Tesis sobre el tema "Saltbush"

[Truncated abstract] Saltbush is one of the few types of forage that will grow on salt affected land but, sheep struggle to maintain weight when grazing saltbush mainly because of its high salt content. Therefore, a strategy to improve salt tolerance of sheep would be beneficial to the profitable use of revegetated saline land. This could be done by manipulating the dietary salt load of pregnant or lactating ewes which could 'program', or permanently alter the physiology of their offspring to allow them to cope better with a high-salt diet as adults. When rat dams consume a high amount of salt during pregnancy, the salt balance mechanisms of their offspring are 'programmed' due to suppression of the offspring's renin-angiotensin system in early development. If this occurs in offspring from ewes grazing saltbush, beneficial adaptations may be programmed in these offspring which could allow them to better cope with the high-salt content of saltbush. I tested the general hypothesis that offspring born to ewes that consumed a high-salt or saltbush diet from mid-pregnancy to early lactation would have an increased capacity to cope with salt that would allow them gain weight when grazing saltbush in later life. To test this hypothesis, I pair-fed ewes either a high-salt diet (14% NaCl) or control diet (2% NaCl) in an animal house from day 60 of gestation until day 21 of lactation. During the same period, I also conducted a field experiment where ewes grazed on saltbush (supplemented with barley) or on pasture (supplemented with lupins). ... This led to the high-salt offspring retaining more salt than control animals. In contrast, the renin activity of saltbush was consistently lower than pasture offspring which allowed them to excrete salt more rapidly. In experiment three, the saltbush offspring gained tissue weight after grazing saltbush for 8 weeks, whereas the offspring in the other three treatments lost weight. High-salt and saltbush offspring also had higher greasy fleece weights at 22 months of age than their respective control groups. Feeding saltbush to ewes from mid-pregnancy to early lactation induces physiological adaptations in their offspring that allow them to cope better with salt and gain weight when grazing saltbush as adults, supporting my hypothesis. However, contrary to expectations, the high-salt offspring did not gain weight when grazing saltbush because their physiological adaptations, such as salt retention, did not allow them to cope better with a salt load. The reason that saltbush offspring showed different adaptations to highsalt offspring is likely to be because saltbush contains not only NaCl but also high amounts of other minerals such as potassium, and other plant compounds, which may influence the adaptive responses of the offspring. This research has direct implications for farmers because it shows they could utilize otherwise unproductive saltland by grazing pregnant ewes on saltbush to 'program' their offspring to gain weight when they graze saltbush later in life.

Bibliography: leaves 105-121. This study reports the first thorough investigation of palatability variation in Atriplex vesicaria Heward ex Benth. (bladder saltbush). Intensive small-plot dietary trials, supported by a paddock dietary experiment, cross-fence comparisons and cafeteria trials, showed that sheep preferentially grazed female saltbushes over male and bisexual ones. Sheep avoided male saltbushes due to a chemical deterrent, and used visual (male flower spike) and olfactory cues to detect male plants. The effect of this selective grazing was to reduce the size and reproductive output of female shrubs. Sheep also tended to return to shrubs they had grazed previously. In the semi-arid regions of South Australia, where bladder saltbush is grazed year-round, physical protection is recommended to maximise survival and reproductive output of heavily grazed shrubs.

Forage halophytes such as saltbush (Atriplex spp) are being widely used to revegetate Australian saline land and can also provide a medium quality fodder source. There is widespread anecdotal evidence that sheep grazing on saltbush are leaner, tastier and juicer. This thesis investigated the potential to produce a high quality carcass with improved eating quality from grazing sheep on saltbush on saline land. The first experimental chapter in this thesis details an animal house experiment investigating the carcass, eating and wool quality and physiological responses of sheep ingesting a 60:40 dried saltbush (Atriplex nummularia):barley grain (S+B), ration verses a 33:25:42 lupin grain:barley grain:oaten hay ration (Control, C) for 10 weeks prior to commercial slaughter (Chapter 4). Subsequently, two field experiments were conducted to examine the effects of grazing saltbush on saline land compared to dry senesced pasture on carcass and eating quality of lambs (Goomalling 2003) and hoggets (Wickepin 2004) (both chapter 6) for 14 weeks. Both chapters demonstrated that the ingestion of saltbush resulted in significantly less fat and in the 2 field experiments the ingestion of saltbush resulted in more lean on the carcass compared to sheep grazing a stubble/pasture (control) ration. These are positive findings for processors as costs of fat denudation are high so the lower the fat content and for farmers because less fat is deposited on the carcass per unit of liveweight gain. The decreased deposition of fat was attributed to the higher protein:energy ratio available for production, secondary compounds in saltbush and lower circulating insulin and higher growth hormone of the S+B fed sheep compared to the control fed sheep. Further work is needed to determine if these beneficial improvements in carcass composition can be achieved without compromising animal production. The long term grazing of saltbush did not result in commercially desirable hot carcass weights unless the sheep were supplemented with a high energy source such as barley. The low growth rates are attributed to a decreased availability of energy substrates, low feed intake and increased energy output of sheep fed high salt diets. The low energy intake of the S+B fed sheep also resulted in an a significantly lower percentage of unsaturated fat and unchanged levels of saturated fat in the fat depots compared to the C treatment. Consumer taste tests conducted on meat from experiments in both chapter 4 and 6 indicated no difference between the treatments for any of the eating quality traits assessed. This can be considered a positive result as sheep can be finished on saltbush without any detriment to eating quality. High vitamin E levels in the meat may have also prevented the development of rancid flavours and aroma. It can be speculated that saltbush does not impart beneficial flavour and aroma volatiles as previously thought; instead the high vitamin E levels inhibit off-flavour and aroma development compared to meat from sheep grazed on dry pasture. The long term ingestion of saltbush also resulted in significantly lower urine specific gravity (USG), muscle dry matter and higher urine weights suggesting that the saltbush fed sheep had a better hydration status compared to control fed sheep. However, this finding did not correspond with higher hot carcass weight or dressing percentages. The increases in muscle fluid content of the saltbush fed sheep were attributed to changes in body composition. The saltbush fed sheep had a higher lean and lower fat content which corresponded with a greater body fluid content as found in the animal house study. Under conditions where the body composition of sheep remains the same, the use of short term strategic feeding of components of saltbush was investigated (mimicked in the form of salt and betaine) to reduce dehydration and subsequent reductions in carcass weight and dressing percentages (Chapter 7). Salt and or betaine were fed for 1 week either prior to a 48 h period of water deprivation or prior to 48 h commercial slaughter process where water was available in lairage from 24-48 h. Under both scenarios the diets did not result in improved dressing percentages, hot carcass weights, muscle dry matter or muscle weights. The ingestion of high salt diet prior to slaughter, did increase fluid retention in the extracellular spaces prior to slaughter however by 48 h both groups were at a similar physiological and therefore similar hydration status. Therefore similar levels of fluid were present in the muscles and no difference in carcass weight or dressing percentage could be expected. An important observation from the second experiment was that the high salt group drunk more water than the low salt fed sheep but the low salt group consumed fluid in lairage also. The low salt fed sheep may have been encouraged to drink water after observing the frequent drinking patterns of the high salt group. This thesis has also shown that saltbush contains high levels of vitamin E (á-tocopherol) (193 mg/kg dry matter). As a result the concentration of á-tocopherol in plasma, liver and muscle of the saltbush fed sheep was elevated compared to those grazing dry pasture. The high muscle concentrations of vitamin E in the saltbush-grazed sheep resulted in improved meat colour stability. The high vitamin E levels did not influence the drip and cooking loss of the meat despite a decrease in the muscle dry matter of the meat. The browning of meat and increased drip loss results in large losses to the meat industry due to value deterioration at the supermarket. There is also great potential for the high vitamin E content in saltbush to be used for the prevention of nutritional myopathy instead of using expensive and labour intensive synthetic supplements. In conclusion, this thesis has provided an insight into the carcass and eating quality of sheep grazed on saltbush based saline pasture systems. The most significant findings were that

