Study was conducted to evaluate in vitro digestibility of native warm-season grasses. Three grasses were used: big bluestem (Andropogon gerardii Vitman), little bluestem (Schizachyrium scoparium Nash), and indiangrass (Sorghastrum nutans Nash). There were no differences in NDF, ADF, FAT and OM of the three grass species. However, DM, hemicellulose and CP were slightly different in the three grass species. Also, the frequency nested in cutting effects was determined. In vitro dry matter disappearance of big bluestem, little bluestem and indiangrass was evaluated to determine rate of disappearance. The 100 % indiangrass revealed the greatest rate of disappearance for IVDMD and 100 % little bluestem grass the least, respectively. However, that of other proportion mixtures of treatments and 100 % big bluestem grass were in between. There were no differences in in vitro neutral detergent fiber disappearances among treatments.

No description available.

<p>Control of weeds that have survived a postemergence (POST) herbicide often need to be controlled in order to prevent seed production and interference with crops. The most efficacious herbicides and timings used for respray applications has not been determined in many problematic weed species. Previous research has demonstrated that weeds clipped to simulate a failed herbicide application responded differently to herbicide applications to regrowth based on herbicide used and weed species. Other research is conflicting as to the optimum timing of an herbicide respray application with various herbicides. Gaining a better understanding of how to maximize respray herbicide performance will help growers and land managers to preserve crop yield and prevent weed seed production in the event of POST contact herbicide failure. The objectives of this research were to determine the optimum respray herbicide and timing combinations for control of four problematic weed species in the midwestern United States that have survived an application of either glufosinate or fomesafen: waterhemp<i> </i>[<i>Amaranthus tuberculatus</i> (Moq.) J. D. Sauer], Palmer amaranth (<i>Amaranthus palmeri</i> S. Watts), giant ragweed (<i>Ambrosia trifida</i> L.), and horseweed (<i>Erigeron canadensis</i> L). Through a series of field and greenhouse experiments we determined that respray herbicide, respray application timing, initial herbicide, and level of injury from the initial application influence efficacy of the respray herbicide in a species-specific manner. Waterhemp regrowth following a failed glufosinate application was controlled most effectively by applying glufosinate or fomesafen 7 to 11 days after initial treatment. When following fomesafen, applications of 2,4-D 3-7 days after initial treatment or glufosinate 7 to11 days after initial treatment were most effective. Control of Palmer amaranth regrowth following either initial herbicide is best achieved with respray applications of glufosinate, fomesafen, or 2,4-D applied no later than 7 days after initial treatment. The best strategy to control giant ragweed regrowth following a failed fomesafen applications is to apply 2,4-D, dicamba, fomesafen, or glufosinate at any timing between 3 and 11 days after initial treatment. Efficacy of the respray glufosinate application was maximized when applied 11 days after the initial application rather than 3 days after initial application. Horseweed regrowth was best controlled by 2,4-D, dicamba, or glufosinate applied at any timing between 3 and 11 days after the initial application. Where injury from the initial herbicide application is high, there were fewer differences among herbicide treatments and treatment timings. A greenhouse bioassay revealed that as waterhemp injury from an initial glufosinate application increases, control with a respray herbicide also increases. Therefore, complete control of weed regrowth is achieved more easily with increasing injury from the initial application. This research suggests that timing of herbicide respray applications is more urgent than previously thought, so scouting must be done within days of a contact herbicide application to ensure adequate control. </p>

