Thesis (M.Sc. )--Memorial University of Newfoundland, 1997. / Bibliography: leaves 77-80.

Thesis (M.Sc.)--College of William and Mary. / Vita. Includes bibliographical references.

abstract: The characteristics of the wintertime 500hPa height surface, the level of non-divergence and used for identifying/observing synoptic-scale features (ridges and troughs), and their impact on precipitation are of significance to forecasters, natural resource managers and planners across the southwestern United States. For this study, I evaluated the location of the 500hPa mean Pacific ridge axis over the winter for the period of 1948/49 to 2011/12 and derived the mean ridge axis in terms of location (longitude) and intensity (geopotential meters) from the NCEP/NCAR Reanalysis dataset. After deriving a mean ridge axis climatology and analyzing its behavior over time, I correlated mean location and intensity values to observed wintertime precipitation in select U.S. Climate Divisions in Arizona, Colorado, Nevada, Utah and New Mexico. This resulted in two findings. First specific to the 500hPa ridge behavior, the ridge has been moving eastward and also has been intensifying through time. Second, results involving correlation tests between mean ridge location and intensity indicate precipitation across the selected Southwest Climate Divisions are strongly related to mean ridge intensity slightly more than ridge location. The relationships between mean ridge axis and observed precipitation also are negative, indicating an increase of one of the ridge parameters (i.e. continued eastward movement or intensification) lead to drier winter seasons across the Southwest. Increased understanding of relationships between upper-level ridging and observed wintertime precipitation aids in natural resource planning for an already arid region that relies heavily on winter precipitation. / Dissertation/Thesis / M.A. Geography 2013

Abstract For effective management of stream salmonids, it is essential to (i) assess the productive potential of a stream in relation to species-specific habitat requirements, and to (ii) identify the key factors underlying any bottleneck periods during the life cycle of a fish. For this purpose, this PhD-thesis focuses on the mechanisms of habitat selection by juvenile salmonids in boreal streams. Habitat preference curves for depth, water velocity, substrate and instream cover for brown trout (Salmo trutta L.) in river Kuusinkijoki, northeastern Finland, indicated that larger trout preferred deeper stream areas than age-0 trout did. In summer, all size-classes of trout preferred small substrates, whereas in winter, areas with cobble-boulder substrates were preferred. Winter presents a bottleneck period for trout in boreal streams; therefore winter habitat curves should be incorporated into habitat-hydraulic models when estimating habitat suitable for riverine trout in areas with severe winter conditions. The preference curves of age-0 trout were validated by correlating age-0 trout density with habitat availability at multiple sites in two boreal rivers where trout densities were monitored in 1988-1995. Substrate preference curve was effective in predicting trout densities among sites, whereas among-year variation in trout densities was best predicted by depth-related preference curves. The responses of age-0 brown trout and grayling (Thymallus thymallus (L.)) to enhancement structures were investigated in artificial stream flumes. For both species a crucial habitat factor was the availability of flow refuges, especially in winter. In another experiment, age-1 trout dominated over age-0 trout when competing for velocity and overhead cover they both found suitable, emphasizing the role of intraspecific interactions in habitat selection by trout. These results suggest that the provision of a broad diversity of microhabitats should be a major goal in rehabilitation programs for fishery purposes. A new method, combining GIS-assisted (Geographical Information System) approach with geostatistical tools, facilitated the detection of fish distribution patterns in a spatially heterogenous stream habitat. The method will likely prove valuable when determining appropriate sampling scale(s) for future studies of fish habitat selection in relation to benthic prey. Unlike Arctic bullhead (Cottus poecilopus, Heckel), trout did not show any aggregation with their benthic prey according to spatially-referenced data on the distribution of lotic fishes and benthic macroinvertebrates within a stream reach.

<p> Previous studies on subjective response to noise have been conducted during the summer months. These studies have served as the basis for noise standards and legislation; therefore an implicit assumption has been made that response to noise is similar in summer and winter. Whether or not this applies equally well to the winter months, which represent approximately one-half of the year, warranted investigation. Data on summer and winter responses to comparable noise levels were collected and hypotheses were tested for differences in response to overall noise levels and to specific noise sources. The results indicated that there were no significant differences between summer and winter responses.</p> / Thesis / Master of Arts (MA)

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Corn silage is one of the major components in dairy cattle rations in the United States. Many factors affect the nutritional composition of corn for silage, such as cropping system, including cover crops, and the composition of the corn plant cell wall. The objectives of the first study were to determine the nutritional quality of different winter crops for silage and to determine the impact of the various winter crops on the succeeding productivity of corn and sorghum. Experimental plots were planted with 15 different winter crop treatments: 5 winter annual grasses in monoculture or with one of two winter annual legumes (crimson clover [CC] and hairy vetch [HV]). After harvesting the winter crops, each plot was planted with either corn or forage sorghum. Crimson clover increased DM yield compared to monocultures but HV did not. Adding legumes increased the crude protein concentration, but reduced the fiber and sugar concentrations of the forages. Even though in vitro neutral detergent fiber digestibility was reduced with the addition of legumes, the concentration of highly digestible non-fibrous components is greater in the mixtures than the monocultures, increasing the nutritive value of the silage. The objective of the second study was to determine the cell wall (CW) composition along the corn stalk. Three phytomers of corn plants were examined: center (C) of ear insertion, upper (U) and lower (L) phytomers. Each phytomer was cut into 4 sections: top (T), middle (M), bottom (B), and node (N). The CW, uronic acid (UA), glucose (GLU), and lignin concentrations did not change among phytomers. The concentrations of arabinose (ARA) and xylose (XYL) were greater in the U than in the L phytomers. Concentrations of CW, ARA, and XYL increased from B to T within the phytomer, but UA and GLU concentrations decreased from B to T. Lignin did not change within the phytomer. In mature corn for silage, changes within the corn internode may be more useful in determining how the environment changes the CW. / Ph. D.

Master of Science