Forage halophytes such as saltbush (Atriplex spp) are being widely used to revegetate Australian saline land and can also provide a medium quality fodder source. There is widespread anecdotal evidence that sheep grazing on saltbush are leaner, tastier and juicer. This thesis investigated the potential to produce a high quality carcass with improved eating quality from grazing sheep on saltbush on saline land. The first experimental chapter in this thesis details an animal house experiment investigating the carcass, eating and wool quality and physiological responses of sheep ingesting a 60:40 dried saltbush (Atriplex nummularia):barley grain (S+B), ration verses a 33:25:42 lupin grain:barley grain:oaten hay ration (Control, C) for 10 weeks prior to commercial slaughter (Chapter 4). Subsequently, two field experiments were conducted to examine the effects of grazing saltbush on saline land compared to dry senesced pasture on carcass and eating quality of lambs (Goomalling 2003) and hoggets (Wickepin 2004) (both chapter 6) for 14 weeks. Both chapters demonstrated that the ingestion of saltbush resulted in significantly less fat and in the 2 field experiments the ingestion of saltbush resulted in more lean on the carcass compared to sheep grazing a stubble/pasture (control) ration. These are positive findings for processors as costs of fat denudation are high so the lower the fat content and for farmers because less fat is deposited on the carcass per unit of liveweight gain. The decreased deposition of fat was attributed to the higher protein:energy ratio available for production, secondary compounds in saltbush and lower circulating insulin and higher growth hormone of the S+B fed sheep compared to the control fed sheep. Further work is needed to determine if these beneficial improvements in carcass composition can be achieved without compromising animal production. The long term grazing of saltbush did not result in commercially desirable hot carcass weights unless the sheep were supplemented with a high energy source such as barley. The low growth rates are attributed to a decreased availability of energy substrates, low feed intake and increased energy output of sheep fed high salt diets. The low energy intake of the S+B fed sheep also resulted in an a significantly lower percentage of unsaturated fat and unchanged levels of saturated fat in the fat depots compared to the C treatment. Consumer taste tests conducted on meat from experiments in both chapter 4 and 6 indicated no difference between the treatments for any of the eating quality traits assessed. This can be considered a positive result as sheep can be finished on saltbush without any detriment to eating quality. High vitamin E levels in the meat may have also prevented the development of rancid flavours and aroma. It can be speculated that saltbush does not impart beneficial flavour and aroma volatiles as previously thought; instead the high vitamin E levels inhibit off-flavour and aroma development compared to meat from sheep grazed on dry pasture. The long term ingestion of saltbush also resulted in significantly lower urine specific gravity (USG), muscle dry matter and higher urine weights suggesting that the saltbush fed sheep had a better hydration status compared to control fed sheep. However, this finding did not correspond with higher hot carcass weight or dressing percentages. The increases in muscle fluid content of the saltbush fed sheep were attributed to changes in body composition. The saltbush fed sheep had a higher lean and lower fat content which corresponded with a greater body fluid content as found in the animal house study. Under conditions where the body composition of sheep remains the same, the use of short term strategic feeding of components of saltbush was investigated (mimicked in the form of salt and betaine) to reduce dehydration and subsequent reductions in carcass weight and dressing percentages (Chapter 7). Salt and or betaine were fed for 1 week either prior to a 48 h period of water deprivation or prior to 48 h commercial slaughter process where water was available in lairage from 24-48 h. Under both scenarios the diets did not result in improved dressing percentages, hot carcass weights, muscle dry matter or muscle weights. The ingestion of high salt diet prior to slaughter, did increase fluid retention in the extracellular spaces prior to slaughter however by 48 h both groups were at a similar physiological and therefore similar hydration status. Therefore similar levels of fluid were present in the muscles and no difference in carcass weight or dressing percentage could be expected. An important observation from the second experiment was that the high salt group drunk more water than the low salt fed sheep but the low salt group consumed fluid in lairage also. The low salt fed sheep may have been encouraged to drink water after observing the frequent drinking patterns of the high salt group. This thesis has also shown that saltbush contains high levels of vitamin E (alpha-tocopherol) (193 mg/kg dry matter). As a result the concentration of alpha-tocopherol in plasma, liver and muscle of the saltbush fed sheep was elevated compared to those grazing dry pasture. The high muscle concentrations of vitamin E in the saltbush-grazed sheep resulted in improved meat colour stability. The high vitamin E levels did not influence the drip and cooking loss of the meat despite a decrease in the muscle dry matter of the meat. The browning of meat and increased drip loss results in large losses to the meat industry due to value deterioration at the supermarket. There is also great potential for the high vitamin E content in saltbush to be used for the prevention of nutritional myopathy instead of using expensive and labour intensive synthetic supplements. In conclusion, this thesis has provided an insight into the carcass and eating quality of sheep grazed on saltbush based saline pasture systems. The most significant findings were that ingesting saltbush can reduce the carcass fat content, improve meat colour stability and not result in any detriment to eating quality. A potentially useful way to incorporate these results into an Australian farming system may be to use saltbush on a short term basis, not for the length of period grazed in this thesis. The short term use of saltbush should provide sufficient grazing time for an elevation of vitamin E levels in the muscle to improve meat colour stability, increase the amount of lean and decrease fat levels of a carcass all without changing eating quality and decreasing liveweight. Further work is needed to ensure that these benefits can be achieved without compromising animal production. The opportunity to utilise saltbush to produce leaner carcasses with better colour stability may encourage farmers to consider previously unproductive land planted to saltbush to be a highly useful enterprise.