Made available in DSpace on 2014-06-11T19:22:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-08-28Bitstream added on 2014-06-13T19:07:35Z : No. of bitstreams: 1 siqueira_gf_me_botfca.pdf: 855761 bytes, checksum: 59ef306636208d8e19ab66bbdaa297ed (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A maturação natural, em início de safra, pode ser deficiente, mesmo em variedades precoces e o emprego de maturadores químicos destaca-se como uma ferramenta importante para antecipar o processo de maturação, promover melhorias na qualidade da matéria-prima a ser processada, otimizar os resultados agro-industriais e econômicos e auxiliar no planejamento da safra. Dentre os produtos utilizados, o glifosato é um dos que proporciona maior eficiência na antecipação da colheita, contudo, frequentemente diminui a rebrota da soqueira reduzindo a produtividade do canavial na safra posterior. Técnicos e produtores têm misturado o glifosato a outros maturadores, sem embasamento técnico-científico, acreditando melhorar a eficiência desses e como forma de redução de custo. O projeto teve por objetivo estudar a eficácia da mistura de glifosato a sulfometuron metil ou etil-trinexapac, e as alterações fisiológicas na cana-de-açúcar bem como suas implicações na produtividade, qualidade tecnológica e na rebrota da soqueira, em aplicação em início de safra. O projeto de pesquisa foi instalado e conduzido nos anos agrícolas de 2007 e 2008 em cana soca, em área pertencente ao GRUPO COSAN, Unidade Barra, no município de Igaraçu do Tietê, Estado de São Paulo. O delineamento experimental utilizado foi em blocos casualizados com cinco repetições. O experimento foi constituído de seis tratamentos: 1 – testemunha, sem aplicação de maturador, 2 - aplicação de glifosato (produto comercial Roundup), 3 - aplicação de sulfometuron metil (produto comercial Curavial), 4 - aplicação de etil-trinexapac (produto comercial Moddus), 5 - aplicação da mistura glifosato + sulfometuron metil e 6 - aplicação da mistura glifosato + etil-trinexapac. As doses... / The natural maturation, early harvest, may be poor, even in early varieties and the use of chemical ripeners stands out as an important tool to advance the maturation process, further improvements in the quality of raw material to be processed, optimize results agro-industrial and economic and assist in the planning of the harvest. Among the products used, glyphosate is one that provides greater efficiency in anticipation of the harvest, however, often reduces the regrowth of the ratoon cane reducing the productivity of sugarcane in crop later. Technicians and producers have mixed the glyphosate with other ripeners, without basement technical-scientific, believing to improve the efficiency and as to reduce costs. The project aimed to study the effectiveness of the mixture of glyphosate to sulfometuron methyl or ethyltrinexapac, and physiological changes in sugar cane and its implications on productivity, technological quality and in the regrowth of the ratoon cane in application beginning of the season. The study was installed and conducted in the years 2007 and 2008 in ratoon cane, in area belonging to the COSAN GROUP, Barra Unit, in Igaraçu do Tietê, São Paulo. The experimental design was in a randomized block design with five replications. Each experiment consisted of six treatments (1 - control, without application of ripener, 2 - application of glyphosate (commercial product Roundup), 3 - application of sulfometuron methyl (commercial product Curavial), 4 - application of ethyl-trinexapac (commercial product Moddus), 5 - application of the mixture glyphosate + sulfometuron methyl and 6 - application of the mixture glyphosate + ethyl-trinexapac. The doses were, respectively: 0,4 L c.p. ha-1, 20 g ha-1, 0,8 L c.p. ha-1, 0,2 L c.p. ha-1 + 15 g c.p. ha-1 e 0,2 L c.p. ha-1 + 0,5 g c.p. ha-1. The variety... (Complete abstract click electronic access below)

