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Full-Text Articles in Life Sciences
A Bat-Guano-Derived Δ15N And Δ13C Record Of Paleoenvironmental Change: Zidită Cave, Romania, Daniel Martin Cleary
A Bat-Guano-Derived Δ15N And Δ13C Record Of Paleoenvironmental Change: Zidită Cave, Romania, Daniel Martin Cleary
USF Tampa Graduate Theses and Dissertations
Because nitrogen isotopes are fractionated along the soil-plant-insect-bat-guano pathway, it may be possible to reconstruct environmental and climatic changes reflected in the nitrogen isotopic composition of guano. A 1.5-m core of bat guano from Zidită Cave (western Romania) provides a record of climatic and anthropogenic influence on the regional nitrogen cycle and paleoenvironmental controls on nitrogen transforming processes. Increasing and decreasing trends of nitrogen isotopic composition (δ15N values) correspond well with changes in the influence of farming practices, deforestation, and forest expansion. These influences likely had a significant effect on the openness of the nitrogen cycle, resulting in …
Evidence Of Late Quaternary Fires From Charcoal And Siliceous Aggregates In Lake Sediments In The Eastern U.S.A., Joanne P. Ballard
Evidence Of Late Quaternary Fires From Charcoal And Siliceous Aggregates In Lake Sediments In The Eastern U.S.A., Joanne P. Ballard
Doctoral Dissertations
The late-glacial transition to the Holocene, 15,000–11,600 cal yr BP, is an enigmatic period of dynamic global changes and a major extinction event in North America. Fire is an agent of disturbance that transforms the environment physically and chemically, and affects plant community composition. To improve understanding of the linkages between fire, vegetation, and climate over the late glacial and Holocene in the eastern U.S., I analyzed lake-sediment cores for charcoal and indicators of wood ash, and compared results to existing pollen records. A new microscopic charcoal record from Anderson Pond, Tennessee revealed high fire activity from 23,000–15,000 cal yr …
Biogeochemical Cycling In Lake Superior Tributaries: Seasonality, Quantity And Quality Of Export, Ashley Anne Coble
Biogeochemical Cycling In Lake Superior Tributaries: Seasonality, Quantity And Quality Of Export, Ashley Anne Coble
Dissertations, Master's Theses and Master's Reports - Open
Seasonal and spatial variability in environmental factors may affect dissolved organic matter composition and nutrient transformation and retention in streams. The objective of this research was to quantify and describe seasonality, quantity, and quality of nutrient processing and export of ammonium (NH4), soluble reactive phosphate (SRP), and dissolved organic carbon (DOC) into Lake Superior through intensive study in a small 1st order watershed coupled with snapshot measurements across 12 tributaries that varied in size, location, and wetland coverage. Our results suggest biodegradable C is exported from a small headwater stream year-round and that DOC mineralization rates can be …
Investigating The Role Of Polyploidy In The Response Of Chamerion Angustifolium To Increased Soil Nitrogen Availability And Insect Herbivory, Alex Bales
Dissertations, Master's Theses and Master's Reports
Human activities have more than doubled the input rate of nitrogen to terrestrial ecosystems. Increased soil nitrogen availability is associated with increased plant productivity, changes in plant resource allocation strategies, and changes in interactions between plants and their associated insect herbivores. For example, nitrogen-rich conditions can alter the physiological and chemical properties of plants in ways that increase their ability to deter herbivore attack (resistance) and maintain fitness following herbivore attack (tolerance). The ecological tolerance of plants to such abiotic and biotic environments is thought to be influenced by autopolyploidy, a commonly occurring phenomenon in plants in which individuals have …