Forage halophytes such as saltbush (Atriplex spp) are being widely used to revegetate Australian saline land and can also provide a medium quality fodder source. There is widespread anecdotal evidence that sheep grazing on saltbush are leaner, tastier and juicer. This thesis investigated the potential to produce a high quality carcass with improved eating quality from grazing sheep on saltbush on saline land. The first experimental chapter in this thesis details an animal house experiment investigating the carcass, eating and wool quality and physiological responses of sheep ingesting a 60:40 dried saltbush (Atriplex nummularia):barley grain (S+B), ration verses a 33:25:42 lupin grain:barley grain:oaten hay ration (Control, C) for 10 weeks prior to commercial slaughter (Chapter 4). Subsequently, two field experiments were conducted to examine the effects of grazing saltbush on saline land compared to dry senesced pasture on carcass and eating quality of lambs (Goomalling 2003) and hoggets (Wickepin 2004) (both chapter 6) for 14 weeks. Both chapters demonstrated that the ingestion of saltbush resulted in significantly less fat and in the 2 field experiments the ingestion of saltbush resulted in more lean on the carcass compared to sheep grazing a stubble/pasture (control) ration. These are positive findings for processors as costs of fat denudation are high so the lower the fat content and for farmers because less fat is deposited on the carcass per unit of liveweight gain. The decreased deposition of fat was attributed to the higher protein:energy ratio available for production, secondary compounds in saltbush and lower circulating insulin and higher growth hormone of the S+B fed sheep compared to the control fed sheep. Further work is needed to determine if these beneficial improvements in carcass composition can be achieved without compromising animal production. The long term grazing of saltbush did not result in commercially desirable hot carcass weights unless the sheep were supplemented with a high energy source such as barley. The low growth rates are attributed to a decreased availability of energy substrates, low feed intake and increased energy output of sheep fed high salt diets. The low energy intake of the S+B fed sheep also resulted in an a significantly lower percentage of unsaturated fat and unchanged levels of saturated fat in the fat depots compared to the C treatment. Consumer taste tests conducted on meat from experiments in both chapter 4 and 6 indicated no difference between the treatments for any of the eating quality traits assessed. This can be considered a positive result as sheep can be finished on saltbush without any detriment to eating quality. High vitamin E levels in the meat may have also prevented the development of rancid flavours and aroma. It can be speculated that saltbush does not impart beneficial flavour and aroma volatiles as previously thought; instead the high vitamin E levels inhibit off-flavour and aroma development compared to meat from sheep grazed on dry pasture. The long term ingestion of saltbush also resulted in significantly lower urine specific gravity (USG), muscle dry matter and higher urine weights suggesting that the saltbush fed sheep had a better hydration status compared to control fed sheep. However, this finding did not correspond with higher hot carcass weight or dressing percentages. The increases in muscle fluid content of the saltbush fed sheep were attributed to changes in body composition. The saltbush fed sheep had a higher lean and lower fat content which corresponded with a greater body fluid content as found in the animal house study. Under conditions where the body composition of sheep remains the same, the use of short term strategic feeding of components of saltbush was investigated (mimicked in the form of salt and betaine) to reduce dehydration and subsequent reductions in carcass weight and dressing percentages (Chapter 7). Salt and or betaine were fed for 1 week either prior to a 48 h period of water deprivation or prior to 48 h commercial slaughter process where water was available in lairage from 24-48 h. Under both scenarios the diets did not result in improved dressing percentages, hot carcass weights, muscle dry matter or muscle weights. The ingestion of high salt diet prior to slaughter, did increase fluid retention in the extracellular spaces prior to slaughter however by 48 h both groups were at a similar physiological and therefore similar hydration status. Therefore similar levels of fluid were present in the muscles and no difference in carcass weight or dressing percentage could be expected. An important observation from the second experiment was that the high salt group drunk more water than the low salt fed sheep but the low salt group consumed fluid in lairage also. The low salt fed sheep may have been encouraged to drink water after observing the frequent drinking patterns of the high salt group. This thesis has also shown that saltbush contains high levels of vitamin E (alpha-tocopherol) (193 mg/kg dry matter). As a result the concentration of alpha-tocopherol in plasma, liver and muscle of the saltbush fed sheep was elevated compared to those grazing dry pasture. The high muscle concentrations of vitamin E in the saltbush-grazed sheep resulted in improved meat colour stability. The high vitamin E levels did not influence the drip and cooking loss of the meat despite a decrease in the muscle dry matter of the meat. The browning of meat and increased drip loss results in large losses to the meat industry due to value deterioration at the supermarket. There is also great potential for the high vitamin E content in saltbush to be used for the prevention of nutritional myopathy instead of using expensive and labour intensive synthetic supplements. In conclusion, this thesis has provided an insight into the carcass and eating quality of sheep grazed on saltbush based saline pasture systems. The most significant findings were that ingesting saltbush can reduce the carcass fat content, improve meat colour stability and not result in any detriment to eating quality. A potentially useful way to incorporate these results into an Australian farming system may be to use saltbush on a short term basis, not for the length of period grazed in this thesis. The short term use of saltbush should provide sufficient grazing time for an elevation of vitamin E levels in the muscle to improve meat colour stability, increase the amount of lean and decrease fat levels of a carcass all without changing eating quality and decreasing liveweight. Further work is needed to ensure that these benefits can be achieved without compromising animal production. The opportunity to utilise saltbush to produce leaner carcasses with better colour stability may encourage farmers to consider previously unproductive land planted to saltbush to be a highly useful enterprise.

Fourwing saltbush (Atriplex canescens) was seeded in 80 -inch wide water harvesting microcatchments on retired farmland west of Tucson. Eight months after planting the plots that had received one establishment irrigation and weeding had significantly more cover than the unirrigated and unweeded treatments. The percent cover of the uninigated /weeded and irrigated /unweeded treatments was not significantly different. Uninigated and unweeded plots had virtually no cover of saltbush. It appears that establishing saltbush in microcatchments of this size is not feasible without either an establishment irrigation or weed control.