Semiconductor lasers based on gallium arsenide and relatedmaterials are widely used in applications such as opticalcommunication systems, sensing, compact disc players, distancemeasurement, etc. The performance of these lasers can beimproved using a buried heterostructure offering lateralcarrier and optical confinement. In particular, if theconfinement (burying) layer is implemented by epitaxialregrowth of an appropriate aluminium-free semi-insulating (SI)material, passivation of etched surfaces, reduced tendency tooxidation, low capacitance and integration feasibility areadditional advantages. The major impediment in the fabrication of GaAs/AlGaAsburied-heterostructure lasers is the spontaneous oxidation ofaluminium on the etched walls of the structure. Al-oxide actsas a mask and makes the regrowth process extremely challenging.In this work, a HCl gas-basedin-situcleaning technique is employed successfully toremove Al-oxide prior to regrowth of SI-GaInP:Fe and SI-GaAs:Fearound Al-containing laser mesas by Hydride Vapour PhaseEpitaxy. Excellent regrowth interfaces, without voids, areobtained, even around AlAs layers. Consequences of usinginadequate cleaning treatments are also presented. Regrowthmorphology aspects are discussed in terms of different growthmechanisms. Time-resolved photoluminescence characterisation indicates auniform Fe trap distribution throughout the regrown GaInP:Fe.Scanning capacitance microscopy measurements demonstrate thesemi-insulating nature of the regrown GaInP:Fe layer. Thepresence of EL2 defects in regrown GaAs:Fe makes more difficultthe interpretation of the characterisation results in the nearvicinity of the laser mesa. GaAs/AlGaAs buried-heterostructure lasers, both in-planelasers and vertical-cavity surface-emitting lasers, withGaInP:Fe as burying layer are demonstrated for the first time.The lasers exhibit good performance demonstrating thatSI-GaInP:Fe is an appropriate material to be used for thispurpose and the suitability of our cleaning and regrowth methodfor the fabrication of this type of semiconductor lasers.Device characterisation indicates negligible leakage currentalong the etched mesa sidewalls confirming a smooth regrowthinterface. Nevertheless, experimental and simulation resultsreveal that a significant part of the injected current is lostas leakage through the burying material. This is attributed todouble carrier injection into the SI-GaInP:Fe layer.Simulations also predict that the function of GaInP:Fe ascurrent blocking layer should be markedly improved in the caseof GaAs-based longer wavelength lasers. <b>Keywords:</b>semiconductor lasers, in-plane lasers, VCSELs,GaAs, GaInP, semi-insulating materials, hydride vapour phaseepitaxy, regrowth, buried heterostructure, leakage current,simulation.

<p>Semiconductor lasers based on gallium arsenide and relatedmaterials are widely used in applications such as opticalcommunication systems, sensing, compact disc players, distancemeasurement, etc. The performance of these lasers can beimproved using a buried heterostructure offering lateralcarrier and optical confinement. In particular, if theconfinement (burying) layer is implemented by epitaxialregrowth of an appropriate aluminium-free semi-insulating (SI)material, passivation of etched surfaces, reduced tendency tooxidation, low capacitance and integration feasibility areadditional advantages.</p><p>The major impediment in the fabrication of GaAs/AlGaAsburied-heterostructure lasers is the spontaneous oxidation ofaluminium on the etched walls of the structure. Al-oxide actsas a mask and makes the regrowth process extremely challenging.In this work, a HCl gas-based<i>in-situ</i>cleaning technique is employed successfully toremove Al-oxide prior to regrowth of SI-GaInP:Fe and SI-GaAs:Fearound Al-containing laser mesas by Hydride Vapour PhaseEpitaxy. Excellent regrowth interfaces, without voids, areobtained, even around AlAs layers. Consequences of usinginadequate cleaning treatments are also presented. Regrowthmorphology aspects are discussed in terms of different growthmechanisms.</p><p>Time-resolved photoluminescence characterisation indicates auniform Fe trap distribution throughout the regrown GaInP:Fe.Scanning capacitance microscopy measurements demonstrate thesemi-insulating nature of the regrown GaInP:Fe layer. Thepresence of EL2 defects in regrown GaAs:Fe makes more difficultthe interpretation of the characterisation results in the nearvicinity of the laser mesa.</p><p>GaAs/AlGaAs buried-heterostructure lasers, both in-planelasers and vertical-cavity surface-emitting lasers, withGaInP:Fe as burying layer are demonstrated for the first time.The lasers exhibit good performance demonstrating thatSI-GaInP:Fe is an appropriate material to be used for thispurpose and the suitability of our cleaning and regrowth methodfor the fabrication of this type of semiconductor lasers.Device characterisation indicates negligible leakage currentalong the etched mesa sidewalls confirming a smooth regrowthinterface. Nevertheless, experimental and simulation resultsreveal that a significant part of the injected current is lostas leakage through the burying material. This is attributed todouble carrier injection into the SI-GaInP:Fe layer.Simulations also predict that the function of GaInP:Fe ascurrent blocking layer should be markedly improved in the caseof GaAs-based longer wavelength lasers.</p><p><b>Keywords:</b>semiconductor lasers, in-plane lasers, VCSELs,GaAs, GaInP, semi-insulating materials, hydride vapour phaseepitaxy, regrowth, buried heterostructure, leakage current,simulation.</p>

