Academic literature on the topic 'Water Stress Indices'

Heavy metal stress will induce the change of the bio-parameters like chlorophyll, nitrogen and water content of rice. In this paper, we analyzed the traditional spectral index which has strong relationship in general with the three bio-parameters using hyperspectral data acquired by ASD. It is found that some indies do not work well when the heavy metal stress exists, however, some indies still has ability to estimate the above three bio-parameters. A new interpretation is proposed to classify the stress level based on both the physical mechanism analysis and the statistic model after we describe and discuss studies on the expression of spectral indices of rice under heavy metal stress. The 3-axes spectral indices spaces, which are constructed of 3 spectral indices sensitive to rice’s chlorophyll concentration, nitrogen concentration and water concentration respectively, are used to visualize the linkage between heavy metal stress and spectrum of rice canopy.

Heavy metal stress will induce the change of the bio-parameters like chlorophyll, nitrogen and water content of rice. In this paper, we analyzed the traditional spectral index which has strong relationship in general with the three bio-parameters using hyperspectral data acquired by ASD. It is found that some indies do not work well when the heavy metal stress exists, however, some indies still has ability to estimate the above three bio-parameters. A new interpretation is proposed to classify the stress level based on both the physical mechanism analysis and the statistic model after we describe and discuss studies on the expression of spectral indices of rice under heavy metal stress. The 3-axes spectral indices spaces, which are constructed of 3 spectral indices sensitive to rice’s chlorophyll concentration, nitrogen concentration and water concentration respectively, are used to visualize the linkage between heavy metal stress and spectrum of rice canopy.

. Effect of different irrigation levels on yield, dry matter production, water use efficiency and leaf area index were studied: Relationship of water use under differential irrigation was round to be significant on three accumulated stress indices derived from canopy temperature, viz., canopy temperature, stress degree days and crop water stress index. Final grain yields were significantly correlated with these indices. It was envisaged that these indices can be exploited for crop yield prediction at large scale farmer's field for operational applications

Periods of soil water stress have been recurrent in the Cerrado region and have become a growing concern for Brazilian tropical pasture areas. Thus, the search for forage grasses more tolerant to water stress has intensified recently in order to promote more sustainable livestock. In a greenhouse experiment, the degree of water stress tolerance of nine tropical forage grass cultivars was studied under different soil water regimes. The investigation followed a 9 × 3 factorial design in four randomized blocks. Nine cultivars from five species of perennial forage grasses were tested: Urochloa brizantha (‘BRS Piatã’, ‘Marandu’, and ‘Xaraés’), Panicum maximum (‘Aruana’, ‘Mombaça’, and ‘Tanzânia’), Pennisetum glaucum (‘ADR 300’), Urochloa ruziziensis (‘Comum’), and Paspalum atratum (‘Pojuca’). These cultivars were grown in pots under three soil water regimes (high soil water regime—HSW (non-stressful condition), middle soil water regime—MSW (moderate water stress), and low soil water regime—LSW (severe water stress)). Plants were exposed to soil water stress for 25 days during the tillering and stalk elongation phases. Twelve tolerance indices, including tolerance index (TOL), mean production (MP), yield stability index (YSI), drought resistance index (DI), stress tolerance index (STI), geometric mean production (GMP), yield index (YI), modified stress tolerance (k1STI and k2STI), stress susceptibility percentage index (SSPI), abiotic tolerance index (ATI), and harmonic mean (HM), were calculated based on shoot biomass production under non-stressful (YP) and stressful (YS) conditions. Soil water stress decreased leaf area, plant height, tillering capacity, root volume, and shoot and root dry matter production in most cultivars, with varying degrees of reduction among tropical forage grasses. Based on shoot biomass production under controlled greenhouse conditions, the most water-stress-tolerant cultivars were P. maximum cv. Mombaça and cv. Tanzânia under the MSW regime and P. maximum cv. Aruana and cv. Mombaça under the LSW regime. P. maximum cv. Mombaça has greater adaptability and stability of shoot biomass production when grown under greenhouse conditions and subjected to soil water stress. Therefore, this forage grass should be tested under field conditions to confirm its forage production potential for cultivation in tropical regions with the occurrence of water stress. The MP, DI, STI, GMP, YI, k2STI, and HM tolerance indices were the most suitable for identifying forage grass cultivars with greater water stress tolerance and a high potential for shoot biomass production under LSW regime.

Since water is increasingly becoming an expensive and limited resource, it is necessary to improve crop water use efficiency (WUE) to save water while maintaining high yields. The objective of this research was to evaluate the effects of moderate water stress compared to well-watered conditions (supplying 50 or 100% of the maximum evapotranspiration (ETm)) on dry aboveground biomass yield (AB-Y), dry whole biomass yield (WB), tuber yield, irrigation WUE, and WUE at early harvest (E-TY, E-IWUE, E-YWUE), and at final harvest (F-TY, F-IWUE, F-YWUE), on WUE for dry aboveground biomass (AB-WUE) and for dry whole biomass (WB-WUE), on sink/source ratio and dry matter content of tubers in two potato cultivars—Sieglinde and Spunta, in two planting dates (early and late). Moderate water stress, compared to well-watered conditions, resulted in a small decrease in E-TY (−14%) and F-TY (−11%), but a high increase in E-IWUE (+69%) and F-IWUE (+78%), making savings in irrigation water of roughly 380 or 600 m3 per crop cycle in relation to early or final harvest. Moderate water stress improved in Sieglinde IWUE, YWUE, and WB-WUE at final harvest, whereas Spunta appeared more appropriate for early harvest. In the late planting date, the crop used water better compared to the early planting, resulting in a greater increase in IWUE (+77 vs. +66%) and an, albeit, slight increase in the WUE. It would, therefore, be convenient to apply the moderate water stress in the late planting, saving a further 100 m3 of irrigation water. The highest yield, IWUE, and YWUE were reached when moderate water stress was applied in both planting dates on cv. Spunta for early harvest and on cv. Sieglinde for final harvest. It was possible to increase WUE indices and save water, not only by water management, but also by choosing opportune planting dates and cultivars.

Wheat is one of the most important crops in the world. Its yield is greatly influenced by global climate change and scarcity of water in the arid and semi-arid areas of the world. So, exploration of gene resources is of importance to wheat breeding in order to improve the crop ability of coping with abiotic stress environment. Wild relatives of wheat are rich repositories of beneficial genes that confer tolerance or resistance not only to drought but also to other environmental stresses. In the present study, the changes in leaf relative water content (RWC), free proline content, and malondialdehyde (MDA) accumulation of five wild wheat species including T. boeticum (YS-1L), T. dicoccum var. dicoccoides (YS-2L), T. araraticum (ALLT), and two cultivated varieties of T. turgidum ssp. durum (MXLK and 87341), with two well-known common wheat cultivars (SH6 and ZY1) possessing strong drought resistance and sensitiveness, respectively, as references were investigated during 3-day water stress and 2-day recovery, in order to assess the drought tolerance of these wild wheat species. The laboratory experiment was conducted under two water regimes (stress and non-stress treatments). Stress was induced to hydroponically grown two weeks old wheat seedlings with 20% PEG 6000. Stress treatment caused a much smaller decrease in the leaf RWC and rise in MDA content in YS-1L compared to the other wheat species. From the data it was obvious that YS-1L was the most drought tolerant among studied species having significantly higher proline and RWC while lower MDA content under water stress conditions. The order of water stress tolerance of these species according to the three parameters is: YS-1L > YS-2L > SH6 > 87341 > ZY1 > MXLK > ALLT. We speculate that the observed drought stress tolerance at a cellular level was associated with the ability to accumulate proline and high water level conservation.

