This problem consists of classifying the four major pastures of the McKamy ranch into McConnell's four categories, by means of examinations based on these qualities and characteristics.

Despite the agronomic benefits of exotic grass plantings for pasture and rangeland forage, exotic grass invasions are capable of having dramatic and widespread impacts on native communities and ecosystems. Exotic Old World bluestem grasses (OWBG; Bothriochloa and Dichanthium spp.) have become increasingly invasive throughout the central and southern U.S. Little is known regarding the impacts of OWBG invasion on native grassland and savannah ecology and how to successfully control OWBG invasions in natural areas. Accordingly, this dissertation research had several objectives: 1) Evaluate the efficacy of herbicide and/or disking to control OWBG; 2) Assess the relative competitive ability of the OWBG, Kleberg bluestem (Dichanthium annulatum); 3) Evaluate herbicide application and native grass seeding to rehabilitate an OWBG invaded coastal prairie; 4) Examine whether ecosystem function differs between areas dominated by OWBG vs. native coastal prairie; and 5) Characterize the germinable soil seed bank of an OWBG invaded coastal prairie. Herbicide treatments of imazapyr, glyphosate, and imazapyr + glyphosate were found to provide effective, albeit temporary, OWBG control (often less than six months). A combination regimen of disking followed by herbicide treatments, regardless of herbicide active ingredient or application rate, controlled OWBG more effectively than herbicide alone or herbicide followed by disking. Herbicide treatments followed by native grass seeding did not markedly rehabilitate coastal prairie invaded by OWBG. OWBG appeared to reinvade from the seed and/or bud bank suggesting the restoration of OWBG invaded grasslands will likely require aggressive and repetitive control methods to completely extirpate OWBG at a given site before native plantings occur. A seed bank survey revealed the density of OWBG germinable seeds increases dramatically with increasing OWBG invasion (i.e., canopy cover) while the native grass seed bank is generally depauperate even when levels of OWBG invasion were low. Dominance of OWBG appears to have altered native coastal prairie ecosystem function; yet the directionality and extent of OWBG effects were strongly soil texture dependent. Here, ecosystem function parameters between areas dominated by OWBG compared to native prairie differed most often on sandy loam vs. clay soil. Moreover, DeWit replacement series experiments revealed the relative competitive ability of Dichanthium annulatum was significantly greater than the native grass, little bluestem (Schizachyrium scoparium). OWBG will likely persist throughout the central and southern Great Plains, USA, for years to come and intensive management efforts will be necessary to keep OWBG invasions under control in natural areas of high conservation value.

In a warm, dry grassland in southeastern Arizona dominated by C₄ grasses the only C₃ grass found was restricted to dry, exposed ridge crests within the hottest and driest part of the region. This was precisely the opposite of what one would predict from physiological and biogeographic considerations, which would lead one to expect a C₃ grass in this environment to be growing on cooler or moister areas that would mitigate the effects of the inhospitable climate. Cover of C₄ grasses was very low on these ridge crests, and increased downslope with the greater volume of water available to high values on the lower slopes and in washes. It was suggested that this C₃ grass, Stipa neomexicana, had a very high tolerance of water stress, but a very poor tolerance of competition, and was limited to unfavorably dry sites by its competitively superior C₄ neighbors. Most species, regardless of photosynthetic type, could not survive in the harsh ridge crest environment, which therefore offered a refuge from competition. The hypothesis of competitive exclusion was tested by removal experiments conducted at ridge crest, midslope and lower slope positions along the topographic gradient of decreasing Stipa neomexicana and increasing C₄ grass cover. The predictions made under this hypothesis were confirmed. The presence of competitors limited the growth of mature plants, flower production, seedling establishment and seedling survival. The beneficial effects of the removal of competitors increased downslope. Competition depressed estimated finite rates of population increase for Stipa neomexicana. This depression was most severe on the lower slope. It was concluded that increasing competition from C₄ grasses along the topographic gradient was responsible for restricting Stipa neomexicana to the unfavorable ridge-crest sites.

No description available.