La réduction des dimensions des dispositifs CMOS (Complementary Metal Oxide Semiconductor) implique de nombreux défis dans la formation de jonctions. La recroissance par épitaxie en phase solide (SPER) à des températures inférieures à 600 °C est une technique attrayante dans la mesure où elle permet de réaliser des jonctions abruptes avec une forte concentration de dopants actifs et qui sont nécessaires pour les nœuds avancés tels que le 20 nm et au-delà. Dans ce manuscrit, on présente un modèle atomistique basé sur la méthode Monte-Carlo cinétique sur réseau (LKMC) afin de simuler la cinétique de SPER dans le silicium. Le modèle s'appuie sur la description phénoménologique des mécanismes microscopiques de recristallisation proposé par Drosd et Washburn dans [J. Appl. Phys. 53, 397 (1982)] en distinguant des événements {100}, {110} et {111} selon le plan local de recroissance et a été implémenté dans le simulateur MMonCa [Appl. Phys. Lett. 98, 233109 (2011)]. Il s'agit de la même base que le modèle de Martín-Bragado et Moroz [Appl. Phys. Lett. 95, 123123 (2009)] qui a été implémenté dans le simulateur commercial Synopsys SProcess KMC. Néanmoins, dans notre travail, la formation de macles lors des évènements {111} a été introduite ce qui a nécessité des changements importants dans l'implémentation. Le modèle a été calibré sur des résultats expérimentaux et permet de prédire l'anisotropie et la dépendance en température. En particulier, il a été utilisé afin d'expliquer la formation de zones défectueuses dans les dispositifs FDSOI à l'issue de la SPER à une température réduite. Le modèle LKMC a, en outre, été étendu dans le but d'inclure l'influence d'une contrainte non-hydrostatique et la recroissance accélérée du fait de la présence de dopants actifs. Les effets d'une contrainte non-hydrostatique ont été introduits en utilisant le concept de tenseur d'activation proposé par Aziz, Sabin et Lu dans [Phys. Rev. B 44, 9812 (1991)] et seulement quatre paramètres indépendants sont nécessaires. La présence de dopants ionisés cause une accélération de la vitesse de recroissance qui est attribué à un effet lié à la position du niveau de Fermi à l'interface amorphe/cristal. Un solveur 3D auto-cohérent de l'équation de Poisson avec le modèle de Thomas-Fermi a été implémenté et couplé avec le modèle LKMC afin de prendre en compte la courbure des bandes à l'interface amorphe/cristal. La correction phénoménologique de décalage du niveau de Fermi généralisé (GFLS) proposée par Williams et Elliman dans [Phys. Rev. Lett. 51, 1069 (1983)] a été utilisée pour modifier les fréquences de recristallisation des évènements microscopiques. Des simulations de la vitesse de recroissance en fonction de la température pour différentes concentrations de dopants ont montré un bon accord avec les données expérimentales. En résumé, dans ce manuscrit, un modèle unifié de SPER basé sur une approche LKMC est présentée. Il prend en compte l'influence de différents paramètres sur la cinétique de recroissance et ayant un intérêt technologique tels que la température, l'orientation cristalline, la contrainte et la présence de dopants. Le modèle est, en soi, tridimensionnel et permet donc d'explorer les phénomènes de recroissance impliquant plusieurs fronts de recristallisation et qui ont lieu lors du procédé de fabrication de dispositifs électroniques réels. / Complementary metal oxide semiconductor (CMOS) device scaling involves many technologicalchallenges in terms of junction formation. Solid phase epitaxial regrowth (SPER) at temperaturesbelow 600 ˝C is an attractive technique since it enables to form highly–activated andabrupt junctions that are required for advanced technology nodes such as 20 nm and beyond.In this manuscript, we present a comprehensive atomistic