Factors which affect iron bioavailability have been repeatedly and extensively investigated. A model, derived from these studies, has been developed for estimating available iron from meal data. However, many dietary surveys report only average daily intakes of iron, and do not report the iron present in single meals. No model to estimate available iron from daily iron intake has been presented in the literature. Dietary questionnaires were kept for two nonconsecutive weekdays by 355 male and 382 female Utah school children, mean age 7.5 years, assisted by their parents, and recorded by household measure. Data, first recorded as meals eaten, were used to develop three models for the estimation of available iron from total daily iron intake. It was concluded that available iron can be estimated from total iron intake by two of these models, as compared with the currently used model, which estimates available iron from data recorded by meal. Additionally, meal patterns of those factors involved with the estimation of available iron were investigated. The intake of dietary ascorbic acid and total iron was found to be evenly distributed among meals; approximately 10% of these nutrients was consumed as snacks. Of the meat, fish, poultry and the iron in those products consumed; 36% was taken at lunch, and 54% at dinner. Only 5% of the meat, fish, and poultry iron was consumed as snacks. The available iron distribution for breakfast, lunch, dinner, and snacks was 21.0%, 30.8%, 42.5% and 5.7%, respectively. Previous studies have investigated the characteristics of diets which provide 9 mg of iron per 1000 kcal of energy consumed. These diets have been shown to include larger portions of vegetables, fruits, and cereal products. In this study, these high-iron dense characteristics were studied as they pertain to total available iron intake. It was concluded that the high-iron dense diet receives more total available iron from the nonheme iron than from the heme iron consumed. Thus, it is conceivable that those dietary characteristics shown to provide a high-iron dense diet may also provide a high available iron intake.

When crested wheatgrass (Agropyron desertorum) grows in mixture with sagebrush (Artemisia tridentata), its production declines. Its production increases when grown in mixture with fourwing saltbush (Atriplex canescens), according to previous reports. This study investigated soil water extraction and potassium (K) nutrition of the two shrubs to identify possible causes of the differential responses of crested wheatgrass. Crested wheatgrass had reduced, rather than increased, nitrogen (N) and K yield in mixture with fourwing saltbush. No differences in N and phosphorous (P) concentrations were observed between sagebrush and fourwing saltbush, but fourwing saltbush had a much higher K concentration and returned nearly twice as much K to the soil as sagebrush by throughfall and litterfall. Throughfall additions were much greater than those from litterfall. AK-fertilization/water-stress, two-factor greenhouse experiment was conducted with crested wheatgrass. High- and medium-K-fertilization treatments had highest tissue K concentration, but biomass yield was reduced in waterstressed plants with high K-fertilization. A difference of 1.56 MPa in osmotic adjustment was observed between waterstressed plants with high K-fertilization and irrigated, low-K-fertilization plants. These results suggest that K accumulation in fourwing saltbush may be a factor for enhanced crested wheatgrass productivity. Crested wheatgrass grown in mixture with fourwing saltbush had lowered predawn and mid-day xylem water potentials compared with monoculture and sagebrush mixture plots, but no other treatment differences were observed for any species. Fourwing saltbush monoculture plots had the most uniform water extraction rates and may compete less for water than sagebrush when crested wheatgrass extraction rates are highest.

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.

