This research examined the mechanisms by which temperature, water availability and nitrogen (N) affect the dry matter (DM) yield potential of cocksfoot (Dactylis glomerata L.) dominant pastures. The experiment was a split plot design with main plots of fully irrigated (I) or dryland (D), sub-plots of N fertiliser at 800 kg N/ha in 2003/04; and 1600 kg N/ha in 2004/05 (+N) or 0 kg N/ha (-N). The potential environmental yield of an established 8 year old cocksfoot dominant pasture was 21.9 t DM/ha/y from I+N pastures compared with 9.8 t DM/ha by I-N pastures and 15.1 t DM/ha/y by D+N pastures. The lowest yields were from dryland pastures with no N which produced 7.5 t DM/ha/y in 2003/03 and 5.0 t DM/ha/y in 2004/05. The effect of seasonal temperatures on the DM production, when periods of water stress were excluded, was quantified using thermal time accumulated above a base temperature of 3°C as 7.0 kg DM/°Cd/ha for N fertilised pastures and 3.3 kg DM/°Cd/ha for pastures with no N. The 2.5 t DM/ha difference in yields of D-N pastures in 2003/04 and 2004/05 was the result of the duration, extent and timing of the water stress period. In both years the critical limiting deficit (DL) was calculated as 78 mm from the soil moisture deficit in the 0-0.8 m soil layers. Beyond DL yield decreased at a rate of 1.45%/mm in +N and –N pastures, relative to fully irrigated control pastures. Yields of D+N and D-N pastures were similar during periods of water stress with 0.4±0.1 t/DM/ha produced during the rotation ending 30/12/2003. This was less than from either the I-N (1.2 t DM/ha) or I+N (3.5 t DM/ha) pastures due to the reduction in the amount of photosynthetically active radiation intercepted by the canopies of the dryland pastures. However, in the rotation ending 2/5/2004, after autumn rain alleviated drought conditions, yield of the D+N pasture was 2.1 t DM/ha compared with 1.7 t DM/ha by I+N pastures. The effect of N on yield was described using a nutrition index which showed that as DM yield increased N% in the herbage declined. This is a function of the ratio between metabolic and structural N requirements rather than caused by ontogeny alone. Specific leaf N was determined at two harvests and appeared constant at a given point in time (1.0-1.6 g N/m² leaf). In contrast, specific pseudostem N increased from 0.8-1.0 g N/m² pseudostem at an NNI of 0.4 in –N pastures to 2.6-3.0 g N/m² pseudostem at an NNI of 1.2 in the +N pastures. Differences between the yields of +N and –N pastures were caused by differences in radiation use efficiency (RUE) as determined by the linear relationship (R²=0.76) between RUE and the nitrogen nutrition index (NNI). In this thesis, empirical relationships for the effects of temperature, water availability and N were derived and the physiological mechanisms which underlie these descriptions were identified. These relationships provide clear and simple explanations of the effects of environmental variables on the productivity of cocksfoot based pastures which will enhance understanding of the benefits and limitations of cocksfoot, particularly in dryland farming systems.

