Thesis (Ph.D.)--University of Central Florida, 2009. / Adviser: Pedro F. Quintana-Ascencio. Includes bibliographical references.

Made available in DSpace on 2016-03-07T19:20:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-07-22. Added 1 bitstream(s) on 2016-03-07T19:23:58Z : No. of bitstreams: 1 000858190.pdf: 497225 bytes, checksum: 49429e3ce57d24db8c035352d28bb8ea (MD5) / O Brasil destaca-se como um dos maiores produtores de pimenta no mundo. Dentre as cultivares mais produzidas, a pimenta dedo-de-moça (Capsicum baccatum) apresenta grande relevância. Os carurus (Amaranthus spp.) são plantas com grande potencial de interferência em áreas olerícolas devido às condições favoráveis fornecida pelo ambiente agrícola, notadamente nos estágios iniciais de crescimento das culturas. Assim, objetivou-se avaliar a interferência do caruru-roxo (A. hybridus) nas características de crescimento e produtivas da pimenta dedo-de-moça. Para isso, se utilizou como parcelas caixas de fibrocimento em que se manteve a população da pimenta dedo-de-moça fixada em uma planta no centro da caixa e variou-se a população de caruru-roxo em densidades crescentes de 1, 2, 3 e 4 plantas 0,36 m2, distantes 5 e 10 cm da pimenteira. O delineamento experimental utilizado foi o inteiramente casualizado, sendo que para a pimenteira, os tratamentos foram dispostos no esquema fatorial 2x4+test, que corresponderam a duas distâncias, quatro densidades de caruru-roxo e testemunha isenta da presença de planta daninha. Foram avaliadas características de crescimento e produtividade da pimenta dedo-de-moça até os 90 dias após o plantio. O caruru-roxo apresentou interferência negativa sobre a pimenta dedo-de-moça independente da distância e densidade, para as características de crescimento apenas o diâmetro do caule foi afetado aos 45 DAP e para as características produtivas numero de frutos, massa fresca de frutos, massa seca de frutos, sementes, folhas e caule, todas foram afetadas apresentando grande redução do potencial produtivo da cultura. O caruru-roxo também apresentou redução no acumulo de massa seca independente da distancia e da densidade em que se encontravam / Brazil stands out as one of the world's largest pepper growers. Among the most produced cultivars, Aji Amarillo pepper (Capsicum baccatum L.) are highly relevant. The pigweeds (Amaranthus sp.) are plants with great interference potential with crops due the favorable conditions provided by the agricultural environment, particularly in the early stages of crop growth. Therefore, this study aimed to evaluate the interference of smooth pigweed (Amaranthus hybridus) on growth and productive characteristics of Aji Amarillo pepper. In order to do so, cement boxes were used as experimental parcels in which the proportion of pepper population was fixed, in the center of the box, varying the population smooth pigweed in the increasing densities of 1, 2, 3, and 4 plants 0.36 m2, at 5 and 10 cm distance from the pepper plant. The experimental design was completely randomized, and for the pepper, the treatments were arranged in a 2x4 factorial design + control, corresponding to two distances and four densities of smooth pigweed, and a weed free control parcel. Growth and productivity characteristics were evaluated until 90 days after planting. The smooth pigweed showed negative interference with Aji Amarillo pepper regardless of distance and density for growth characteristics, being only the stem diameter affected at 45 DAP, and the productive characteristics of fruit number, fresh fruit matter, dry matter of fruits, seeds, leaves and stem, all were affected, featuring greatly reduction in the crops potential productivity. Smooth pigweed also decreased in biomass accumulation, independent of distance and density it was planted

Mycorrhizae have been used in restoration for decades. However, studies assessing the use of mycorrhizae in Bromus tectorum-invaded areas of the Great Basin are limited. Two greenhouse pot experiments were conducted to assess the role of mycorrhizae in sagebrush restoration. The first objective (Chapter 2) was to determine the response of Pseudoroegneria spicatum, Elymus elymoides, and B. tectorum to mycorrhizal symbiosis by altering phosphorus, density, species, presence of mycorrhizae and water levels in a 5 factor design. To assess the mycorrhizal response, a variety of morphological and physiological traits were measured, such as tissue P concentration, specific root length, specific leaf area, carbon isotope discrimination, etc. The effects of the different treatment combinations were analyzed using ANOVA. The second objective (Chapter 3) was to determine the role of different inocula in competition between the three grasses. Species, density, and inoculum type were altered in a 3 factor design. Inoculum was cultured on Allium plants. The effect of locally cultured inoculum on the species was compared to the effect of commercial inoculum. The response of each species to mycorrhizae with different species compositions and densities was assessed. Morphological measurements were used to determine each species response to the different factor combinations. The effects of the different treatment combinations were analyzed using ANOVA. This research provides land managers with information regarding the efficacy of using local versus commercial inocula and whether they should use mycorrhizae in restoring their systems.

