: 1 Farah_FabianoTurini_D.pdf: 1540946 bytes, checksum: 0e09d57826ae49c86eaf13c03ab0d5cc (MD5) Previous issue date: 2009 / Resumo: Não informado. / Abstract: Not informed. / Doutorado / Doutor em Biologia Vegetal

Dans cette thèse, nous étudions différentes structures de végétation issues de l’auto-organisation spatiale. Ce phénomène est visible dans des zones (semi-)arides où le potentiel d’évaporotranspiration dépasse sensiblement la moyenne des précipitations annuelles. Ce déficit hydrique freine le développement des plantes individuelles et, au niveau communautaire, stimule des comportements de « clustering » même si la topographie est isotrope. Dans ce contexte, nous adoptons une approche basée sur l’équation F-KPP non-locale permettant de formuler ces hypothèses en termes de propriétés des plantes individuelles.Une partie importante de cette thèse concerne l’étude d’un exemple de structure de végétation localisée bien connu dans la littérature, les cercles de fées. Les cercles de fées ont été découverts dans le désert de Namibie. Cependant, ces dernières années, ils ont aussi été observés en Australie. Plusieurs hypothèses ont été proposées dans la littérature. Nous proposons la compétition non-locale forte entre plantes individuelles (en utilisant un noyau de type Lorentzien) comme ingrédient principal pour expliquer la formation des cercles de fées. Le couplage non-local fort influence l’interaction entre fronts dans le régime bistable (loin de toute forme d’instabilité briseuse de symétrie). Dans le cas d’un couplage non-local faible, par exemple dans un noyau Gaussien, l’interaction entre fronts est toujours attractive. Par conséquent, les structures localisées qui résultent de l’interaction des fronts sont instables. Le couplage non-local fort peut induire la stabilisation de structures localisées que nous interprétons comme étant des cercles de fées. Notre mécanisme permet d’expliquer les principales caractéristiques des cercles de fées, comme la relation entre leur diamètre et la disponibilité des ressources. De plus, nous avons appliqué ces résultats à d’autres modèles de végétation. Nos résultats concordent avec les observations sur le terrain.Nous avons analysé la formation de « spots » de végétation dans la région Andine en Bolivie. Nous avons étudié comment un modèle standard d’interaction-redistribution génère des « spots », de longueur d’onde d'approximativement 1.36m, via une instabilité qui brise la symétrie. En considérant des paramètres réalistes, nos résultats concordent avec les observations sur le terrain.Enfin, nous avons étudié la formation de structure en forme de spirale dans un système qui couple la végétation et les herbivores dans un modèle proie-prédateur. Nous avons trouvé que le mécanisme qui induit la formation de spirales est l’excitabilité. Nos observations sur le terrain et nos résultats numériques du modèle montrent que les spirales de végétation ont une profondeur de quelques centimètres et une longueur de quelques mètres. En ce qui concerne l'échelle de temps, nos estimations donnent une période de rotation de l’ordre de 10 ans. / Option Physique du Doctorat en Sciences / info:eu-repo/semantics/nonPublished

This thesis deals with the use of remote sensing data for studying and monitoring vegetation changes. Thanks to archival materials, we can now make extensive studies at the landscape and global level without the need for large-scale old field data. From the Middle Ages, we can rely on different types of maps, for vegetation studies, these are mainly forestry maps. Since the 1930's, aerial photographs have been available in Europe, and satellite imagery was available since the 1970's. Availability and quality of satellite imagery had increased rapidly during my study. The most recent data source are unmanned aerial systems and methods of processing their data, which allow inexpensive detailed mapping of large areas. The presented publications do not only solve ecological research questions, but also contribute to solving current environmental problems in the Czech Republic, from nature conservation in National Parks and protected areas to monitoring of plant invasions. I have used archival forest maps for the reconstruction and analysis of large disturbances (windthrow and subsequent gradations of bark beetle) in forests of Šumava and the Bavarian Forest in 1868-1870. Species composition, as well as environmental factors derived from digital elevation model, were analyzed. The same topic was also...

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy / The study aimed to differentiate the effect of rainfall and grazing on the compositional change of savanna grasslands, and to explain responses in terms of the life history patterns of the main species, An extinction prone perennial grass under heiry grazing was identified as a palatable, obligate seed reproducer with low seed production and poor dispersal (e.g. Themeda triandra and Reteropogon contortus), wnich could become extinct if the established population and the seed bank were eliminated. Aristrida species were expected to show the converse pattern. Grazing was manipulated for three or five years, and rainfall for one year, on a sandveld site, and two clay soil sites which supported the same species in different amounts, respectively. (Abbreviation abstract) / Andrew Chakane 2019

No description available.