Most Australian studies on estuarine plankton have examined distribution and abundance in relation to hydrological changes, primary productivity and associated nutrient dynamics. Relatively few have examined the complex interactions between zooplankton grazers and the type and quality of food available, or the role of zooplankton grazers in structuring phytoplankton communities, or their contribution to the nutrient pool. The ecological role of zooplankton grazers in the Swan River estuary, Perth, Western Australia, was examined as part of a collaborative research project directed by the Western Australian Estuarine Research Foundation, which was established in response to concern about increasing intensity and persistence of algal blooms. The present study focussed on one component of the zooplankton, the Copepoda, as model zooplankton grazers. A regular zooplankton monitoring programme, undertaken over a two year period, provided data on seasonal patterns of abundance and distribution of zooplankton over a broad spectrum of physical conditions. Relationships were identified between habitat variables, such as algal biomass, dissolved oxygen, salinity and suspended solids and zooplankton distribution, relative abundance and species composition. Prior to the inception of this study, it was assumed that copepod species composition, abundance and richness in the Swan River estuary may have changed over time, in response to long-term declines in water quality. Comparison of historical copepod monitoring data with current data did not detect any such change and it was concluded that there was greater variation in copepod species composition, abundance and richness within years than between years and that no significant change had occurred between 1966 and 1997. / However, an absence or reduction in abundance of copepods in areas of very high algal biomass (>80 pg chlorophyll a.L-1) suggests that local loss of water quality may have an impact on copepods over a small spatial scale within the estuary. Different aspects of the interactions between zooplankton grazers and phytoplankton were studied. Zooplankton grazing rates were measured in situ during algal blooms and in the laboratory under controlled conditions to determine the potential for zooplankton grazers to reduce algal biomass. Field and laboratory experiments supported the hypothesis that copepods and other zooplankton can exert 'top-down control' over phytoplankton biomass, but that the type and biomass of phytoplankton present affected their ability to exert this control. The results of the field and laboratory grazing experiments, along with literature data, were used to provide input data for a model of zooplankton and phytoplankton dynamics during a dinoflagellate bloom in the Swan River estuary. The model was tested against biomass measurements of zooplankton and phytoplankton to determine how well it predicted actual changes in the plankton community. The simulated output closely followed the measured Page x field data and fitted regression curves and provided information about diurnal patterns of phytoplankton production, respiration and migration and hydrodynamic transport, which was not available from field data. It was shown that zooplankton grazing, particularly grazing by microzooplankton, was the process contributing most to the observed decline in dinoflagellate biomass. Nutrient availability is one of several factors determining productivity of phytoplankton. Nutrients within copepod faecal pellets are relocated by faecal deposition to sediments, where microbial activity leads to the remineralisation of these nutrients. / Quantification of metabolic excretion of nutrients by copepods and the rate at which pellets are produced by copepod grazers, the concentration of nutrients within faecal pellets and the rate at which these nutrients are released indicated that copepods may play an important role in nutrient regeneration during summer and autumn when allochthonous nutrients are unavailable. At other times of the year, it is unlikely that copepods play an important role in nutrient regeneration. The research has provided a more detailed level of understanding of the interactions between zooplankton, phytoplankton and their environment. The data is ideally suited for use in a computer model to predict the effects of management actions on the Swan River estuary. This would allow pre-emptive management strategies to be developed and lessen the focus on reactive management.

