• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 11
  • 8
  • 6
  • Tagged with
  • 33
  • 33
  • 33
  • 33
  • 23
  • 14
  • 14
  • 8
  • 6
  • 6
  • 5
  • 5
  • 5
  • 5
  • 5
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Remote sensing-based identification and mapping of salinised irrigated land between Upington and Keimoes along the lower Orange River, South Africa

Mashimbye, Zama Eric 04 1900 (has links)
Thesis (MA (Geography and Environmental Studies))--University of Stellenbosch, 2005. / Salinisation is a major environmental hazard that reduces agricultural yields and degrades arable land. Two main categories of salinisation are: primary and secondary soil salinisation. While primary soil salinisation is caused by natural processes, secondary soil salinisation is caused by human factors. Incorrect irrigation practices are the major contributor to secondary soil salinisation. Because of low costs and less time that is associated with the use of remote sensing techniques, remote sensing data is used in this study to identify and map salinised irrigated land between Upington and Keimoes, Northern Cape Province, in South Africa. The aim of this study is to evaluate the potential of digital aerial imagery in identifying salinised cultivated land. Two methods were used to realize this aim. The first method involved visually identifying salinised areas on NIR, and NDVI images and then digitizing them onscreen. In the second method, digital RGB mosaicked, stacked, and NDVI images were subjected to unsupervised image classification to identify salinised land. Soil samples randomly selected and analyzed for salinity were used to validate the results obtained from the analysis of aerial photographs. Both techniques had difficulties in identifying salinised land because of their inability to differentiate salt induced stress from other forms of stress. Visual image analysis was relatively successful in identifying salinised land than unsupervised image classification. Visual image analysis correctly identified about 55% of salinised land while only about 25% was identified by unsupervised classification. The two techniques predict that an average of about 10% of irrigated land is affected by salinisation in the study area. This study found that although visual analysis was time consuming and cannot differentiate salt induced stress from other forms; it is fairly possible to identify areas of crop stress using digital aerial imagery. Unsupervised classification was not successful in identifying areas of crop stress.
22

Estoque de biomassa e carbono na região noroeste do estado do Rio Grande do Sul, Brasil / Biomass and carbon stock in the northwestern region of the Rio Grande do Sul state, Brazil