Anthropogenic noise may interfere with avian acoustic communication, however some species alter the structure of vocalizations, to improve transmission in noise. Here, I conducted playback experiments to determine whether compressor stations, generator or grid-powered screw pump oil wells, and overall ambient noise levels affected responses of Savannah sparrows (Passerculus sandwichensis) to conspecific alarm calls at their nests. I also measured the structure of alarm calls, to determine whether Savannah sparrows altered vocalizations in noise. On control sites, Savannah sparrows responded to alarm calls by delaying provisioning visits. At compressor station sites, the loudest infrastructure treatment, they showed less of a delay. Close to compressor stations, Savannah sparrows lowered the frequency and increased the bandwidth of alarm calls. These findings suggest the compressor stations may interfere with anti-predator communication, but that Savannah sparrows can alter the structure of alarm calls at these sites, perhaps mitigating some effects of noise. / October 2016

The amount of semi-natural grasslands has decreased in the agricultural landscape and because of this many grassland species are declining. Semi-natural grasslands are dependent on management, but different studies suggest that different management methods are most favorable to species richness and abundance. The aim of this study was to compare the effects of mowing and grazing on butterfly and bumblebee abundance in Swedish semi-natural grasslands. We used data collected through the Swedish environmental monitoring program NILS. We identified 31 comparable meadows and chose 1-10 pastures in the area surrounding each meadow. For six different species groups we calculated the number of individuals found per 100 m. By standardizing the values of the difference between the means for meadows and pastures we were able to compare the effects of the two methods on abundance in each species group. No species group showed a preference for pastures. A significant preference for meadows was found for two butterfly species groups. The four other groups showed a trend to prefer meadows before pastures. According to our study the recommended management method should be mowing, considering protection of butterflies and bumblebees.

Doctor of Philosophy / Department of Geography / Kendra K. McLauchlan / Throughout the Holocene, North American grassland vegetation has shifted in composition and spatial extent. However, it has been difficult to characterize these changes because the drivers—particularly climate, fire, topography, or grazing from large herbivores—operate at different spatial and temporal scales. Long-term archives such as lacustrine sediment cores, and the proxy records they contain, can help illustrate vegetation changes on relevant timescales. Yet, accurate interpretations of grassland vegetation composition from pollen (a common proxy used to infer vegetation of the past) remain limited by the number of calibrations of pollen and the drivers of vegetation change in modern conditions. This research addresses those gaps by evaluating grassland vegetation at different spatial and temporal scales in the context of modern and historical drivers. First, I reconstruct vegetation composition and diversity, fire activity, and erosion activity at a sub-regional scale over the last 9,300 years by analyzing pollen, charcoal, and magnetic data from a sediment core from a grassland lake in southern Minnesota. Second, I quantify the relationships between modern grassland pollen and fire, grazing, and topography at a fine spatial and temporal resolution, using pollen samples collected annually from traps at Konza Prairie Biological Station in the Flint Hills of Kansas. Finally, I synthesize modern pollen assemblages across the Great Plains to create a transfer function that quantitatively links precipitation and temperature with pollen. I apply this function to pollen data from the past to interpret the climate history of three sites across the Great Plains, including the aforementioned site in southern Minnesota. The results from this research suggest that grassland vegetation diversity remained relatively resilient to the climatic fluctuations of the Holocene, including the driest time at 5,000 yr BP. In addition, this work facilitates more informed interpretations of fossil pollen by effectively calibrating modern grassland pollen assemblages with their abiotic and biotic drivers.