Relationships between nutrient heterogeneity, root foraging behavior and short-term competitive interactions were investigated for six species native to southeastern USA. Monoculture, two- and six-species garden plots were established and fertilized to create spatially homogeneous or heterogeneous nutrient conditions. After 3.5 months, root proliferation in rich patches (precision) and aboveground biomass response to heterogeneity were assessed in monocultures, and competitive outcomes (aboveground biomass) were determined from mixed-species plots. In monoculture plots, two species were relatively precise foragers, but no species showed significant aboveground biomass response to nutrient treatment. Correlations between precision and aboveground biomass were weak (-0.40 < r < 0.17). In two-species plots, interspecific competition was influenced by soil heterogeneity in two of six cases tested (P < 0.05), and precision was the behavior most correlated with competitive success. In six-species plots, spatial pattern of nutrients had no influence on aboveground growth or competition. Results suggest that heterogeneity influences competition, but the influence is context-specific and generally small. Precision may be the foraging behavior that most influences interspecific interactions. / Ph. D.

Orientador: Pedro Luís da Costa Aguiar Alves / Banca: Davi Rodrigo Rossatto / Banca: Roberto Estêvão Bragion de Toledo / Resumo: O objetivo neste trabalho foi avaliar a coexistência de Urochloa decumbens (capim-braquiária) e Synedrellopsis grisebachii (agriãozinho) e elucidar detalhes sobre a interferência entre as mesmas. Foram realizados dois experimentos: um modelo substitutivo, para determinar as interferências intra e interespecíficas das espécies em monocultivo e em coexistência, e um modelo substitutivo em dialelo com divisórias permeável e impermeável para avaliação da coexistência e do potencial alelopático entre as duas espécies. Para a determinação da população crítica a ser usada no experimento substitutivo, foram plantadas nas densidades de 1, 2, 4, 8, 16, 24 e 32 plantas por vaso cada uma das espécies e colhidas, secadas e pesadas as partes aéreas, para serem analisadas por meio de análise de regressão. O experimento substitutivo teve como proporções porcentuais de capim-braquiária e agriãozinho, respectivamente, 100:0, 75:25, 50:50, 25:75 e 0:100. Foram colhidas as partes aéreas e analisadas pelos métodos qualitativos e quantitativos. O ensaio substitutivo em dialelo consistiu no plantio de quatro ou oito plantas em caixas contendo areia, onde foram plantados o capim-braquiária e o agriãozinho em monocultivo ou em coexistência, sendo que foram analisados três tratamentos dentro dos cultivos: uma divisória permeável, uma impermeável e nenhuma divisória. Foi realizada análise de variância e análise por índices ecológicos para determinar a capacidade competitiva. Foram necessárias 16 plantas para a população crítica do capim-braquiária. A análise qualitativa indica que as duas espécies têm decréscimo na produção de biomassa em coexistência. A análise quantitativa indica que o agriãozinho possui maior competitividade que o capim-braquiária nos estágios iniciais, fato que pode ser devido a um efeito alelopático / Abstract: This study evaluates the coexistence of Urochloa decumbens (Surinam grass) and Synedrellopsis grisebachii (Cinderella weed). Two experiments were conducted: a replacement series, to determine intra and interspecific interferences of both species grown in monoculture and in coexistence, and a diallel replacement series using permeable and impermeable barriers between said species to evaluate allelopathic and general interference among them. In order to determine the critical population density to be used in the replacement series, 1, 2, 4, 8, 16, 24 and 32 plants were planted in the same box and harvested 40 days after, dried and weighted, to be analyzed trough regression analysis. Replacement series experiment used the percentage densities for Surinam grass and Cinderella weed of 100:0, 75:25, 50:50, 25:75 and 0:100. The above-ground parts were harvested, dried and analyzed through qualitative and quantitative methods. The diallel replacement series consisted of four or eight plants in sand-filled boxes on growth chamber environment, being the species grown in monoculture or coexisting with each other, and three treatments were analyzed: a permeable one, an impermeable one and one without barrier between the plants. Analysis of variance and ecological coefficient analysis were performed to determine the competitive capacity. 