This is an experiment on seeding fourwing saltbush (Atriplex canescens) in 80-inch wide waterharvesting microcatchments on retired farmland west of Tucson. At 32 months after planting plots that received the establishment irrigation had more cover than unirrigated plots. Keeping plots free of competing weeds also gave some advantage. However, the coefficient of variation was very high, and none of these differences was statistically significant.

Halogeton (Halogeton glomeratus) is a halophytic, invasive species that displaces Gardner’s saltbush (Atriplex gardneri) on saline rangelands. Forage kochia (Bassia prostrata) is a potential species to rehabilitate these ecosystems. This study compared the salinity tolerance of these species and tall wheatgrass (Thinopyrum ponticum) and alfalfa (Medicago sativa). Plants were evaluated for 28 days in hydroponics where they were maintained at 0, 150, 200, 300, 400, 600, and 800 mM NaCl. Shoot growth and ion accumulation were determined. Alfalfa and tall wheatgrass were severely affected by salt with both species’ shoot mass just 32% of control at 150 mM NaCl. Alfalfa did not survive above 300 mM NaCl, while, tall wheatgrass did not survive at salt levels above 400 mM NaCl. In contrast, forage kochia survived to 600 mM, but produced little shoot mass at that level. Halogeton exhibited ‘halophytic’ shoot growth, reaching maximum mass at 141 mM, and not less mass than the control until salinity reached 400 mM. Gardner’s saltbush did not show a dramatic decrease in dry mass produced until it reached salt levels of 600 and 800 mM NaCl. Forage kochia yielded high amounts of dry mass in the absence of salt, but also managed to survive up to 600 mM NaCl. Salt tolerance ranking (GR50 = 50% reduction in shoot mass) was Gardner’s saltbush=halogeton>forage kochia> alfalfa>tall wheatgrass. Both halogeton and Gardner’s saltbush actively accumulated sodium in shoots, indicating that Na+ was the principle ion in osmotic adjustment. In contrast, forage kochia exhibited a linear increase (e.g. passive uptake) in Na+ accumulation as salinity increased. This study confirmed that halogeton is a halophytic species and thus well adapted to salt-desert shrubland ecosystems. Gardner’s saltbush, also a halophyte, was equally salt tolerant, suggesting other factors are responsible for halogeton displacement of Gardner’s saltbush. Forage kochia is a halophytic species that can survive salinity equal to seawater, but is not as salt tolerant as Gardner’s saltbush and halogeton.

Secondary salinisation is an increasing problem in Australia. Both native and exotic saltbush (Atriplex) species have been used for rehabilitation and forage production on saline soils, particularly A. amnicola, a species native to north Western Australia, which has very good forage potential. Establishment of saltbush stands is usually by direct sowing of fruits and frequent failure of establishment is due to the very low fruit fill obtained from fruit collected from existing saltbush stands (commonly less than 20%). At present there are very few dedicated seed production stands of Atriplex. In order to establish and manage such stands for maximum seed production, the causes of poor fruit fill must be determined. Earlier observations showed that fruit fill in A. amnicola declined from 70% to 80% in late winter, to between 20% and 30% prior to harvest in December. Limitation of mineral nutrients to mother plants and of assimilates to developing seeds, and environmental and genotypic influences which may account for this seed abortion, were examined in the field and glasshouse. Although initial observations did not indicate that pollination and fertilisation were major influences on fruit fill, they also were examined to determine to what extent they may limit fruit fill in A. amnicola. No incompatibility was seen in the diallele crosses made between five male and five female clones of A. amnicola, but pollen supply did limit fruit fill. A 1 to 1 sex ratio was required to optimise fruit fill and yield. Sexual lability of individual plants in a population of A. amnicola caused the population ratio to shift from a ratio of 3 males to 2 females, to a 1 to 1 sex ratio, but the change in sex ratio had no effect on fruit filling. Seed abortion which may result from nutritional limitations to mother plants and limitations of assimilate to developing seeds, were examined. Addition of nitrogen and phosphorus fertiliser did not improve fruit fill at harvest. This response is not unusual in native Australian plants that are adapted to very low nutrient soils. High levels of fruit pruning (50% and 75%) to reduce competition between sinks for assimilate increased fruit fill by 5%. In unpruned plants, earlier developing fruits in the distal region of stems had higher levels of fruit fill than proximal fruits. By contrast, in the pruned plants, the increase in total fruit fill resulted from increasing proximal fruit fill to the same level as the distal fruits. The effects of salinity, pH, soil texture and compaction, gravimetric water content and depth of water table were examined for their effects on fruit fill in A. amnicola. Duration of waterlogging was found to be the most significant factor causing seed abortion. Genotypic influences were also very important in determining fruit fill. Of the three female clones tested in the field, one clone had a mean fruit fill of 70% compared to 40% for the others. However, this clonal difference was not maintained under the most severe levels of waterlogging and salinity, indicating that environmental effects were more significant. To assess further the effects of waterlogging on fruit fill and seed abortion in A. amnicola, a controlled pot experiment was conducted, which aimed to mimic the climatic conditions in the field. Plants were waterlogged for 5 weeks in the middle of winter, for 5 weeks at the onset of spring when temperatures began to rise and for 10 weeks throughout winter and spring. Waterlogging of Atriplex amnicola, for up to ten weeks had no affect on fruit fill. This is in direct contrast with results from the field where waterlogging reduced fill by approximately 15% after 30 days and 70% after 135 days. For all treatments, fruit fill decreased from 50% to 27% in the first five weeks. This discrepancy between field and controlled experimental results may be due to the conditions of low vapour pressure deficit (VPD) which existed for the controlled experiments. The evapotranspirational demand of A. amnicola under those conditions was such that the effect of waterlogging for 10 weeks was minimal. However, the increased seed abortion seen in the field may have occurred under conditions of high VPD, where evapotranspirational demand was much greater and the waterlogged roots of the plants were unable to take up enough water. The seed abortion which occurred in the first five weeks was strongly correlated with large rainfall events which may have led to substantial dilution for short periods, of the salt solution used to maintain waterlogging. Lack of available ions to supply the rapid uptake required to maintain turgor may have accounted for the seed abortion. By contrast to the lack of effects on fruit fill, waterlogging treatment significantly depressed fruit yield. Waterlogging for ten weeks decreased yield to the same extent as the 5 week treatment in early spring. Both treatments decreased yield to a greater extent than waterlogging for 5 weeks during winter. This effect supports the results from the field where yield was reduced by nearly 80% by 135 days of waterlogging. It is concluded from the present study that the establishment of dedicated seed production plots requires selected female genotypes planted at a 1 to 1 ratio with male genotypes, on mildly saline sites that are not subject to prolonged periods of waterlogging in winter. The interactive effects of VPD, waterlogging and salinity on fruit fill in A. amnicola need to be tested to allow predictions to be made on the quality of seed crops in different seasons.

