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Articles 1 - 5 of 5
Full-Text Articles in Life Sciences
Urban Impacts To Forest Productivity, Soil Quality, And Canopy Structure In Forest Park, Portland, Oregon, Andrew David Addessi
Urban Impacts To Forest Productivity, Soil Quality, And Canopy Structure In Forest Park, Portland, Oregon, Andrew David Addessi
Dissertations and Theses
Land use practices and exposure to low impact disturbances associated with an urban environment can alter forest structure and function. Past and ongoing research in Forest Park, a large urban forest in Portland, Oregon, suggests that mature mixed Douglas-fir (Psuedotsuga meziesii)-hardwood stands in the more urban end of the park lack a shade-tolerant conifer understory composed of the late successional conifer tree species, such western hemlock (Tsuga heterophylla) and western red-cedar (Thuja plicata). 5-year plot remeasurement data that characterizes productivity and mortality patterns did not show a strong relationship to urban proximity. Plot productivity …
Symbiosis With Nitrogen-Fixing Rhizobia Influences Plant Defense Strategy And Plant-Predator Interactions, Adrienne Louise Godschalx
Symbiosis With Nitrogen-Fixing Rhizobia Influences Plant Defense Strategy And Plant-Predator Interactions, Adrienne Louise Godschalx
Dissertations and Theses
As sessile organisms, plants evolved a plethora of defenses against their attackers. Given the role of plants as a primary food source for many organisms, plant defense has important implications for community ecology. Surprisingly, despite the potential to alter entire food webs and communities, the factors determining plant investment in defense are not well-understood, and are even less understood considering the numerous symbiotic interactions in the same plant. Legume-rhizobia symbioses engineer ecosystems by fixing nitrogen from the atmosphere in trade for plant photosynthates, yet connecting symbiotic resource exchange to food web interactions has yet to be established. Here I test …
Ecosystem Recovery In Estuarine Wetlands Of The Columbia River Estuary, Sarah Ann Kidd
Ecosystem Recovery In Estuarine Wetlands Of The Columbia River Estuary, Sarah Ann Kidd
Dissertations and Theses
In the restoration of tidal wetland ecosystems, potential drivers of plant community development range from biotic controls (e.g. plant competition, seed dispersal) to abiotic controls (e.g. tidal flooding, salinity levels). How these controls influence the success of tidal wetland restoration are only partly understood, but have important implications for wetland habitat recovery. Specifically, the extent to which the existing native and non-native seed banks in tidally reconnected wetlands interact with these controls is not clear, yet the potential success of passive restoration methods depends upon this understanding.
For a 54-year chronosequence of eleven tidal wetland restoration sites in the Lower …
An Efficient Pipeline For Assaying Whole-Genome Plastid Variation For Population Genetics And Phylogeography, Brendan F. Kohrn
An Efficient Pipeline For Assaying Whole-Genome Plastid Variation For Population Genetics And Phylogeography, Brendan F. Kohrn
Dissertations and Theses
Tracking seed dispersal using traditional, direct measurement approaches is difficult and generally underestimates dispersal distances. Variation in chloroplast haplotypes (cpDNA) offers a way to trace past seed dispersal and to make inferences about factors contributing to present patterns of dispersal. Although cpDNA generally has low levels of intraspecific variation, this can be overcome by assaying the whole chloroplast genome. Whole-genome sequencing is more expensive, but resources can be conserved by pooling samples. Unfortunately, haplotype associations among SNPs are lost in pooled samples and treating SNP frequencies as independent estimates of variation provides biased estimates of genetic distance. I have developed …
Let The Seeds Fall Where They May: Investigating The Effect Of Landscape Features On Fine-Scale Seed Dispersal, Monica R. Grasty
Let The Seeds Fall Where They May: Investigating The Effect Of Landscape Features On Fine-Scale Seed Dispersal, Monica R. Grasty
Dissertations and Theses
Seed dispersal is a crucial ecological and evolutionary process that allows plants to colonize sites and expand their ranges, while also reducing inbreeding depression and facilitating the spread of adaptive genetic variation. However, our fundamental understanding of seed dispersal is limited due to the difficulty of directly observing dispersal events. In recent years, genetic marker methods have furthered our understanding of colonization and range expansion due to seed dispersal. Most investigations focus on regional scales of dispersal, due to low levels of variation in the chloroplast genome (cpDNA), which can serve as an indirect measure of seed dispersal. Here, I …