Bumblebees are a group of valuable pollinators that are declining all over the world. The main reason is believed to be habitat loss due to the changes in agriculture. The changes in agriculture influence the structure of the vegetation and flower abundance, which are of great importance to the abundance of bumblebees. The aims of this study were to get a better understanding of bumblebees and what preferences they might have regarding vegetation height and flower abundance in semi-natural grasslands. This study is based on data collected by a Swedish national environmental monitoring program in 2006-2010. Data on twelve bumblebee species were analysed using a generalized linear model based on the dependent variables of occurrence/ non-occurrence. The target variables used in the analysis were flower abundance, vegetation height and standard deviation of vegetation height. The species-wise analyses mostly showed no or weak positive relationships between the bumblebee occurrence and the three target variables. Grouping the species-wise results into ecologically meaningful guilds and analysing them did not increase the explanatory power of flower abundance or vegetation characteristic, but vegetation height showed significant (positive) results in relation for the forest dwelling species and the species group non-parasite and parasite. The results of this study were considerably weaker than expected. Flower abundance and variation in vegetation height could not explain the occurrence of bumblebees. However, the results of this study show that vegetation height is of importance to the occurrence of bumblebees. Bumblebees in general seem to prefer a higher vegetation height. Based on the findings of this study I would recommend a low intensity of grazing in semi-natural grasslands.

A drive into the country will soon confirm the effects of agriculture on the environment. Different agricultural practices such as vast fields of monocultures, forests of exotic timber, and large intensive feed lots of livestock, will be evident. The need to provide food for an increasing population particularly in Africa is the driving force behind the intensification of agriculture. The production of increased food supply is often considered without knowledge of the impacts on the environment. The North East District of Botswana is a small district compared to other districts of Botswana but unlike these large districts the population density is comparably high with a demand for agricultural space. Botswana is a desert margins area under threat of desertification with many signs of desertification being evident throughout the country. The main agricultural activity in the North East District is livestock farming with horticulture being practiced on the banks of sandy river beds. The district provided an ideal area to compare the impacts of different livestock farming techniques. Four different approaches of livestock farming were examined with the number of livestock cattle in particular, being a noticeable difference and the grazing intensity of these cattle being another important difference. This study examined the impacts of these different grazing techniques on the environment with a particular reference to birds. Data was collected using a point count system with 28 points evenly spaced in a grid across the different land uses. Each point was subject to a total of six surveys with summer and winter having three surveys each. It was expected that bird numbers and species would be impacted by the grazing intensity while the different feeding and nesting guilds may also respond to grazing intensity. Statistical analysis included geostatistical analysis, uni-variant, mult-variant and non-metric multi-dimensional scaling. The results show that birds were impacted by grazing intensity with species richness and bird numbers being negatively affected. However, feeding and nesting guilds were impacted differently. Climate change and land degradation are a reality and will impact on avian diversity and sound management practices need to be implemented to protect biodiversity in marginal areas. / Thesis (Master of Environmental Sciences)--North-West University, Potchefstroom Campus, 2013

A drive into the country will soon confirm the effects of agriculture on the environment. Different agricultural practices such as vast fields of monocultures, forests of exotic timber, and large intensive feed lots of livestock, will be evident. The need to provide food for an increasing population particularly in Africa is the driving force behind the intensification of agriculture. The production of increased food supply is often considered without knowledge of the impacts on the environment. The North East District of Botswana is a small district compared to other districts of Botswana but unlike these large districts the population density is comparably high with a demand for agricultural space. Botswana is a desert margins area under threat of desertification with many signs of desertification being evident throughout the country. The main agricultural activity in the North East District is livestock farming with horticulture being practiced on the banks of sandy river beds. The district provided an ideal area to compare the impacts of different livestock farming techniques. Four different approaches of livestock farming were examined with the number of livestock cattle in particular, being a noticeable difference and the grazing intensity of these cattle being another important difference. This study examined the impacts of these different grazing techniques on the environment with a particular reference to birds. Data was collected using a point count system with 28 points evenly spaced in a grid across the different land uses. Each point was subject to a total of six surveys with summer and winter having three surveys each. It was expected that bird numbers and species would be impacted by the grazing intensity while the different feeding and nesting guilds may also respond to grazing intensity. Statistical analysis included geostatistical analysis, uni-variant, mult-variant and non-metric multi-dimensional scaling. The results show that birds were impacted by grazing intensity with species richness and bird numbers being negatively affected. However, feeding and nesting guilds were impacted differently. Climate change and land degradation are a reality and will impact on avian diversity and sound management practices need to be implemented to protect biodiversity in marginal areas. / Thesis (Master of Environmental Sciences)--North-West University, Potchefstroom Campus, 2013

Three studies were undertaken from 2006 to 2007 to examine litter (dead plant material) in southwestern Manitoba pastures. First, the relationship between litter and soil microclimate was tested across five pasture sites. The amount of litter biomass was not strongly related to soil moisture, though near-surface soil temperatures were reduced when litter was present. Second, the effect of four simulated grazing strategies on the litter layer was measured in six pastures. It was found that after three years of simulated grazing, litter was present in largest quantities in the least-frequently grazed treatments. Finally, a field survey was conducted assessing the quantity of litter present in native pastures across Manitoba. Litter was quite variable and averaged 1902 kg/ha over two years. This research confirmed the value of litter as an indicator of sustainable pasture management, though it remains unclear whether litter is important to pastures from the perspective of soil microclimate.