Gardner saltbush ecosystems are increasingly being invaded by halogeton, a competitive annual weed that increases soil surface salinity and reduces plant biodiversity. This study was established on the Flaming Gorge National Recreation Area, in the Ashley National Forest near Manila, UT to evaluate the ability of forage kochia, Russian wildrye, tall wheatgrass, Indian ricegrass and Gardner saltbush, in monocultures and binary mixtures with Gardner saltbush, to establish and compete in ecosystems dominated by halogeton. A dormant seeding, with and without prior disking, was conducted to determine the ability of plant materials to establish. A spaced-plant evaluation was used to determine the competitive ability of fully established plants by measuring halogeton densities at four 10 cm intervals (10-20, 20-30, 30-40, and 40-50 cm) distal from transplants. Gardner saltbush, tall wheatgrass, and Indian ricegrass did not establish or persist beyond the first year in either study. Conversely, Russian wildrye and forage kochia established and persisted, with Russian wildrye establishment higher (P ≤ 0.05) in the disked treatment (4.5 and 1.7 plants m-2, respectively) and no-till favoring (P ≤ 0.05) forage kochia establishment (2.0 and 0.8 plants m-2, respectively). Spaced-plants of these species reduced halogeton by 52% relative to the control. Furthermore, by the second year of evaluation, the competitive ability of Russian wildrye and forage kochia had extended to 50 cm distal from transplant. Transplant survival and halogeton frequency were highly correlated (r = -0.67, P = 0.0001), indicating the important of persistence. These results suggest that Russian wildrye and forage kochia can establish, persist, and compete with halogeton, thereby providing an opportunity for reclamation of halogeton-invaded areas. Conversely, direct restoration to Gardner saltbush and Indian ricegrass does not appear likely

This study examines the environmental and socio-economic effects associated with the planting of Atriplex nummularia Lindl. (Oldman saltbush) in the karoo. This is the first study of its kind on oldman saltbush and serves as an important scoping exercise in assessing the impact of saltbush on its surrounds and in identifying additional aspects which require investigation. The environmental parameters investigated include microclimatic effects, soil induced changes, salinity effects on the germination of selected karoo species and compositional changes in the indigenous plant community within a saltbush plantation. When compared to indigenous karoo plant species oldman saltbush is found to ameliorate soil temperatures and increase surface soil salinity (specifically sodium chloride), on an individual plant basis. Salinity is shown to have a differential effect on the germination of selected karoo shrubs. The indigenous plant community within a forty year old saltbush plantation is impoverished with both density of individuals and species richness being markedly reduced. Saltbush is identified as an unsuitable nurse plant for the majority of karoo shrubs. Farm size in relation to both actual and intended area established to saltbush is considered. The area of saltbush already established in the karoo is considered too insignificant to have any wide socio-economic impact. Farmers who intend planting large areas of their farms to saltbush are in the minority. It is those farmers who already have some saltbush planted, who intend planting more. Ecologically based management guidelines are presented, suggesting practices which minimize the detrimental effects of saltbush on soil salinity and the indigenous plant community. These guidelines are practical and in keeping with the overall objectives of optimum resource utilisation and the national grazing strategy for South Africa.

The main hypothesis tested in this thesis was that poor animal production from saltbush pastures is due to the negative effects of high sodium chloride (NaCl) and potassium chloride (KCl) on the ruminal environment, and subsequent effects on microbial populations and products of rumen fermentation. This main hypothesis was tested in two experiments. In the first experiment (Chapter Four) the effects of saltbush and a formulated high-salt diet on the ruminal environment and microbial populations were measured over 24-hours following feeding. Feeding both the saltbush and high-salt diet increased the salinity of the rumen fluid, but the formulated high-salt diet caused a decrease in ruminal pH while the saltbush caused an increase. This resulted in differences in the composition of the ruminal microbial populations between the sheep fed different diets. In the second experiment (Chapter Five) the effects of saltbush and a formulated highsalt diet on rumen fermentation were measured. Sheep fed saltbush had inefficient rumen fermentation and this was only partially explained by the high salt content of the diet. Diets containing high levels of NaCl and KCl provided low levels of net energy to sheep, but sheep fed saltbush lost more energy as methane and faecal energy compared to sheep fed the formulated high-salt diet. Inefficient rumen fermentation could help to explain poor animal production from saltbush pastures. Energy supplements such as barley grain can improve the value of saltbush pastures as feed for sheep, but there is no information on how much supplement is required. A third experiment (Chapter Six) was designed to test the hypothesis that there would be an optimal amount of barley required to improve the efficiency of rumen fermentation in sheep fed saltbush. Barley and straw were combined in a pellet and substituted for saltbush at 0, 20, 40, 60, 80 and 100% of the maintenance ration. Feeding barley and straw improved the efficiency of rumen fermentation in sheep fed saltbush, with an optimal level of supplementation at 60% of the maintenance diet. This is likely to be lower (approximately 20% of maintenance) if barley is fed without straw.

