Thesis (M.S.)--Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: Brett E. Olson. Includes bibliographical references (leaves 36-40).

Thesis (Ph.D.)--Murdoch University, 2006. / Thesis submitted to the Division of Health Sciences. Bibliography: leaves 220-241.

No description available.

Thesis (M. Agr. Sc.) -- Lincoln University, 2008. / Also available via the World Wide Web.

Thesis (Ph. D.)--University of Adelaide, 1994. / Includes bibliographical references (leaves 259-291).

Global warming is expected to affect the arctic harsher than other regions of the globe. Many plant species will face conditions that contradict their adaptations in a warming climate. Changes in habitat can lead to drastic changes in biodiversity as well as exerting a strong selective pressure for plants to evolve and adapt quickly. Herbivore grazing in the arctic also affects plant ecosystems e.g. by lowering biodiversity and changing species composition and may influence their response to warming. The aim of this study was to examine whether grazing influences plants’ adaptation to rising temperatures. Geothermally warmed areas have been used as in situ proxy systems for effects of warming climates on ecosystems. Grændalur, a geothermally warmed valley in southwest Iceland, was used as a study site to explore the effects of warming and grazing on ecosystems. Three soil temperature gradient transects were established there and each transect has six fenced-off plots, at different soil temperatures (ambient +0, +1, +3, +5, +10 and +20°C), and paired plots outside the fence that were grazed by sheep. Species richness, evenness, Shannon-Wiener and Simpson’s diversity, species cover, and composition as well as plant height were measured in these plots inside and outside the fence. In addition, flowering and vegetative Ranunculus acris (meadow buttercup) individuals were counted in each plot to assess grazing effects on flowering success. Grazing did not influence the plant community response to warming. Rising temperature decreased species richness and both Shannon-Wiener and Simpson’s diversity, and drove changes in community composition. Plant height increased with rising temperatures but decreased with grazing. Grazing also significantly reduced R. acris flowering. These results highlight the need for sustainable grazing management in Iceland, as well as the significance global warming has for plant communities.

Sheep with esophageal fistulas were used to determine the daily intake, nutritive content and digestibility of forage at three periods and two stocking intensities during the spring of 1972 on a typical foothill range in northern Utah. Heavy grazing under a season-long regime did not influence the concentrations of dietary chemical components when compared to moderate grazing; however, it did depress the digestibility of cellulose and organic matter. There was a significant decline in the dietary chemical components due to forage maturation. Digestibility of organic matter and cellulose were significantly higher in the early spring as compared to late spring. Daily intake was depressed as a result of the heavy grazing only in early spring. Heavy grazing intensities on short-term pastures influenced the content of lignin, cellulose and protein in the diet. Digestibility of cellulose and organic matter was depressed during early and late spring as a result of the heavy grazing intensities while protein digestibility was depressed throughout the season. Intake was significantly lower under heavy grazing in the intermediate period than it was under moderate grazing.

This study examined the nutritional responses of mule deer during winter on range subjected to a system of spring livestock grazing. The specific purposes were 1) to determine the quality (crude protein, digestible energy, and digestibility) of diets consumed by mule deer in winter on ranges grazed and ungrazed by sheep in spring, 2) to determine the level of forage intake, as determined by the external indicator chromic oxide, for deer under the same grazing regimes, 3) to compare forage intake estimates determined by the external indicator (chromic oxide) with results obtained by ocular estimation, and 4) to determine the forage intake level and quality consumed by fawns, adult does, and yearling male castrates used as experimental subjects during one season of the study. The study was conducted within the framework of a completely random experimental design with two treatments. Variables noted for each unit observed included treatment (previously grazed and not grazed by sheep), season (early-winter versus late-winter), weeks within season (four weeks per season), and sex-age class of animal (fawns, does, castrates). The study site , located at Hardware Ranch, Cache County, Utah, was a shrub:grass:forb community with sagebrush and bitterbrush as co-dominants. Two adjacent 2.4 hectare pastures were fenced. A sheep grazing treatment of 150 sheep days per hectare was applied in late May, 1974 and again in late May, 1975 to one pasture. Hand-reared mule deer were placed in each pasture at a stocking rate of about 100 deer days per hectare for three six-week seasons, two beginning in early November 1974 and 1975, and the other beginning near the middle of March, 1975. Artificial diets were carefully formulated for analyses of the forage quality indices. These formulations were based on the determined botanical composition of diets consumed by the mule deer. Forage intake was determined for two seasons by use of the external indicator method utilizing chromic oxide and these values derived were compared to intake levels determined by an ocular estimation method. No treatment differences existed for forage quality across the three seasons of this study. Mean values for the three qualitative parameters evaluated were: crude protein content, 9.9 percent; digestible energy content, 2.2 kcals/g forage consumed; and dry matter digestibility, 45.5 percent. There were no treatment differences in the level of forage intake, as determined by the external indicator, across two seasons of this study. Mean intake level was 38.1 g/kg body weight per day. No treatment differences existed for the ocular estimation method of determining forage intake and this method was judged to be inferior to the external indicator method of determining forage intake. Few temporal changes between treatments occurred in forage quality and quantity during the early-winter seasons. Some t emporal differences between treatments did exist for forage quality and quantity during the late weeks of the late-winter 1975 season. Deer displayed a marked shift from browse to herbaceous plant material during spring green-up. Deer on the pasture previously grazed by sheep began this shift about one week earlier than those deer on the pasture not grazed by sheep. Interpretation of the results of the forage quality and forage quantity evaluations suggest that deer on the sheep- grazed treatment deferred use of available browse plants and consumed more herbaceous plant material. Therefore, by shortening the length of time that over-wintering deer are dependent upon a browse-dominated diet of lower palatability, lowered quality, and lowered intake, the animals should survive the winter in better physical condition. Thus, this study has shown that sheep grazing of mule deer winter range caused no detriment to the nutritional well-being and may indeed benefit deer to a small degree, particularly at the time of spring green-up. This suggests that a greater animal production per unit area of rangeland can be realized through common use grazing.

