Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 72 for “"N-availability"”.
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Biogeochemical effects of an invasive grass across a land-use gradient: linking alterations of nitrogen cycling to depleted soil carbon pools
… depleted soil organic C pools and increased N availability. Structural equation modelling demonstrated that N uptake and preference under M. vimineum resulted in greater mass-specific microbial activity which, in turn, led to diminished soil organic C stocks. This suggests that M. vimineum may …
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Interactive effects of fire and grazing on soil and forage nitrogen dynamics in a tallgrass prairie
… we quantified soil N pools, inorganic N availability (NH₄⁺, NO₃⁻), potentially mineralizable N (PMN), autoclavable citrate-extractable (ACE) protein, extracellular enzyme activities, and forage quality (N concentration) across burn intervals, grazing regimes, and topographic positions. …
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Changes in Soil Nitrogen Following Biosolids Application to Loblolly Pine (Pinus Taeda L.) Forest in the Virginia Piedmont
… rate, and timing affect forest floor and soil N availability in pine plantations. The objectives of this study were to determine the effect of different types, rates, and season of application of biosolids on forest floor and soil N. The study was established in a 17-year-old loblolly pine …
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Plant nitrogen availability in selected Virginia soils
… incubation procedure as an index of organic N availability. Plant available N was measured by N uptake of successive wheat crops grown in the greenhouse. Multiple linear regression models for different groups of samples were used to determine the contribution of the different soil N fractions …
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Soil resource heterogeneity and site quality in Southern Appalachian hardwood forests: Impact of decomposing stumps, geology and salamander abundance
… Understanding processes that affect nutrient availability in these forests is essential for sound forest management. Three interconnected research projects regarding soil resource heterogeneity were designed to increase our understanding of this ecosystem. The objective of these projects were …
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Effects of Biosolids on Carbon Sequestration and Nitrogen Cycling
… has been demonstrated to improve nutrient availability (mainly N and P) and improve organic matter in soils, but the effects of biosolids on C sequestration and N cycling in the Mid-Atlantic region is not well understood. The objectives were: 1) to investigate soil C sequestration at sites …
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Interacting effects of soil nitrogen supply and light availability on understory sapling growth and foliar attributes
Light availability in forest understories is a well recognized constraint on sapling growth, but limitations in soil nitrogen (N) availability, and the link to foliar photosynthetic capacity, typically receive less consideration in describing stand dynamics. My primary hypothesis is that light and …
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Interactive effects of hemlock mortality and nitrogen availability on nutrient pools and fluxes in the southern Appalachian Mountains
… I evaluated the potential for variation in N availability to influence the magnitude of effects of hemlock decline on N and P dynamics in mixed hardwood stands. I measured N and P pools and fluxes at three elevations (low, mid, high) subjected to increasing atmospheric N deposition where …
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Microbial and metazoan effects on nutrient dynamics during leaf decomposition in streams
… streams which spanned a gradient of nitrate availability. I found wide variations in nutrient fluxes across time and space, perhaps due to macroinvertebrate-induced changes in microbial assemblage composition. Secondly, I explored the roles of endogenous and exogenous N in meeting microbial …
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Nutrient Retention and Cycling in Southeastern U.S. Loblolly Pine (Pinus taeda L.) and Sweetgum (Liquidambar styraciflua L.) Plantations
… the forest floor and increased mineral soil N availability, and determine loblolly pine forest floor decomposition rate and release of nutrients in a simulated disturbance environment. Research was conducted at a 25-year old loblolly pine (Pinus taeda L.) plantation in NC (SETRES) and 13-year …
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Evaluation of nitrogen availability indices
… the reliability of recommendations from three N availability indices and four laboratory methods to measure extractable organic N (EON), and the accuracy and repeatability of the Horiba Cardy Nitrate meter in determining NO$\sb3$-N content in soils and solution.
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Nitrogen Management and Weed Suppression in Organic Transition
… weeds and, 3) to compare the effect on N availability and broccoli yield potential of incorporating cover crops with conventional tillage (CT) or mulching cover crops with no-tillage (NT) practices. Broccoli was grown during the third year of organic transition in the spring and fall of …
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Nitrogen and genotype effects on assimilate partitioning and resistance to Striga in maize
… be mediated by amount, source and timing of N availability; and if the efficacy of N is contingent upon its regulation of assimilate partitioning. An additional objective was to determine how level is influenced by genotype. One experiment evaluated N rates of 0, 30, 60 and 90 kg ha$\sp{-1}$ …
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Ectomycorrhizal associations in tropical montane forest: insights into their influence on nutrient cycling and functional responses to soil fertility
… nutrient economies, thereby reducing the availability of limiting resources to competing species. After testing these three hypotheses I found no evidence for positive feedback on Oreomunnea abundance caused by either pathogen resistance or the formation of mycorrhizal networks. Instead, …
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Environmental controls on the abundance, diversity, growth, and activity of ammonia-oxidizing microorganisms in temperate forest soils
… of soil variables, such as pH and nitrogen (N) availability, within the geographically-constrained area of the Coweeta Basin. First, I used amplicon-based pyrosequencing to independently assess the diversity of ammonia-oxidizing archaea (AOA) and bacteria (AOB) at several sites within Coweeta. I …
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Effects of nitrogen and water on growth, photosynthesis, and leaf properties of deciduous tree species with consequences for gypsy moth herbivory
… the hypothesis that plants exposed to elevated N availability are more susceptible to drought and insect herbivory. I grew seedlings of gray birch (Betula populifolia), yellow birch (B. alleghaniensis), and red oak (Quercus rubra) for two years under varying levels of N and water availability in …
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Developing tools to identify factors that limit production in coastal marshes
… In leaf tissue, C:N decreased with increasing N-availability and [Na] increased with increasing salinity. [Mn] and [Ca] in leaf tissue decreased with increased flooding. In the field study, C:N increased seasonally. Biomass was most highly correlated with [Na] in spring and with both [Na] and C:N …
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Characterization of a major cluster of genes involved in nitrogen fixation and another required for indole-3-acetic acid biosynthesis in the sugarcane endophyte, Acetobacter diazotrophicus
… could stimulate plant growth regardless of N availability, as evidenced by the significant growth difference between plants inoculated with wild type and uninoculated plants. Under N-limiting conditions plants inoculated with wild type had greater height and biomass than plants inoculated with …
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Nitrogen spiraling in stream ecosystems spanning a gradient of chronic nitrogen loading
… study of the relationships between nitrogen (N) availability and spiraling (the paired processes of nutrient cycling and advective transport) in stream ecosystems. Anthropogenic activities have greatly increased rates of N loading to aquatic ecosystems. However, streams may be important sites for …
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Effects of a Control Release Nitrogen Fertilizer and Thinning on the Nitrogen Dynamics of a Mid-Rotation Loblolly Pine Stand in the Piedmont of Virginia
… effects of the two fertilizer treatments on N availability and loss as: total KCl extractable-N, total ion exchange membrane-N (IEM-N), N mineralization, and N volatilization, in a mid-rotation loblolly pine plantation in the Piedmont of Virginia. In addition, mid-summer and mid-winter …
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