Drought and water scarcity due to global warming, climate change, and social development have been the most death-defying threat to global agriculture production for the optimization of water and food security. Reflectance indices obtained by an Analytical Spectral Device (ASD) Spec 4 hyperspectral spectrometer from tomato growth in two soil texture types exposed to four water stress levels (70–100% FC, 60–70% FC, 50–60% FC, and 40–50% FC) was deployed to schedule irrigation and management of crops’ water stress. The treatments were replicated four times in a randomized complete block design (RCBD) in a 2 × 4 factorial experiment. Water stress treatments were monitored with Time Domain Reflectometer (TDR) every 12 h before and after irrigation to maintain soil water content at the desired (FC%). Soil electrical conductivity (Ec) was measured daily throughout the growth cycle of tomatoes in both soil types. Ec was revealing a strong correlation with water stress at R2 above 0.95 p < 0.001. Yield was measured at the end of the end of the growing season. The results revealed that yield had a high correlation with water stress at R2 = 0.9758 and 0.9816 p < 0.01 for sandy loam and silty loam soils, respectively. Leaf temperature (LT °C), relative leaf water content (RLWC), leaf chlorophyll content (LCC), Leaf area index (LAI), were measured at each growth stage at the same time spectral reflectance data were measured throughout the growth period. Spectral reflectance indices used were grouped into three: (1) greenness vegetative indices; (2) water overtone vegetation indices; (3) Photochemical Reflectance Index centered at 570 nm (PRI570), and normalized PRI (PRInorm). These reflectance indices were strongly correlated with all four water stress indicators and yield. The results revealed that NDVI, RDVI, WI, NDWI, NDWI1640, PRI570, and PRInorm were the most sensitive indices for estimating crop water stress at each growth stage in both sandy loam and silty loam soils at R2 above 0.35. This study recounts the depth of 858 to 1640 nm band absorption to water stress estimation, comparing it to other band depths to give an insight into the usefulness of ground-based hyperspectral reflectance indices for assessing crop water stress at different growth stages in different soil types.

ABSTRACT Sugarcane (Saccharum officinarum L.) is a crop of vital importance to Brazil, in the production of sugar and ethanol, power generation and raw materials for various purposes. Strategic information such as topography and canopy temperature can provide management technologies accessible to farmers. The objective of this study was to determine water stress indices for sugarcane in irrigated areas, with different exposures and slopes. The daily water stress index of the plants and the water potential in the soil were evaluated and the production system was analyzed. The experiment was carried out in an “Experimental Watershed”, using six surfaces, two horizontal and the other ones with 20 and 40% North and South exposure slopes. Water stress level was determined by measuring the temperatures of the vegetation cover and the ambient air. Watering was carried out using a drip irrigation system. The results showed that water stress index of sugarcane varies according to exposure and slope of the terrain, while areas whose water stress index was above 5.0 oC had lower yield values.

The capability to measure the magnitude of water stress in plants is useful for precision irrigation scheduling and other purposes. This paper reports an evaluation of leaf (TL) and canopy (Tc) temperatures, leaf minus air (TL -Ta) and canopy minus air (Tc -Ta) temperatures, and leaf water stress index (LWSI) and crop water stress index (CWSI) in detecting stress in pearl millet (Pennisetum americanum (L.) Leeke) over two growing seasons. Baselines which were used to compute LWSI and CWSI were obtained. The upper and lower baselines for the Tc data, respectively, were Tc -Ta = 4.10 C and Tc -Ta = 3.87- .2001VPD where VPD is vapor pressure deficit in mbars. For the TL data, the upper and lower baselines, respectively, were TL -Ta = 1.97oC and TL -Ta = 1.308- .03006VPD. Tests against photosynthesis, transpiration, and grain yield showed that LWSI and CWSI are better indices of stress than TL -Ta, Tc -Ta, TL, Tc, or Ta. Average seasonal LWSI and CWSI ranged from approximately 0.03 for non- stressed to 0.80 for stressed plants. The reliability of LWSI and CWSI to detect stress and their relation with grain yield suggested the possibility of using these indices for irrigation scheduling decisions.

Increased water scarcity due to changing climate, population growth, and economic development is a major threat to the sustainability of irrigated agriculture in the Western United States and other regions around the world. Management practices, such as controlled deficit irrigation, that seek to maximize the productivity of a limited water supply are critical. When using controlled deficit irrigation, remote sensing of crop canopy temperature is a useful tool for assessing crop water status and for more precise irrigation management. However, there is potential that nutrient deficiencies could compound the interpretation of water status from leaf temperature by altering leaf color and radiation balance. One objective of this thesis was to evaluate whether nitrogen fertility status of maize interacts with remotely sensed leaf temperature under full and limited irrigation. Another objective was to evaluate the effect of varying irrigation and nitrogen regimes on three water stress indices: Crop Water Stress Index (CWSI), Degrees Above Non-Stressed (DANS), and Degrees Above Canopy Threshold (DACT). Replicated studies were conducted using maize grown in both the glasshouse and the field. The glasshouse study consisted of combinations of well-watered and drought irrigation and sufficient and deficient nitrogen levels, while the field study consisted of combinations of well-watered, limited or controlled deficit, and drought irrigation and sufficient, sufficient delayed, and deficient nitrogen levels. In the glasshouse, leaf chlorophyll content was reduced moderately by limited irrigation and more so by N deficiency. For most observations in the glasshouse, the remotely sensed leaf temperatures were affected by irrigation, but not by N level. With drought irrigation, leaf temperature averaged 29.0° C, compared to 27.9 °C for the well-watered treatment. Similar results were observed in the field, illustrating the utility of canopy temperature in detecting water stress and that the measurement was not confounded by N status. It was also found that irrigation had a significant effect on all three water stress indices. For example, in the glasshouse, cumulative DANS was 32.2 for the drought treatment and 15.5 for the well-watered treatment. Similar results were found for other stress index measurements both in the glasshouse and the field. DANS underestimated stress on days when the reference crop was stressed and overestimated stress on low temperature days. DACT risks finding no stress when temperatures are below the canopy threshold temperature of 28.0 °C. Thus, CWSI is the most effective index, given that it takes humidity and air temperature into account. Indices were only weakly related to leaf area, biomass or grain yield, or crop water productivity. Linear regression of Nitrogen Sufficiency Index and its effect on crop growth found significant effects on biomass and grain yield, crop water productivity, and final leaf area. Thus, water stress indices are useful tools in evaluating crop water status, but consideration of other factors, such as nutrient status, must be taken for prediction of crop growth and yield.

Three nontaxonomic indices; ATP/Chlorophyll a(ATP/Chla), ATP/ADP, and Chlorophyll a/Pheopigment (Chla/Pheo) were compared to the taxonomic measures of species diversity (d) and species richness as indicators of stress in aquatic environments. Field and laboratory microcosm responses of indigenous microbial communities exposed to municipal sewage treatment plant (STP) effluent were monitored. The STP effluent produced increased adenylate concentrations, ATP/ADP and ATP/Chla ratios, and decreased Chla, Chla/Pheo, d, and species richness relative to upstream reference communities. Nontaxonomic responses were consistent in four separate field tests.

Significant differences in responses were discernible in 3 d when communities were transferred from reference to polluted sites. Chla/Pheo decreased more rapidly than other measurements. The predictive capability of laboratory flowâ through microcosm tests was examined by simultaneously transferring communities from upstream reference sites to downstream field sites and to various dilutions of field effluent in the laboratory.