Variations in Leaf Area Index (LAI) can greatly alter output values and patterns of various models that deal with energy flux exchange between the land surface and the atmosphere. Customarily, such models are initiated by LAI estimated from satellite-level Vegetation Indices (VIs) including routinely produced Normalized Difference Vegetation Index (NDVI) products. However, the accuracy from LAI-VI relationships greatly varies due to many factors, including temporal and spatial variations in LAI and a selected VI. In addition, NDVI products derived from various sensors have demonstrated variations in a certain degree on describing temporal and spatial variations in LAI, especially in semi-arid areas. This thesis therefore has three objectives: 1) determine a suitable VI for quantifying LAI temporal variation; 2) improve LAI estimation by considering both temporal and spatial variations in LAI; and 3) evaluate routinely produced NDVI products on monitoring temporal and spatial variations in LAI.<p> The study site was set up in conserved semi-arid mixed grassland in St. Denis, Saskatchewan, Canada. One 600 m - long sampling transect was set up across the rolling typography, and six plots with a size of 40 × 40 m each were randomly designed and each was in a relatively homogenous area. Plant Area Index (PAI, which was validated to obtain LAI), ground hyperspectral reflectance, ground covers (grasses, forbs, standing dead, litter, and bare soil), and soil moisture data were collected over the sampling transect and plots from May through September, 2008. Satellite data used are SPOT 4/5 images and 16-day Moderate Resolution Imaging Spectroradiometer (MODIS) 250m, 1km as well as 10-day SPOT-vegetation (SPOT-VGT) NDVI products from May to October, 2007 and 2008. The results show that NDVI is the most suitable VI for quantifying temporal variation of LAI. LAI estimation is much improved by considering both temporal and spatial variations. Based on the ground reflectance data, the r2 value is increased by 0.05, 0.31, and 0.23 and an averaged relative error is decreased by 1.57, 1.62, and 0.67 in the early, maximum, and late growing season, respectively. MODIS 250m NDVI products are the most useful datasets and MODIS 1km NDVI products are superior to SPOT-VGT 1km composites for monitoring intra-annual spatiotemporal variations in LAI. The proposed LAI estimation approach can be used in other studies to obtain more accurate LAI, and thus this research will be beneficial for grassland modeling.

Variations in Leaf Area Index (LAI) can greatly alter output values and patterns of various models that deal with energy flux exchange between the land surface and the atmosphere. Customarily, such models are initiated by LAI estimated from satellite-level Vegetation Indices (VIs) including routinely produced Normalized Difference Vegetation Index (NDVI) products. However, the accuracy from LAI-VI relationships greatly varies due to many factors, including temporal and spatial variations in LAI and a selected VI. In addition, NDVI products derived from various sensors have demonstrated variations in a certain degree on describing temporal and spatial variations in LAI, especially in semi-arid areas. This thesis therefore has three objectives: 1) determine a suitable VI for quantifying LAI temporal variation; 2) improve LAI estimation by considering both temporal and spatial variations in LAI; and 3) evaluate routinely produced NDVI products on monitoring temporal and spatial variations in LAI.<p> The study site was set up in conserved semi-arid mixed grassland in St. Denis, Saskatchewan, Canada. One 600 m - long sampling transect was set up across the rolling typography, and six plots with a size of 40 × 40 m each were randomly designed and each was in a relatively homogenous area. Plant Area Index (PAI, which was validated to obtain LAI), ground hyperspectral reflectance, ground covers (grasses, forbs, standing dead, litter, and bare soil), and soil moisture data were collected over the sampling transect and plots from May through September, 2008. Satellite data used are SPOT 4/5 images and 16-day Moderate Resolution Imaging Spectroradiometer (MODIS) 250m, 1km as well as 10-day SPOT-vegetation (SPOT-VGT) NDVI products from May to October, 2007 and 2008. The results show that NDVI is the most suitable VI for quantifying temporal variation of LAI. LAI estimation is much improved by considering both temporal and spatial variations. Based on the ground reflectance data, the r2 value is increased by 0.05, 0.31, and 0.23 and an averaged relative error is decreased by 1.57, 1.62, and 0.67 in the early, maximum, and late growing season, respectively. MODIS 250m NDVI products are the most useful datasets and MODIS 1km NDVI products are superior to SPOT-VGT 1km composites for monitoring intra-annual spatiotemporal variations in LAI. The proposed LAI estimation approach can be used in other studies to obtain more accurate LAI, and thus this research will be beneficial for grassland modeling.