The mixed-grass prairie region of southwestern Manitoba is a hotspot for many endangered grassland birds. This region has been degraded to less than a quarter of its historical amount of mixed-grass prairie. Remaining prairie is primarily used for livestock grazing. The objective of this study was to evaluate the contribution of sustainable land management practices, such as rotational grazing, in the conservation of this region. In 2008 and 2009, I compared the abundances of grassland birds on two grazing regimes, twice-over rotation and season-long, to ungrazed fields. Bird surveys were done during the breeding season and were conducted using 100-m fixed-radius point-count plots. I determined the effects of treatment, landscape and vegetation characteristics on songbird abundances using generalized linear mixed models. Grassland birds selected grazed pastures over ungrazed fields in both years, and species richness of obligate grassland birds was significantly greater (α = 0.10) on season-long than twice-over pastures (β = 0.419, p = 0.032, in 2008 and β = 0.502, p = 0.043 in 2009). Season-long grazing may actually benefit grassland bird communities by creating somewhat temporally stable areas of high use and low use within the pasture. However, nesting success studies and long-term monitoring are necessary to further understand how twice-over rotation grazing systems contribute to the conservation of grassland birds in southwestern Manitoba.

Understanding the nutrient dynamics of pastures is essential to their profitable and sustainable management.  Tall fescue [Schendonorus phoenix (Scop.) Holub.] is the predominant forage species in Virginia pasturelands.  Although tall fescue pasture is common, little research has attempted to document how soil and herbage nutrient concentrations change through time.  This thesis summarizes two studies conducted within the context of a larger grazing systems project near Steele's Tavern, VA.  The objectives were to: (1) examine temporal changes in plant available soil nutrient concentrations in four grazing systems, (2) determine how hay feeding and use of improved forages affected soil and herbage nutrient concentrations (3) examine the relationship between and variability within soil and herbage nutrient concentrations, (4) analyze the seasonal variation in herbage mineral concentration with regard to beef cattle requirements, and (5) create a statistical model to predict variation in herbage mineral concentration across the growing season.  Analysis of plant and soil nutrients through 5 years of grazing produced several important findings.  Soil pH, P, and Ca, Mg, and B declined through five years of grazing.  Higher concentrations of herbage N and K and soil P, K, Fe, Zn, and Cu were measured in hay feeding paddocks.  Herbage nutrient concentrations showed less variability in P and K than did soil test results.  Fertility testing in pastures is important to monitor changing nutrient concentrations, and this study showed that herbage analysis may provide a more stable and accurate assessment of pasture fertility than soil testing.  Pasture herbage, grown without fertilization, contained sufficient concentrations of macronutrients to meet the requirements of dry beef cows through the growing season and to meet the requirements of lactating beef cows in April.  A model was developed using soil moisture and relative humidity that predicted (R2 = 0.75) variation in herbage mineral concentration throughout the growing season.  As described in this thesis, use of modeling to predict nutrient dynamics in pasture could allow for more efficient mineral supplementation strategies that lead to improved profitability, nutrient retention, and livestock health. / Master of Science

Includes bibliographical references (leaves 105-121) / x, 121, [39] leaves : ill., maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / 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?

308 p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Dept. of Botany, University of Adelaide, 1976

This thesis investigated the role of carbohydrates in the dietary choices of ruminants with an emphasis on dairy cows. The first two experiments investigated the ability of sheep to select between feeds based on their carbohydrate degradability. A further two indoor experiments using dairy cows were designed to establish whether post-ingestive feedback from rumen fluid propionic acid concentration influenced preference. The final experiment examined the potential of ryegrass bred for high water soluble carbohydrate (WSC) concentrations to increase the long-term (9 days) preferences and intake of grazing dairy cows. / Constraints to intake imposed by offering sheep access to only one feed were overcome by offering a choice between two feeds simultaneously. Within each choice, sheep generally selected the more slowly degradable option. However, when overall NDF intake could be maintained at approximately 800g/day, the rapidly degraded feed was preferred. / Dairy cows were able to form associations between flavour and postingestive feedback from rumen propionic acid concentration. Although a dose-dependent response was not observed between the concentration of ruminal propionic acid infusion and preference intensity, there was a correlation between ruminal propionic acid concentration and energy status of the cow. In the subsequent experiment, the comparative effect of propionate supplied in the form of salt (instead of acid) on food preference was confounded by a flavour bias. / Diurnal WSC monitoring of perennial ryegrass cultivars bred in the U.K. for 'typical' and 'high' WSC concentrations, expressed similar concentrations at different times of the day and year when grown in northern Victoria. Consequently, in a test of preference between the cultivars, cows showed only slight preference that was not based on WSC concentration. In other choices between adjacent monocultures, cows selected a mixed diet of 62% white clover and 38% ryegrass. / It was concluded that the ideal diet from the animals' perspective is influenced by the rumen propionic acid concentration and the energy status of the animal. Further, an important priority for the ruminant is to maintain an adequate supply of structural carbohydrates to the rumen. Further work is needed to identify the benefits of feeding pasture with higher WSC, but this might be a difficult objective under Australian field conditions until plant material becomes available that more reliably expresses high WSC.

Includes bibliographical references (leaves 105-121) / x, 121, [39] leaves : ill., maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / 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?