Master of Science

L'optimisation de la gestion de l'eau en agriculture est essentielle dans les zones semi-arides afin de préserver les ressources en eau qui sont déjà faibles et erratiques dues à des actions humaines et au changement climatique. Cette thèse vise à utiliser la synergie des observations de télédétection multispectrales (données radar, optiques et thermiques) pour un suivi à haute résolution spatio-temporelle des besoins en eau des cultures. Dans ce contexte, différentes approches utilisant divers capteurs (Landsat-7/8, Sentinel-1 et MODIS) ont été developpées pour apporter une information sur l'humidité du sol (SM) et le stress hydrique des cultures à une échelle spatio-temporelle pertinente pour la gestion de l'irrigation. Ce travail va parfaitement dans le sens des objectifs du projet REC "Root zone soil moisture Estimates at the daily and agricultural parcel scales for Crop irrigation management and water use impact: a multi-sensor remote sensing approach" (http://rec.isardsat.com/) qui visent à estimer l'humidité du sol dans la zone racinaire (RZSM) afin d'optimiser la gestion de l'eau d'irrigation. Des approches innovantes et prometteuses sont mises en place pour estimer l'évapotranspiration (ET), RZSM, la température de surface du sol (LST) et le stress hydrique de la végétation à travers des indices de SM dérivés des observations multispectrales à haute résolution spatio-temporelle. Les méthodologies proposées reposent sur des méthodes basées sur l'imagerie, la modélisation du transfert radiatif et la modélisation du bilan hydrique et d'énergie et sont appliquées dans une région à climat semi-aride (centre du Maroc). Dans le cadre de ma thèse, trois axes ont été explorés. Dans le premier axe, un indice de RZSM dérivé de LST-Landsat est utilisé pour estimer l'ET sur des parcelles de blé et des sols nus. L'estimation par modélisation de ET a été explorée en utilisant l'équation de Penman-monteith modifiée obtenue en introduisant une relation empirique simple entre la résistance de surface (rc) et l'indice de RZSM. Ce dernier est estimé à partir de la température de surface (LST) dérivée de Landsat, combinée avec les températures extrêmes (en conditions humides et sèches) simulée par un modèle de bilan d'énergie de surface piloté par le forçage météorologique et la fraction de couverture végétale dérivée de Landsat. La méthode utilisée est calibrée et validée sur deux parcelles de blé situées dans la même zone près de Marrakech au Maroc. Dans l'axe suivant, une méthode permettant de récupérer la SM de la surface (0-5 cm) à une résolution spatiale et temporelle élevée est développée à partir d'une synergie entre données radar (Sentinel-1) et thermique (Landsat) et en utilisant un modèle de bilan d'énergie du sol. L'approche développée a été validée sur des parcelles agricoles en sol nu et elle donne une estimation précise de la SM avec une différence quadratique moyenne en comparant à la SM in situ, égale à 0,03 m3 m-3. Dans le dernier axe, une nouvelle méthode est développée pour désagréger la MODIS LST de 1 km à 100 m de résolution en intégrant le SM proche de la surface dérivée des données radar Sentinel-1 et l'indice de végétation optique dérivé des observations Landsat. Le nouvel algorithme, qui inclut la rétrodiffusion S-1 en tant qu'entrée dans la désagrégation, produit des résultats plus stables et robustes au cours de l'année sélectionnée. Dont, 3,35 °C était le RMSE le plus bas et 0,75 le coefficient de corrélation le plus élevé évalués en utilisant le nouvel algorithme
Optimizing water management in agriculture is essential over semi-arid areas in order to preserve water resources which are already low and erratic due to human actions and climate change. This thesis aims to use the synergy of multispectral remote sensing observations (radar, optical and thermal data) for high spatio-temporal resolution monitoring of crops water needs. In this context, different approaches using various sensors (Landsat-7/8, Sentinel-1 and MODIS) have been developed to provide information on the crop Soil Moisture (SM) and water stress at a spatio-temporal scale relevant to irrigation management. This work fits well the REC "Root zone soil moisture Estimates at the daily and agricultural parcel scales for Crop irrigation management and water use impact: a multi-sensor remote sensing approach" (http://rec.isardsat.com/) project objectives, which aim to estimate the Root Zone Soil Moisture (RZSM) for optimizing the management of irrigation water. Innovative and promising approaches are set up to estimate evapotranspiration (ET), RZSM, land surface temperature (LST) and vegetation water stress through SM indices derived from multispectral observations with high spatio-temporal resolution. The proposed methodologies rely on image-based methods, radiative transfer modelling and water and energy balance modelling and are applied in a semi-arid climate region (central Morocco). In the frame of my PhD thesis, three axes have been investigated. In the first axis, a Landsat LST-derived RZSM index is used to estimate the ET over wheat parcels and bare soil. The ET modelling estimation is explored using a modified Penman-Monteith equation obtained by introducing a simple empirical relationship between surface resistance (rc) and a RZSM index. The later is estimated from Landsat-derived land surface temperature (LST) combined with the LST endmembers (in wet and dry conditions) simulated by a surface energy balance model driven by meteorological forcing and Landsat-derived fractional vegetation cover. The investigated method is calibrated and validated over two wheat parcels located in the same area near Marrakech City in Morocco. In the next axis, a method to retrieve near surface (0-5 cm) SM at high spatial and temporal resolution is developed from a synergy between radar (Sentinel-1) and thermal (Landsat) data and by using a soil energy balance model. The developed approach is validated over bare soil agricultural fields and gives an accurate estimates of near surface SM with a root mean square difference compared to in situ SM equal to 0.03 m3 m-3. In the final axis a new method is developed to disaggregate the 1 km resolution MODIS LST at 100 m resolution by integrating the near surface SM derived from Sentinel-1 radar data and the optical-vegetation index derived from Landsat observations. The new algorithm including the S-1 backscatter as input to the disaggregation, produces more stable and robust results during the selected year. Where, 3.35 °C and 0.75 were the lowest RMSE and the highest correlation coefficient assessed using the new algorithm

To protect and restore the biological integrity of streams, we need to be able to both detect biological degradation and infer likely causes of impairment. Managers often use biological indices to measure biological condition and detect degradation. However, the ability to detect degradation can be limited by the performance of the indices we develop. Index performance varies widely, but the sources of this variation are often unclear. In addition, although bioassessments are useful tools for detecting biological degradation, they do not identify stressors associated with impairment. My thesis research had two general goals: 1) develop statistically and ecologically robust indices to measure biological condition in Nevada streams and 2) quantify relationships between land uses, stressors, and biological condition to infer likely causes of degradation. I developed two biological indices for Nevada streams, a multimetric index (MMI) and observed to expected (O/E) taxa ratios, and determined if index performance was related to site isolation and sample evenness. The Nevada O/E indices were relatively imprecise compared with those from other regions, which likely results from low assemblage predictability associated with spatial isolation of aquatic habitats in arid regions. In contrast, the Nevada MMI was more precise than most previously developed MMIs, likely the result of using models to reduce natural variation in index scores. Sample evenness was positively associated with both O/E and MMI scores. Adjustments of index scores for sample evenness increased index precision, but also altered relative differences in index values and therefore inferences of biological impairment at specific sites. I also quantified relationships between biological condition, instream stressors, and land uses and used a weight of evidence approach to infer likely causes of degradation. Land uses such as agriculture, urbanization, and mining were associated with the spatial distributions of instream stressors, and these stressors were associated with variation in biological condition. Total dissolved solids and metal contamination were the stressors most strongly associated with biological condition. By detecting biological degradation and identifying important stressors and their potential sources, the tools I developed should help managers target conservation and restoration efforts and improve their ability to protect freshwater resources.

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The work was performed aiming to evaluate the effect of water deficit on growth of neem seedlings and water relations. The experimental design was entirely randomized, with seven treatments (100, 80, 60, 40, 20% of pot capacity, without water and re-watering). The height, number of leaves and stem diameter were analyzed weekly. At the end of the experiment, dry matter of the leaves,shoots, roots, root to shoot ratio and biomass allocation were determined. Leaf area, leaf area ratio and specific leaf area were also calculated. Leaf water potential (predawn and noon), relative water content and contents of compatible solutes were evaluated at the same day. Water stress reduced the height, number of leaves and shoot diameter in the plants of the severe treatments. Water stress reduced leaf, stem and root dry matter. Biomass allocation was sufficient to reduce only in case of leaves. Leaf area was also reduced; however, there were no significant differences in leaf area ratio and specific leaf area. The recovery of the re-watering plants was evident by emitting new leaves. Leaf water potential was reduced by the water deficit in the treatments with 20% of pot capacity and without. The same behavior was verified for the relative water content. On the re-watering plants, though was verified rehabilitation of plants but at the end of experiment, these plants showed reductions in the leaf water potential and relative water content. Carbohydrates, proteins and proline contents increased with the water deficit. This elevation was possible because of reduction in relative water content. The results indicate that neem seedlings reduced leaf water potential because of the reduction on the relative water content and this specie can be cultivated, at the initial phase of development, under 80% of pot capacity, with highest production.
A pesquisa teve como objetivo avaliar a influência do déficit hídrico no crescimento e nas relações hídricas de plantas jovens de nim indiano. O delineamento experimental utilizado foi inteiramente casualizado, com sete tratamentos hídricos (100, 80, 60, 40 e 20% da capacidade de pote (CP), suspensão de rega e Reirrigado). Foram avaliados semanalmente altura, número de folhas e diâmetro do caule. Ao final do experimento, as plantas foram levadas à estufa para obtenção da matéria seca das folhas, caule, raízes e total. De posse destes dados, foram calculadas a alocação de biomassa das folhas, caule e raízes. Também foram calculadas a área foliar, a razão de área foliar e a área foliar específica. O potencial hídrico foliar foi avaliado em três épocas (30, 45 e 60 dias após a diferenciação dos tratamentos hídricos) em dois horários de avaliação (pré-dawn e meio-dia). O teor relativo de água também foi avaliado em três épocas (30, 45 e 60 dias após a diferenciação dos tratamentos hídricos) utilizando-se as folhas da análise do potencial hídrico de meio-dia. O déficit hídrico reduziu a altura, número de folhas e diâmetro do caule das plantas nos tratamentos mais severos. Os efeitos do estresse também foram observados na redução da matéria seca das folhas, caule, raízes e total. Na alocação de biomassa, houve redução apenas na alocação para as folhas. Também ocorreram reduções significativas na área foliar, mas a razão de área foliar e a área foliar específica não diferiram entre os tratamentos. As plantas reirrigadas mostraram recuperação, evidenciada principalmente, pela emissão de novas folhas. Em todas as épocas e horários de avaliação, as plantas reduziram o potencial hídrico foliar nos tratamentos com 20% da CP, suspensão de rega e reirrigado. Nestes mesmos tratamentos, o teor relativo de água mostrou alteração semelhante, com reduções significativas nas três épocas de avaliação. Nas plantas do tratamento reirrigado, nas avaliações às 24h e 15 dias após essa reposição, foram verificadas recuperações significativas, mas, à medida que a umidade do solo decrescia, foram verificadas novas reduções no potencial hídrico foliar e teor relativo de água. Com relação às quantificações de carboidratos solúveis, proteínas solúveis e prolina livre, foram verificados aumentos significativos de acordo com a severidade dos tratamentos. Correlacionando esses dados com o teor relativo de água, verificou-se que o aumento na concentração de solutos se deu principalmente em função da redução na quantidade de água da célula.Deste modo, sugere-se que o nim indiano reduz o potencial hídrico foliar em função da queda no conteúdo relativo de água e, conclui-se também, que esta espécie pode ser cultivada na fase inicial de desenvolvimento com 80% da capacidade de pote, obtendo-se o máximo de produção.