LiDAR (Light Detection and Ranging) directly measures canopy vertical structures, and provides an effective remote sensing solution to accurate and spatiallyexplicit mapping of forest characteristics, such as canopy height and Leaf Area Index. However, many factors, such as large data volume and high costs for data acquisition, precludes the operational and practical use of most currently available LiDARs for frequent and large-scale mapping. At the same time, a growing need is arising for realtime remote sensing platforms, e.g., to provide timely information for urgent applications. This study aims to develop an airborne profiling LiDAR system, featured with on-the-fly data processing, for near real- or real- time forest inventory. The development of such a system involves implementing the on-board data processing and analysis as well as building useful regression-based models to relate LiDAR measurements with forest biophysical parameters. This work established a paradigm for an on-the-fly airborne profiling LiDAR system to inventory regional forest resources in real- or near real- time. The system was developed based on an existing portable airborne laser system (PALS) that has been previously assembled at NASA by Dr. Ross Nelson. Key issues in automating PALS as an on-the-fly system were addressed, including the design of an archetype for the system workflow, the development of efficient and robust algorithms for automatic data processing and analysis, the development of effective regression models to predict forest biophysical parameters from LiDAR measurements, and the implementation of an integrated software package to incorporate all the above development. This work exploited the untouched potential of airborne laser profilers for realtime forest inventory, and therefore, documented an initial step toward developing airborne-laser-based, on-the-fly, real-time, forest inventory systems. Results from this work demonstrated the utility and effectiveness of airborne scanning or profiling laser systems for remotely measuring various forest structural attributes at a range of scales, i.e., from individual tree, plot, stand and up to regional levels. The system not only provides a regional assessment tool, one that can be used to repeatedly, remotely measure hundreds or thousands of square kilometers with little/no analyst interaction or interpretation, but also serves as a paradigm for future efforts in building more advanced airborne laser systems such as real-time laser scanners.

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Thesis (M.S.)--Miami University, Dept. of Botany, 2005. / Title from first page of PDF document. Document formatted into pages; contains [1], v, 38 p. : ill. Includes bibliographical references (p. 35-38).

Estimativas do rendimento da soja são informações importantes que podem auxiliar as instituições na tomada de decisão quanto à políticas de comercialização. São consideradas também, na liberação de recursos para o financiamento da produção e seguro agrícola. Modelos matemáticos, que se baseiam nas relações clima planta, denominados modelos agrometeorológicos, podem estimar o rendimento médio de grãos, através de dados meteorológicos e biofísicos da cultura, como exemplo: o IAF (Índice de área foliar) da soja pode ser associado ao Kc (Coeficiente de cultura) para estimar o estádio fenológico, e esta informação, ser associada à parametrização dos modelos. O objetivo geral deste trabalho foi avaliar as possibilidades de se utilizar imagens do sensor MODIS, para estimar parâmetros biofísicos da soja, aplicáveis à modelagem do rendimento de grãos. A área de estudo abrangeu a porção norte do estado do Rio Grande do Sul. Foram obtidas as imagens do IAF, MOD15A2, e dos índices de vegetação NDVI (Índice de vegetação por diferença normalizada) e NDWI (Índice de umidade por diferença normalizada), do produto MOD13Q1. Foram analisadas duas safras: 2003/04 e 2004/05. O período de safra foi de 15 de outubro até 30 de abril. Foram geradas máscaras de cultivo para as safras, e aplicadas sobre as imagens. Inicialmente, foram comparadas as médias do IAF, MOD15A2, às outras estimativas do IAF obtidas a partir de funções de relação com o NDVI, e analisados os diagramas de dispersão para cinco datas. Então foi estimado o Kc_1 com as médias do IAF, MOD15A2, conforme Martorano (2007), e comparadas ao Kc_2 ajustado conforme