Erthal, Daniele Arndt 15 February 2017 (has links)
The remnants of vegetation native to the Atlantic Forest account for about 22% of their original cover and are in different stages of regeneration. The typologies belonging to the biome and found in the northwest of the state of Rio Grande do Sul are mixed ombrophilous forest and deciduous seasonal forest. Amid the consequences of the current dynamics of land use and occupation caused by man, there is the fragmentation of primary and secondary forests, where an area continues to result in a large number of isolated fragments of different sizes. Among the various environmental services provided by forest ecosystems, the most important is the sequestration and storage of carbon in the form of biomass. Thus, the role of native forests in the removal and stocking of carbon is fundamental, demonstrating the need to develop new methods that estimate forest biomass and carbon by non-destructive methods. The objective of the present work is to estimate and study the dynamics of biomass and forest carbon stock in successional stages of regeneration in the Northwest Region of the State of Rio Grande do Sul. The study area is located in the Northwest of the State of Rio Grande do Sul , Covering two microregions, Três Passos and Frederico Westphalen. For this study two methodologies were developed to estimate the forest biomass stock, both based on remote sensing data. The study in the first methodology was carried out for the dates of 1985, 1994, 2005 and 2014, and covers an area of 9,046.9 km². The classification of forest successions in regeneration stages was a continuation of the work of Rosa (2016), where the size classes: initial (<5 ha), medium (5 - 10 ha), advanced (> 10 ha), later Biomass for them. For the second methodology, images from each year were used from 1985 to 2014, where the NDVI was calculated, and through regression generated for the global model, to obtain the IAF and to estimate the forest biomass. Subsequently, comparing both methodologies were compared among themselves, and compared with values provided by the methodology of the Brazilian Forest Service. For the first study, forest biomass in 2014 in the Northwest Region of the state of Rio Grande do Sul was 80,831 Gg, divided into three stages of initial (659 Gg) regeneration (2,549 Gg) and advanced (77,623 Gg) regeneration. In the study area, there are three protected areas, the Turvo State Park, the Nonoai Indigenous Reserve and the Guarita Indian Reserve, which account for almost 25% of the total stock of the region, and are significant areas in the carbon stock. The carbon estimated by the first methodology was 296 Gg for the initial stage, 1,147 for the medium stage and 34,930 for the advanced stage, totaling 36,373 Gg. For the second methodology, it was possible to observe the great relation between the increase of the LAI as a function of NDVI and the forest biomass in 2014 was 61,156 Gg, where 602 Gg corresponds to the initial regeneration stage, 8,287 Gg for the medium stage and 52,267 Gg for The advanced stage of regeneration. The estimated total carbon for the study area in 2014 according to the second methodology was 27,520 Gg CO2, of which 271 Gg were present in the initial stage, 3,729 Gg in the medium stage and 23,520 Gg in the advanced stage of regeneration. In the comparison of the methodologies developed in this study, a difference of 19,675 Gg was obtained, due mainly to the effects of edges of the studied fragments. Comparing the first and second methodologies developed with that provided by the Brazilian Forest Service, only 10 and 14.30% of the estimated values for forest biomass were obtained. / Os