Master of Science - Science / The replacement of indigenous grasslands by commercial forestry plantations on the mountainous eastern escarpment of South Africa, has inevitably led to alteration of nutrient cycling. The overall objective of this study was to determine the nutrient status (soil, litter and foliar nutrient concentrations) of Pinus patula and Eucalyptus grandis plantations and adjacent grasslands. The 2, 13 and 30 year old P. patula plantations and adjacent Driekop grassland were located relatively high up on the escarpment (altitudes ranging between 950–1610 m) and were underlain by dolomite while the 2, 8 and 13 year old E. grandis plantations and adjacent Brooklands grassland were located lower down (altitudes ranging between 900–1100 m) and were underlain by granite. It was assumed that the nutrient status of the soil under the plantations and the adjacent grasslands were similar prior to afforestation. Samples were collected once in winter (August 2002) and once in summer (January 2003). Soil samples were collected to a depth of 20 cm and litter material, to a maximum depth of 20cm. Lower canopy foliar samples were collected within the lowermost metre of the canopies and upper canopy foliar samples were collected within the uppermost metre of the canopies. The data were analysed in the laboratory for various elements and soil physical parameters. The soil pH was lower under the P. patula (pH 4.8-5.2) and E. grandis plantations (pH 4.6-5.3) when compared with the soil under the adjacent grasslands (pH 5.3-5.6). The soil under the P. patula plantations had lower exchangeable base cation concentrations (204-300 mg kg-1) compared with the adjacent Driekop grassland (452-645 mg kg-1), while there were no clear trends when comparing the exchangeable basic cation concentrations in the E. grandis plantations and the adjacent Brooklands grassland. The soil aluminium saturation was similar between the plantations, ranging between 39.7 and 63.3% in the P. patula plantations and 27.4 and 75.6% in the E. grandis plantations. The grasslands had lower soil aluminium saturations, ranging between 17.7 and 35.7% in the Driekop grassland and 17.5 and 39.1% in the Brooklands grassland. Exudates from mycorrhizal associations chelate iv acidic cations, rendering plantations more tolerant of acidic soils. Soil total nitrogen, phosphorus and carbon in the plantations were similar to the adjacent grasslands. Higher nitrogen mineralisation rates in the P. patula plantations corresponded with higher litter and foliar total N concentrations relative to the adjacent Driekop grassland, while there were no clear trends when comparing rates of N mineralisation in the E. grandis plantations and the Brooklands grassland. The concentrations of foliar amino acids and protein were significantly higher (p<0.01) in the plantation foliage, when compared the grassland foliage. The amino acid arginine, occurred in higher proportions relative to other amino acids in plantation foliage, when compared with the relative proportions found in the grasslands. Relative to nitrogen, foliar ratios indicated that phosphorus and potassium were the most limiting nutrients for the plantations, which possibly resulted in N storage in the form of protein and amino acids. The soil and foliage were the more sensitive indicators of the nutrients status than litter. Differences in nutrients concentrations between the lower and upper canopies in both plantations were minor and no major trends were found. Therefore the sub division of lower and upper canopies is not recommended for further foliar nutrient analyses. Age related trends were unclear as a result of higher soil clay contents found in the 13 year old P. patula plantation and the 8 year old E. grandis plantation as well as the various silvicultural practices implemented. In terms of the relative impacts of P. patula and E. grandis plantations, the results of this study imply that the upper 20cm of soil was more impacted under the P. patula plantations than under the E. grandis plantations, in terms of reduced base cation and increased acid cation concentrations. The P. patula plantations are shallow rooters and thus the base cation status of the upper soil horizons may affect the sustainability of the P. patula plantations.

The atmospheric (CO2) partial pressure is expected to continue to increase and the scenario is that the CO2 partial pressure will reach 50-70 Pa during the 21st century.The rise in CO2 will have a direct influence on plant growth and development because CO2 is the primary substrate for photosynthesis.The aim of the studies described in this thesis was to investigate the response of grasses belonging to two subtypes to a range of CO2 partial pressures under conditions where light intensity, water and N supplies were varied.Two species which are naturalized in Australia, Panicum coloratum (NAD-ME) and Cenchrus ciliaris (NADP-ME) were chosen for a series of experiments conducted in matched growth chambers. The response of C4 plants is particularly important for Australia because they dominate the tropical grasslands that occupy 75% of the continent and form the basis for the pasture industry. Following the extensive research conducted in this study, it can be concluded that the inevitable rise in atmospheric CO2 partial pressure will increase the growth of C4 grasses when other resources are not limiting.Growth of C4 grasses will be stimulated to a greater extent under conditions of drought. / Doctor of Philsophy (PhD)

Semi- natural grasslands are species-rich and also one of the most threatened biotopes in Europe. The area of these grasslands has declined and grassland vegetation is threatened as a result of lack of management and land use change. Appropriate management is therefore required to maintain the conservation values and high species richness of semi- natural grasslands. Traditional management, that is, grazing or annual mowing is expensive, which motivates evaluation of alternative cheaper methods of management. Burning is less costly and therefore I evaluated burning along with the conventional methods. The study addressed the main question: is burning an option to mowing and grazing? I searched the literature for available studies suitable for metaanalysis, but located only detailed reports from a series of eleven Swedish long-term field trials. In addition, I collected data in the only one of these trials still running. To facilitate metaanalysis, l used different indicator systems of classification of grassland plants then calculating the odds for a random record being an indicator after one, eight, fourteen, twenty-eight and thirty-nine spring burns. The results show an increasing proportion of grassland indicators of good management in the mowed and grazed plots compared with the burnt plots, indicating a general negative effect of burning on grassland plants compared with mowing and grazing. Hence, burning is not an appropriate long-term management method if the aim is to maintain vegetation diversity in semi-natural grassland.