Given the rapidly increasing visitation levels to Fraser Island, there is increasing concern that tourist activities may threaten the long-term ecological health of the region's unique dune lakes. This project aimed to investigate the consequences of tourist use of Fraser Island's dune lakes and to develop appropriate monitoring tools and management objectives in light of the projected increases in visitation levels in the foreseeable future. The initial phase of this research aimed to identify the relative importance of some of the most popular dune lakes on the island as key destinations for tourists. Tourist surveys, in conjunction with the development of a Tourist Pressure Index (TPI), which quantifies logistic, social and natural variables, identified Lakes McKenzie, Allom and Birrabeen as the lakes most at risk from excessive tourist use. In addition, analyses of water quality in 15 lakes on Fraser Island aimed to determine the current trophic status of dune lakes on Fraser Island and the ecological implications of tourist use of these systems. Detailed comparisons of nutrient and chlorophyll a concentrations in five popular dune lakes in February 1990 (data from Arthington et al. 1990) and February 1999 suggested that productivity has increased significantly in the past decade. More detailed examinations of nutrient and algal variables in five popular perched dune lakes revealed that while ambient nutrient and phytoplankton chlorophyll a concentrations remained relatively stable, periphyton chlorophyll a concentrations increased over the course of the 1999-2000 summer in most lakes. Significantly, these increases were found only in heavily visited (disturbed) sites in the clear lakes examined (McKenzie and Birrabeen). In these lakes, where algal growth is likely to be only limited by nutrient availability, tourist nutrient additions may stimulate excessive periphyton production. Experimental algal bioassays identified that phytoplankton and to a lesser degree periphyton growth was stimulated by nutrient additions in all five perched dune lakes. However, the degree to which growth was stimulated was both lake and nutrient (nitrogen versus phosphorus versus nitrogen + phosphorus) dependent, highlighting the variable nature of systems within a relatively small geographic range. Since periphyton biomass was higher in heavily visited areas of lakes and was likely to be stimulated by nutrient additions by tourists, stable isotope analyses of littoral zone food webs were conducted to quantify the percent contribution of periphyton to consumer diets. There was a trend towards higher periphyton contributions in systems identified as key tourist locations (on the basis of their TPI scores) and this indicates that increasing visitation may increase the contribution of periphyton to littoral zone food webs, both via increases in the quantity and quality of periphyton as a food resource. To further explore the contribution of periphyton in littoral zone food webs of heavily visited lakes, a 15N-tracer addition experiment was conducted to establish the fate of nutrient additions within the littoral zone. Nutrients were added in quantities that mimicked those likely from tourists, to enable a realistic appraisal of the fate of tourist additions. As expected, periphyton rapidly assimilated the added 15N-tracer and was found to be the first and most significant sink for nutrients entering the littoral zone. Finally, the results from this research were used to develop a conceptual model of nutrient enrichment for perched dune lakes on Fraser Island. The model indicates that although nutrient additions from tourists may lead to undesirable increases in periphyton biomass, the degree to which this is deemed to be a detrimental ecological outcome is likely to be mediated by water level fluctuations and the consumptive capacity of grazers. Given that excessive periphyton growth is likely to be seen as negative impact of tourism, regular periphyton monitoring (biomass and percent contribution to littoral zone food webs) should be built into an updated monitoring program for this series of dune lakes. Whilst the implementation of periphyton monitoring is likely to enable the early detection of deleterious impacts of excessive tourist use, it is likely that the long-term conservation of the region will, in the future, require the implementation of strict visitation level guidelines, to ensure that the irreversible consequences of long term additions of nutrients are ameliorated.

Intermittently Closed and Open Lake Lagoons (ICOLLs) are very common along the southern NSW coastline. Expanding urban populations are expanding and these systems are under increasing pressure from anthropogenic activities that change landscape processes and significantly alter the amounts of organic and inorganic constituents entering their waters. Once efficient cycling of nutrients in ICOLLs is overcome, the symptoms of eutrophication establish and the entire ecosystem suffers. These systems have great ecological, social, and economic values that require insightful, well balanced, and educated management to promote sustainable use of these often-sensitive areas. Corunna and Nangudga Lake are ICOLLs in the Eurobodalla Shire on the south coast of NSW. These two ICOLLs receive discharges from catchments covered by native vegetation and grassland. The primary objective of this research component was to quantify catchment exports of total nitrogen (TN), total phosphorus (TP), suspended solids (SS), particulate organic matter (POM) and dissolved organic carbon (DOC) from three small coastal sub catchments that deliver constituents into Corunna and Nangudga Lakes. As part of this investigation the fates of catchment loads in the ICOLLs were established focusing on the lakes water column response to catchment loads and the biogeochemical cycling of nitrogen and phosphorus in sediments.