remanescentes de vegetação nativa da Mata Atlântica contabilizam cerca de 22% de sua cobertura original e se encontram em diferentes estágios de regeneração. As tipologias pertencentes ao bioma e que se encontram no noroeste do estado do Rio Grande do Sul são floresta ombrófila mista e floresta estacional decidual. Em meio às consequências da atual dinâmica do uso e ocupação do solo causadas pelo homem, está a fragmentação de florestas primárias e secundárias, onde uma área continua resulta em um grande número de fragmentos isolados e de diferentes tamanhos. Entre os diversos serviços ambientais prestados pelos ecossistemas florestais, se destaca o sequestro e estocagem do carbono na forma de biomassa. Assim é fundamental o papel das florestas nativas na remoção e estoque do carbono, demonstrando a necessidade de desenvolver novos métodos que estimem a biomassa e carbono de florestas por meio de métodos não destrutivos. O objetivo do presente trabalho é estimar e estudar a dinâmica do estoque da biomassa e do carbono florestal em estágios sucessionais de regeneração na Região Noroeste do Estado do Rio Grande do Sul. A área de estudo está localizada no Noroeste do Estado do Rio Grande do Sul, abrangendo duas microrregiões, Três Passos e Frederico Westphalen. Para este estudo foram desenvolvidas duas metodologias para estimar o estoque de biomassa florestal, ambas baseadas em dados de sensoriamento remoto. O estudo na primeira metodologia foi realizado para as datas de 1985, 1994, 2005 e 2014, e abrange área de 9.046,9 km². A classificação das sucessões florestais em estágios de regeneração se deu por continuidade ao trabalho de Rosa (2016), onde as classes de tamanho: inicial (< 5 ha), média (5 – 10 ha), avançada (> 10 ha), depois estimadas a biomassa para elas. Para a segunda metodologia, foram usadas imagens de todos os anos desde 1985 a 2014, onde foi calculado o NDVI, e através de regressão gerada para o modelo global, se obter o IAF e estimar a biomassa florestal. Posteriormente, comparou-se ambas as metodologias foram comparadas entre si, e comparadas com valores fornecidos pela metodologia do Serviço Florestal Brasileiro. Para o primeiro estudo, a biomassa florestal em 2014 na Região Noroeste do estado do Rio Grande do Sul foi de 80.831 Gg, divididos em três estágios de regeneração inicial (659 Gg) médio (2.549 Gg) e avançado (77.623 Gg). Na área de estudo, estão presentes três áreas protegidas, o Parque Estadual do Turvo, a Reserva indígena de Nonoai e a Reserva indígena do Guarita, as quais possuem quase 25% do estoque total da região, e são áreas significativas no estoque de carbono. O carbono estimado pela primeira metodologia foi de 296 Gg para o estágio inicial, 1.147 para o estágio médio e 34.930 para o estágio avançado, totalizando 36.373 Gg. Para a segunda metodologia, foi possível observar a grande relação entre o aumento do IAF em função do NDVI estimando a biomassa florestal em 2014 foi de 61.156 Gg onde 602 Gg correspondem ao estágio de regeneração inicial, 8.287 Gg para o estágio médio e 52.267 Gg para o estágio avançado de regeneração. O total de carbono estimado para a área de estudo em 2014 conforme a segunda metodologia foi de 27.520 Gg CO2 sendo desses 271 Gg presentes no estágio inicial, 3.729 Gg no estágio médio e 23.520 Gg no estágio avançado de regeneração. Na comparação das metodologias desenvolvidas neste estudo, obteve-se uma diferença de 19.675 Gg, devido principalmente aos efeitos de bordas dos fragmentos estudados. Comparando-se a primeira e a segunda metodologias desenvolvidas com a fornecida pelo Serviço Florestal Brasileiro, obteve-se apenas 10 e 14,30% dos valores estimados para a biomassa florestal.
23