Matzenauer, 2002. Foi calculado o balanço hídrico meteorológico da cultura a fim de se obter o Índice de Satisfação das Necessidades de Água das plantas (ISNA), sendo ISNA_1 considerando o Kc_1, e o ISNA_2, o Kc_2. Foram obtidos os índices de correlação entre o ISNA_1 e 2 e os índices NDVI e NDWI, para o ciclo completo da cultura e para períodos de baixo ISNA. Como resultado, o IAF, MOD15A2 apresentou coerência com a evolução do IAF durante o ciclo, porém, em média, apresentou valores inferiores aos observados por Fontana et al. (1992) e Martorano (2007). Já como estimador do Kc, apresentou coeficientes de variação inferiores ao observado no Kc_2. Observou-se também que no IAF, MOD15A2 ocorriam valores superestimados do Kc entre a semeadura e o máximo desenvolvimento, e após, subestimados, o que potencializou períodos de déficit hídrico acentuado durante a floração e enchimento de grãos, em ambas as safras. Já, avaliando os índices de correlação, o ISNA_1, apresentou correlações de maior significância com os índices de vegetação do que o ISNA_2. Com isso podemos supor que, mesmo o IAF, MOD15A2 não tendo apresentado valores compatíveis com os da soja, demonstrou maior significância nas correlações, o que indica que imagens MODIS, podem gerar estimativas adequadas tanto do IAF, quanto do Kc, e também, representar adequadamente as condições hídricas. É recomendável avaliar estimativas do IAF da soja, a partir de suas relações com o NDVI, a fim de se obter resultados compatíveis com a soja. / Estimates of soybean yield are useful information that can assist institutions in decisions related by commercial policies. It is considered also in financing of production and agricultural insurance. Mathematical models, which are based in clime plant relationship known as Agrometeorological Models, can provide an estimate for grain yield through meteorological and biophysical data correlated with the culture, as an example: the LAI (Leaf Area Index) of soybean can be related with the Kc (Culture's coefficient) to estimate the phenological stage, and this information, applied to model's parameters. The main objective of this work was evaluated of possibilities of MODIS's images, in estimation of biophysical parameters, which are applicable in yield's modeling for soybean. The studying area was a portion of northern of State of Rio Grande do Sul. Were obtained images from LAI, MOD15A2, and vegetation indexes, NDVI (Normalized Difference Vegetation Index) and NDWI (Normalized Difference Water Index) from MOD13Q1 product. Were analyzed two harvests: 2003/04 and 2004/05. The length of time for harvest was 15th October to 30th April. Soybean's areas was detected and masks were applied on the images. Firstly, were compared the means between LAI, MOD15A2 and two different methodologies of LAI's estimation based on relationship with NDVI. The scatter plots were discussed between LAI, MOD15A2 and other methodologies, for five key-dates. The culture's coefficient Kc_1 was estimated through LAI, MOD15A2, according to Martorano (2007), and compare with Kc_2, which were obtained from fitted culture's coefficient by Matzenauer (2002). The water balance were calculated aiming the index for Plant's water satisfaction needs (ISNA), which, ISNA_1 has considered the Kc_1, and ISNA_2, the Kc_2. Correlation indexes were obtained between ISNA_1 and 2, and vegetation indexes NDVI and NDWI, for the whole culture's cycle and specific periods of low ISNA. As results, LAI, MOD15A2, has presented coherence with soybean's cycle progress, however, as a rule, it presents lower values, comparing to Fontana et al. (1992) and Martorano (2007). Even now as a Kc's estimator, Kc_1 has presented lower variation's coefficient compared to Kc_2. Was observed also overrated in Kc_1 between the sowing to maximum development, and after, underestimated, what provokes periods of accented hydric deficiency during flowering and grain forming stages, in both harvests. Now, as to correlation's indexes, we observed more significance correlations between both vegetation's indexes and ISNA_1. This way, these results has indicated that remote sensing images can provide accurate estimates of IAF as much as Kc, and also indicate the hydric conditions of plants. It is recommended to improve the LAI's mean values on the images, exploring the relationship with NDVI, looking for adequate values for the case of soybean.