<p>Syftet med denna litteraturstudie var att via litteraturen beskriva nutritionens betydelse för sårläkning. Studien genomfördes som en deskriptiv litteraturstudie där metoden bestod av att söka vetenskapliga artiklar i databaserna Medline, Cinahl och Academic Search Elite. Sjutton artiklar valdes ut. Resultatet visade att patienter med bensår eller trycksår i många fall inte når upp till de näringsrekommendationer som finns. Det visade sig vara vanligt att dessa patienter ligger vid gränsen för att vara undernärda. Det upptäcktes att det är sällan som kostintaget täcker energibehovet. Framför allt var zinknivåerna genomgående väldigt låga och det visar även att det är brist på en hel del andra ämnen. Ämnen som visat sig speciellt fördelaktiga för sårläkning är protein, vitamin C, zink samt arginin. För patienter med brännskador däremot har det visat sig att saltet ornithine α-ketoglutarate minskar proteinkatabolismen samt förbättrar proteinsyntesen, vilket är en förutsättning för sårläkning. Slutsatsen med föreliggande studie var att nutritionen är viktig och kan ha en avgörande betydelse för sårläkning.</p> / <p>The purpose with this literature study was that through literature describe the nutrition’s significance for healing wounds. The study was made as a descriptive literature study where the method was conducted by searching scientific articles in the databases Medline, Cinahl and Academic Search Elite. Seventeen articles were chosen. The result showed that patients with leg ulcers or pressure sores in many cases don’t attain the recommendations for nutrition that are available. It showed that it is normal that these patients are on the border of being undernourished. It was discovered that the nutrient intake rarely covers the energy needs. Above all the zinc levels were throughout very low and that shows that there is also lack of some other substances. The substances that have been shown especially good for healing wounds are protein, vitamin C, zinc and arginine. However, for patients with burn injuries the salt ornithine α-ketoglutarate has been shown to reduce protein catabolism and also improve protein synthesis, which are essential to healing wounds. The conclusion from this study was that nutrition may be an important but also a determining factor to healing wounds.</p>

Many large terrestrial ecosystems have patterned landscapes as a result of a positive feedback system between vegetation communities and environmental factors. One example is tree island habitats in the Florida Everglades. Although they only occupy a small portion of the Everglades landscape, tree islands are important features as the focus of nutrient accumulation and wildlife biodiversity in the Everglades ecosystem. The hardwood hammock community on the elevated head of tree island habitats can accumulate high phosphorus concentration in the otherwise P-limited Everglades ecosystem. In this dissertation, I examined two hypotheses derived from the chemohydrodynamic nutrient accumulation model, which suggests that high transpiration of tree island hammock plants is the driving force for nutrient accumulation in tree island soil. According to this model, I hypothesized that tree islands with lower dry season transpiration should have less phosphorus accumulated than the tree islands with higher dry season transpiration. By examining the water use and nutrient status from 18 tree islands in both slough (perennially wet) and prairie (seasonally wet) locations, I was able to compare water availability and nutrient accumulation in slough and prairie tree islands with different marsh hydroperiods. Chapter 1 uses elemental and stable isotope analysis to look at water stress and nutrient concentration in tree island plants. I showed that the prairie tree island plants suffer from drought stress during the dry season, when the marshes in the prairies dry out. Prairie tree islands also have lower soil and plant P concentration than the slough tree islands. Moreover, I showed that foliar N isotope ratio serves as a stable proxy for community level P availability for tree island plants, and prairie tree island plants have less P available than slough tree island plants. In Chapter 2, I showed that the satellite imagery derived normalized difference water index (NDWI) provides a robust indicator of community level canopy water content of these tree islands. NDWI, used as a proxy for water status, was positively related to foliar N isotope ratio, which suggests that water availability is linked to nutrient availability in the tree island hardwood hammock plant communities. These findings are consistent to the chemohydrodynamic nutrient accumulation model. In Chapter 3, I used sap flow sensors on individual trees to provide a real-time measurement of plant transpiration. I showed that tree island plant transpiration is affected by multiple factors including weather fluctuations, marsh water depth regulated by local water management, and canopy structure of different tree islands. Overall, my dissertation establishes a link between tree island plant water use and nutrient accumulation. It could be potentially important for future restoration plan of tree islands and Everglades hydrological management.