This thesis investigated the effect of drought stress on agronomical, and physiological characteristics of sesame plants during growth and development, and analysed such responses using Fuzzy set theory (FST) and Artificial Neural Networks (ANN), two mathematical modeling tools. Subjected to cultivar and developmental stages exposed to drought, tested sesame cultivar/s expressed versatile morphological adaptations and adjusted leaf osmotic potential as a drought tolerant mechanism to survive drought conditions. The thesis proposed FST models with various membership functions to describe germination, growth and yield responses of sesame cultivars, and ANN models to forecast sesame yield under given climatic conditions.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
The cultivation of cowpea (Vigna unguiculata L. Walp) in Brazil has been frequently carried out without irrigation, with frequent occurrence of dry periods during the crop cycle. The negative effects of water deficit on plant production can be intensified by weed infestations and result in lower crop performance. Therefore, the objective of the work was to evaluate the effects of temporary water deficits on the soil and of competition in the growth and dry matter partition, macronutrient accumulation and efficiency, and physiological characteristics of cowpea (Vigna unguiculata L. cv BRS Guariba) and two weeds Commelina benghalensis L. and Waltheria indica L. For that, an experiment was carried out in a greenhouse of the Department of Plant Sciences of the Federal University Rural Semi-Arid. The experimental unit corresponded to a plastic vessel with a volumetric capacity of 10 dm-3. The experimental design for the randomized blocks, with four replications. The treatments were arranged in a 5x2 factorial, with the first factor corresponding to the types of interaction between the species (V. unguiculata + C. benghalensis; V. unguiculata + W. indica; V. unguiculata, C. benghalensis and W. indica in monoculture), and the second, of water regimes (Irrigated and Water deficit). The water deficit was simulated when the the cowpea plants were with the second definite trefoil (stage V4), being maintained for eleven days, until the photosynthetic rate of the culture, at 9:00 am, reached values close to zero, when irrigation was resumed. From the date of the suspension of irrigation, the plants were submitted to the following evaluations: water potential at pre-dawn and at noon; stomatal conductance; transpiration; and net photosynthetic rate; until the CO2 assimilation rates of the plants submitted to the water deficit were similar to those of the irrigated ones. At the end of the experiment, we evaluated: the number of leaves per plant; the leaf area; the dry mass of leaves, stems, roots, and total; the dry mass partitioning; and macronutrient accumulation and partition. The water deficit reduced the water potential and the gas exchange of the plant species, cultivated alone or in interaction. Cowpea and C. benghalensis tolerated the water deficit in the soil through the strict control of the stomatal opening, being categorized as more water conservative species. Competition among plants anticipated the negative effects of soil water deficit. Waltheria indica presented greater competition capacity for water, having delayed the recovery of cowpea. The soil water deficit reduced nutrient content in the following decreasing order: cowpea - Ca (stem), K (root), Mg (leaf) and N (root); C. benghalensis - N, P and K (stem); and W. indica – K, N, P, Ca and Mg (leaf). The water deficit reduced the N and P utilization efficiency of cowpea, and of Mg of C. benghalensis. The competition provided variable effect on the accumulation and efficiency of macronutrients utilization of cowpea and weeds C. benghalensis and W. indica. The cowpea suffered greater interference with the W. indica weed when cultivated on soil not irrigated. C. benghalensis presented high potential for macronutrient cycling in the two water regimes. The water deficit reduced the growth of cowpea plants, C. benghalensis and W. indica. The competition between plants increased the effects of temporary water deficit in the soil. The W. indica leaf was the organ most affected by the water deficit. W. indica has greater capacity competition for water with V. unguiculata than C. benghalensis
O cultivo de feijão-caupi (Vigna unguiculata L. Walp) no Brasil tem sido frequentemente realizado em condições de sequeiro, o que aumenta a possibilidade de ocorrência de veranicos durante o ciclo da cultura. Os efeitos negativos do déficit hídrico podem ser intensificados por infestações de plantas daninhas e resultar em menor desenvolvimento da cultura. Diante disso, o objetivo do trabalho foi avaliar os efeitos de déficit hídrico temporário no solo e da competição no crescimento e partição de massa seca, acúmulo e eficiência de macronutrientes, e nas características fisiológicas de feijão-caupi (Vigna unguiculata L. cv BRS Guariba) e das plantas daninhas trapoeraba (Commelina benghalensis L.) e malva-branca (Waltheria indica L.). Para tanto, foi realizado experimento em casa de vegetação do Departamento de Ciências Vegetais da Universidade Federal Rural do Semi-Árido. A unidade experimental correspondeu a um vaso plástico com capacidade volumétrica de 10 dm-3. O delineamento experimental foi em blocos casualizados, com quatro repetições. Os tratamentos foram arranjados em esquema fatorial 5x2, com o primeiro fator correspondente aos tipos de interação entre as espécies (feijão-caupi + trapoeraba; feijão + malva-branca; feijão-caupi, trapoeraba e malva-branca em monocultivo), e o segundo dos regimes hídricos (Irrigado e Déficit hídrico). O déficit hídrico foi simulado quando as plantas de feijão-caupi estavam com o segundo trifólio definitivo (estádio V4), sendo mantida por onze dias, até a taxa fotossintética da cultura, às 09h00min da manhã, alcançar valores próximos de zero, momento em que foi retomada a irrigação. A partir da data da suspensão da irrigação, as plantas foram submetidas às seguintes avaliações: potencial hídrico ao préamanhecer e ao meio-dia; condutância estomática; transpiração e a taxa fotossintética líquida; até que as taxas de assimilação de CO2 das plantas submetidas ao déficit hídrico fossem semelhantes às das irrigadas. Ao final do experimento, foram avaliados: o número de folhas por planta; a área foliar; a massa seca de folhas, caules, raízes, e total; a partição de massa seca; o acúmulo e partição de macronutrientes. O déficit hídrico reduziu o potencial hídrico e as trocas gasosas das espécies, cultivadas isoladamente ou em interação. O feijão-caupi e C. benghalensis toleraram o déficit hídrico no solo por meio do rígido controle da abertura estomática, sendo espécies mais conservadoras. A competição entre plantas antecipou os efeitos negativos do déficit hídrico no solo. Waltheria indica apresentou maior capacidade de competição por água, tendo atrasado a recuperação do feijão-caupi. O déficit hídrico no solo reduziu o conteúdo dos nutrientes na seguinte ordem decrescente: feijão-caupi - Ca (caule), K (raiz), Mg (folha) e N (raiz); C. benghalensis - N, P e K (caule); e W. indica – K, N, P, Ca e Mg (folha). O déficit hídrico reduziu a eficiência de utilização de N e P do feijão-caupi, e de Mg da C. benghalensis. A competição proporcionou efeito variável sobre o acúmulo e eficiência de utilização de macronutrientes de feijão-caupi e das plantas daninhas C. benghalensis e W. indica. O feijão-caupi sofreu maior interferência com a planta daninha W. indica quando cultivado em solo não irrigado. C. benghalensis apresentou elevado potencial para ciclagem de macronutrientes nos dois regimes hídricos. O déficit hídrico reduziu o crescimento das plantas de feijão-caupi, C. benghalensis e W. indica. A competição entre plantas aumentou os efeitos do déficit hídrico temporário no solo. A folha de W. indica foi o órgão mais afetado pelo déficit hídrico. A W. indica tem maior capacidade de competição por água com o feijão-caupi do que a C. benghalensis.
2017-07-13