O uso do IVDN no estudo da degradação ambiental de bacias hidrográficas do litoral sul do estado da Paraíba

Lucena, Alysson Pereira de 27 March 2014 (has links)
Made available in DSpace on 2015-05-14T12:09:35Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 4567922 bytes, checksum: 9d5c646bb1c124ff4e411ed6bc7dc654 (MD5) Previous issue date: 2014-03-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This work aims the implementation of the Index Normalized Difference Vegetation (NDVI) in the study of environmental degradation of watersheds of rivers and river Gramame Abiai-Papocas, both located on the south coast of Paraíba state. The survey was conducted from images of Landsat 5 TM satellite, the years 1989, 2001 and 2006. Initially Atmospheric and radiometric corrections were performed. From the corrected images extracted and it was made thematic maps tracks the NDVI, which highlighted the density of vegetation cover. Then on-site visits, in which sampling points chosen as representative in supervised classification by regions, satellite images, which resulted in the preparation of thematic maps of land use were collected were performed. Topographic information from the Digital Elevation Model (DEM) images The Shuttle Radar Topography Mission (SRTM) thematic maps describing the ground from the height of each pixel in the drainage network relationship were made using the algorithm Height Above the Neareast Drainage (HAND). Then crosses the NDVI data with land use and with the HAND were carried out to justify the responses of NDVI, as well as evaluating its relationship with the land uses and the gap compared the drainage network. From the intersection of NDVI with HAND verified the presence of vegetation with greater biomass in the lower regions. With the crossing of the maps of land use and NDVI was observed that a large number of areas with exposed soils showed NDVI values in the range of -0.25 to 0.15. As for vegetation degradation in river basins, there was a decrease in NDVI values for 2001 and 1989 regeneration 2001 for 2006 observed an increasing convergence of natural vegetation in farmland and urban expansion without planning.; and that much of the degradation are derived from the practice of mining and farming without the use of soil conservation techniques. It was also found that data obtained in research enabled the generation of information that can be used in other research and aid decision makers in formulating geared to minimizing the environmental degradation in the watersheds studied public policy / Esse trabalho teve como objetivo a aplicação do Índice de Vegetação da Diferença Normalizada (IVDN) no estudo da degradação ambiental das bacias hidrográficas do rio Gramame e dos rios Abiai-Papocas, ambas situadas no litoral sul do Estado da Paraíba. A pesquisa foi realizada a partir de imagens do satélite Landsat 5 TM, dos anos de 1989, 2001 e 2006. Inicialmente foram realizadas correções atmosférica e radiométrica. A partir das imagens corrigidas extraiu-se e confeccionou-se os mapas temáticos de faixas do IVDN, que destacaram a densidade da cobertura vegetal. Em seguida foram realizadas visitas in loco, nas quais foram coletados pontos amostrais, adotados como representativos na classificação supervisionada por regiões, das imagens de satélite, que resultou na confecção dos mapas temáticos de uso do solo. Com informações topográficas do Modelo Digital de Elevação (MDE) de imagens The Shuttle Radar Topography Mission (SRTM) foram confeccionados os mapas temáticos da descrição do terreno a partir da altura de cada pixel em relação rede de drenagem, utilizou-se o algoritmo Height Above the Neareast Drainage (HAND). Em seguida, foram realizados cruzamentos dos dados do IVDN com os de uso do solo e com os do HAND, objetivando justificar as repostas do IVDN, assim como, avaliar a relação deste com os usos do solo e com o desnível em relação à rede de drenagem. A partir do cruzamento do IVDN com o HAND foi verificada a presença de vegetação com maior biomassa nas regiões mais baixas. Com o cruzamento dos mapas do uso do solo e do IVDN observou-se que grande parte das áreas com solos expostos apresentaram valores de IVDN na faixa de -0,25 a 0,15. Quanto à degradação da vegetação nas bacias hidrográficas, houve uma diminuição dos valores de IVDN de 1989 para 2001 e uma regeneração de 2001 para 2006. Observou-se um aumento da convergência da vegetação natural em terras agrícolas e em expansões urbanas sem planejamento; e que grande parte das áreas degradadas são proveniente da prática da mineração e da agricultura sem a utilização de técnicas conservacionistas do solo. Verificou-se ainda, que dados obtidos na pesquisa possibilitou a geração de informações que poderão ser utilizadas em outras pesquisas, no auxílio a tomadores de decisão e na formulação de políticas públicas voltadas para a minimização da degradação ambiental nas bacias hidrográfica estudadas
24