In order to understand vegetational gradients which develop in response to environmental gradients, the physiological capabilities of each species must be examined in relation to the observed environmental gradient. The distributions of three temperate zone shrub species which occupy different positions on the spur ridges of Brush Mountain may be influenced by their tolerances to light and moisture. Greenhouse studies indicate that <i>R. maximum</i> has a 60 % reduction in photosynthesis at water potentials below -1.0 MPa. <i>R. nudiflorum</i> has only a 30 % reduction and <i>K. latifolia</i> has less than 10 % reduction. Seasonal pressure volume curve determinations, conductance measurements, and water potential measurements of plants in the natural environment indicated that photosynthesis is not affected by water potential in <i>K. latifolia</i>. <i>R. maximum</i> has a significant reduction in conductance during drought which may limit photosynthesis. R. nudiflorum appears to begin senescence prior to severe drought in this area. Greenhouse experiments of adaptability to increasing light intensity show that <i>K. latifolia</i> and <i>R. nudiflorum</i> can significantly increase their light saturation point and maximum rate of photosynthesis in high light environments. <i>R. maximum</i> does not increase its photosynthesis rate in high light environments and appears to undergo chloroplast degradation when grown in high irradiance. Gradient analysis of vegetation on Brush Mountain shows that <i>R. maximum</i> reaches its highest importance in low light, high moisture sites. <i>K. latifolia</i> is most important in low moisture, high irradiance sites. <i>R. nudiflorum</i> is infrequent in the study area but occurs mostly in moderate moisture and irradiance sites. The distributions of <i>R. maximum</i> and <i>K. latifolia</i> appear to match their experimentally determined physiological tolerances. The results for <i>R. nudiflorum</i> are inconclusive. / Master of Science

This case study used Zhongwei City in northwest China to quantify the urbanization and revegetation processes (1990-2011) through a unified sub-pixel measure of vegetation cover. Research strategies included: (1) Conduct sub-pixel vegetation mapping (1990, 1996, 2004, and 2011) with Random Forest (RF) algorithm by integrating high (OrbView-3) and medium spatial resolution (Landsat TM) data; (2) Examine simple Dark Object Subtraction (DOS) atmospheric correction method to support temporal generalization of sub-pixel mapping algorithm; (3) And characterize patterns of vegetation cover dynamics based on change detection analysis. We found the RF algorithm, combined with simple DOS, showed good generalization capability for sub-pixel vegetation mapping. Predicted sub-pixel vegetation proportions were consistent for "pseudo-invariant" pixels. Vegetation change analysis suggested persistent urban development within the city boundary, accompanied by a continuous expansion of revegetated area at the city fringe. Urban development occurred at both the suburban and urban core areas, and was mainly shaped by transportation networks. A transition in revegetation practices was documented: the large-scale governmental revegetation programs were replaced by the commercial afforestation conducted by industries. This study showed a slight increase in vegetation cover over the time period, balanced by losses to urban expansion, and a likely severe degradation of vegetation cover due to conversion of arable land to desert vegetation. The loss of arable land and the growth of artificial desert vegetation have yielded a dynamic equilibrium in terms of overall vegetation cover during 1990 to 2011, but in the long run vegetation quality is certainly reduced. / Master of Science

[Truncated abstract] Ecologists are increasingly interested in quantifying local interacting processes and their impacts on spatial vegetation patterns. In arid and semiarid ecosystems, theoretical models (often spatially explicit) of dynamical system behaviour have been used to provide insight into changes in vegetation patterning and productivity triggered by ecological events, such as fire and episodic rainfall. The incorporation of aerial imagery of vegetation patterning into current theoretical model remains a challenge, as few theoretical models may be inferred directly from ecological data, let alone imagery. However, if conclusions drawn from theoretical models were well supported by image data then these models could serve as a basis for improved prediction of complex ecosystem behaviour. The objective of this thesis is therefore to innovate methods for inferring theoretical models of vegetation dynamics from imagery. ... These results demonstrate how an ad hoc inference procedure returns biologically meaningful parameter estimates for a germ-grain model of T. triandra vegetation patterning, with VLSA photography as data. Various aspects of the modelling and inference procedures are discussed in the concluding chapter, including possible future extensions and alternative applications for germ-grain models. I conclude that the state-and-transition model provides an effective exploration of an ecosystem?s dynamics, and complements spatially explicit models designed to test specific ecological mechanisms. Significantly, both types of models may now be inferred from image data through the methodologies I have developed, and can provide an empirical basis to theoretical models of complex vegetation dynamics used in understanding and managing arid (and other) ecological systems.