Grass-dominated ecosystems in many regions around the world have experienced increased abundance of woody plants during the past 100 yrs. In the Rio Grande Plains of southern Texas, subtropical woodlands, dominated by C3 trees/shrubs capable of symbiotic N2-fixation, have become significant components of landscapes that were once dominated by C4 grasslands. Upland areas in this region now consist of small discrete clusters and large groves of woody vegetation embedded in a grassy matrix, while lower-lying portions of the landscape are dominated by closed-canopy woodlands. I used soil δ13C in conjunction with aerial photography and geostatistics to quantify landscape-scale vegetation dynamics in uplands of this savanna parkland. Spatial patterns of soil δ13C in grids and transects traversing woody patches indicated larger woody groves were formed from small discrete clusters of woody plants that spread laterally and eventually coalesced. Soil δ13C contour maps revealed some clusters are currently growing rapidly towards each other and might coalesce into groves in the near future, while some clusters remained relatively stable. Kriged maps of soil δ13C provided a strong spatial context for future studies aimed at understanding the functional consequences of this change in landscape structure. The dominant invading woody plant, honey mesquite (Prosopis glandulosa), was important in determining the spatial pattern of soil δ13C, supporting the hypothesis that they serve as recruitment foci and facilitate the establishment of subordinate woody species. Leaf δ15N values suggested that the N2-fixing mesquite influenced the N nutrition of nearby non-N2-fixing shrubs, thus, suggesting a mechanism by which mesquite could facilitate establishment of other woody species. In closed-canopy drainage woodlands, however, spatial patterns of soil δ13C were no longer controlled by the presence of mesquite, but by the amount of soil organic carbon and soil texture. The positive correlation between silt+clay and soil δ13C indicates that the formation of organomineral complexes and microaggregates may slow SOC turnover rates and favor the persistence of C4-derived SOC from the original grassland. This study enhances our understanding of potential patterns, causes and consequences of grassland to woodland conversions which are underway today in many grass-dominated ecosystems around the world.

Syftet med denna litteraturstudie var att via litteraturen beskriva nutritionens betydelse för sårläkning. Studien genomfördes som en deskriptiv litteraturstudie där metoden bestod av att söka vetenskapliga artiklar i databaserna Medline, Cinahl och Academic Search Elite. Sjutton artiklar valdes ut. Resultatet visade att patienter med bensår eller trycksår i många fall inte når upp till de näringsrekommendationer som finns. Det visade sig vara vanligt att dessa patienter ligger vid gränsen för att vara undernärda. Det upptäcktes att det är sällan som kostintaget täcker energibehovet. Framför allt var zinknivåerna genomgående väldigt låga och det visar även att det är brist på en hel del andra ämnen. Ämnen som visat sig speciellt fördelaktiga för sårläkning är protein, vitamin C, zink samt arginin. För patienter med brännskador däremot har det visat sig att saltet ornithine α-ketoglutarate minskar proteinkatabolismen samt förbättrar proteinsyntesen, vilket är en förutsättning för sårläkning. Slutsatsen med föreliggande studie var att nutritionen är viktig och kan ha en avgörande betydelse för sårläkning. / The purpose with this literature study was that through literature describe the nutrition’s significance for healing wounds. The study was made as a descriptive literature study where the method was conducted by searching scientific articles in the databases Medline, Cinahl and Academic Search Elite. Seventeen articles were chosen. The result showed that patients with leg ulcers or pressure sores in many cases don’t attain the recommendations for nutrition that are available. It showed that it is normal that these patients are on the border of being undernourished. It was discovered that the nutrient intake rarely covers the energy needs. Above all the zinc levels were throughout very low and that shows that there is also lack of some other substances. The substances that have been shown especially good for healing wounds are protein, vitamin C, zinc and arginine. However, for patients with burn injuries the salt ornithine α-ketoglutarate has been shown to reduce protein catabolism and also improve protein synthesis, which are essential to healing wounds. The conclusion from this study was that nutrition may be an important but also a determining factor to healing wounds.