DELINEAMENTO DE ZONAS POTENCIAIS PARA MANEJO DIFERENCIADO EM NÍVEL DE TALHÃO APARTIR DE DADOS DE COLHEITA E DE IMAGENS DE SATÉLITE / DESIGN AREAS FOR POTENTIAL MANAGEMENT IN DIFFERENTIAL FIELD LEVEL HARVEST DATA FROM AND SATELLITE IMAGES

Veiverberg, Kelly Taline 26 April 2016 (has links)
Precision agriculture has been used to assist farmers to choose the best management strategies, by identifying variability present in the area and from that, to determine the limiting factors and propose different management alternatives, according to the needs of each zone. It is important to create instruments that respond to one of the main issues, common to all of those who have ambition to the adoption and implementation of production modernization techniques: the technical and economic viability of modern production agriculture. The aim of this study was to relate stability maps for yield productivity and stability maps by Normalized Difference Vegetation Index (NDVI) for determination of management zones. The study was based on an analysis of five years of crop yield data and five satellite images Landsat 5 and Landsat 8 for Vegetation Index (NDVI) data for 2007 (wheat), 2008 (soybean), 2009 (soybean), 2013 (wheat) and 2014 (soybean). With processed data, stability maps for yield productivity and stability maps by Normalized Difference Vegetation Index (NDVI) were generated, following data parameters and coefficient of variation. Both maps were compared and validated by the Kappa index. As a result, we obtained a weak Kappa index relationship (0.2623), but 57.48% of the area could be classified correctly, when comparing the correlation maps. We concluded that crossing data of areas classified by productivity yield and NDVI is valid and that the zoning method for NDVI method is a way to determines areas, but with greater emphasis in areas classified as "Stable High." / A agricultura de precisão surge para auxiliar o produtor na escolha das melhores estratégias de manejo, permitindo identificar a variabilidade presente na área e, a partir disso, averiguar os fatores limitantes e propor alternativas de manejo diferenciado, de acordo com as necessidades de cada zona de manejo. É necessário criar instrumentos que respondam a uma das principais questões, comum a todos aqueles que têm ambição à adoção e aplicação de técnicas de modernização da produção: a viabilização técnica-econômica da produção moderna na agricultura. O objetivo deste trabalho foi relacionar mapas de Estabilidade de Rendimento por produtividade e de Estabilidade de Rendimento por Índice de Vegetação por Diferença Normalizada para determinação de zonas de manejo. O estudo foi baseado na análise de cinco anos de dados de produtividade, em rendimento absoluto, e consecutivamente, cinco imagens de satélite Landsat 5 e Landsat 8, para Índice de Vegetação por Diferença Normalizada (NDVI), dados referentes aos anos de 2007 (cultura do trigo), 2008 (cultura de soja), 2009 (cultura de soja), 2013 (cultura de trigo) e 2014 (cultura de soja). Com esses dados processados foram gerados os mapas de Estabilidade de Rendimento por Produtividade e Estabilidade de Rendimento por NDVI, seguindo parâmetros de dados relativizados e coeficiente de variação. Com os dois mapas de Estabilidade processados, foi feito o comparativo e validação dos dados através do índice Kappa. Como resultado obteve-se um índice Kappa de fraca relação com valor de 0,2623, porém 57,48% da área pode ser classificada corretamente quando comparando zonas geradas por mapas de produtividade com zonas geradas por mapas de NDVI. Concluiu-se, assim, que o cruzamento dos dados das zonas classificadas em Estabilidade de Rendimento por Produtividade e Estabilidade de Rendimento por NDVI é válido e que o método de definição de zonas por Estabilidade de Rendimento por NDVI permite determinar zonas, porém com maior ênfase em zonas classificadas como Estável Alta .
25

Beaver Movements On Managed Land In The Southeastern United States

McClintic, Lance Forest 11 May 2013 (has links)
I studied movement characteristics and vegetative resources effects on home range size of beavers at Redstone Arsenal (RSA) in north central Alabama, USA. Beavers were captured and radio tagged from 11 wetlands during winter and spring of 2011. I monitored movements of radio-tagged beavers using radio telemetry from May 2011–April 2012. Beavers moved faster, presumably more favorable to central place foraging, in wetland as they proceeded farther away from the central place, but did not in upland. Additionally, distributions of hourly distances from lodges were bimodal. Home range, core areas, and distance from lodge did not differ between age classes. Home range sizes increased with increasing habitat productivity and resource dispersion, whereas home ranges decreased with temporal variation in resources throughout the year. Quantity and spatial distribution of resources and patterns of foraging behavior influence movements and home ranges of central place foragers.
26

Delineation of mass movement prone areas by Landsat 7 and digitial image processing

Howland, Shiloh Marie 05 December 2003 (has links) (PDF)
The problem of whether Landsat 7 data could be used to delineate areas prone to mass movement, particularly debris flows and landslides, was examined using three techniques: change detection in NDVI (Normalized Difference Vegetation Index), change detection in band 5, and the tasseled cap transformation. These techniques were applied to areas that had recently experienced mass movement: Layton, Davis County and Alpine, Spanish Fork Canyon and Santaquin, Utah County. No distinctive spectral characteristics were found with any of these techniques with two possible explanations: 1. That despite improved spatial resolution in Landat 7 over its predecessors and improved digital image processing capabilities, the resolution is still too low to detect these characteristics or 2. That the aspects of a slope that make it prone to mass movement are undetectable at any resolution by remote sensing. Change detection in NDVI examined if areas that remained unchanged (defined as < 5% change) between August 14, 1999 and October 17, 1999 correlated to areas that are prone to mass movement. There was no correlation. Change detection in band 5 was examined between August 14, 1999 and October 17, 1999, October 17, 1999 and May 28, 2000, and August 14, 1999 and May 28, 2000. An interesting result is that the Shurtz Lake and Thistle landslides (Spanish Fork Canyon) showed changes of greater than 30% during August 14, 1999 - October 17, 1999 and October 17, 1999 - May 28, 2000. These changes were limited to these landslides and not seen in abundance in surrounding areas. A similar localization of 30% change was seen in the Cedar Bench landslide (Layton) for the same time periods. There were no other correlations. The tasseled cap ransformation shows areas of dominate greenness, soil brightness or wetness. None of these factors had distinctive patterns in the areas studied when compared to surrounding, mass movement-prone areas so no conclusions can be drawn about the utility of the tasseled cap transformation as it relates to areas of potential mass movement.
27

