http://ir.library.oregonstate.edu/dspace The ScholarsArchive digital repository system captures, stores, indexes, preserves, and distributes digital research material. Search the Channel search http://ir.library.oregonstate.edu/dspace/simple-search http://hdl.handle.net/1957/9249 Title: The use of ơ¹⁵N and ơ¹³C to analyze food webs and identify source-sink relationships in riparian canopy vegetation of the Oregon Coast Range <br/> <br/>Abstract: In the Coast Range of western Oregon, some natural resource managers are converting red alder-dominated riparian areas to conifers to increase the future source of in-stream large wood for salmonid habitat. However, studies in Alaska have shown red alder-dominated riparian areas support greater invertebrate biomass compared to conifer-dominated areas. In addition, red alder can influence the nutrient dynamics of a site with N-rich litter inputs. Thus, these forest conversions have the potential to change riparian food webs and nutrient dynamics. The objectives of this thesis were to determine the utility of natural abundance stable isotopes of nitrogen and carbon in food web analyses and to describe nutrient dynamics and source-sink relationships in red alder- and Douglasfir- dominated riparian areas of the central Oregon Coast Range. We address three questions in this study: 1) What is the degree and source of δ15N and δ13C variation in foliage of Douglas-fir and red alder? 2) Are Douglas-fir and red alder isotope signatures sufficiently distinct to be used in food web analysis? and 3) Are there differences in nutrient dynamics and source-sink relationships between Douglasfir- and red alder-dominated riparian areas? To address these questions, we sampled foliage, litterfall, forest floor material, and soil from ten Douglas-fir- and red alder-dominated riparian sites as well as foliage from plantation Douglas-fir and red alder for δ15N, δ13C, and nutrient concentrations. Douglas-fir had greater variation in foliage δ15N within a tree crown, within a site, and among sites than red alder. Red alder had consistent foliage at all scales, near 1 .5%o, a value that is characteristic of nitrogen fixing species. Both species had similar levels of variation in foliage δ13C at all scales. Douglas-fir was slightly enriched in '3C compared to red alder suggesting greater water-use efficiency in Douglas-fir. Overall, the difference between δ15N and δ13C of red alder and Douglas-fir at our study sites were, on average, less than 2.O%o. It is unlikely stable isotopes could be used over broad geographic areas as a tool for determining the contributions of Douglas-fir versus red alder to food webs, although site-specific research may be possible where Douglas-fir and red alder demonstrate greater isotopic differences. Douglas-fir and red alder exhibited opposite source-sink relationships with soil for N exchange: Douglas-fir was a sink for soil N whereas red alder served as a N source. Douglas-fir sites had a higher N status and lower soil δ15N along the stream compared to upslope, trends not found at red alder sites. Soil δ15N near streams on Douglas-fir sites was similar to the soil δ15N on red alder sites suggesting that a legacy of past red alder along the stream may have contributed to the N status and soil δ15N gradients on Douglas-fir sites. Soil δ15N and soil δ15N did not indicate a presence of marine N on our sites. δ15N and δ13C of foliage and soil suggested decomposition processes of leaf litter differed between Douglas-fir and red alder, likely due to different lifter chemistries and possible influences on decomposition enzymes. A shift in species composition from red alder-dominated to Douglas-fir-dominated riparian areas would alter source-sink relationships with soil N and litter decomposition processes, although some legacies of soil enrichment in N by red alder would persist. <br/> <br/>Description: Graduation date: 2004 http://hdl.handle.net/1957/9247 Title: Rural Studies Program Annual Report 2006-2007 http://hdl.handle.net/1957/9246 Title: Trade and productivity effects on firm behavior : the case of Korean manufacturing <br/> <br/>Abstract: This dissertation’s three essays investigate trade and productivity effects on firm behavior based on new heterogeneous-firms trade models in the case of Korea. In the first essay, firms’ decision to export in the case of Korean manufacturing industries is examined, where the change in firms’ productivity before and after exports are analyzed. In particular, two common hypotheses of export decision - self-selection and learning-by-exporting- are tested using a dynamic model of firm export behavior and a Korean firm-level panel database. Evidence of self-selection is found in only three out of eight industries, but that of learning-by-exporting is limited. Sunk-cost or previous-export-experience effect on the predicted export probability is relatively larger than that of firms’ productivity and size. The second essay investigates the effect of trade cost changes on firms’ entry and exit in Korean manufacturing. Empirical support is found for new trade theories’ predictions on firm entry and exit, and the number of exporting firms, and changes in market share following trade-cost changes. However, Korean manufacturing appears to differ from some of the outcomes of the heterogeneous-firms theory, especially in the result that large firms are less likely to be a new exporter. Rather, smaller and less capital-intensive firms tended to enter the export market. In general, the results of this essay show that changing trade costs had important consequences for the structure of manufacturing activity in Korea. In the final essay, the differences in the scale economies of exporters and non-exporters in Korean manufacturing are investigated. Results from estimating a production function show that exporters face diseconomies of scale in four of five industries. A matching technique confirms the difference in returns to scale between exporters and non-exporters. The evidence that size and hence, scale economies may be less important for trade participation and gains from overseas market, bodes well for small or medium exporters. In summary, this dissertation has improved the understanding of the relationships among trade, productivity and firm behavior. The key determinant of firms’ export behavior in the Korean context appears to be previous experience in overseas markets. Not surprisingly, the Korean government has invested heavily in lowering their firms’ cost of accessing foreign markets. In industries where Korea has a comparative advantage, high productivity of firms appears to promote trade participation. However, productivity growth in other industries is low and falling, in some cases. A balanced approach to investments in productivity and export promotion would sustain and improve Korean manufacturing’s competitiveness in global markets. <br/> <br/>Description: Graduation date: 2009 http://hdl.handle.net/1957/9245 Title: Essays on environment and the spatial distribution of economic activities <br/> <br/>Abstract: Environmental quality and the spatial distribution of economic activities affect each other in many ways. The primary purpose of this dissertation is to contribute to understanding the complex interrelationship and its policy implications. This dissertation consists of three essays. The first essay examines the roles that locational amenities and increasing returns to scale play in the formation of urban development patterns and regional economic growth. The spatial distribution of amenities is shown to be a major determinant; and the effects of amenities are reinforced by external scale economies and localized information spillovers, both of which promote agglomeration and human capital accumulation. Workers in amenity locations are more productive because of increasing returns, which encourage investment on human capital development. The decentralized equilibrium is not optimal because of the externalities associated with human capital investments. The efficiency can be improved by public policies encouraging human capital investments. Such policies also increase the number and size of cities and the pace of urbanization and economic growth. The second essay examines the effects of natural disasters on population growth across U.S. counties during the period of 1960-2000. Results suggest that except earthquakes and most serious hurricanes, the risks of natural disasters have no statistically significant effects on population growth. We also estimate the effects of natural disasters on county socioeconomic and demographic characteristics, including human capital, age and ethnic composition of population, industrial composition, and income inequality, which correlate with county population growth. The insignificance of those effects indicates that natural disasters have no indirect effects on population growth, either. The third essay considers the roles of mandatory building codes for regulating land development in a natural disaster-prone area as self-insurance and self-protection. To find the optimal building codes, a simple urban economics model is constructed for the analysis. A number of comparative statics results are presented to describe how optimal building codes are affected by the endowed probability of the disaster, the expected loss, productivity levels of self-insurance and self-protection, and socioeconomic characteristics of the area such as wage, population, and the share of land area in the risky region. <br/> <br/>Description: Graduation date: 2009