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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Feeding stations of feeder lambs (Ovis aires) as an indicator of diminished forage quality and supply while grazing south central Arizona alfalfa (Medicago sativa L.)

Harper, John Michael, 1954- January 1992 (has links)
Grazing trials were conducted on irrigated fall/winter pastures near Maricopa, Arizona where 270 feeder lambs were stocked in 16-ha paddocks to explore the use of grazing behavior as an indicator of forage quantity and quality. Sheep behavior was monitored by filming the grazing periods with a VHS camera and recording the length of time that an individual spent at a feeding station, defined here as a feeding station interval. Other measurements included observed steps between feeding stations (step-sets), feeding stations min⁻¹, steps min⁻¹ and biting rate. As grazing progressed, lambs increased the number of feeding station intervals that were less than 5 seconds long and increased the number of feeding stations min⁻¹ significantly (p ≤ 0.05). Feeding stations min⁻¹ were negatively correlated (r ≤ -0.94) with crude protein, digestible energy and quantity of selected forage. Throughout the grazing trial lambs appeared to prefer the leaves to the stems. Steps min⁻¹ were only moderately correlated to forage quantity and quality. Bites min⁻¹ were not correlated to forage quantity and quality. Feeding stations min⁻¹ as a method of monitoring animal behavior during feeding periods might allow the manager to recognize nutritional limitations in the available forage and perhaps adjust management strategies accordingly.

Seedbed ecology and emergence of Lehmann lovegrass (Eragrostis lehmanniana Nees) as influenced by burning

Sumrall, Lee Bradford, 1962- January 1990 (has links)
Lehmann lovegrass (Eragrostis lehmanniana Nees) is a warm-season bunchgrass native to South Africa which dominates many desert grasslands in southern Arizona. To determine why fire results in high seedling recruitment of this species, seedbank germination and field seedling emergence were measured in relation to (1) no treatment, (2) burning, (3) clipping and herbicide and (4) herbicide only. Treatments were replicated over 2 years on a stand of Lehmann lovegrass at the Santa Rita Experimental Range. Canopy removal, by either clipping or burning, significantly increased seedling emergence in seedbank bioassays prior to summer rains both years. Bioassay emergence was 826, 415, 350 and 199 seedling/m2 in 1988 from the dead-clip, burn, dead-standing and control treatments, respectively. Field seedling emergence was significantly increased with canopy removal both years and seedling densities were 281, 142, 3, and 0.1 seedlings/m2 for the dead-clip, burn, dead-standing and control treatments, respectively in 1988. The ability of this grass to reestablish after canopy disturbance may result from a greater range in sol temperatures and increases in red light reaching the seedbed.

Seasonal variation in utilization estimates on sideoats grama plants

DeMuth, Carol Ann, 1957- January 1990 (has links)
The variability in utilization estimates using seasonal production data from clipped sideoats grama plants was studied in southeastern Arizona. Three intensities of clipping at four seasons were studied. Regrowth was also examined. Current growth was highest in October and lowest in June, whereas, standing dead material was lowest in February and highest in June. By April 1986, 39% of peak current growth was already produced. Total peak standing crop occurred in October. The sum of current growth and regrowth from heavy clipping was greater than for plants clipped heavily only in October. The opposite was true for moderate and control clippings. Actual utilization was calculated using peak current growth as a basis for calculating percentage utilization. Relative utilization was based on standing crop at each season of clipping treatments. Generally, relative utilization estimates overestimated utilization when compared to actual utilization estimates based on current growth.

A spatial modeling approach for predicting forage production and utilization on a semidesert grassland

Wissler, Craig Alan, 1959- January 1993 (has links)
Geographic analysis procedures and multiple linear regression techniques are applied to the problem of generalizing forage production and utilization information from sample point data. The study involves the application of these procedures to predict the spatial variability of mean production and utilization of Digitaria californica on the Santa Rita Experimental Range near Tucson, Arizona. Analysis of ten-year means from data collected between 1957 and 1966 indicate that variability in production is a function of mean summer precipitation and elevation. Variability in utilization is found to be a function of land slope and distance from livestock water. Geostatistical procedures are used to estimate mean summer precipitation. A geographic information system (GIS) is used to automate multiple linear regression functions for points in a raster data structure. The geographic analysis procedures are used to describe the spatial variability of the data in a mapped form. Management applications of the approach are demonstrated.

Packstock hoofprint depth and soil strength relationships in wet meadow soils of Sequoia and Kings Canyon National Parks, California

Neuman, Michael John, 1964- January 1996 (has links)
Penetrometer soil strength and the depth of packstock hoofprints were studied in two subalpine meadows in an attempt to develop a method for determining the seasonal readiness of wilderness meadows for packstock grazing at Sequoia & Kings Canyon National Parks, California. Soil and vegetation parameters (bulk density, water content, percent gravel, sand, silt, clay, and organic matter, above-ground biomass, and below-ground biomass in two diameter size classes) were also studied in order to understand their influence on soil strength and hoofprint depth. Of the four penetrometer tip sizes tested on a Lang penetrometer, a 9/16" diameter tip was found to be a good predictor of hoofprint depth. Both 9/16" soil strength and hoofprint depth were well predicted by soil water content and meadow vegetation type.