Ph.D., Faculty of Science, University of the Witwatersrand, 2011
Deep-level gold mining in the Witwatersrand Basin Goldfields (WBG) of central South Africa is characterised by the production of extensive unlined tailings storage facilities (TSFs) comprising large quantities of pulverised rock and water contaminated with salts and a wide range of other inorganic pollutants (Weiersbye et al., 2006). There are more than 200 such TSFs covering a total area of more than 400 km2 (Rosner et al., 2001), and significant contaminated “footprint” areas occur after removal and reprocessing of the original TSFs (Chevrel et al., 2003). It is estimated that the Witwatersrand Basin contains six billion tons of gold and uranium tailings (Chevrel et al., 2003), 430 000 tons of uranium (Council of Geoscience, 1998; Winde, 2004a; b; c) and approximately 30 million tons of sulphur (Witkowski and Weiersbye, 1998a). An estimated 105 million tons of waste per annum is generated by the gold mining industry within the WBG (Department of Tourism, Economic and Environmental Affairs, 2002; Chamber of Mines of South Africa, 2004). A major environmental problem resulting from deep level mining in the WBG is the contaminated water that seeps from TSFs into adjacent lands and groundwater. Van As (1992) reported on the significant environmental hazards resulting from the storage of highly pulverised pyrite rock waste in TSFs (Straker et al., 2007). Adjacent lands become polluted through near-surface seepage, and this is enhanced by the movement of polluted groundwater in shallow aquifers that are commonly 1-30 m below ground (Funke, 1990; Hodgson et al., 2001; Rosner et al., 2001; Naicker et al., 2003). The impact of the mines and the TSFs extends far beyond their localities (Cogho et al., 1990). The Vaal River catchment receives a large proportion of the pollutants from WBG mining activities, with consequent acidification and salinisation of surface and ground waters. Salt discharges to the Vaal River were estimated to be 170 000 t/annum (Best, 1985), whereas discharges from the Free State gold mines south of the Vaal catchment were estimated at 350 000 t/annum of salts (Cogho et al., 1990). Concern also exists over the spread of dangerous contaminants such as uranium, chromium and mercury (Coetzee et al., 2006; Winde, 2009). Engineering solutions to these problems are hindered by the large sizes and great extent of TSFs, the high and indefinite costs involved, and the typically low hydraulic conductivity in affected aquifers, which makes the “pump and treat” option impractical. An alternative phytoremediation strategy is to establish belts or blocks of trees in strategic areas surrounding the TSFs in order to reduce the seepage of contaminated water into adjacent lands and groundwater bodies. The major reasons why trees are likely to have a greater impact on seepage water than the existing grasslands that characterise the area around most TSFs in the WBG, are that some tree species have the potential to develop very deep root systems and to continue transpiring water throughout the year. This is in contrast to seasonally dormant grasslands. In addition, some tree species are known to be tolerant to salts and other pollutants. Trees are thus potentially able to reach deep water tables, take up large quantities of water, and remove some of the pollutants in this water. It is crucial for a successful implementation of this strategy to know on what sites trees are able to access mine seepage water, and consequently maintain a high year-round rate of water use. If this access is limited, then growth and water use will be curtailed during the long winter dry season, and control of seepage will be considerably below potential. A primary aim of this study was to develop methodologies to discriminate between water-stressed and non-water-stressed trees currently growing in three gold mining districts (Welkom, Vaal River, West Wits) within the WBG. This information was required to assess what site types are likely to support adequate tree growth and permit high rates of water use and seepage control. The tree species selected were those most widely occurring in these areas, and include the non-native species Eucalyptus sideroxylon A. Cunningham ex Woolls and Eucalyptus camaldulensis Dehnhardt, as well as the indigenous species Searsia lancea L.f. Various remote sensing technologies including leaf-level spectroscopy, satellite and airborne remote sensing images were evaluated for their usefulness in detecting levels of winter-time water stress. Four commonly used ground-truthing techniques (predawn leaf water potential, leaf chlorophyll fluorescence, leaf chlorophyll and carotenoid pigment content, and leaf water content) were used for localised measurements of plant water stress and for ground-truthing of remotely sensed data on 75 sample sites and 15 sample sites. This study provided a unique opportunity to test and compare the use of stress reflectance models derived from different remote sensing data acquired at different spatial and spectral resolutions (i.e. multispectral and hyperspectral) for the same geographical location. The use of remote sensing to examine the spectral responses of vegetation to plant stress has been widely described in the scientific literature. A collation of published spectral reflectance indices provided the basis for investigating the use of hand-held remote sensing technology to detect plant water stress, and was used as a stepping stone to further develop spectral plant water stress relationships for specific tree species in this study. Seventy seven spectral reflectance indices and specific individual spectral wavelengths useful for detecting plant water stress, plant pigment content, the presence of stress related pigments in vegetation, and changes in leaf cellular structure, were investigated using hand-held spectroscopy. Ground-based measurements of plant water stress were taken on 75 sample trees. In this study, the measurement of predawn leaf water potential has been identified as a key methodology for linking remotely sensed assessments of plant water stress to actual plant water stress; a reading of -0.8 MPa was used to separate stressed trees from unstressed trees in the landscape (Cleary and Zaerr, 1984). The results of the predawn leaf water potential measurements ranged from -0.56 to -0.68 MPa at unstressed sites, and from -0.93 to -1.78 MPa at stressed sites. A novel approach of using spectral reflectance indices derived from previous studies was used to identify specific indices which are applicable to South Africa and to the three species investigated in the WGB. Maximal multiple linear regression models were derived for all possible combinations of plant water stress measurements and the 77 spectral reflectance indices extracted from leaf-level spectral reflectance data, and included the interactions of district and species. The results of the multiple linear regression models indicated that the (695/690) index, DATT index (850-710)/(850-680), near infra-red index (710/760) and the water band (900/970) index performed well and accounted for more than 50% of the variance in the data. The stepwise regression model derived between chlorophyll b content and the DATT index was selected as the “best” model, having the highest adjusted R2 of 69.3%. This was shown to be the most robust model in this application, which could be used at different locations for different species to predict chlorophyll content at the leaf-level. Satellite earth observation data were acquired from two data sources for this investigation; the Hyperion hyperspectral sensor (United States Geological Survey Earth Resources Observation Systems) and the Proba Chris pseudo-hyperspectral sensor (European Space Agency). The Hyperion sensor was selected to obtain high spatial and spectral resolution data, whereas the Proba Chris sensor provided high spatial and medium spectral resolution earth observation data. Twelve vegetation indices designed to capture changes in canopy water status, plant pigment content and changes in plant cellular structure, were selected and derived from the satellite remote sensing imagery. Ground-based measurements of plant water stress undertaken during late July 2004 were used for ground-truthing the Hyperion image, while measurements undertaken during July 2005 and August 2005 were used for ground-truthing the Proba Chris images. Predawn leaf water potential measurements undertaken for the three species, ranged from -0.42 to -0.78 MPa at unstressed sites, and -0.95 to -4.66 MPa at stressed sites. Predawn leaf water potentials measured for E. camaldulensis trees sampled in species trials in Vaal River were significantly different between stressed and non stressed trees (t = 3.39, 8df, P = 0.009). In contrast, E. camaldulensis trees sampled near a pan within the Welkom mining district, which had greater access to water but were exposed to higher concentrations of salts and inorganic contaminants, displayed differences in total chlorophyll content (t = -2.20, 8df, P = 0.059), carotenoid content (t = -5.68, 8df, P < 0.001) and predawn leaf water potential (t = 4.25, 8df, P = 0.011) when compared to trees sampled on farmland. E. sideroxylon trees sampled close to a farm dam in the West Wits mining district displayed differences in predawn leaf water potential (t = 69.32, 8df, P < 0.001) and carotenoid content (t = -2.13, 8df, P = 0.066) when compared to stressed trees further upslope away from the water source. Multiple linear regressions revealed that the predawn leaf water potential greenness normalised difference vegetation index model, and the predawn leaf water potential water band index model were the “best” surrogate measures of plant water stress when using broad band multispectral satellite and narrow-band hyperspectral satellite data respectively. It was concluded from these investigations that vegetation indices designed to capture changes in plant water content/plant water status and spectral changes in the red edge region of the spectrum, performed well when applied to high spectral resolution remote sensing data. The greenness normalised difference vegetation index was considered to be a fairly robust index, which was highly correlated to chlorophyll fluorescence and predawn leaf water potential. It is recommended that this index has the potential to be used to map spatial patterns of winter-time plant stress for different genera/species and in different geographical locations. Airborne remote sensing surveys were conducted to investigate the application of high spatial resolution remote sensing data to detect plant water stress. Multispectral airborne imagery was acquired by Land Resource International (PTY) Ltd, South Africa. Ground-based measurements of plant water stress were carried out during July and August 2005.Four individual spectral bands and two vegetation spectral reflectance indices, which are sensitive to changes in plant pigment content, were derived from the processed multispectral images viz. red, green, blue and near-infrared spectral bands and the normalised difference vegetation index (NDVI) and greenness normalised difference vegetation index (GNDVI).The results of the multispectral airborne study revealed that carotenoid content together with the green spectral waveband resulted in the “best” surrogate measure of plant water stress when using broad-band multispectral airborne data. Airborne remote sensing surveys were conducted by Bar-Kal Systems Engineering Ltd, Israel, to investigate the application of hyperspectral airborne imagery to detect plant water stress. Six vegetation spectral reflectance indices designed to capture changes in plant pigment and plant water status/content, were derived from the processed hyperspectral images. When using airborne hyperspectral data, predawn leaf water potential with the normalized difference water index was selected as the most appropriate model. It was concluded, upon evaluation of the multiple linear regression models, that the airborne hyperspectral data produced several more regression models with higher adjusted R2 values (Ra2 range 6.2 - 76.2%) when compared to the airborne multispectral data (Ra2 range 6 - 50.1). Exploration of relationships between vegetation indices derived from leaf-level, satellite and airborne spectral reflectance data and ground-based measurements used as “surrogate” measures of plant water stress, revealed that several prominent and recurring spectral reflectance indices could be applied to identify species-specific plant water stress within the Welkom, Vaal River and West Wits mining districts. The models recommended for mapping and detecting spatial patterns of plant water stress when using different sources of remote sensing data are as follows: the chlorophyll b DATT spectral reflectance model when derived from leaf-level spectral reflectance data, can be applied across all three mining districts the predawn leaf water potential GNDVI spectral reflectance model and predawn leaf water potential water band index spectral reflectance model when utilising satellite multispectral and hyperspectral remote sensing data carotenoid content green band spectral reflectance model can be used for airborne multispectral resolution data predawn leaf water potential NDVI spectral reflectance model is best suited for airborne high spatial and hyperspectral resolution data. These results indicate that measurements of predawn leaf water potential and plant pigment content have been identified as key methodologies for ground-truthing of remotely sensed data and can be used as surrogate measures of plant water stress. Some preliminary research was undertaken to evaluate if wood anatomy characteristics could be used as a non-destructive and rapid low-cost survey approach for identifying trees which are experiencing long-term plant stress. Seventy two wood core samples were extracted and analysed. Predawn leaf water potential measurements were used to classify stressed and unstressed trees. Relative differences in radial vessel diameter, vessel frequency and wood density were examined. Comparison of the radial vessel diameter and vessel frequency measurements revealed significant differences in three of the five comparative sampling sites (p <0.05). The results of the density analyses were significantly different for all five comparative sampling sites (p < 0.01). In general, trees experiencing higher plant water stress displayed smaller vessel diameters, compared to less stressed or healthy trees. Sites which were influenced by high levels of contaminated water also displayed smaller vessel diameters, indicating that the uptake of contaminants could affect the wood anatomy of plants. Trees considered to be experiencing higher plant water stress displayed higher vessel frequency. This preliminary study showed that plant stress does influence the wood anatomical characteristics (radial vessel diameter, vessel frequency and wood density) in E. camaldulensis, E. sideroxylon and S. lancea in the three mining districts. Spatial patterns of trees, mapped in the three gold mining districts, Welkom (27º57´S, 26º34´E) in the Free State Province, Vaal River (26º55´S, 26º40´E) located in the North West Province, and West Wits (26º25´S, 27º21´E) located in Gauteng, which were not experiencing winter-time water stress were correlated to site characteristics such as average soil depth, percent clay in the topsoil, groundwater chloride and sulphate concentrations, total dissolved solids, electrical conductivity and groundwater water level. The spectral reflectance model derived between predawn leaf water potential and the green normalised difference vegetation index using broad-band multispectral Proba Chris satellite data was used to map spatial patterns of unstressed trees across the three mining districts. Very high resolution (75 cm) multispectral airborne images acquired by LRI in 2005 were used to demarcate and classify vegetation using the maximum likelihood supervised classification technique. Interpolated surfaces of groundwater chloride and sulphate concentrations, total dissolved solids, electrical conductivity, pH and groundwater table levels were created using the kriging geostatistical interpolation technique for each mining district. Random sample analyses between stressed and unstressed trees were extracted in order to determine whether site characteristics were significantly different (using t-tests). Site characteristic surfaces which were significantly different from stressed areas were spatially linked to trees which were not experiencing winter-time plant water stress for each tree species investigated in each mining district. This spatial correlation was used to make recommendations and prioritise sites for the establishment of future block plantings. Analysis of the site characteristic data and the geophysical surveys undertaken in the three mining districts which provided detailed information on groundwater saturation and an indication of the salinity conditions, confirmed the presence of relatively shallow and saline groundwater sources. This would imply that tree roots could access the relatively shallow groundwater even during the dry winter season and assist in containing contaminated groundwater seeping into surrounding lands. Keywords : airborne imagery, ground-based measurements of plant water stress, hyperspectral, leaf-level spectroscopy, multispectral, satellite imagery, spatial patterns of unstressed trees, spectral reflectance indices