Detecting an invasive shrub in deciduous forest understories using remote sensing

Wilfong, Bryan N. 11 August 2008 (has links)
No description available.
28

Improving Soil Moisture Assessment of Turfgrass Systems Utilizing Field Radiometry

Roberson, Travis L. 31 January 2019 (has links)
The need for water conservation continues to increase as global freshwater resources dwindle. In response, many golf course superintendents are implementing new methods and tools to become more frugal with their water applications. For example, scheduling irrigation using time-domain reflectometer (TDR) soil moisture sensors can decrease water usage. Still, TDR measurements are time-consuming and only cover small scales, leading to many locations being unsampled. Remotely sensed data such as the normalized difference vegetation index (NDVI) offer the potential of estimating moisture stress across larger scales; however, NDVI measurements are influenced by numerous stressors beyond moisture availability, thus limiting its reliability for irrigation decisions. An alternative vegetation index, the water band index (WBI), is primarily influenced by water absorption within a narrow spectral range of near-infrared light. Previous research has established strong relationships between moisture stress of creeping bentgrass (CBG) grown on sand-based root zones, a typical scenario for golf course putting greens. However, this relationship characterizes only a small portion of total acreage across golf courses, which limits widespread adoption. In our research, '007' CBG and 'Latitude 36'hybrid bermudagrass (HBG) were grown on three soil textures, USGA 90:10 sand (S), sand loam (SL) and clay (C), arranged in a 2 x 3 factorial design, randomized within six individual dry-down cycles serving as replications. Canopy reflectance and volumetric water content (VWC) data were collected hourly between 0700 and 1900 hr using a hyperspectral radiometer and an embedded soil moisture sensor, until complete turf necrosis. The WBI had the strongest relationship to VWC (r = 0.62) and visual estimations of wilt (r = -0.91) compared to the green-to-red ratio index (GRI) or NDVI. Parameters associated with non-linear regression were analyzed to compare grasses, soils, indices, and their interactions. The WBI and GRI compared favorably with each other and indicated significant moisture stress approximately 28 hr earlier than NDVI (P = 0.0010). WBI and GRI respectively predicted moisture stress 12 to 9 hr before visual estimation of 50% wilt, whereas NDVI provided 2 hr of prediction time (P = 0.0317). When considering the time to significant moisture stress, the HBG lasted 28 hr longer than CBG, while S lasted 42 hr longer than either SL and C (P ≤ 0.0011). Nonlinear regression analysis showed that WBI and GRI can be useful for predicting moisture stress of CBG and HBG grown on three diverse soils in a highly controlled environment. Our results provide substantial evidence and direction for future research investigating how WBI and GRI can expedite moisture stress assessment and prediction on a large-acreage basis. / Master of Science in Life Sciences / Managed turfgrasses provide several benefits including filtering pollutants, cooling their surroundings, generating oxygen, preventing erosion, serving as recreational surfaces, and increasing landscape aesthetics. Intensively managed turfgrass systems, such as on golf courses and sports fields, require more inputs to maintain acceptable conditions. Freshwater use is often excessive on intensively managed turfgrasses to maintain proper plant growth. Drought conditions often limit water availability, especially in regions with limited rainfall. Turf managers tend to over-apply water across large acreage when few localized areas begin to show symptoms of drought. Additionally, turf managers sometimes wrongly identify stressed areas from other factors as ones being moisture-deprived. Advancements such as the use of soil moisture meters have simplified irrigation decisions as an aid to visual inspections for drought stress. While this method enhances detection accuracy, it still provides no solution to increase efficiency. Expanding our current knowledge of turfgrass canopy light reflectance for rapid moisture stress identification can potentially save both time and water resources. The objective of this research was to enhance our ability to identify and predict moisture stress of creeping bentgrass (CBG) and hybrid bermudagrass (HBG) canopies integrated into varying soil textures (USGA 90:10 sand (S), sand loam (SL) and Clay (C)) using light reflectance measurements. Dry-down cycles were conducted under greenhouses conditions collecting soil moisture and light reflectance data every hour from 7 am to 7 pm after saturating and withholding water from established plugs. Moisture stress was most accurately estimated over time using two vegetation indices, the water band index (WBI) and green-to-red ratio index (GRI), with approximately ninety percent accuracy to visible wilt stress. The WBI and GRI predicted moisture stress of CBG in all soil types and HBG in SL and C approximately 14 hours before the grasses reached 50% wilt. While light reflectance varies on exposed soils, our research shows that underlying soils do not interfere with measurements across typical turfgrass stands. This research provides a foundation for future research implementing rapid, aerial measurements of moisture stressed turfgrasses on a broad application of CBG and HBG on constructed or native soils.
29