A expansão da floresta sobre o campo, a partir do estabelecimento de araucárias isoladas (nucleação), forma uma paisagem única no planalto sul-brasileiro, sendo que o uso de uma abordagem de metacomunidades pode auxiliar a compreender melhor esse processo. Existem quatro modelos de metacomunidades que explicam a relação entre comunidades locais: dinâmica de manchas, seleção de espécies, efeitos de massa e neutro. Esses modelos possuem diferentes premissas quanto aos processos de nicho e de dispersão que atuam na dinâmica da metacomunidade. No entanto, há uma lacuna entre a teoria e o teste desses modelos em estudos empíricos. Uma forma de testar mais claramente esses modelos é através de uma abordagem funcional. Nesse contexto, o objetivo do trabalho foi avaliar a importância (i) de atributos relacionados às estratégias de dispersão e de crescimento das espécies, (ii) da abundância das espécies no pool regional e (iii) do tamanho da mancha, na organização de comunidades de indivíduos lenhosos juvenis em áreas de nucleação florestal sobre o campo, a fim de compreender quais modelos de metacomunidades melhor explicam esse processo. Para tanto, calculamos o CWM (Community Weighted Mean) e índices de diversidade funcional, considerando a ocorrência (sesFD) e a abundância (sesFDis) das espécies, para tamanho da semente e área foliar específica (SLA), em manchas florestais de distintos tamanhos e na floresta contínua adjacente ao campo, e testamos se as áreas diferem entre si de acordo com o tipo de ambiente. Avaliamos ainda se a abundância relativa das espécies nas áreas de nucleação é determinada pela abundância das mesmas na floresta contínua, através do uso dos modelos de Community Assembly by Trait Selection (CATS). Os resultados foram então comparados com o esperado para cada modelo de metacomunidade. A maior parte dos sítios apresentou índices de diversidade funcional para SLA e tamanho da semente de acordo com o esperado ao acaso. As áreas não diferiram quanto ao CWM para SLA. No entanto, foram observadas diferenças quanto ao CWM para o tamanho da semente, com o favorecimento de espécies com sementes menores em áreas mais abertas, e espécies com sementes maiores em áreas mais sombreadas. De acordo com os modelos CATS, a abundância das espécies no pool regional foi mais importante do que os atributos para a determinação da abundância das mesmas nas comunidades locais. Concluiu-se que o modelo de metacomunidades que melhor explica o processo de nucleação florestal sobre o campo no planalto das araucárias é o modelo de efeitos de massa, o que ressalta a importância da dispersão para a estruturação das comunidades locais. Como a maior parte das espécies lenhosas existentes na área possui dispersão zoocórica, esse resultado indica que a preservação da fauna dispersora é fundamental para a dinâmica desse ecossistema. Com o uso de uma abordagem funcional, em conjunto com os modelos CATS, foi possível testar os quatro modelos de metacomunidades. Assim, o método proposto pode ser aplicado a outros sistemas naturais, auxiliando na compreensão do funcionamento de diferentes metacomunidades. / The forest expansion over the grassland, from the establishment of isolated Araucaria (nucleation) forms a unique landscape in south brazilian plateau, and the use of a metacommunity approach can help to better understand this process. There are four metacommunity models that explain the relationship between local communities: patch-dynamics, species-sorting, mass-effects and neutral. These models have different assumptions about niche processes and dispersion that act in metacommunities dynamics. However, there is a gap between theory and the test of these models in empirical studies. One way to test these models more clearly is through a functional approach. In this context, the objective of this study was to evaluate the importance of (i) attributes related to dispersion and growth species strategies, (ii) species abundance in the regional pool and (iii) patch size, on structuring communities of juvenile woody individuals in forest nucleation areas on the grassland in order to understand which metacommunity model explain this process. Therefore, we calculate the CWM (Community Weighted Mean) and functional diversity indices, considering species occurrence (sesFD) and abundance (sesFDis) for seed size and specific leaf area (SLA), in forest patches of different sizes and in adjacent continuous forest and tested if sites differ according to ambient. Further, we evaluated if species relative abundance in nucleation areas is determined by the abundance in the continuous forest, by the use of Community Assembly by Trait Selection (CATS) models. Then, we compared results with expected for each metacommunity model. Most of sites presented functional diversity values for SLA and seed size as expected by chance. Areas did not differ in CWM to SLA. However, we observed differences for CWM to seed size, favoring species with smaller seeds in more open areas, and species with larger seeds in more shaded areas. According to CATS models, species abundance in regional pool was more important than attributes to determine species abundance in local communities. We concluded that the metacommunity model that best explains forest nucleation on the grassland in Araucaria plateau is the mass-effects model, which emphasizes the importance of dispersion for structuring local communities. As most of existing woody species has zoochorous dispersion, this result indicates that preservation of disperser fauna is essential for ecosystem dynamic. By using a functional approach in combination with CATS models, it was possible to test the four metacommunity models. Thus, the method proposed in this work can be applied to other natural systems, helping understanding different metacommunities operation.

