Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 82-90). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 1978. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Succession and organization of rocky intertidal zone surfgrass beds (Phyllospadix scouleri Hook) were examined experimentally at two sites on the Oregon coast. The interaction of three attributes of the plant -- high persistence, high preemption, and slow recovery -- strongly influences the organization of surfgrass beds. Permanent plots indicate that surfgrass is persistent. Comparisons of experimental surfgrass removal and control plots demonstrate its preemptive ability, because removal plots are invaded by many algal species, but these algae are preempted from control plots. The slow growth of surfgrass rhizomes and the slower recruitment of surfgrass seeds indicate its recovery ability is low. The interaction of these phenomena produces a mosaic of surfgrass and algae in different successional stages. The successional sequence following a disturbance is more complex than predicted by any simple model because of temporal and spatial variation as well as differences in the species replacement mechanism. In some plots the early colonists, the perennial brown algal blade Phaeostrophion irregulare and the annual green algal blade Ulva sp., dominated for three years; in others they were replaced by a suite of middle successional species including the branched red algae Cryptosiphonia woodii. In other plots the slowest growing middle successional species, the branched red alga Rhodomela larix replaced other species. Part of this variability appears to be caused by large waves in the fall and winter, which remove large areas of algal cover, allowing dominant species to be replace by either earlier or later successional species. Part of the variability appears to be caused by local differences in the surfgrass understory before disturbance. Rhodomela larix is usually not completely removed by disturbance and regrows from its holdfast more readily than it recruits from spores. The mechanisms by which later species replace earlier ones differ depending on the successional stage. Established Phaeostrophion inhibits Ulva and filamentous diatoms. In contrast, certain middle successional species are necessary for seeds of the late successional surfgrass to recruit. The barbed seeds become attached to algal species with a central axis approximately 1 mm in diameter but not to algae with other forms. / Graduation date: 1983

Thesis (Ph. D.)--Oregon State University, 2001. / Typescript (photocopy). Includes bibliographical references (leaves 90-95). Also available via the World Wide Web.

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No description available.

A project report submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in partial fulfillment of the requirements for the degree Masters of Science Resource Conservation Biology. / An understanding of the biogeochemistry of carbon and nitrogen in ecosystems is necessary for the sustainability of system function. Transformations, including different land uses, disrupt the natural input:output of soil organic matter and often result in changes in the cycling of carbon and nitrogen. Consequently it is imperative to know how different land uses are likely to alter the pool sizes, flux rates and turnover of carbon and nitrogen in the soil. The savanna and grassland biomes of South Africa include large areas which have been transformed by man and are the main sites of primary and secondary production. Sites in these biomes along a vegetation and soil type gradient have been investigated. Soil samples from a conserved area, a cultivated area and a livestock area have been sampled. A range of soil properties including the potential rate of nitrogen mineralization, total soil carbon and nitrogen, microbial carbon and nitrogen, soil texture, bulk density. pH and standing dead herbaceous biomass have been quantified. These along with values reported in the literature have been used to validate the CENTURY model, which simulates the turnover of ecosystem attributes on the basis of soil organic matter inputs and outputs. Results show that the soil organic matter pool sizes for the sites and land uses were positively correlated with the percentage fines (silt-plus-clay) and site aridity. Sites which were moist and had a percentage of fines greater than 45% tended to have 3 times more C and N. Land use, especially cultivation, reduced the amount of SOM at sites by 50% mainly because of the effects on the light fraction mass. The potential rate of N mineralization was not significantly different between sites but the cultivated land use led to the immobilization of N. Possible reasons for this included the negative impact that cultivation has on soil macroaggregates, the lower <1.0 glkg) input of light fraction, and the low <10%) percentage fines at these sites. Simulations of the SOM fractions using the CENTURY model for six functional types indicate that similar trends emerged but the model greatly overestimated absolute amounts of SOM. In conclusion, the absolute quantities of soil carbon and nitrogen are influenced by climate, soil texture, and land use; but the proportion of soil organic matter fractions do not appear to differ per biome or per land use indicating similar turnover times. / AC 2018

Thesis (Ph.D.)-- University of Adelaide, Dept. of Zoology, 1981.

Thesis (PhD) -- Auckland University of Technology, 2004. / Also held in print (261 leaves, col. ill., 30 cm.) in Wellesley Theses Collection. (T 333.7140993 SHA)

Thesis (M.S.)--Oregon State University, 1999. / Typescript (photocopy). Includes bibliographical references (leaves 163-209). Also available via the World Wide Web.