16 plants per vase were needed for the Surinam grass to achieve the critical population. Qualitative analysis show there is mutual harm to the dry matter allocation of both species. Quantitative analysis shows Cinderella weed as a better competitive species than signal grass during the initial growth phase, fact which may be caused on account of allelopathic processes / Mestre

Orientador: Silvano Bianco / Banca: Mariluce Pascoina Nepomuceno / Banca: Robinson Luiz de Campos Machado Pitelli / Banca: Eduardo Andrea Lemus Erasmo / Banca: Carlos Alberto Mathias Azânia / Resumo: O sistema de colheita no cultivo da cana-de-açúcar influencia a comunidade das plantas daninhas, particularmente a época e a duração do período de convivência com a cana-de-açúcar, que podem prejudicar o desenvolvimento, a produtividade e a qualidade tecnológica da cana. Diante dessa hipótese objetivou-se identificar a interferência de plantas daninhas na produtividade e qualidade tecnológica da cana-de-açúcar em manejo de cana-crua e cana-queimada. Foram conduzidos dois experimentos no Estado de Minas Gerais (Triângulo Mineiro) no período de julho de 2012 a julho de 2013. Cada experimento, sendo um de canacrua e um de cana-queimada, foram conduzidos no delineamento de blocos casualizados, com 16 repetições, com dois tipos de manejo das plantas daninhas (presença e ausência) e nove épocas de avaliação (15, 30, 45, 60, 75, 90, 105, 120 e 145 dias após a brotação). Foram avaliados, para as plantas daninhas, os índices fitossociológicos: densidade relativa, frequência relativa, dominância relativa e importância Relativa. Com base nas equações de regressão sigmoidal, estimou-se o período anterior à interferência, o período total de prevenção à interferência e o período crítico de prevenção à interferência das plantas daninhas na cultura da cana-de-açúcar, aceitando-se 2 e 5% de redução na produtividade. Para a qualidade do caldo da cana foram colhidos, manualmente, 10 colmos aleatórios e encaminhado para o Laboratório de PCTS da Usina Cerradão, no qual foram determinados os dados de pH, brix, fibra, pureza e ATR sendo analisados separadamente, dentro de cada fator e suas interações. O manejo da espécies S. obtusifolia, S. latifolia e R. brasiliensis, quando realizado entre 75 e 80 dias após a brotação (DAB) da cana-de-açúcar colhida sem prévia queima ou 72 e 103 DAB reduziu a produtividade da cultivar RB86 7615 em 5%, sem consequência à qualidade do caldo / Abstract: The harvest system of sugarcane crops affects the weed community, specially the time and duration of weed, presence, which may affect it's development, productivity (yield) and technical quality. Based on this hypothesis, the aim of this work is to evaluate weed interfere on yield ad technical quality of sugarcane harvest with and without burning. The experiments were carried out in a randomized block design, with two treatments (burning and mechanic harvested), nine weed and weed-free periods (15, 30, 45, 60, 75, 90, 105, 120 and 145 days after sprouting), with sixteen repetitions. Weed community in each period was evaluated through to the following phytosociological indexes: relative density, relative frequency, relative dominance and Relative Importance. Based on sigmoidal regression equation, total weed free period and critical weed periods were calculated, accepting to a yield loss tolerance of 2 and 5%. Ten stems were randomly collected and sent to PCTS lab at Cerradão mill where they were analyzed for pH, brix, fiber content, purity and ATR. The handling of the species S. obtusifolia, S. latifolia and R. brasiliensis, when accomplished between 75 and 80 days after the sprouting (DAB) of the sugarcane picked without opinion poll burns or 72 and 103 DAB reduced the productivity of cultivating RB86 7615 in 5%, without consequence to the quality of the broth / Doutor