model relying on the lattice KineticMonte Carlo (LKMC) method to simulate SPER kinetics in silicon. The model is based onthe phenomenological description of the microscopic recrystallization mechanisms proposedby Drosd and Washburn in [J. Appl. Phys. 53, 397 (1982)] by distinguishing among {100},{110} and {111} events depending on the local regrowth plane and has been implemented inthe MMonCa simulator [Appl. Phys. Lett. 98, 233109 (2011)]. This is the same basis than theatomistic model of Martín–Bragado and Moroz proposed in [Appl. Phys. Lett. 95, 123123(2009)] and available in the Synopsys SProcess KMC commercial tool. Nevertheless, in ourwork the formation of twin configurations during {111} events has been incorporated givingrise to significant changes in the implementation. The model has been calibrated on single–directional SPER experiments and allows predicting the regrowth anisotropy and temperaturedependence. In particular, it has been used to explain the formation of defective regions inFDSOI devices annealed with a low processing temperature. In this work, the LKMC modelhas also been extended in order to include the influence of non–hystrostatic stress and dopant–enhanced regrowth that are technologically relevant. Non–hydrostatic stress effects have beenincorporated using the concept of activation strain tensor introduced by Aziz, Sabin and Luin [Phys. Rev. B 44, 9812 (1991)] and only four independent parameters are required. Thepresence of ionized dopants has been shown to cause an enhancement of the regrowth velocitywhich has been attributed to a Fermi level effect. A three–dimensional Thomas–Fermi–Poisson solver has been implemented and coupled with the LKMC model allowing to takeinto account the band bending at amorphous/crystalline interface. The phenomenological generalizedFermi level shifting (GFLS) correction proposed by Williams and Elliman in [Phys.Rev. Lett. 51, 1069 (1983)] has been used to modify the microscopic recrystallization rates.Simulations of the regrowth velocity as a function of temperature for different dopant concentrationshave shown a reasonable agreement with experimental data. In summary, in thismanuscript a unified SPER model relying on the LKMC approach is presented. It takes intoaccount various technologically relevant parameters influencing the regrowth kinetics such astemperature, crystalline orientation, stress and dopants. The model is per se three-dimensionaland can therefore be used to explore multi–directional regrowth phenomena that take place inreal electronic devices.

Oak habitats are rich in saproxylic species, but the habitat is declining with loss of diversity due to encroachment which decrease the vitality of oaks. The present explorative study compared results from a study conducted in 1994, with present species communities to observe if there has been change in species composition and what factors that can explain species diversity and composition. The results revealed that the overall species composition between 1994 and 2018 has changed. There were 130 species recorded in 2018 compared to 108 species in 1994 (31 new species were recorded in 2018, and 9 species lost from the study in 1994). There was a high species turnover recorded per individual tree, and the species composition between the living and encountered dead trees did not differ. Species composition was affected by canopy cover, and trunk circumference (CCA P-value 0.001 and 0.014 respectively). Unlike 1994, there were no variables in 2018 that could explain the association with species numbers. Warmer conditions recorded during the sampling period have probably led to increased flight activity of beetles and therefore increasing chances of capturing more species and individuals. The warmer conditions possibly shadowed the effects of the explanatory variables in explaining the changes in species numbers. Perhaps the change in species composition could also be attributed to existing management interventions that may be supporting an increasing species number of saproxylic beetles, however no strong conclusions could be drawn. Management interventions such as the recruitment of new oaks should be encouraged and intensified in order to provide habitats and support stable populations as the loss of oaks may lead to increased risk of extinction of the saproxylic beetles in the study area.

