49 leaves ; 29 cm Typescript Thesis (M.S.)--University of Oregon, 1974 Includes bibliographical references (leaves 45-49) Unif. Title University of Oregon theses, Dept. of Biology, M.S., 1974

From the 1920's through 1951 several severe fires occurred in the predominantly conifer forest ecosystems of the northern Oregon Coast Range. Of the 211,151 ha. of mapped area, 57 percent was burned. The effects of frequent fires with high severity on forest ecosystems over time at the landscape level is not fully understood. A reconstruction of fire history was conducted to help investigate the effects of fire severity, frequency, and area extent on distribution of postfire tree regeneration, species composition, and stand tree size, as well as on current species composition and stand tree size. I hypothesized that: 1) vegetation patterns (1950's and 1988) would vary with time, because the persistence of disturbance effects (fire, logging, reforestation) on forest vegetative responses varied, and 2) environmental controls (topography, soil, climate) would become the primary influences when disturbance events were absent. In this study historical maps, sketches and notes were used to reconstruct spatial and temporal patterns of fires from the 1920's to 1951 and to identify unburned patches on a Geographic Information System. Relationships between fire regime and postfire and current vegetative patterns were tested. Constructing precise spatial data layers from early maps, produced before the availability of aerial photography or satellite image, was difficult. Historical map accuracy and quality were variable and poor by present day standards. Geographic reference points were used to transform inappropriate map scales. The reconstruction of spatial data was used to characterize spatial patterns of historic fires: my estimates of burn areas were similar to estimates in the literature. To reduce questionable data along fire and vegetation patch boundaries for hypothesis testing, an exclusion approach was used. Data within a 100 m width of fire and vegetation type boundary lines were called a fuzzy zone and removed from raw data. The distribution of various attributes in the reduced data was similar to the distribution of the complete data set. Regression analysis examined the effects of fire, logging, reforestation, topography, climate, and soil type on vegetation patterns. Patterns of postfire (1950's) species composition, tree regeneration and tree size (DBH) were associated with the effects of fires, as well as influences of logging and soil type. Indices of fire occurrences (reflecting the time variation and severity of fires) frequently correlated to the 1950's vegetation patterns. The number of fires (frequency) did not cause great differences in vegetation patterns. Current (1988) species composition and tree size (after absence of fire for more than three decades) were correlated more with terrain variables. Plant succession also influenced the current vegetation patterns. Neither the date or number of fires caused marked differences in distribution of species and tree size, except large conifers were found in areas missed by fires. Postfire and current vegetation patterns were correlated with soil types which reflect the influence of topographic and climatic characteristics. However, historic fires occurred frequently on some soil types. Fires have a confounding influence on soil type. This confounding influence of fire on soil type cannot be avoided. Reforestation efforts appeared to have little influence on the postfire and current vegetation patterns. I inferred that the short time period of reforestation effects did not show its importance on the 1950's vegetation landscape. Although regression analysis results did not support my hypothesis, by 1988, reforested area in the northern Coast Range had increased since 1950's. Most of the large fire-open patches became mixed forest in about 3 decades may still relate to the force of reforestation. On private unburned ownerships conifer forests in 1955 were subsequently cut and replaced by mostly mixed forest by 1988. The analysis supported the hypotheses that soil type, aspect and plant succession were dominant influences on current (1988) vegetation patterns, while forest disturbances such as fire and logging were important influences on the immediate postfire (1950's) patterns. The results not only interpret the relationship between historic disturbances and vegetation distribution, but may also serve as a useful background for the management of the future forest landscape. / Graduation date: 1998 / Presentation date: 1997-07-11

The purposes of this study were: 1) to review the land use history of Oak Creek watershed since European settlement. And 2) to consider the human-caused impacts and their effects associated with different land uses. The study area was classified into three land use patterns: residential, agricultural, and forested areas. Since the European settlement in the mid 1840's, the Oak Creek watershed has experienced changes of land use simultaneous with the development of the city of Corvallis and its vicinity. Associated with this, different impacts have occurred on riparian areas. By and large, these impacts were inherent to each land use. / Graduation date: 1993

Prior to European settlement, native prairie dominated the landscape of the Willamette Valley. Today, due to urbanization, agriculture, and the cessation of burning, only isolated remnants of these grasslands still exist. In response to conservation concerns, there has been a move to restore the remaining prairies in the Willamette Valley, and prescribed burning and sowing native seed are often top candidates for grassland restoration. However, the effects of burning on native seedling establishment and the spread of weedy exotics are largely unknown. In this study, I investigated how prescribed burning affects native and exotic species seedling establishment on three upland prairie vegetation types in the Willamette Valley. The general approach was to sow a known number of seeds from several native and exotic grassland species into experimentally manipulated plots, designed to separate the effects of litter removal from the other effects of burning, and to monitor seedling densities. Germinability and dormancy characteristics of the sowed seeds were also addressed. An additional study focused on the fire temperatures at soil surface in three grassland vegetation types and two burn sizes. Burning increased the establishment of most or all of the sown native species in the two low quality, exotic grass sites. Exotic seedling establishment also tended to increase, but did not differ significantly from unburned plots for most species tested. On the higher quality, native bunchgrass site, burning did not significantly improve native species establishment, but did significantly increase the establishment of short-lived exotic species over those in unburned plots. The germination and dormancy characteristics of the native and exotic species tested indicate that grasses, both native and exotic, are more likely than forbs to be non-dormant in the autumn following dispersal. Forbs, especially native forbs tend to require cold-stratification for maximum germinability. During grassland fire, temperatures at soil surface were relatively cool. Fire temperature intensity was highest in the higher quality native bunchgrass vegetation. These burns reached higher temperatures significantly closer to the soil surface than the plot burns in lower quality sites dominated by annual or perennial exotic grasses. Average temperatures in a two hectare broadcast burn and in replicated 2m x 2.5m plot bums in an annual exotic grassland were very similar. Prescribed burning can be an excellent tool for the restoration of low-quality upland prairies when combined with sowing native seeds in the fall. However, on high-quality prairie, prescribed burning may be a poor restoration choice for promoting native seedlings, as burning promoted weedy species without enhancing native seedling establishment. / Graduation date: 1997