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Arid and semi-arid environments may present salty soils, which hamper plant growth, being removed from productive process constituting degradation cores. Under these conditions, glycophyte plants can’t growth because high levels of salts hinder their metabolism, however, for halophytes this is favorable environment and these plants may represent a key to soil reclamation, extracting salts in the vegetable material produced by phytoremediation technique. The study was conducted in a saline sodic INCEPTISOL from the Cachoeira II Irrigation Perimeter, Serra Talhada (PE), with the objective of evaluating changes in soil physical and chemical properties when under cultivation with the halophyte Atriplex nummularia Lindl, compared with chemical correction with gypsum, and plant growth and production monitoring under two spacing in the pruning management every six months. Samples were taken every six months, with four soil samples (0, 6, 12 and 18 months) and three cuts in the plant 50 cm from the ground surface (6, 12 and 18 months) measuring the material produced at each pruning.The experimental design was randomized blocks, four treatments were evaluated: control (no soil management), chemical correction with gypsum (no crop) and two Atriplex nummularia cultivation, one at 1 x 1 m spacing and other at 2 x 2 m spacing, with four replications. The results of soil chemical and physical analysis revealed the contribution of gypsum application and especially the cultivation of atriplex plants in reducing the problems of salinity-sodicity and improving soil physical properties. The biometric analysis and plant tissue showed the Atriplex nummularia potential for phytoremediation, with emphasis on the 1 x 1 m spacing which presented as the best recommendation of cultivation with frequent pruning due to higher plant material yield and extraction of salt per planted area.
Ambientes sob clima árido e semiárido podem apresentar solos com elevados teores de sais, que dificultam o desenvolvimento de plantas, sendo retirados do processo produtivo e se constituindo núcleos de degradação. Nestas condições, plantas glicófitas não conseguem vegetar pelos elevados teores de sais, que dificultam seu metabolismo, entretanto, para as plantas halófitas este é um ambiente propício, podendo representar um agente recuperador do solo, com a extração de sais na matéria vegetal produzida, pela técnica da fitorremediação. O trabalho foi desenvolvido em um CAMBISSOLO salino sódico do Perímetro Irrigado Cachoeira II, Serra Talhada (PE), com o objetivo de avaliar as alterações nas propriedades físicas e químicas do solo quando submetido ao cultivo com a halófita Atriplex nummularia Lindl, em comparação com a correção química com gesso; e o monitoramento do crescimento e produção da planta sob dois espaçamentos em manejo de poda a cada seis meses. Realizaram-se amostragens semestrais, com quatro coletas de solo (0, 6, 12 e 18 meses) e três cortes na planta a 50 cm da superfície do solo (6, 12 e 18 meses), mensurando-se o material produzido a cada poda. O delineamento experimental utilizado foi blocos ao acaso, onde foram avaliados quatro tratamentos: o controle (sem nenhum manejo do solo), o de correção química com gesso (sem cultivo) e dois com cultivo de Atriplex nummularia Lindl, (espaçamentos 1 x 1 m e 2 x 2 m), com quatro repetições. Os resultados das análises químicas e físicas do solo revelaram a contribuição da aplicação de gesso e especialmente do cultivo de plantas de atriplex na redução dos problemas de salinidade-sodicidade e na melhoria nas propriedades físicas do solo. As análises biométricas e do tecido vegetal das plantas, evidenciaram o potencial fitorremediador da Atriplex nummularia Lindl, com destaque para as plantas no espaçamento 1 x 1 m, que se apresentou como a melhor recomendação de cultivo com podas frequentes, em função do maior rendimento na produção da matéria vegetal e da extração de sais por área plantada.

[Truncated abstract] In order to assess the sustainability of mixed plantings on saline land, this thesis examined the importance of leaf-litter trapping and microsites on recruitment in a salt affected alley-belted (tree/shrub) agricultural system in Western Australia. Located in the low rainfall region (MAR <330 mm) of the wheatbelt, the 60 ha site consists of concentric rows of Eucalyptus sargentii trees with mounded (6 - 11 cm high) 10 -15 m inter-rows of Atriplex spp. Sustainability of this system and fulfilment of productive and ameliorative functions is dependant on successful recruitment (perennials). Although the present study site was conducted on farmland in a Mediterranean-type climate, low annual rainfall and spatial arrangement of perennial shrubs and trees, allow useful comparisons to be made with naturally occurring banded semi-arid systems and vice-versa. Of key interest were leaf-litter redistribution and trapping by tree and shrub rows and whether litter-cover/microsites facilitated/interfered with seedling recruitment (establishment, growth and survival). Litter from the tree row, redistributed by prevailing winds and rain, accumulated adjacent to saltbush seeding mounds, creating a mosaic of bare and littered areas across the site (total litter 10 t/ha over 22 months). Accumulated litter was hypothesized to differentially influence seasonal soil abiotic parameters (depending on litter-cover density) including; salinity, water availability, infiltration rates, water repellency and temperature. These abiotic conditions were also hypothesized to vary between tree and shrub microsites. Biotically, recruitment at this site was also hypothesized to be determined by interactions (positive and negative) between perennial components and understorey annuals/perennial seedlings. Accumulation of litter and resultant heterogeneity was influenced by shrub morphology, microtopography, wind direction and distance from litter source, with increased litter on the leeward sides of hemispherical Atriplex undulata shrubs and shrubs closest to tree rows. ... The importance of tree/shrub microsites varied seasonally, with no influence in winter due to moderate temperatures and increased water availability. In warmer months saltbush mid-row microsites were most favourable for seedling recruitment due to moderate litter-cover; reducing salinity, temperatures and increasing infiltration; and reduced root-competition/shading by the tree row. Tree microsites also directly inhibited seedling recruitment through increased salinities and water repellency. However, trees also indirectly facilitated recruitment in adjacent areas through provision of leaf-litter. As litter-trapping and recruitment patterns at this site mirror those found in semi-arid natural and artificial systems, the results of this study provide useful insights into creating appropriate mimics of low rainfall natural banded woodland and chenopod shrublands. Saltbush seeding mounds, shrub morphology and litter were key components for litter trapping and recruitment heterogeneity at this site. In this tree/shrub alley planting, where litter quantities directly influence vegetation cover densities, future saline plantings need to consider appropriate tree/shrub row spacings and orientation for efficient resource (seeds, litter and water) capture.