The Utah prairie dog (Cynomys parvidens) was listed by the U.S. Fish and Wildlife Service as an endangered species in 1973 because of range-wide population declines. The species was reclassified as threatened in 1984 because of population increases on private lands. Habitat fragmentation coupled with a lack of suitable habitat has impeded species recovery. Desired species habitat conditions include 0-8% shrub cover, 12-40% cool-season grass cover, and 1-10% perennial forb cover. Cool-season grasses are critical for Utah prairie dogs because of high spring energy requirements. Past research suggested that reducing shrub cover may increase cover of desired grasses and forbs. From 2008-2010, I evaluated the effects of high intensity fall sheep grazing and low application of herbicide (tebuthiuron) as tools to reduce shrub cover and enhance grass and forb cover on the Awapa Plateau Utah prairie dog recovery area in south-central Utah. I placed 1700 ewes in 4 ha stratified and randomly selected plots until >70% vegetation utilization was achieved. Five additional randomly-selected plots were treated with tebuthiuron at a rate of ~1.68 kg/ha. Percent cover of grass, forbs, and shrubs was recorded on treatments and paired control plots in June 2009 and 2010 to determine treatment vegetation responses. I also affixed 22 juvenile Utah prairie dogs with radio transmitters to determine if over-winter survival differed relative to treatment. Live shrub cover was lower on grazed plots in year 1 (P<0.001) and in year 2 (P=0.015). Dead shrub cover in grazed plots was higher in year 1 (P<0.001). Grazed plots exhibited increased forb cover from year 1 (P=0.104) to year 2 (P=0.008). Live shrub cover was lower in herbicide plots in year 2 (P=0.002). Dead shrub cover in herbicide plots was higher in year 2 (P=0.006). Tebuthiuron and grazed plots exhibited a reduction in shrub height (P=0.010, P=0.026, respectively). Tebuthiron plots exhibited less grass cover (P=0.034). Intensive sheep grazing and a low application of tebuthiuron reduced both shrub cover and vertical structure, but failed to increase the percent of grass cover when compared to the control plots. All plots exhibited reduced grass cover in 2010 in response to below normal precipitation. However, percent grass cover was higher on the grazed plots. It is possible that low inherent site productivity in combination with below normal average precipitation compromised treatment effects. Because of radio transmitter failure, I was not able to obtain survival data after hibernation. Prairie dog counts and weights did not differ by treatment type. If climate change reduces overall precipitation on the Awapa Plateau, recovery of the Utah prairie dog on this site will be problematic.

As intoxicações por Senecio spp. estão entre as principais causas de morte no Sul do Brasil, sendo o controle desse gênero de plantas prioritário para a pecuária local. Uma área de 5,5 hectares severamente infestada por Senecio brasiliensis e Senecio madagascariensis foi roçada e submetida ao pastejo por ovinos e bovinos. Uma população total de 28.629 plantas, entre S. brasiliensis (10.122) e S. madagascariensis (18.507) foi virtualmente eliminada em um período de dois anos. O número de ovinos foi mantido em três unidades por hectare, mas variáveis lotações de bovinos foram associadas com a disponibilidade de forragem. As principais práticas de manejo sanitário aplicadas aos ovinos foram administrações de anti-helmínticos e controle de ectoparasitas. Biópsias hepáticas, colhidas antes e após o período de estudo, não revelaram qualquer alteração histopatológica associável com seneciose. Os níveis de desempenho dos ovinos foram acompanhados através do controle da reprodução, produção de lã e ganho de peso. O desempenho produtivo dos ovinos mantidos sob o pastejo da área infestada por Senecio spp. foi similar ao grupo controle e comparável com o observado em rebanhos manejados em sistemas extensivos tradicionais no Sul do Brasil. / Since poisoning by Senecio spp. is one of the main causes of cattle death in southern Brazil, control of these plants is a priority for the local livestock production. After the pasture has been mowed, grazing by sheep and cattle was efficient for controlling Senecio brasiliensis and Senecio madagascariensis populations in a 5.5-hectare area that had long been severely infested with these species. A total of 28,629 plants among S. brasiliensis (Flower of souls - 10,122) and S. madagascariensis (fireweed - 18,507) were almost completely eliminated in a two year period. The number of sheep was kept at 3.0 stock units/ ha, but a variable number of cattle were temporarily stocked according to pasture availability. The major sanitary practices applied to the sheep were anthelmintic administration and ectoparasites control. Liver biopsies taken from sheep and cattle before and after experimental period didn´t reveal any change associable with seneciosis. The performance levels of the senecio-grazing sheep were similar to the control group and comparable to those observed in flocks managed under traditional extensive grazing systems in southern Brazil.