Monitoring elk and cattle forage use under a specialized grazing system in Arizona

Halstead, Lacey E., 1970- January 1998 (has links)
The grazing system I studied is intended to promote sustainable elk (Cervus elaphus) and cattle use, attracting elk to cattle-grazed pastures, thus resting the others. My objective was to determine whether the grazing system (1) promotes sustainable levels of forage use and (2) rests half the pastures each year. The grazing system did promote sustainable forage use but did not rest half the pastures; elk used all study pastures. Elk grazing patterns depended more on cover and topography than the grazing system. Essential to the study of grazing interactions are reliable utilization data. My objective was to compare forage use estimates obtained with the paired-plot and 2 height-weight methods (i.e., using on-site height-weight regression curves and the United States Forest Service height-weight gauge). Height-weight methods produced lower but more precise use estimates than the paired-plot method. Height-weight estimates did not differ significantly when calculated with on-site curves or the USFS gauge.

Site stability assessment on a clay loam upland range site

Watters, Susan Elaine, 1959- January 1993 (has links)
Ground cover, species composition, average distance between perennial plants, standing biomass, frequency of bare quadrats, and site stability rating were evaluated as predictor variables in determining the degree of site protection from accelerated soil erosion on a clay loam upland range site. Interpretations of range condition, species diversity, and the WEPP model predicted sediment yield were analyzed to determine their usefulness in detecting a threshold of site protection. Standing biomass, basal cover, average distance between plants and frequency of bare quadrats demonstrated strong correlations to the site stability rating and were useful in examining thresholds of site protection. The WEPP model was useful in determining a threshold of protection with the site stability rating. The diversity index and range condition rating showed poor relationships with the stability indices and plant community attributes measured. Thus, individually, these ratings do not provide and adequate assessment of the degree of site protection.

The role of data sources and simulation model complexity in using a prototype decision support system

Lawrence, Paul Anthony, 1960- January 1996 (has links)
Multiobjective decision support systems (DSS) are gaining acceptance as tools to evaluate resource management systems. Before applying a DSS, a matrix of decision criteria and alternative management systems is populated using information from measured data, expert opinion or simulation models. As each information source exhibits differences in data availability and accuracy, the extent to which outcomes from the DSS are influenced by the source of information remains an important issue. A conceptual framework links the Prototype Decision Support System (P-DSS) developed by the USDA-ARS Southwest Watershed Research Center in Tucson, Arizona, to a conservation practice physical effects matrix. Four rangeland practices of yearlong (YL) and rotation (ROT) grazing, with mesquite trees retained (+M) and removed (-M), are evaluated against eight decision variables that consider soil, water, plants and wildlife habitat. Each decision variable is quantified using data from four experimental watersheds on the Santa Rita Experimental Range, expert opinions, and two simulation modeling approaches. The simple approach uses the Curve Number method, RUSLE and MUSLE, while the complex approach uses the CREAMS hydrology and erosion models. Outcomes from the P-DSS are sensitive to the source of information. When measured data and complex models quantify the decision variables, the YL-M and ROT-M management systems dominate the current system of YL+M. The simple modeling approach identifies ROT+M in addition to YL-M and ROT-M. However, when a frequency of rank methodology is used, the simple and complex modeling approaches identify ROT-M as the preferred system, while the measured data and expert opinion identify YL-M. Ranking the four management systems quantified by simple models matches the ranking obtained from the expert survey. Rank ordering using the complex models agrees with the opinion of the most knowledgeable expert. Simple and complex modeling estimates of sediment yield are significantly different, as are estimates of peak runoff rate. The results suggest that model complexity improved information accuracy but had limited effect on the outcomes from the P-DSS. The effect of information sources on the outcomes from the P-DSS may become more pronounced if the evaluation changes from a relative assessment to one involving quality standards.

The effect of grazing, mowing and herbicide application of johnsongrass (Sorghum halepense (L.) Pers.) in the Nature Conservancy Patagonia-Sonoita Creek Preserve

Mitton, Nancy Louise, 1951- January 1996 (has links)
Johnsongrass (Sorshum halepense (L.) Pers.) occurred in nearly pure stands on the Patagonia-Sonoita Creek Preserve, Santa Cruz County, Arizona prior to grazing. This study investigated the use of grazing, mowing and herbicides to decrease the abundance of johnsongrass, and increase the diversity of other plant species. The grazed only treatment allowed remaining overstory and limited grazing access. Mowing lowered the overstory and provided accessibility to grazing attracting animal utilization of the areas. The herbicided and grazed treatment reduced total johnsongrass productivity, tiller numbers and impacted tiller growth form. Lower percent botanical composition and tiller emergence of johnsongrass plants occurred in 1995 than in 1994. The number of other plant species increased between study years.

Assessment of Watershed Health on Intermittent Watersheds in Southwestern North Dakota

Hecker, Garret Allen 22 September 2017 (has links)
<p> Watersheds are complex systems that are influenced by many factors including geomorphology, climate, soil, vegetation, and land management. Due to this complexity, a watershed assessment that evaluates both the riparian and upland areas has yet to be developed. We proposed investigating a combination of plant community composition within the greenline, upland ecological site function assessment with the Interpreting Indicators of Rangeland Health (IIRH) protocol, and stream morphological parameters. Stream parameters investigated were Rosgen&rsquo;s classification method, bank erosion hazard index (BEHI) and bank height ratio (BHR). This research was conducted on five intermittent streams in southwestern North Dakota. We found that facultative wetland species offered the most protection to intermittent streambanks as a result of hydrology. When assessing the uplands it was determined that there is a positive correlation between rangeland health and riparian health. The stream parameter that showed the strongest relationship was the BEHI.</p><p>

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