AbstractFish passing downstream through hydraulic structures and turbines may risk dying or getting injured. Archimedes screw turbines are frequently considered more “fishfriendly” than conventional turbines. However, to date only a handful of studies assess the impact of Archimedes screws. Within the FIThydro project, we investigated injury and mortality on 2700 bream, roach and eel, including passive barotrauma sensors passing a large Archimedes hydrodynamic screw (10 m head, 22 m length) on three rotational speeds of 30, 40 and 48 Hz. The sensors measured total water pressure, linear acceleration, rotation rate, magnetic field intensity and absolute orientation. They indicated that passage is a chaotic event, and that barotrauma-related injury and mortality are indeed unlikely. Nonetheless, substantial mortality of fish was observed, specifically for bream (42%) and roach (18%) but not for eel (1%). No straightforward relation was found between rotational speeds and fish injury and mortality. The study indicates generally lower mortality and injury rates compared to conventional turbine types. However, fish can still get heavily injured or die, depending on the fish species. Therefore, we stress the need for further studies on Archimedes screws to identify the causes of the observed species-specific injury and mortality rates.

Irrigated agriculture is an important strategic sector for Morocco, contributing to food security and employment. Nowadays, irrigation scheme managers shall ensure that water is optimally used. The main objective was to support the irrigation monitoring and management of wheat in the irrigated perimeter using optical remote sensing and crop modeling. The potential of spectral indices derived from SPOT-5 images was explored for quantifying and mapping surface water content changes at large scale. Indices were computed using the reflectance in red, near infrared, and shortwave infrared bands. A field crop model (AquaCrop) was adjusted and tested to simulate the grain yield and the temporal evolution of soil moisture status. This research aimed at providing a scientific and technical approach to assist policymakers and stakeholders to improve monitoring irrigation and mitigating wheat water stress at field and irrigation perimeter levels in semi-arid areas. The approach could lead to operational management tools for an efficient irrigation at field and regional levels.

Spectral vegetation indices (VIs) are a well-known and widely used method for crop state estimation. These technologies have great importance for plant state monitoring, especially for agriculture. The main aim is to assess the performance level of the selected VIs calculated from space-borne multispectral imagery and point-based field spectroscopy in application to crop state estimation. The results obtained indicate that space-borne VIs react on phenology. This feature makes it an appropriate data source for monitoring crop development, crop water needs and yield prediction. Field spectrometer VIs were sensitive for estimating pigment concentration and photosynthesis rate. Yet, a hypersensitivity of field spectral measures might lead to a very high variability of the calculated values. The results obtained in the second part of the presented study were reported on crop state estimated by 17 VIs known as sensitive to plant drought. An alternative approach for identification early stress by VIs proposed in this study is Principal Component Analysis (PCA). The results show that PCA has identified the degree of similarity of the different states and together with reference stress states from the control plot clearly estimated stress in the actual irrigated field, which was hard to detect by VIs values only.

<em>Abstract</em> .—The biological assessment of inland waters using ecological criteria is becoming more important due to the need to evaluate and monitor aquatic environments that are under heavy environmental stress. Turkey has been trying to develop a model to understand its inland waters in terms of the European Water Framework Directive’s (WFD) European fish index (EFI). The EFI is derived from assessment of five biological elements. The EFI is inappropriate for the conditions in Turkish inland waters; thus, the present study developed a fish-based index of biotic integrity for Turkey (FIBI-TR) as a suggestion. To assess the adequacy of the FIBI-TR, this study gathers field data in two selected basins in 2013 and 2014 according to WFD criteria for biological elements and physicochemical parameters, simultaneously. The FIBI-TR was then compared to the scores derived from the WFD score, which was a cumulative score for all related biological elements, and with other frequently used indices such as the Water Pollution Control Directive and trophic state index. Based on these data, the FIBI-TR seems to be congruent with cumulative WFD scores. However, the FIBI-TR does not agree with other indices based on physicochemical parameters. Detailed research is needed if WFD is to be adapted for Turkey through FIBI-TR.