Estudo da dinâmica do fogo na área da Estação Ecológica Serra Geral do Tocantins: uso de técnicas de sensoriamento remoto

Costa, Jobherlane Farias 29 March 2018 (has links)
A presente pesquisa trata de uma análise da Estação Ecológica Serra Geral do Tocantins (EESGT) localizada entre os Estados do Tocantins e da Bahia, tendo como principal objetivo investigar a ação do fogo, antes e depois da sua criação, ou seja, entre os anos de 1998 e 2015. A metodologia utilizada foi o Sensoriamento Remoto com o qual aplicou-se diferentes técnicas que permitiram observar a ação do fogo com base nos Aspectos Regionais, NDVI, Focos de Calor e Cicatrizes do Fogo (queimadas e incêndios florestais) e a Recorrência destas áreas. Desta maneira, utilizou-se um conjunto de imagens de satélites Landsat Sensor -TM e Ressourcesat - 1, dos anos de 1998, 2001, 2007, 2012 e 2015, obtidas no período seco entre junho e outubro. Com os softwares QGis e ArcGIS® foi aplicado o Índice de Diferença de Vegetação Normalizado (NDVI) que permitiu a identificação de áreas atingidas pelo fogo, as quais foram aferidas ou confirmadas com a sobreposição dos focos de calor e observação visual de uma composição colorida (RGB) de imagem de satélite. No mesmo sentido, foi realizado uma classificação supervisionada de imagens de satélite, o que permitiu a identificação e o delineamento das cicatrizes de fogo e consequentemente, a ação do fogo na área de pesquisa. Entre os resultados obtidos, pode-se observar que no ano de 1998, a ação do fogo correspondeu a cerca de 50% de área, no ano de 2001 cerca de 46%, no ano de 2007 cerca de 68%, no ano de 2012 cerca de 54% e 2015 cerca de 41%. De maneira geral, pode-se observar uma redução da ação do fogo na área da EESGT nos últimos anos, o que pode estar associado“os fatores à diferentes formas” de manejo do fogo, o que precisa ser aprofundado com o andamento de novas pesquisas. Também foi possível observar, que anterior a criação da unidade, até o ano de 2001, os valores correspondentes a ação do fogo (50 e 46%) não reduziram, após a criação da unidade, no ano de 2007(68%) aumentaram. Porém, nos últimos anos ocorre uma redução da ação de fogo anos de 2012 e 2015 (54 e 41%), sendo um sinal positivo quanto a conservação do Cerrado e manutenção da função da unidade. / The present research deals with an analysis of the Estação Ecológica Serra Geral do Tocantins, located between the states of Tocantins and Bahia, with the main objective of investigating the fire action, before and after its creation, that is, between 1998 and 2015. The methodology used was the Remote Sensing with which different techniques were applied to observe the fire action based on the Regional Aspects, NDVI, Heat Sources and Fire Scars (burnings and forest fires) and Recurrence of these areas. A set of Landsat Sensor-TM and Ressourcesat-1 satellite images from 1998, 2001, 2007, 2012 and 2015 were obtained in the dry period between June and October. As the QGis and ArcGIS® software were applied Standardized Vegetation Difference Index (NDVI) that allowed the identification of areas affected by fire, which were measured or confirmed with the overlap of heat fires and visual observation of a color composition (RGB) satellite imagery. n the same direction a supervised classification of satellite images was carried out, which allowed the identification and the design of the fire scars and consequently the fire action in the research area. Among the results obtained, it can be observed that in 1998 the fire action corresponded to about 50% of area, in 2001 about 46%, in 2007 about 68%, in the year of 2012 about 54% and 2015 about 41%. In general, it can be observed a reduction of the fire action in the area of the EESGT in the last years, which may be associated the “factors to the different forms” of fire management, which needs to be deepened with the progress of new researches. It was also possible to observe that before the creation of the unit, until the year 2001, the values corresponding to the action of the fire (50 and 46%) did not reduce, after the creation of the unit, in the year of 2007 (68%) yes they increased. However, in recent years there has been a reduction in the fire action for the years 2012 and 2015 (54 and 41%), which is a positive sign for the conservation of the Cerrado and maintenance of the unit's function.
30