From the 1920's through 1951 several severe fires occurred in the predominantly conifer forest ecosystems of the northern Oregon Coast Range. Of the 211,151 ha. of mapped area, 57 percent was burned. The effects of frequent fires with high severity on forest ecosystems over time at the landscape level is not fully understood. A reconstruction of fire history was conducted to help investigate the effects of fire severity, frequency, and area extent on distribution of postfire tree regeneration, species composition, and stand tree size, as well as on current species composition and stand tree size. I hypothesized that: 1) vegetation patterns (1950's and 1988) would vary with time, because the persistence of disturbance effects (fire, logging, reforestation) on forest vegetative responses varied, and 2) environmental controls (topography, soil, climate) would become the primary influences when disturbance events were absent. In this study historical maps, sketches and notes were used to reconstruct spatial and temporal patterns of fires from the 1920's to 1951 and to identify unburned patches on a Geographic Information System. Relationships between fire regime and postfire and current vegetative patterns were tested. Constructing precise spatial data layers from early maps, produced before the availability of aerial photography or satellite image, was difficult. Historical map accuracy and quality were variable and poor by present day standards. Geographic reference points were used to transform inappropriate map scales. The reconstruction of spatial data was used to characterize spatial patterns of historic fires: my estimates of burn areas were similar to estimates in the literature. To reduce questionable data along fire and vegetation patch boundaries for hypothesis testing, an exclusion approach was used. Data within a 100 m width of fire and vegetation type boundary lines were called a fuzzy zone and removed from raw data. The distribution of various attributes in the reduced data was similar to the distribution of the complete data set. Regression analysis examined the effects of fire, logging, reforestation, topography, climate, and soil type on vegetation patterns. Patterns of postfire (1950's) species composition, tree regeneration and tree size (DBH) were associated with the effects of fires, as well as influences of logging and soil type. Indices of fire occurrences (reflecting the time variation and severity of fires) frequently correlated to the 1950's vegetation patterns. The number of fires (frequency) did not cause great differences in vegetation patterns. Current (1988) species composition and tree size (after absence of fire for more than three decades) were correlated more with terrain variables. Plant succession also influenced the current vegetation patterns. Neither the date or number of fires caused marked differences in distribution of species and tree size, except large conifers were found in areas missed by fires. Postfire and current vegetation patterns were correlated with soil types which reflect the influence of topographic and climatic characteristics. However, historic fires occurred frequently on some soil types. Fires have a confounding influence on soil type. This confounding influence of fire on soil type cannot be avoided. Reforestation efforts appeared to have little influence on the postfire and current vegetation patterns. I inferred that the short time period of reforestation effects did not show its importance on the 1950's vegetation landscape. Although regression analysis results did not support my hypothesis, by 1988, reforested area in the northern Coast Range had increased since 1950's. Most of the large fire-open patches became mixed forest in about 3 decades may still relate to the force of reforestation. On private unburned ownerships conifer forests in 1955 were subsequently cut and replaced by mostly mixed forest by 1988. The analysis supported the hypotheses that soil type, aspect and plant succession were dominant influences on current (1988) vegetation patterns, while forest disturbances such as fire and logging were important influences on the immediate postfire (1950's) patterns. The results not only interpret the relationship between historic disturbances and vegetation distribution, but may also serve as a useful background for the management of the future forest landscape. / Graduation date: 1998 / Presentation date: 1997-07-11

In the Florida Everglades, sawgrass has been displaced by cattail, predominantly resulting from phosphate enrichment. It has been found that phosphate transporters and arbuscular mycorrhizal (AM) fungi play an important role in phosphate uptake in the plants. This study aimed to reveal the symbiosis between AM fungi and sawgrass and cattail and identify the phosphate transporters, especially AM-specific phosphate transporters in these two species. AM colonization was only found in sawgrass roots, not cattail, at low phosphate concentrations in lab and field samples by trypan blue staining. AM fungi could increase sawgrass growth and had little effect on cattail growth. Four phosphate transporters were identified in sawgrass. CjPT1, CjPT2 and CjPT3 were expressed in roots and shoots independent of AM fungi and phosphate availability, while CjPT4 appeared to be an AM regulated phosphate transporter gene and its expression was induced by AM fungi. / by Li Lin. / Thesis (M.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.