La tesi es centra en una anàlisi prèvia de les implicacions de la teoria del cicle de vida aplicada a les destinacions turístiques pel geògraf canadenc Richard W. Butler (1982) i en un estudi del significat de l'aparició del postmodernisme i les seves repercussions en el turisme, a la vegada que es resegueix la història que ha fet possible l'aparició del turisme massificat de sol i platja.
Tot això és la base teòrica imprescindible per poder estudiar empíricament les destinacions de Saltburn (Regne Unit), l'Estartit (Costa Brava) i Cayo Coco (Cuba), utilitzant el cicle de vida per escriure la seva història i veure les polítiques de desenvolupament i regeneració turística que s'han seguit i si aquestes es poden qualificar de postfordistes. La principal conclusió és que el concepte del cicle de vida es limita a ser una eina de diagnòstic a posteriori. El cicle de vida, com a instrument prescriptiu, no serveix. Es específic per a cada destinació, amb unes etapes i punts d'inflexió que només es poden establir en restrospectiva. El cicle de vida és una eina descriptiva molt útil per entendre l'evolució de les destinacions turístiques i els seus mercats, però vigilant de no caure en falses exploracions o perillosos determinismes.
This thesis is based on an analysis of the implications of the life-cycle theory on tourist destinations by the Canadian geographer Richard W. Butler (1982); and on a study of what the emergence of postmodernim and its repercussions on tourism have meant. At the same time, the history that has made the appearance of mass sun and beach tourism possible is reviewed.
All this is the theoretical basis for the empirical study of the tourist destinations of Saltburn (United Kingdom), l'Estartit (Costa Brava) and Cayo Coco (Cuba). Life cycle is used as the instrument for writing their history and seeing what development and tourist regeneration policies they have followed and whether they can be defined as post-Fordist policies.
In conclusion, current tourist models, more inauthentic, diverse and customised, place a question-mark over the Fordist tourist practices of previous decades, although there are still more elements of continuity than of change. The idea now is to make the Fordist tourist model feasible, by using postmodernism as an instrument to give a theoretical and ideological gloss to the model that can be still called Fordist, but that has been adapted to new times and settings.

Includes bibliographical references (leaves 105-121)
x, 121, [39] leaves : ill., maps ; 30 cm.
Investigates the palatability variation in Atriplex vesicaria Heward ex Benth. (bladder saltbush). The main aim of the research was to examine the idea that the sex phenotypes of this species differ in their palatability to sheep, and to characterise some of the temporal and spatial features of the phenomenon. Intensive small-plot dietary trials, supported by a paddock dietary experiment, cross-fence comparisons and cafeteria trials, showed that sheep preferentially grazed female saltbushes over male and bisexual ones. Sheep avoided male saltbushes due to a chemical deterrent, and used visual (male flower spike) and olfactory cues to detect male plants. The effect of this selective grazing was to reduce the size and reproductive output of female shrubs. Sheep also tended to return to shrubs they had grazed previously. In the semi-arid regions of South Australia, where bladder saltbush is grazed year-round, physical protection is recommended to maximise survival and reproductive output of heavily grazed shrubs.
Thesis (Ph.D.)--University of Adelaide, Depts. of Environmental Science & Management and Botany, 1999?

Most research to date has focused on non-pregnant sheep grazing saltbush to fill the summer/autumn feed gap in temperate regions of southern Australia. However, the summer/autumn period coincides with late pregnancy for autumn- or winter-lambing ewes, and feeding saltbush may reduce the amount and cost of supplementary feed that is required to meet the energy demands of late pregnancy. The challenge of dealing with a high-salt diet may be exacerbated during pregnancy since pregnancy is a salt-retaining physiological state, yet a high-salt intake requires an increase in mechanisms to excrete salt. The effect of high dietary salt on the developing foetus(es) has been studied in rodent models, but less so in sheep. Hence the aims of this thesis were to determine whether pregnant ewes can manage a high dietary salt content resembling that found in saltbush, and whether there are consequences to the offspring’s physiological responses to ingested salt. Merino ewes were synchronized for ovulation and artificially inseminated. To mimic the concentration of salt in animals grazing saltbush-based pastures in summer and autumn, a diet of 13% NaCl was fed from insemination through to parturition. It was found that pregnant ewes can be fed a 13% NaCl diet and manage the physiological conflict of high salt and pregnancy by decreasing their aldosterone concentrations and increasing their water consumption. There was no effect of high dietary salt on pregnancy rates, lamb birth weights, lamb survival or milk composition (fat and protein percentages). A series of experiments were conducted to test if the high-salt intake of ewes during pregnancy was associated with a change in the dietary preference for salt and/or changes in physiological responses to ingested salt in the offspring (‘S lambs’ vs. control, ‘C lambs’). C lambs and S lambs were exposed to short- and long-term preference testing to determine if there were differences in their voluntary selection for salt in their diet. There were no significant differences in dietary salt preference between C and S lambs. The lambs were subjected to salt 'challenges' (oral dose of 40 g NaCl in 25% w/v solution) from 3-10 months of age and their water intake, urinary output, sodium excretion and hormone concentrations were measured over the ensuing 23 hours, and compared against counterparts dosed with an equal volume of water without salt. Following the initial salt challenge further experiments were conducted with slight alterations; water intake was manipulated immediately following the salt challenge; two consecutive salt challenges, 8 hours apart, were administered; and C and S lambs were offered salty water (1.5% NaCl) over a period of two days. The results of these salt challenge experiments showed that C and S lambs excreted a salt load at a similar rate, but they differed in the magnitude of changes in water intake and hormone concentrations required to achieve sodium homeostasis. S lambs were able excrete sodium at the same rate as C lambs but without decreasing aldosterone concentrations to the same extent and whilst consuming 400 mL less water in the first two hours post challenge. The aldosterone results suggested a lowered responsiveness to aldosterone and the lower water consumption suggested an altered thirst threshold. The experiment in which water consumption was manipulated suggested that when the supply or access to fresh water is limited, the capacity to remove a salt load is likely to be less impaired in S lambs than C lambs; S lambs were able to excrete the salt load faster than the C lambs when the availability of drinking water was limited. From the experiment in which lambs were treated with two consecutive salt challenges, the rate of sodium excretion increased after the second dose, but there remained no difference in the rate of excretion between C and S lambs; all animals were able to excrete 95% of the administered dose of sodium within 23 hours. The final experiment in which animals were given salty water (1.5% NaCl) for a period of two days showed consistent results with the previous experiments for water consumption and aldosterone concentrations between C and S lambs. There was no difference in sodium excretion between C and S lambs. A novel finding was a markedly lower voluntary feed intake in S lambs than C lambs. Although mechanisms for this are unknown, it may have profound effects on the productivity of the animals. The experiments reported in this thesis provide new information of relevance to pregnant ewes grazing halophytic forages. It is apparent that they can withstand a high NaCl content typical, of a saltbush-based pasture. Further work is warranted to conclude whether high salt during pregnancy is (i) beneficial to the offspring in regards to a higher capacity to deal with excess salt under farming conditions and (ii) consistently associated with a lower voluntary feed intake of the offspring.
http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1290752
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2007.