Medusahead (Taeniatherum caput-medusae ssp. asperum (Simk.) Melderis) is a Eurasian annual grass that infests large areas of U.S. rangelands, dominating former bunchgrass/shrub sites. Squirreltail (Elymus elymoides (Raf.) Swezey) is a native perennial grass that has demonstrated the ability to establish in stands of medusahead. A study conducted on two sites near Burns, OR had the objectives of quantifying competition between medusahead and squirreltail, and determining the effect of moisture availability on competition. Two hundred plots were arranged in a factorial design. Measurements were taken of plant growth, seed production, soil moisture, and climate. Results for the two years are contrasting. The first year was very dry. Medusahead grew and reproduced well, producing a seed crop up to 10 times the amount planted; squirreltail grew poorly and did not reproduce. Samples of squirreltail seed retrieved from the plots in late summer were found to have remained dormant since seeding. The second year had above-average precipitation. Medusahead grew and reproduced well again. Squirreltail grew and reproduced abundantly on one of the sites, both on freshly-seeded plots and on plots containing dormant seeds and surviving plants from the previous year. In all cases, medusahead exhibited stronger interspecific and intraspecific competitive effects than did squirreltail seedlings. With adequate soil moisture, squirreltail reduced average weight and median seed production of individual medusahead plants, but did not reduce medusahead seed production per square meter. Medusahead succeeded in a drought year by utilizing deep soil moisture, and utilized shallower moisture in a wet year. During a wet year in plots containing mature squirreltail, medusahead utilized shallower moisture, while squirreltail strongly utilized much deeper moisture. Interspecific competitive interference by medusahead on squirreltail seedlings suggests the potential benefits of suppressing medusahead during the seeding year for squirreltail in a rehabilitation effort, especially if climatic conditions are conducive to squirreltail germination and establishment. / Graduation date: 1997

Three general questions are studied regarding plant carbon allocation strategies. (1) The R* Rule states that the superior competitor in a plant community should exclude all others by minimizing available limiting nutrient concentration below the level needed for survival of its competitors. I asked whether a plant carbon allocation strategy that minimizes the concentration of available limiting nutrient is consistent with Lotka's (1922) conjecture that ecosystems should evolve to maximize total energy flow (primary production). (2) In landscapes such as the Everglades, areas of landscape with higher energy flow (primary production) than the surrounding area also have higher available concentrations of limiting nutrient, rather than lower concentrations, which might be expected from the R* rule. I asked whether this pattern can be explained. (3) I asked how optimal allocation of carbon to plant defense allocation strategies might depend on different conditions of nutrient availability, shading, and herbivory. To address all three questions, I used a model revised from the G'DAY model (Comins and McMurtrie 1993) to study tree allocation of carbon resources between foliage, roots, and defense. With regard to the first question, I found that the allocation strategy that leads to minimum concentration of available nutrients is the same as the strategy for which energy flux to roots, rather than total energy flux, is maximized. Further, I found that the strategy that was competitively dominant was neither the strategy for which total energy flux was maximized, nor that for which available nutrient concentration was minimized. With regard to the second question, I found that, if a patch of vegetation on a landscape is able to capture nutrients from the surrounding landscape, for example, through relatively higher evapotranspiration, it could lead to the opposite of what is expected from the R* rule; that is, available limiting nutrient concentration is maximized when carbon flow to the roots is maximized. With regard to the last question, I found that under high herbivory, the optimal plant strategy for allocation of carbon to defense depends on the available nutrient concentration and amount of radiation to the plant, in agreement with some theoretical predictions.

