Life Sciences Commons^™

Long-Term Effects Of Rice Rotation, Tillage, And Fertility On Near-Surface Soil Carbon And Nitrogen Cycling, Jill Marie Motschenbacher

Graduate Theses and Dissertations

Rice (Oryza sativa L.)-based cropping systems are different from other row crops due to the flood-irrigation scheme used from about one month after planting to a few weeks prior to harvest. The frequent cycling between anaerobic (i.e., flooding during the growing season) and aerobic (i.e., generally, the remainder of the year) conditions can influence the rate of soil organic matter (SOM) decomposition, which can greatly influence carbon (C) and nitrogen (N) storage and sequestration in the soil over time. Therefore, a study was conducted on a silt-loam soil (fine, smectitic, thermic, Typic Albaqualf) at the Rice Research and Extension Center …

Nitrite Oxidation In Geothermal Springs: Evidence Of An Upper Temperature Limit For Thermophilic Nitrite-Oxidizing Bacteria Of 60 - 65 °C, Tara Edwards

UNLV Theses, Dissertations, Professional Papers, and Capstones

Despite growing evidence of the importance of nitrification in terrestrial geothermal environments, little is known about nitrite oxidation in these environments. In order to further our knowledge, this study combined cultivation-dependent and -independent approaches with measurements of nitrogen speciation along the outflow channels of two Great Basin geothermal springs. Enrichment cultures were inoculated with sediment slurries from sites ranging in temperature from 42 - 87 °C at the sources and along the outflows of >15 hot springs. While attempts to enrich nitrite-oxidizing bacteria (NOB) from sites greater than or equal to 61 °C were unsuccessful, NOB were enriched from five …

The Impact Of Selected Forage Legumes On Cattle Performance, Forage Production, And Soil Quality, And Evaluation Of Legume Persistence Under Grazing, Bradley Edward Briggs

Graduate Theses and Dissertations

Interest in substituting legumes for N fertilizer in beef cattle grazing systems has recently increased with rising fertilizer prices. Legumes are well known for their ability to fix atmospheric N and decrease dependence on input of N fertilizer. However, there are still difficulties associated with legume utilization including establishment and persistence. Two experiments were conducted to evaluate legume performance under herbivory. The objective of Experiment 1 was to compare forage production and beef cattle gains from annual ryegrass [Lolium multiflorum (L.)] and bermudagrass [Cynodon dactylon (L.) Pers.] pastures fertilized with N or overseeded with legumes. Gelbvieh × Angus …

Plant Establishment And Soil Microenvironments In Utah Juniper Masticated Woodlands, Kert R. Young

Theses and Dissertations

Juniper (Juniperus spp.) encroachment into sagebrush (Artemisia spp.) and bunchgrass communities has reduced understory plant cover and allowed juniper trees to dominate millions of hectares of semiarid rangelands. Trees are mechanically masticated or shredded to decrease wildfire potential and increase desirable understory plant cover. When trees are masticated after a major increase in tree population density and associated decrease in perennial understory cover, there is a risk that invasive annual grasses will dominate because they are highly responsive to the increased resource availability that commonly follows removal of the main resource user. To determine if tree mastication increases …

Factors Affecting The Reduction Of Carbon To Nitrogen Ratio In Composted Separated Solids, Mark Fagundes

Dairy Science

The objective of the study was to determine the factors involved in the reduction of carbon to nitrogen ratio in composted separated solids. A single compost windrow was laid on a 6,000 jersey cow dairy farm located in Madera County. Samples were obtained from six separate positions on the pile, every other day. Direct pile measurements on the date of sampling included pile temperature (surface and core), height, width and curvature. Samples were removed from the windrow during each sampling meeting to determine the percent dry matter content. The collected samples were sent out to Denele Analytical Inc. to determine …

Landscaping Perceptions And Behaviors: Socio-Ecological Drivers Of Nitrogen In The Residential Landscape, Leesa Souto

Electronic Theses and Dissertations

Driven by individual influences such as beliefs, attitudes, personal norms, and abilities, as well as by social influences like community norms, mandates, and the market, suburban homeowners are motivated to select and maintain a turf grass landscape. In many areas of Florida, effective suburban lawn maintenance requires regular inputs of nitrogenous fertilizer, some of which is lost to the environment, contributing to water quality degradation and ecosystem dysfunction. Reducing nitrogen inputs to aquatic systems requires a better understanding of the links between residential landscape management and the potential for fertilizer loss. This dissertation examines the linkages between the human behaviors …

Variability In Hydrology And Ecosystem Properties And Their Role In Regulating Soil Organic Matter Stability In Wetlands Of West-Central Florida, Sharon Jean Feit

USF Tampa Graduate Theses and Dissertations

Soil organic matter (SOM) provides many ecosystem services that are necessary for continued ecosystem function. The accumulation of SOM in an ecosystem is a function of its persistence time which can range from days to thousands of years. Ecosystem properties including dominant vegetation type, soil texture, and soil moisture in various habitats can regulate the persistence time of SOM.

Wetlands, because of their associated ecosystem properties, promote SOM accumulation, but little has been done to determine the ecosystem properties that regulate its persistence over time. In west-central Florida, urbanization and increased water demands have suppressed water tables in isolated wetland …

Ecosystem Impacts Of The Invasive Shrub Lonicera Maackii Are Influenced By Associations With Native Tree Species, Megan Marie Poulette

Theses and Dissertations--Biology

Invasive species are significant drivers of global environmental change, altering the stability and functioning of numerous ecosystems. The exotic shrub Lonicera maackii is an aggressive invader throughout much of the eastern United States. While much is known about its population and community impacts, little is known about effects on ecosystem processes.

This dissertation documents changes in ecosystem processes associated with L. maackii growing beneath three native tree species (Fraxinus quadrangulata, Quercus muehlenbergii, Carya ovata) in a savanna in Kentucky. Like many invasive plants, L. maackii litter decomposed and lost nitrogen (N) rapidly, especially in comparison with …