Most research to date has focused on non-pregnant sheep grazing saltbush to fill the summer/autumn feed gap in temperate regions of southern Australia. However, the summer/autumn period coincides with late pregnancy for autumn- or winter-lambing ewes, and feeding saltbush may reduce the amount and cost of supplementary feed that is required to meet the energy demands of late pregnancy. The challenge of dealing with a high-salt diet may be exacerbated during pregnancy since pregnancy is a salt-retaining physiological state, yet a high-salt intake requires an increase in mechanisms to excrete salt. The effect of high dietary salt on the developing foetus(es) has been studied in rodent models, but less so in sheep. Hence the aims of this thesis were to determine whether pregnant ewes can manage a high dietary salt content resembling that found in saltbush, and whether there are consequences to the offspring’s physiological responses to ingested salt. Merino ewes were synchronized for ovulation and artificially inseminated. To mimic the concentration of salt in animals grazing saltbush-based pastures in summer and autumn, a diet of 13% NaCl was fed from insemination through to parturition. It was found that pregnant ewes can be fed a 13% NaCl diet and manage the physiological conflict of high salt and pregnancy by decreasing their aldosterone concentrations and increasing their water consumption. There was no effect of high dietary salt on pregnancy rates, lamb birth weights, lamb survival or milk composition (fat and protein percentages). A series of experiments were conducted to test if the high-salt intake of ewes during pregnancy was associated with a change in the dietary preference for salt and/or changes in physiological responses to ingested salt in the offspring (‘S lambs’ vs. control, ‘C lambs’). C lambs and S lambs were exposed to short- and long-term preference testing to determine if there were differences in their voluntary selection for salt in their diet. There were no significant differences in dietary salt preference between C and S lambs. The lambs were subjected to salt 'challenges' (oral dose of 40 g NaCl in 25% w/v solution) from 3-10 months of age and their water intake, urinary output, sodium excretion and hormone concentrations were measured over the ensuing 23 hours, and compared against counterparts dosed with an equal volume of water without salt. Following the initial salt challenge further experiments were conducted with slight alterations; water intake was manipulated immediately following the salt challenge; two consecutive salt challenges, 8 hours apart, were administered; and C and S lambs were offered salty water (1.5% NaCl) over a period of two days. The results of these salt challenge experiments showed that C and S lambs excreted a salt load at a similar rate, but they differed in the magnitude of changes in water intake and hormone concentrations required to achieve sodium homeostasis. S lambs were able excrete sodium at the same rate as C lambs but without decreasing aldosterone concentrations to the same extent and whilst consuming 400 mL less water in the first two hours post challenge. The aldosterone results suggested a lowered responsiveness to aldosterone and the lower water consumption suggested an altered thirst threshold. The experiment in which water consumption was manipulated suggested that when the supply or access to fresh water is limited, the capacity to remove a salt load is likely to be less impaired in S lambs than C lambs; S lambs were able to excrete the salt load faster than the C lambs when the availability of drinking water was limited. From the experiment in which lambs were treated with two consecutive salt challenges, the rate of sodium excretion increased after the second dose, but there remained no difference in the rate of excretion between C and S lambs; all animals were able to excrete 95% of the administered dose of sodium within 23 hours. The final experiment in which animals were given salty water (1.5% NaCl) for a period of two days showed consistent results with the previous experiments for water consumption and aldosterone concentrations between C and S lambs. There was no difference in sodium excretion between C and S lambs. A novel finding was a markedly lower voluntary feed intake in S lambs than C lambs. Although mechanisms for this are unknown, it may have profound effects on the productivity of the animals. The experiments reported in this thesis provide new information of relevance to pregnant ewes grazing halophytic forages. It is apparent that they can withstand a high NaCl content typical, of a saltbush-based pasture. Further work is warranted to conclude whether high salt during pregnancy is (i) beneficial to the offspring in regards to a higher capacity to deal with excess salt under farming conditions and (ii) consistently associated with a lower voluntary feed intake of the offspring.
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2007.

Renewable sources of thermal and chemical energy are needed in order to satisfy the world’s ever growing energy needs while limiting the rise of global temperatures below 2 °C above pre-industrial levels. Plant biomass is a vast resource which if harnessed properly could help revolutionise the global energy economy. Hydrothermal Carbonisation (HTC) is a technology wherein biomass exposed to subcritical water at 180 °C – 260 °C is thermochemically converted into an energy-dense “hydrochar” with strong thermal and elemental similarities to fossil coal. However, key aspects of the HTC reaction remain unknown, especially with regard to the degradation of the key biochemical macromolecules hemicellulose, cellulose, lignin and protein. In this thesis, three novel biomasses, Australian saltbush, hemp and macroalgae, were subjected to HTC and the hydrochars analysed for fuel properties and biochemical composition. The breakdown of the key macromolecules was then described using kinetic modelling to build a mechanistic model of the overall conversion of biomass to hydrochar. Each of the three biomasses underwent profound chemical changes during the HTC reaction, resulting in much lower oxygen content, and much higher carbon content. This caused the energy content of the hydrochars to rise to levels that rivaled or even exceeded those observed in fossil lignites. In addition, the ash content of the biomass was reduced, although certain reaction conditions at higher intensities saw the reabsorbence of inorganic elements back into the char. A twin-pathway mechanistic model was adapted and developed from the literature to describe the overall HTC process and the formation of two different kinds of hydrochar: Mechanism 1, involving solid phase conversions that yield “primary char” derived directly from undissolved and partially converted starting material; and Mechanism 2, a two-step pathway that involves the degradation of the feedstock into dissolved intermediates, and the subsequent repolymerisation of those intermediates into “secondary char”. Using this model as a framework of the backdrop of the HTC reaction, the kinetics of the degradation step in each macromolecule where then analysed in detail. There were numerous broad similarities in the behaviour of the key macromolecules between the different biomasses, in spite of their different origins. The degradation of polysaccharides was determined mainly by the degree of crystallinity; non-crystalline hemicellulose degraded very quickly in every biomass in a pseudo-first order reaction, often being completely eliminated from the feedstock within minutes. On the other hand, highly crystalline cellulose was more recalcitrant, and the reaction orders and rates of degradation of cellulose varied considerably across the three biomasses, although it was consistently slower than its non-crystalline counterparts. Variations in the degree of crystallinity in both cellulose and hemicellulose appeared to result in dramatic differences in the degradation kinetics. Lignin was found to be partially susceptible to HTC degradation, with the majority being dissolved with similar kinetics to hemicellulose, and the remainder being inert. The mechanism of the degradation of protein in macroalgae was opaque and difficult to model, with proteins possibly undergoing Maillard reactions with carbohydrates. It is hoped that the methods presented here, especially regarding the biochemical analyses of the hydrochars, can form a major facet of future research and industrial development of HTC.
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2020