A estrutura do dossel e o acúmulo de forragem resultam de processos integrados de adaptação às condições ambientais e de manejo vigentes que incluem desde o fluxo de tecidos em indivíduos na comunidade vegetal até padrões de adaptação em nível de população de plantas. Baseado na hipótese de que estratégias de pastejo rotativo modificam as relações entre indivíduos da comunidade vegetal e alteram a proporção entre classes de perfilhos com consequências sobre a dinâmica dos processos morfogênicos e componentes do acúmulo de forragem do dossel o objetivo deste trabalho foi avaliar como estão integradas as respostas morfogênicas e as características estruturais de perfilhos basais e aéreos ao longo da rebrotação e seu reflexo sobre o acúmulo de forragem e estrutura do dossel de capim-elefante cv. Napier de janeiro de 2011 a abril de 2012. Os tratamentos corresponderam a combinações entre duas condições pós- (alturas pós-pastejo de 35 e 45 cm) e duas condições pré-pastejo (95% e máxima interceptação de luz - IL95% e ILMáx) e foram alocados às unidades experimentais (piquetes de 850 m2) segundo arranjo fatorial 2x2 e delineamento de blocos completos casualizados, com quatro repetições. Estratégias distintas de crescimento foram utilizadas pelo capim-elefante cv. Napier em resposta às metas de IL pré-pastejo. Estas foram caracterizadas por mudança na proporção e população das diferentes classes de perfilhos ilustrada pela maior relação aéreos/(basais+vasos condutores) nos pastos manejados com a meta ILMáx. A maior competição por recursos luminosos, função dos longos períodos de rebrotação para essa meta de IL pré-pastejo resultou em alongamento de colmos mais intenso e redução nas taxas de alongamento foliar por dia de filocrono durante as fases intermediária e final da rebrotação. Esse padrão de resposta, associado à menor velocidade de crescimento de perfilhos aéreos relativamente a basais, resultou em menores taxas de crescimento de folhas e maior taxa de crescimento de colmos, com consequente diminuição na taxa de acúmulo líquido de folhas nos pastos manejados com a meta ILMáx relativamente àqueles manejados com a meta IL95%. Pastos manejados com a meta IL95% apresentam alturas de dossel estáveis na condição pré-pastejo ao longo das épocas de maior disponibilidade de fatores de crescimento (85 cm). Maior relação aéreos/(basais+vasos condutores) foi verificada no outono e inverno, resultado que corrobora a expressiva participação de perfilhos aéreos nos componentes do acúmulo de forragem nessas épocas do ano. As metas pós-pastejo não interferiram sobre a proporção de perfilhos basais e aéreos e sobre a dinâmica dos processos morfogênicos ao longo da rebrotação, mas influenciaram de forma distinta as características morfogênicas e estruturais de perfilhos basais e aéreos e a velocidade de rebrotação, sendo que menores intervalos de pastejo foram obtidos nos pastos manejados a 45 cm. As metas de IL pré-pastejo possuem papel central na definição dos mecanismos compensatórios determinantes da habilidade competitiva do capim-elefante cv. Napier, os quais são maximizados com a meta IL95%. / Sward structure and herbage accumulation result in integrated processes of plant adaptation to environmental and management conditions ranging from the turnover of tissues on individual tillers to aspects of tiller population dynamics in a community level. Based on the hypothesis that strategies of rotational stocking management modify the relationships among individuals within a plant community and alter the proportion of different tiller categories, interfering with the dynamics of morphogenetic responses and components of herbage accumulation, the objective of this study was to evaluate how the morphogenetic responses and structural characteristics of basal and aerial tillers are integrated during regrowth and what are the consequences to herbage accumulation and sward structure of elephant grass from January 2011 to April 2012. Treatments corresponded to combinations between two post- (post-grazing heights of 35 and 45 cm) and two pre-grazing conditions (95% and maximum canopy light interception during regrowth - LI95% and LIMáx), and were allocated to experimental units (850 m2 paddocks) according to a 2x2 factorial arrangement and a randomised complete block design, with four replications. Distinct growth strategies were used by elephant grass cv. Napier in response to LI pre-grazing management targets. These