Der Anteil an nicht-einheimischen Pflanzenarten (Neophyten), die durch menschlichen Einfluss in neue Gebiete eingebracht worden sind, hat in den letzten zwei Jahrhunderten deutlich zugenommen. Weltweit gefährdet die Invasion von Neophyten beträchtlich die einheimische Biodiversität und Ökosystemfunktionen. Verschiedene biologische Eigenschaften (z.B. hohe Zuwachsrate und schnelle Vermehrung) führen zu einer besseren Konkurrenzfähigkeit von invasiven Arten und verursachen Veränderungen in der natürlichen Artzusammensetzung. Eine genauere Erfassung der Eigenschaften, die Neophyten zu starken Konkurrenten machen, könnte dabei helfen pflanzliche Invasionen besser zu verstehen und zukünftig effektiver zu steuern. Topfversuche ermöglichen die Untersuchung von Pflanzeninteraktionen unter kontrollierten Bedingungen ohne den schwer kalkulierbaren Einfluss heterogener Umweltfaktoren. Allerdings führen die Langlebigkeit und die größeren Dimensionen von Baumindividuen zu mehr Problemen in Topfversuchen im Vergleich zur Untersuchung krautiger Pflanzen. Aus diesem Grund wurde im Rahmen eines Reviews Literatur ausgewertet, um einen Überblick über die praktische Durchführung von Topfversuchen, die sich ausschließlich mit Baumarten beschäftigen, zu geben. Es ist offensichtlich, dass der Vorteil von Topfversuchen zugleich auch einen Nachteil darstellt: Aufgrund der kontrollierten Bedingungen sind Topfversuche in ihrer Eignung natürliche Gegebenheiten zu imitieren immer eingeschränkt. Die Zuverlässigkeit von Topfversuchen bei der Vorhersage des Baumwachstums unter natürlichen Bedingungen ist daher problematisch. Eine Möglichkeit um die Übertragbarkeit von Topfversuchen zu verbessern, könnte die Durchführung zusätzlicher Felduntersuchungen sein. In einem Topfversuch wurden die, durch Unterschiede in der Wuchsrate, Biomasseproduktion und Biomasseverteilung bedingten, Konkurrenzmechanismen von zwei einheimischen (Quercus robur L., Carpinus betulus L.) und zwei nicht-einheimischen Baumarten untersucht (Prunus serotina Ehrh., Robinia pseudoacacia L.). Einjährige Jungpflanzen wurden verschiedenen intra- und interspezifischen Konkurrenzbedingungen ausgesetzt, mit oder ohne den Einfluss von Wurzelkonkurrenz. Um die Konkurrenzmechanismen genauer zu bestimmen, wurde zwischen Wurzel- und Sprosskonkurrenz unterschieden, indem entweder ober- oder unterirdische Plastiktrennwände in die Töpfe integriert wurden. Es wurde angenommen, dass die Gesamtbiomasseproduktion der Neophyten im Vergleich zur Biomasseproduktion der einheimischen Baumarten signifikant höher ist und dies zu einer Verringerung der Biomasse von Q. robur und C. betulus führt. Des Weiteren wurde der Einfluss der unterirdischen Konkurrenz auf das Wachstum und die Biomasseverteilung der einheimischen Arten gemäß der ‚balanced-growth hypothesis‘ untersucht. Unsere Ergebnisse bestätigen die Annahmen, dass die Biomasseproduktion der beiden Neophyten P. serotina und R. pseudoacacia signifikant höher ist und dies zu einem großen Konkurrenzvorteil und zu einer Biomassereduktion der beigemischten konkurrenzschwächeren einheimischen Arten führt. Der Konkurrenzdruck auf Q. robur und C. betulus wurde