557 research outputs found
Population ecology and management of the invasive plant, Lespedeza cuneata
Lespedeza cuneata is one of the worst invasive plants across much of the North American Great Plains. In this dissertation, I describe the combination of field experimentation, statistical modeling and spatially explicit computer simulations that I used to investigate the persistence and spread of an L. cuneata invasion in a native prairie site. Management treatments reduced local infestations, but failing to treat led to large increases of L. cuneata. Density-based models with even simple spatial information were more predictive than presence/absence models of untreated conditions. The effect of herbicide was so strong that it negated the predictive value of model variables. The simulations indicated that imperfect detectability can reduce the overall treatment effectiveness when treatment intensity was low. The effect of imperfect detectability on spread could be minimized with intensive treatment. Taken together, these results indicate that continual management efforts over multiple years are necessary to control established infestations
The Hydrogeology of Nags Head Woods, Dare County, North Carolina
Nags Head Woods, a coastal maritime forest located on a barrier island in eastern North Carolina, stabilizes a back-barrier dune system bordering a tidal marsh. The purpose of this study is to provide basic information about the groundwater geology in Nags Head Woods and to predict the effects upon water levels due to municipal pumping of Fresh Pond, a large lake near the center of the island.
Clean, fine-to-medium sands dominate the top of the surficial (water table) aquifer, underlain by silty fine-to-coarse sands at -4 m elevation. A silty clay bed of very low permeability is present at -12 m to -21 m elevation.
The natural water table across the island forms an elongate dome which crests east and northeast of Fresh Pond. Municipal pumpage of Fresh Pond lowers lake water levels by 1.5 m to 2.0 m.
A finite-difference model (PLASM) was used to predict the effects of pumping from Fresh Pond
Shallow Thrust and Outer Rise Earthquakes in Northwestern Pacific Subduction Zones and their Role in Subduction Zone Water Budgets with Special Focus on the Mariana Islands
This dissertation utilizes accurate earthquake locations and focal mechanisms to examine two distinct regions within shallow subduction zones: the shallow plate interface and the subduction zone trench and outer rise. In particular, I focus on the shallow plate interface and outer rise of the Mariana Subduction Zone and then expand the focus to examine the outer rise at other Northern and Western Pacific Subduction Zones. By understanding where earthquakes occur in these regions, we hope to obtain a better understanding of the cycling of water through subduction zones, mineralogical changes in the presence of water, and the effects of water and hydrous minerals on faulting processes within the shallow subduction zone. The first project is focused on the Northern Mariana shallow plate interface and reveals that small plate interface earthquakes occur at greater depths than previously thought. I show that the earthquake magnitude varies with depth, which may reveal varying conditions of stress, hydration, structure, or mineralogy along the fault. For the second and third projects, I focus on the subduction outer rise; at this setting, extensional earthquakes near the top of the bending, incoming oceanic plate are thought to provide pathways for water to enter and hydrate the plate. The stresses within the plate may also be impacted by locking along the subduction plate interface. At the Mariana subduction zone, I observe differences in stress distributions within the incoming plate between the Southern and Central regions; this difference may be related to greater locking along the Southern Mariana plate interface. Our results for the Northern and Western Pacific show that extensional outer rise earthquakes occur to ~10-15 km within the incoming plate mantle at most subduction zones. If this entire depth range is hydrated, as much as ~10^9-10^10 Tg/Myr of water may be subducted at the Northwestern Pacific; however, lateral heterogeneities in outer rise faulting would result in reduced concentrations of input water
A survey to determine the specific activities in the bookkeeping cycle which are performed by employees with various occupational titles.
Thesis (Ed.M.)--Boston Universit
Evolution in Yoderimyinae (Eomyidae: Rodentia), with new material from the White River Formation (Chadronian) at Flagstaff Rim, Wyoming
Three species of Yoderimyinae (Eomyidae: Rodentia) are recognized from the lower part of the White River Formation (early to medial Chadronian) in the Flagstaff Rim area, Wyoming. The new material allows an improved diagnosis for the subfamily. The enamel microstructure of Yoderimyinae supports its inclusion in the Eomyidae. A new genus, Zemiodontomys, is established for Yoderimys burkei Black, and new material, including upper dentition, is referred to this species. This genus differs from Yoderimys in having higher crowned and more lophodont teeth and in lacking P3. A second new genus, Litoyoderimys, is established for Yoderimys lustrorum Wood, and a new species, L. auogoleus, is referred to the genus. This genus has lower crowned, more cuspate teeth than Yoderimys. Through early and medial Chadronian time, evolution in yoderimyines includes the following morphologic transformations: increase in size; increase in crown height and lophodonty of cheek teeth; reduction of P3 (from double-rooted, to single-rooted, to absent); increase in relative size of P4 and p4; and increased longitudinal torsion of the mandibl
Recipe for scandal
So, you’re a young, ambitious, politically-inclined individual hoping to take the post-graduate world by storm, but you’re not sure how to do that? The answer is simple: be part of a SCANDAL. How do I be a part of a scandal? It’s simple
New material of the Oligocene muroid rodent Nonomys, and its bearing on muroid origins. American Museum novitates ; no. 2712
14 p. : ill. ; 26 cm.Includes bibliographical references (p. 14)."New material shows that Nonomys simplicidens has the dental formula, and some of the dental characters, of the Cricetidae. These are combined with an hystricomorphous zygomasseteric structure like that in Dipodoidea, i.e., the enlarged foramen for the medial masseter is separated by a lamina of bone from a smaller foramen which transmits the infraorbital nerve and blood vessels, and there is virtually no development of a zygomatic plate. This ambiguous combination of characters is seen also in late Eocene Simimys, which has been classified as a dipodoid and as a muroid. Nonomys and Simimys are interpreted as members of an early radiation of myodont rodents, with derived characters that place them in the Muroidea rather than Dipodoidea, but with a combination of characters that excludes them from any presently defined family"--P. [1]
Multiple Generations of Carbon in the Apex Chert and Implications for Preservation of Microfossils
This is the publisher's version, also available electronically from "http://online.liebertpub.com".While the Apex chert is one of the most well-studied Archean deposits on Earth, its formation history is still not fully understood. Here, we present Raman spectroscopic data collected on the carbonaceous material (CM) present within the matrix of the Apex chert. These data, collected within a paragenetic framework, reveal two different phases of CM deposited within separate phases of quartz matrix. These multiple generations of CM illustrate the difficulty of searching for signs of life in these rocks and, by extension, in other Archean sequences
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