<em>Abstract</em> .—The biological assessment of inland waters using ecological criteria is becoming more important due to the need to evaluate and monitor aquatic environments that are under heavy environmental stress. Turkey has been trying to develop a model to understand its inland waters in terms of the European Water Framework Directive’s (WFD) European fish index (EFI). The EFI is derived from assessment of five biological elements. The EFI is inappropriate for the conditions in Turkish inland waters; thus, the present study developed a fish-based index of biotic integrity for Turkey (FIBI-TR) as a suggestion. To assess the adequacy of the FIBI-TR, this study gathers field data in two selected basins in 2013 and 2014 according to WFD criteria for biological elements and physicochemical parameters, simultaneously. The FIBI-TR was then compared to the scores derived from the WFD score, which was a cumulative score for all related biological elements, and with other frequently used indices such as the Water Pollution Control Directive and trophic state index. Based on these data, the FIBI-TR seems to be congruent with cumulative WFD scores. However, the FIBI-TR does not agree with other indices based on physicochemical parameters. Detailed research is needed if WFD is to be adapted for Turkey through FIBI-TR.

At local or regional scales, where Landsat has been extensively applied to monitor burned areas, semi- or fully-automated methods are not very common. Koutsias et al. (2013) developed and improved (2021) a semi-automatic method to map burned areas consisted of a set of rules that are valid especially when the post-fire image has been captured shortly after the fire. However, the rule-based approach is not free of errors that eventually create limitations to adopt this method for reconstructing the fire history in a fully automated mode. In this work, we improved the method by incorporating vegetation indices. The vegetation indices evaluated were the: (i) Normalized Difference Vegetation Index (NDVI), (ii) Ratio Vegetation Index (RVI), (iii) Normalized Burn Ratio (NBR), (iv) Normalized Difference Water Index (NDWI) and (v) Shortwave Infrared Water Stress Index (SIWSI).

Coral reefs are one of the most sensitive, productive, and invaluable biological resources on the earth. However, coral reefs are facing unprecedented stress due to ongoing climate changes and intensified anthropogenic disturbances globally. Elevated Sea Surface Temperature (SST) has emerged as the most imminent threat to the thermos-sensitive reef-building corals. The 2010–2014-2016 El Niño Southern Oscillation (ENSO) caused prolonged marine heat waves (MHWs) that led to the most widespread coral bleaching and mortality in the tropical Indi-Pacific regions. Coral bleaching prediction is vital for the management of the reef biodiversity, ecosystem functioning, and services. Recent decades, satellite remote sensing has emerged as a convenient tool for large-scale coral reef monitoring programs. As thermal stress is a critical physical attribute for coral bleaching hence, the present study examines the effectiveness of the elevated SSTs as a proxy to predict coral bleaching in shallow water marginal reefs. Advanced Very High-Resolution Radiometer (AVHRR) satellite data from the NOAA Coral Reef Watch’s (CRW) platform has been used for this study. Coral bleaching indices like Bleaching Threshold (BT), Positive SST Anomaly (PA), and Degree Heating Weeks (DHW) are computed to analyze the thermal stress on the coral reefs. The computed thermal stress from satellite-derived SST data over regions concurrence with the mass coral bleaching (MCB) events. This study concludes that in the last decades (2010 to 2019) the coral cover around these regions has dramatically declined due to higher SST, which indicates that the thermal stress induced recurrent bleaching events attributed to the coral loss.

Piping systems are subjected to a wide range of anticipated and/or postulated dynamic loading. With the exception of steam propelled water slug flow transient, thee dynamic loading result in response reversals that have not the characteristics of sustained loading. Dynamic test to failure did not exhibit the classical collapse catastrophic failure mode. The dynamic response reversals exhibited gradual ratcheting and fatigue crack growth that concurrently lead to the failure. The stress intensity classifications provided by the piping stress indices, in conjunction with Edmunds and Beer or Bree Plate ratchet models, are utilized to estimate the accumulated ratchet strains in the pipe component. The allowed maximum accumulating local ratchet strain is set arbitrarily to 10%, which is less than half of the measured ratchet strains found in the dynamic tests. Simple criteria for evaluating the degradation level in the piping components subjected to the concurrent ratchet-fatigue failure mechanisms are presented. The approach utilizes a methodology similar to that used in the creep-fatigue interaction damage provided in the ASME Section III, Subsection NH, Appendix-T. Replacing the creep strain term by that of the ratchet strain, and replacing the bilinear damage function with the square root function, yields the ratchet-fatigue degradation criteria formulations presented in this paper. Considerations for the plastic buckling due to the accumulated compressive ratchet strains as well as the primary component of the piping thermal expansion stress due to elastic follow-up are also presented.

Optimization of water use relies on accurate measurement of water status of crops. Stem water potential (SWP) has become one of the most popular methods to monitor the water status of almond trees. However, it needs to take twice visit and at least thirty minutes to obtain one measurement, which makes it very difficult to understand the water status information in the orchard level. Unmanned aerial vehicle (UAV) based remote sensing promises to deliver reliable and precise field-scale information more efficiently by providing multispectral higher-resolution images with much lower cost and higher flexibility. This paper aims to extract almond water status from UAV-based multispectral images via building the correlation between SWP and vegetation indices. Different from the traditional method that focuses on normalized difference vegetation index (NDVI) means, higher-order moments of non-normalized canopy distribution descriptors were discussed to model SWP measurements. Results showed that the proposed methods performed better than traditional NDVI mean.

The present study focuses on the friction factors of a colloidal suspension flow in circular and square tubes. The colloidal suspension was made of silicon dioxide nanoparticles dispersed in distilled water at a concentration of 9.58% by volume. The viscosity and shear stress of the suspension were measured and it was found that the fluid exhibited non-Newtonian behavior. The rheological behavior of the suspension could be adequately modeled as a power-law generalized Newtonian fluid (GNF). When the consistency and the flow behavior indices of the suspension were properly evaluated, the friction factors of the suspension flowing in tubes with circular and square cross-sections exhibited similarities with those of Newtonian fluid flow. In fully-developed laminar flow, the Poiseuille number for the suspension was similar to that for a Newtonian fluid flow. In turbulent flow, the Dodge and Metzner’s relations for the friction factor and a generalized Reynolds number can be used to adequately describe the suspension in turbulent flow. Observations from the friction factor measurements showed that the onsets of transition to turbulent flow vary with the cross-sectional shape of the tube and differ from those of Newtonian fluid flow. This might suggest that the cross-sectional shape of the flow passage and the presence of nanoparticles could affect the onset of transition to turbulent flow for the suspension.

Using the connection between water and energy as a case study, we present a model that uses the effects of geospatial and temporal context on embedded energy to approximate resource sustainability for water. First, the basic steps of calculating the energy intensity for a given location are discussed. Intensity is presented in units of energy per volume of water. In the case of supplying fresh water, energy intensity depends upon the quality of the original resource, its location relative to the end use location, and the type of technology in use to move and treat the water. Pumping, and conveyance, purification, distribution, wastewater treatment, and system inefficiencies (e.g. evaporative losses, leaks) increase the total energy investment, while water recycling decreases the total investment. Lift and purification are typically the greatest contributors to the overall energy intensity of a fresh water supply, but system inefficiencies can have a substantial impact as well. Over time, growing cities tend to progress from using their least energy intensive water resources (e.g. untreated surface water) to their most energy intensive (e.g. long distance transfers, desalinated water lifted to high elevations) as water demands begin to outstrip supplies. As a function of water availability, we assign each location an intensity value that approaches the intensity of its next “best” (i.e., least energy intensive) source of water. Hence, an area which is depleting its available surface and groundwater may have desalinated surface or groundwater as its next (and last) resort. The area would be characterized as undergoing water stress, and relatively less sustainable than areas which use their local fresh water supplies with no perceivable negative impact. An operating principle of this research is that with enough energy, it is possible to supply any location with fresh water. Desalinated ocean water, moved over long distances and lifted to great heights represents that upper limit. Working backwards from this extreme scenario, it is possible to not only move away from the paradigm of unitless or vague sustainability indices, but to quantify resource scarcity in a way that is both intuitive and actionable. The model is also self-correcting: areas may reduce the energy intensity of a sustainable water supply through better management of existing fresh water resources or through technological innovations that produce fresh water from degraded sources in an energy efficient manner. A major conclusion of this research is that the amount of energy necessary to maintain a reliable supply of fresh water greatly varies by location and technology choice. Further, many areas of the country overuse their local fresh water sources. To create a durable water supply, such areas can 1) reduce their use of local fresh water to sustainable levels and invest in alternative water sources—at a high financial and energy cost, or 2) aggressively pursue water efficiency measures so that they can both reduce their reliance on local fresh water sources and avoid the high costs associated with alternative water supplies. Additionally, by converting water use to energy consumption as a function of scarcity, it is possible to weigh the relative importance of water use efficiency to conservation in other areas (e.g. electricity, direct heating, waste disposal).