The signature of sea surface temperature anomalies on the dynamics of semiarid grassland productivity

Chen, Maosi, Parton, William J., Del Grosso, Stephen J., Hartman, Melannie D., Day, Ken A., Tucker, Compton J., Derner, Justin D., Knapp, Alan K., Smith, William K., Ojima, Dennis S., Gao, Wei 12 1900 (has links)
We used long-term observations of grassland aboveground net plant production (ANPP, 19392016), growing seasonal advanced very-high-resolution radiometer remote sensing normalized difference vegetation index (NDVI) data (1982-2016), and simulations of actual evapotranspiration (1912-2016) to evaluate the impact of Pacific Decadal Oscillation (PDO) and El Nino-Southern Oscillation (ENSO) sea surface temperature (SST) anomalies on a semiarid grassland in northeastern Colorado. Because ANPP was well correlated (R-2 = 0.58) to cumulative April to July actual evapotranspiration (iAET) and cumulative growing season NDVI (iNDVI) was well correlated to iAET and ANPP (R-2 = 0.62 [quadratic model] and 0.59, respectively), we were able to quantify interactions between the long-duration (15-30 yr) PDO temperature cycles and annual-duration ENSO SST phases on ANPP. We found that during cold-phase PDOs, mean ANPP and iNDVI were lower, and the frequency of low ANPP years (drought years) was much higher, compared to warm-phase PDO years. In addition, ANPP, iNDVI, and iAET were highly variable during the cold-phase PDOs. When NINO-3 (ENSO index) values were negative, there was a higher frequency of droughts and lower frequency of wet years regardless of the PDO phase. PDO and NINO-3 anomalies reinforced each other resulting in a high frequency of above-normal iAET (52%) and low frequency of drought (20%) when both PDO and NINO-3 values were positive and the opposite pattern when both PDO and NINO-3 values were negative (24% frequency of above normal and 48% frequency of drought). Precipitation variability and subsequent ANPP dynamics in this grassland were dampened when PDO and NINO-3 SSTs had opposing signs. Thus, primary signatures of these SSTs in this semiarid grassland are (1) increased interannual variability in ANPP during cold-phase PDOs, (2) drought with low ANPP occurring in almost half of those years with negative values of PDO and NINO-3, and (3) high precipitation and ANPP common in years with positive PDO and NINO-3 values.

Page generated in 0.195 seconds