The Darlingtonia fens, found on serpentine soils in southern Oregon, are distinct communities that frequently undergo dramatic changes in size and shape in response to a wide array of environmental factors. Since few systems demonstrate a balance among high water tables, shallow soils, the presence of heavy metals, and limited nutrients, conservative efforts have been made to preserve them. This dissertation investigates the role of fire on nutrient cycling and succession in three separate fens, each a different time since fire. I specifically analyze the spatial distributions of soil properties, the physical and ecological characteristics of ecotones between Jeffrey pine savanna and Darlingtonia fens, and the vegetation structure of fire-disturbed systems. Soil, water, and vegetation sampling were conducted along an array of transects, oriented perpendicular to community boundaries and main environmental gradients, at each of the three fens. Abrupt changes in vegetation, across communities, were consistently identified at each of the three sites, although statistical analysis did not always identify distinct mid-canopy communities. Below-ground variables were likewise distinguished at the fen and savanna boundary for two of the three sites. At the third site, discontinuities did not align with the fen boundaries, but followed fluctuations in soil NH4. My results suggest that below-ground discontinuities may be more important than fire at preserving these uniquely-adapted systems, while vegetation undergoes postfire succession from fen to mid-canopy to savanna after approximately 100 years since fire. Although restoration of ecosystem structure and processes was not the primary focus of this study, my data suggest that time since fire may drive ecosystem processes in a trajectory away from the normal succession cycle. Moreover, time since fire may decrease overall vigor of Darlingtonia populations.

From June 1998 to July 1999, the dynamics of the plankton in Hagg Lake and Barney Reservoir were studied with the purpose to identify the succession dynamics of the planktonic species, to test the Plankton Ecology Group (PEG) model, and to explore the relationships between these successions and the physical and chemical variables.

While community ecologists have traditionally focused on local-scale processes, it has become apparent that a broader perspective, which explores the community-level ramifications of material fluxes within and between ecosystems, is necessary to effectively evaluate bottom-up influences on community structure and dynamics. In this dissertation, I employed ecosystem principles to understand these processes in rocky intertidal communities. I specifically examined the roles of sessile invertebrates in mediating the transfers and transformations of carbon and nitrogen in intertidal ecosystems. First, I quantified the links between nearshore pelagic and rocky intertidal systems. By assimilating suspended particulate organic material (seston), mussels and other sessile invertebrates serve as mediators of material exchange from pelagic to benthic ecosystems. I evaluated these trophic linkages along productivity gradients on the coasts of New Zealand and Oregon, which allowed me to address the influences of seston quality and quantity on the growth and ammonium excretion rates of mussels. My results highlight the necessity of simultaneously considering both seston quantity (total organic particulates) and quality (phytoplankton availability) in evaluating benthic-pelagic coupling. Second, I assessed the utilization of invertebrate-excreted ammonium by macroalgae in high-intertidal pools. Sessile invertebrates not only serve as mediators of material transfer into intertidal ecosystems, they also chemically transform that material, converting particulate organic nitrogen, which is unusable by macroalgae, into ammonium, which algae readily assimilate. l showed that especially in high-zone pools, which are isolated from the ocean for 80% of the time, invertebrate-excreted ammonium is an important nitrogen source for macroalgae. Ammonium accumulated in tide pools and was subsequently taken up by algae. This novel positive interaction influenced community structure: macroalgal species richness increased with the rate of invertebrate-mediated ammonium loading in pools. Finally, by experimentally manipulating macroalgae and invertebrates in laboratory mesocosms, I quantified the effect of ammonium loading on algal growth. I demonstrated that algal nitrogen assimilation rates increased with the rate of ammonium accumulation in tide pools, which resulted in enhanced growth when invertebrates were present. Together, these studies suggest that by merging community and ecosystem perspectives we can gain unique and important insights into the bottom-up processes influencing intertidal systems. / Graduation date: 2004

ix, 73 leaves : ill. ; 28 cm Typescript Thesis (M.S.)--University of Oregon Includes vita and abstract Bibliography: leaves 71-73 Another copy on microfilm is located in Archives University of Oregon theses, Dept. of Biology, M.S., 1982

Typescript. Includes vita and abstract. Bibliography: Includes bibliographical references (leaves 87-100). Description: xiii, 100 leaves : ill. ; 29 cm.

Typescript. Includes vita and abstract. Bibliography: Includes bibliographical references (leaves 283-301). Description: xxx, 301 leaves : ill. ; 29 cm.