vor allem durch die Wurzelkonkurrenz der nicht-einheimischen Arten verursacht. Die Ausschaltung von unterirdischen Pflanzeninteraktionen durch Trennwände führte somit zu einem Anstieg der Biomasseproduktion der beiden einheimischen Arten. Demzufolge scheint sogar ein begrenztes Wurzelvolumen bessere Wachstumsbedingungen zu bieten als direkter Wurzelkontakt mit invasiven Konkurrenten. In Übereinstimmung mit der ‚balanced-growth hypothesis‘ reagieren Q. robur und C. betulus auf die starke unterirdische Konkurrenz durch die Neophyten, indem sie mehr Biomasse in Richtung der Wurzeln transportieren. Die verstärkte Investition der Pflanzen in die Wurzeln geht vor allem zu Lasten von Blatt- und Astbiomasse. Außerdem hat sich gezeigt, dass Artenmischungen aus einheimischen und nicht-einheimischen Bäumen mehr Biomasse produzieren, als man anhand des Wachstums dieser Arten in Monokulturen erwartet hätte. Im Vergleich zu Monokulturen oder Mischungen beider Neophyten war der Konkurrenzdruck für P. serotina und R. pseudoacacia in Mischungen mit den weniger produktiven einheimischen Baumarten geringer. Bei Betrachtung der beiden nicht-einheimischen Arten wird deutlich, dass P. serotina signifikant mehr Biomasse produziert. Trotzdem hat R. pseudoacacia aufgrund der starken Wurzelkonkurrenz einen negativen Einfluss auf die Biomasseproduktion von P. serotina. Wachsen die beiden konkurrenzstarken Neophyten zusammen in einem Topf, produzieren sie weniger Biomasse als in den entsprechenden Monokulturen. Es gibt Anzeichen dafür, dass die starke Konkurrenzfähigkeit der invasiven Neophyten oftmals zu Lasten ihrer Stresstoleranz geht. Damit einhergehend zeigten die beiden nicht-einheimischen Arten im Topfversuch eine höhere Mortalitätsrate: Vor allem P. serotina scheint zudem empfindlich gegenüber Schatten, Trockenheit und Überflutung zu sein. Möglicherweise könnte diese Schwachstelle der Neophyten genutzt werden, um eine weitere Ausbreitung einzudämmen.

The difference in the ability of plants to obtain resources has been used to predict the competition outcomes. Competitive interactions between plants can be influenced by trophic interactions. If mycorrhizae increase the growth of inferior competitors, then it can prevent competitive exclusion. I examined the effect of mycorrhizae on competitive interactions and found that inferior competitors had slow growth in the absence of mycorrhizae, but greater growth with mycorrhizae. By providing greater growth responses to inferior versus superior competitors, mycorrhizae promoted coexistence. In a separate experiment, I looked at the effects of whole soil biota on competitive ability. Coexistence can occur if dominant competitors experience negative feedback and or if inferior competitors experience positive feedback. I examined Plantago lanceolata L. specific feedback effects on competitive ability of 21 co-occurring species. I found that feedback effects did not affect hierarchies, and that positive feedback did not improve species competitive ability. / NSERC (Natural Science and Engineering Research Council), University of Guelph, Queen Elizabeth II Graduate Scholarship for Science and Technology