were characterised by changes in the proportion and population of different tiller classes, as illustrated by the higher [aerial tillers/(basal tillers + stems of conduction)] ratio of swards managed with the LIMax target. The more intense competition for light, consequence of longer regrowth periods for this LI pre-grazing target resulted in higher rates of stem elongation and lower leaf elongation rates per phyllochron day during the intermediate and final phases of regrowth. Such pattern of response, associated with the lower growth rate of aerial relative to basal tillers, resulted in lower rates of leaf growth and higher rates of stem growth, which determined reduction in rates of net leaf accumulation on swards managed with the LIMax target relative to those managed with the LI95% target. Swards managed with the LI95% target showed stable values of sward height pre-grazing (85 cm) during months of active plant growth (September 2011 to April 2012). Higher values of the [aerial tillers/(basal tillers + stems of conduction)] ratio were recorded during autumn and winter, a result in line with the expressive contribution of aerial tillers to herbage accumulation at that time of the year. Targets of post-grazing height used did not interfere with the proportion of basal and aerial tillers in plant population and with the dynamics of the morphogenetic responses throughout regrowth, but influenced in a different manner the morphogenetic and structural characteristics of basal and aerial tillers and growth rate during regrowth, with shorter grazing intervals recorded on swards managed at 45 cm. Targets of LI pre-grazing play a central role in defining the compensatory mechanisms determining the competitive ability of elephant grass cv. Napier, which are maximised with the LI95% target.

A superfície da terra foi modificada nos últimos 50 anos mais do que em qualquer outro período da História, mais intensa e rápida nos trópicos pela expansão das frentes de ocupação humana sobre floresta madura. A Amazônia brasileira, caracterizada pela alternância de ciclos econômicos extrativistas, exemplifica esse processo. Entre o abandono de áreas degradadas e a abertura de novas frentes de ocupação, ocorre a regeneração florestal. A floresta secundária tem uma reconhecida importância para o restabelecimento das funções dos ecossistemas e dos estoques de nutrientes perdidos da floresta madura, mas ignorados por muitos anos de taxas oficiais de desmatamento na Amazônia brasileira. Este estudo apresenta uma abordagem utilizando Análise de Imagens Baseada em Objetos Geográficos (GEOBIA) para classificar os estágios de sucessão secundária numa área com cerca de 11.124 km² na região de Santarém (Pará, Brasil). Dentre os resultados, foram produzidas 19 diferentes classificações cobrindo o período 1984 a 2016, que permitiu identificar a redução da floresta madura e da floresta secundária devido à expansão da fronteira agrícola. Outro resultado relevante foi a modelagem de uma árvore de decisão aplicável às imagens de refletância de superfície coletadas pelos satélites LANDSAT, processando esses atributos de classificação em um aplicativo de mineração de dados / The earth surface was modified in the last 50 years more than in any other period of the History, more intense and fast in the tropics by the expansion of human occupation frontiers on the mature forest. The Brazilian Amazon, characterized by alternating extractive economic cycles, exemplifies this process. Between the degraded areas abandonment and the new occupation fronts, forest regeneration takes place. The secondary forest has a recognized importance for the restoration of ecosystem functions and the nutrient stocks lost from the mature forest but ignored for many years of official deforestation rates in the Brazilian Amazon. In this study, an approach using Geographic Object-Based Imaging Analysis (GEOBIA) is presented to classify the stages of secondary succession in an area with near 11,124 km² on Santarém region (Pará State, Brazil). Among the results, 19 different classifications were produced covering the period 1984 to 2016, which allowed identify the reduction of mature forest and secondary forest due to agricultural frontier expansion. Another relevant result was the modeling of a decision tree applicable to surface reflectance images collected by the LANDSAT satellites, processing these classifications attributes in a data mining software