A evapotranspiração (ET) é um fenômeno natural que influencia diretamente mudanças no clima local e global, possuindo grande importância hidrológica e meteorológica. Este trabalho teve como objetivo estimar a ET através do método Penman-Monteith, e comparar com os resultados estimados pelo Método da Covariância de Vórtices Turbulentos. Os dados de IAF (Índice de Área Foliar) para descrição da vegetação foram obtidos a partir do sensor MODIS e de medições em campo da Rede SulFlux. A área de estudo desta pesquisa localizou-se no município de Cachoeira do Sul-RS, em uma propriedade de cultivo de arroz irrigado. O período de estudo referiu-se a safra que estendeu-se de outubro de 2010 a março de 2011. Os resultados mostraram que o IAF e as estimativas de ET apresentam um comportamento temporal semelhante. A comparação entre os resultados das estimativas de ET, utilizando dados obtidos em campo e estimados através de sensoriamento remoto, foram satisfatórios. No entanto, o resultado que apresentou os maiores valores para a ET foi proveniente do sensor MODIS. Sendo assim, pode-se concluir que a estimativa da ET, a partir de dados de vegetação, obtidos através de técnicas de sensoriamento remoto, constituem-se como uma alternativa para os métodos de ET que utilizam dados de vegetação medidos em campo. / The Evapotranspiration (ET) is a natural phenomenon that directly causes changes in the local and global climate, having a great hydrologic and meteorological importance. This work has as objective to estimate ET through the Penman-Monteith method and compare with the estimated results by the Eddy Covariance Method. The LAI (Leaf Area Index) data for the vegetation description were obtained from the MODIS sensor and from field measurements of the SulFlux network. The field of study of this research had place in the city of Cachoeira do Sul – Rio Grande do Sul state, in a irrigated rice crop property. The study period is referred to the crop that extended from October 2010 to March 2011. The results showed that the LAI and the ET estimates have a similar temporal behavior. The comparison between the results of ET estimates, using data obtained in field and estimated through remote sensing, were satisfactory. However, the result that showed the highest values for ET was from the MODIS sensor. This way, it can be concluded that the ET estimate, through vegetation data, obtained by remote sensing techniques, are an alternative for the ET methods that use vegetation field measured data.

A evapotranspiração (ET) é um fenômeno natural que influencia diretamente mudanças no clima local e global, possuindo grande importância hidrológica e meteorológica. Este trabalho teve como objetivo estimar a ET através do método Penman-Monteith, e comparar com os resultados estimados pelo Método da Covariância de Vórtices Turbulentos. Os dados de IAF (Índice de Área Foliar) para descrição da vegetação foram obtidos a partir do sensor MODIS e de medições em campo da Rede SulFlux. A área de estudo desta pesquisa localizou-se no município de Cachoeira do Sul-RS, em uma propriedade de cultivo de arroz irrigado. O período de estudo referiu-se a safra que estendeu-se de outubro de 2010 a março de 2011. Os resultados mostraram que o IAF e as estimativas de ET apresentam um comportamento temporal semelhante. A comparação entre os resultados das estimativas de ET, utilizando dados obtidos em campo e estimados através de sensoriamento remoto, foram satisfatórios. No entanto, o resultado que apresentou os maiores valores para a ET foi proveniente do sensor MODIS. Sendo assim, pode-se concluir que a estimativa da ET, a partir de dados de vegetação, obtidos através de técnicas de sensoriamento remoto, constituem-se como uma alternativa para os métodos de ET que utilizam dados de vegetação medidos em campo. / The Evapotranspiration (ET) is a natural phenomenon that directly causes changes in the local and global climate, having a great hydrologic and meteorological importance. This work has as objective to estimate ET through the Penman-Monteith method and compare with the estimated results by the Eddy Covariance Method. The LAI (Leaf Area Index) data for the vegetation description were obtained from the MODIS sensor and from field measurements of the SulFlux network. The field of study of this research had place in the city of Cachoeira do Sul – Rio Grande do Sul state, in a irrigated rice crop property. The study period is referred to the crop that extended from October 2010 to March 2011. The results showed that the LAI and the ET estimates have a similar temporal behavior. The comparison between the results of ET estimates, using data obtained in field and estimated through remote sensing, were satisfactory. However, the result that showed the highest values for ET was from the MODIS sensor. This way, it can be concluded that the ET estimate, through vegetation data, obtained by remote sensing techniques, are an alternative for the ET methods that use vegetation field measured data.