The Board on Nuclear Codes and Standards (BNCS) recently decided to promote standards that use risk-informed design methods. In civil engineering practice a risk informed method, namely the Load and Resistance Factor Design (LRFD), has been in usage for quite some time. It is possible to extend such methods to the design of safety-related piping as well. This paper provides a brief overview of the LRFD method. Discussion is included for load factors to be used to account for the uncertainties in piping loads (e.g., internal pressure, sustained weight, etc.) and resistance factors to be used for addressing the uncertainties in strength of piping and analysis methods. Different load factors and resistance factors can be suggested for each load type and resistance type (e.g., hoop stress, bending stress, etc.). A design example for a feed water Class 2 piping system is provided to demonstrate the benefits of LRFD. This way, benefits such as the achievement of consistent reliability levels and the facilitation of a detailed risk analysis of mechanical systems are illustrated. Finally, the challenges associated with development of the LRFD method for nuclear piping are discussed. Such challenges pertain to the selection of the appropriate target reliability indices for piping, the development of equations for components such as tees, elbows, etc.

In recent years, offshore reservoirs have been developed in deeper and deeper water environments, where floating production, storage and offloading (FPSO), semi-submersibles, spars and TLPs are considered to be the most economically viable platforms. Steel Catenary Risers (SCRs) are being considered for these production units in deepwater development such as Northern North Sea. A variety of uncertainties are associated with material behaviour, environmental loading, hydromechanics modelling, structural modelling, and fatigue / corrosion / wear characteristics, especially at hang-off and touch down points. To improve the understanding of SCR behaviour and increase the confidence in the design of such systems in deep water environment, a probabilistic reliability-based methodology that systematically accounts for the inherent uncertainties is needed. By using a probabilistic mechanics approach, the existing deterministic design/analysis methods are improved with introduction of uncertainties in model parameters. This paper concentrates on the probability of failure associated with the current design practice of fatigue analysis of SCRs. A probabilistic methodology for fatigue reliability is developed, which utilizes deterministic cumulative fatigue damage indicators calculated from DeepC, namely the stress levels and cycles associated with the various sea states and the fatigue strength of the members. Uncertainties in structural load and material properties are accounted for by assigning probability distributions and standard deviations to the deterministic stress levels. Furthermore, fatigue strength parameters, Miner’s indices, and capacities are modelled as random variables. First order reliability method (FORM) and second order reliability method (SORM) are employed for estimating fatigue reliability. The methodology is applied to two deterministic case studies, involved either a semi-submersible or a FPSO platform. The effect of uncertainties in parameters on fatigue reliabilities is investigated. Additional insight is gained from the parametric sensitivity studies on the fatigue strength parameters.

For deepwater development in the Gulf of Mexico, steel catenary risers (SCRs) supported from both SPAR and semi-submersible platforms have proven to be successful solutions for in-field flowlines, tie-backs, and export systems. It is envisaged that this will continue to be a promising solution in ultra deep-water applications, up to and beyond 10,000 ft. The study, commissioned by the Mineral Management Service (MMS), investigated the reliability of large-diameter SCRs in ultra-deepwater operations. The primary damage mode considered is fatigue failure. A probabilistic methodology for fatigue reliability is developed, which utilizes deterministic cumulative fatigue damage indicators, namely the stress levels and cycles associated with the various sea states and the fatigue strength of the members. Uncertainties in structural load and material properties are accounted for by assigning probability distributions and standard deviations to the deterministic stress levels. Furthermore, fatigue strength parameters, Miner’s indices, and capacities are modeled as random variables. First order reliability method (FORM) is employed for estimating fatigue reliability. The methodology is applied to three deterministic case studies presented by Intec Engineering (2006a, 2006b). The case studies involved either a SPAR or a semi-submersible platform. For the sake of brevity, a case study involving only a SPAR platform is presented in this paper. The effect of uncertainties in parameters on fatigue reliabilities is investigated. It is observed that the fatigue reliability estimates followed similar trends as the deterministic cumulative damage results, and hence can be used to complement deterministic estimates. Additional benefit and insight gained from the probabilistic study, which can be used for design decisions, include information regarding probabilistic importance and probabilistic sensitivity analysis. For case study presented here, it is seen that in general, uncertainty in the fatigue strength exponent (m) has the highest impact on fatigue reliability of SCRs. The second most important random variable is the stress range (S), which captures uncertainties in parameters such as loads and material properties. Parametric sensitivity studies on the fatigue strength parameters indicate that SCR reliability is sensitive to both the standard deviation and probability distribution of the parameters, thus highlighting the need for accurate probabilistic calibration of the random variables.

Potato yield and quality are highly dependent on an adequate supply of nitrogen and water. Opportunities exist to use airborne hyperspectral (HS) remote sensing for the detection of spatial variation in N status of the crop to allow more targeted N applications. Thermal remote sensing has the potential to identify spatial variations in crop water status to allow better irrigation management and eventually precision irrigation. The overall objective of this study was to examine the ability of HS imagery in the visible and near infrared spectrum (VIS-NIR) and thermal imagery to distinguish between water and N status in potato fields. To lay the basis for achieving the research objectives, experiments in the US and in Israel were conducted in potato with different irrigation and N-application amounts. Thermal indices based merely on thermal images were found sensitive to water status in both Israel and the US in three potato varieties. Spectral indices based on HS images were found suitable to detect N stress accurately and reliably while partial least squares (PLS) analysis of spectral data was more sensitive to N levels. Initial fusion of HS and thermal images showed the potential of detecting both N stress and water stress and even to differentiate between them. This study is one of the first attempts at fusing HS and thermal imagery to detect N and water stress and to estimate N and water levels. Future research is needed to refine these techniques for use in precision agriculture applications.

Drought stress is a major limitation to bread wheat (Triticumaestivum L.) productivity and its yield stability in arid and semi-arid regions of world including parts of Israel and the U.S. Currently, breeding for sustained yields under drought stress is totally dependent on the use of yield and several key physiological attributes as selection indices. The attempt to identify the optimal genotype by evaluating the phenotype is undermining progress in such breeding programs. Osmotic adjustment (OA) is an effective drought resistance mechanism in many crop plants. Evidence exists that there is a genetic variation for OA in wheat and that high OA capacity supports wheat yields under drought stress. The major objective of this research was to identify molecular markers (RFLPs, restriction fragment length polymorphisms; and AFLPs, amplified fragment length polymorph isms) linked to OA as a major attribute of drought resistance in wheat and thus to facilitate marker-assisted selection for drought resistance. We identified high and low OA lines of wheat and from their cross developed recombinant inbred lines (RILs) used in the molecular tagging of OA in relation to drought resistance in terms of plant production under stress. The significant positive co-segregation of OA, plant water status and yield under stress in this RIL population provided strong support for the important role of OA as a drought resistance mechanism sustaining wheat production under drought stress. This evidence was obtained in addition to the initial study of parental materials for constructing this RIL population, which also gave evidence for a strong correlation between OA and grain yield under stress. This research therefore provides conclusive evidence on the important role of OA in sustaining wheat yield under drought stress. The measurement of OA is difficult and the selection for drought resistance by the phenotypic expression of OA is practically impossible. This research provided information on the genetic basis of OA in wheat in relations to yield under stress. It provided the basic information to indicate that molecular marker assisted selection for OA in wheat is possible. The RIL population has been created by a cross between two agronomic spring wheat lines and the high OA recombinants in this population presented very high OA values, not commonly observed in wheat. These recombinants are therefore an immediate valuable genetic recourse for breeding well-adapted drought resistant wheat in Texas and Israel. We feel that this work taken as a whole eliminate the few previous speculated . doubts about the practical role of OA as an important mechanism of drought resistance in economic crop plants. As such it should open the way, in terms of both concept and the use of marker assisted selection, for improving drought resistance in wheat by deploying high osmotic adjustment.